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Title: Being Well-Born
An Introduction to Eugenics
Author: Michael F. Guyer
Editor: M. V. O'Shea
Release Date: May 21, 2012 [EBook #39751]
Language: English
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BEING WELL-BORN
BEING WELL-BORN
AN INTRODUCTION TO EUGENICS
_By_
MICHAEL F. GUYER, PH. D.
Professor of Zoology, The University of Wisconsin
Childhood and Youth Series
_Edited by_ M. V. O'SHEA
Professor of Education, The University of Wisconsin
INDIANAPOLIS
THE BOBBS-MERRILL COMPANY
PUBLISHERS
COPYRIGHT 1916
THE BOBBS-MERRILL COMPANY
PRESS OF
BRAUNWORTH & CO.
BOOKBINDERS AND PRINTERS
BROOKLYN, N. Y.
TO MY WIFE
HELEN M. GUYER
EDITOR'S INTRODUCTION
The writer recalls that when he was a young boy, he heard the grown-up
people in the community earnestly and incessantly debating the question:
Does heredity play a greater part in shaping one's mind and body than does
his environment? From that day to this he has listened to men and women in
every walk of life discussing the relation of heredity to environment in
determining human traits. Teachers and parents are constantly asking: "Are
such and such characteristics in my children due to their inheritance or
to the way they have been trained?" Students of juvenile delinquency and
of mental defect and deficiency are searching everywhere for light on this
matter. It is not to be wondered at that practically all people are
peculiarly interested in this problem, since it concerns intimately one's
personal traits, and it constantly confronts any one who is responsible
for the care and culture of the young.
It is suggestive to note how people differ in their views regarding the
extent to which a child's physical and mental qualities and capacities are
fixed definitely by his inheritance. The writer has often heard students
in university classes discuss the subject; and their handling of the
problem has shown how superficially and even superstitiously most persons
regard the mechanism and functions of heredity. It is significant also to
observe what extreme views many people hold regarding the possibility of
affecting a child's traits and abilities by subjecting him to specific
influences during his prenatal life. In any group of one hundred persons
chosen at random, probably seventy-five will believe in specific prenatal
influence. Many of them will believe in birthmarks due to peculiar
experiences of the mother. A popular book recently published asserts among
other things that if a mother will look upon beautiful pictures and listen
to good music during the prenatal period of her child, the latter will
possess esthetic traits and interests in high degree. On the other hand,
people generally do not seem to think that degenerate parents beget only
degenerate children. Alcoholics, feeble-minded persons and the like are
permitted to bring children into the world.
Very few people have any precise knowledge of the mechanism of heredity.
The whole thing is inscrutable to them, and is shrouded in mystery.
Superstition flourishes among even intelligent persons in respect to
heredity, and errors due to education, and tragedies resulting from
vicious social organization are all alike ascribed to its uncontrollable
forces. Most people are none the wiser because they do not know to what
extent the physical and mental defects and deviations of individuals are
due to inheritance or to the malign influences of the individual's
environment and training.
Professor Guyer, who has studied the whole problem in a thoroughgoing,
scientific way, has prepared this book with a view to illuminating some of
the mysteries that surround the subject of heredity, and to dispelling
the illusions that persist regarding it. He shows the method which nature
follows in the development of the individual. He presents the laws which
have become established respecting the extent to which and the manner in
which immediate and remote ancestors contribute to the child's physical
and mental organism. He answers many questions which those who are engaged
in social work or in education in the home or the school are asking
to-day. He discusses subjects upon which every serious-minded person
wishes to be informed. He has thus made a book which is both of
theoretical and of practical interest.
He has written in a style which should make his book attractive to the
parent and the teacher as well as to the student of the complicated
mechanism of inheritance. Only a few special terms are used, and these
should not give any reader trouble, because the treatment throughout is so
concrete that the meaning of the terms will be easily grasped. Further,
the book is illustrated, with many attractive and instructive
illustrations which will show at a glance the working of the principles of
inheritance which are developed in the text.
This book may be heartily commended to all who are interested in questions
of human nature, education and social reform. It should enable the parent,
the teacher and the legislator to understand more clearly than most of
them now do in how far children's traits and possibilities are or can be
fixed by inheritance as contrasted with environmental conditions and
nurture in home, school, church and institutional life.
M. V. O'SHEA.
Madison, Wisconsin.
PREFACE
One of the most significant processes at work in society to-day is the
awakening of the civilized world to the rights of the child; and it is
coming to be realized that its right of rights is that of being well-born.
Any series of publications, therefore, dealing primarily with the problems
of child nature may very fittingly be initiated by a discussion of the
factor of well-nigh supreme importance in determining this nature,
heredity.
No principles have more direct bearing on the welfare of man than those of
heredity, and yet on scarcely any subject does as wide-spread ignorance
prevail. This is due in part to the complexity of the subject, but more to
the fact that in the past no clear-cut methods of attacking the manifold
problems involved had been devised. Happily this difficulty has at least
in part been overcome.
It is no exaggeration to say that during the last fifteen years we have
made more progress in measuring the extent of inheritance and in
determining its elemental factors than in all previous time. Instead of
dealing wholly now with vague general impressions and speculations,
certain definite principles of genetic transmission have been disclosed.
And since it is becoming more and more apparent that these hold for man as
well as for plants and animals in general, we can no longer ignore the
social responsibilities which the new facts thrust upon us.
Since what a child becomes is determined so largely by its inborn
capacities it is of the greatest importance that teachers and parents
realize something of the nature of such aptitudes before they begin to
awaken them. For education consists in large measure in applying the
stimuli necessary to set going these potentialities and of affording
opportunity for their expression. Of the good propensities, some will
require merely the start, others will need to be fostered and coaxed into
permanence through the stereotyping effects of proper habits; of the
dangerous or bad, some must be kept dormant by preventing improper
stimulation, others repressed by the cultivation of inhibitive tendencies,
and yet others smothered or excluded by filling their place with desirable
traits before they themselves come into expression.
We must see clearly, furthermore, that even the best of pedagogy and
parental training has obvious limits. Once grasp the truth that a child's
fate in life is frequently decided long before birth, and that no amount
of food or hospital service or culture or tears will ever wholly make good
the deficiencies of bad "blood," or in the language of the biologist, a
faulty germ-plasm, and the conviction must surely be borne home to the
intelligent members of society that one thing of superlative importance in
life is the making of a wise choice of a marriage mate on the one hand,
and the prevention of parenthood to the obviously unfit on the other.
In the present volume it is intended to examine into the natural
endowment of the child. And since full comprehension of it requires some
understanding of the nature of the physical mechanism by which hereditary
traits are handed on from generation to generation, a small amount of
space is given to this phase. Then, that the reader may appreciate to
their fullest extent the facts gathered concerning man, a review of the
more significant principles of genetics as revealed through experiments in
breeding plants and animals has been undertaken. The main applications of
these principles to man is pointed out in a general discussion of human
heredity. Finally, inasmuch as all available data indicate that the fate
of our very civilization hangs on the issue, the work concludes with an
account of the new science of eugenics which is striving for the
betterment of the race by determining and promulgating the laws of human
inheritance so that mankind may intelligently go about conserving good and
repressing bad human stocks.
In order to eliminate as many errors as possible and to avoid oversights I
have submitted various chapters to certain of my colleagues and friends
who are authorities in the special field treated therein. While these
gentlemen are in no way responsible for the material of any chapter they
have added greatly to the value of the whole by their suggestions and
comments. Thus I am indebted to Professor Leon J. Cole for reading the
entire manuscript; to Professors A. S. Pearse and F. C. Sharp for reading
Chapter VII; to Professor C. R. Bardeen for reading special parts; to
Doctor J. S. Evans for reading Chapter VI and part of V; to Doctor W. F.
Lorenz, of the Mendota Hospital, for reading Chapter VIII; to Judge E. Ray
Stevens for reading Chapter IX, and to Helen M. Guyer for several readings
of the entire manuscript.
Grateful acknowledgment is made to all of these readers, to various
publishers and periodicals for the use of certain of the illustrations, to
the authors of the numerous books and papers from which much of the
material in such a work as this must necessarily be selected, and to my
artist, Miss H. J. Wakeman, for her painstaking endeavors to make her work
conform to my ideas of what each diagram should show.
M. F. G.
CONTENTS
CHAPTER PAGE
I HEREDITY 1
Blood heritage--Kind determined by origin--Ancestry a network--
Ancestry in royalty--Offspring derived from one parent only--Dual
ancestry an aid in studying heredity--Reversion--Telegony--
Prenatal influences apart from heredity--Parent body and germ not
identical--A hereditary character defined--Hereditary mingling a
mosaic rather than a blend--Determiners of characters, not
characters themselves, transmitted--Our knowledge of heredity
derived along three lines--The method of experimental breeding--
The statistical method--Galton's law of regression--Correlations
between parents and offspring--The biometrical method,
statistical, not physiological--Mental as well as physical
qualities inheritable.
II THE BEARERS OF THE HERITAGE 20
The cell the unit of structure--Unicellular organisms--Importance
of cell-theory--Heredity in unicellular forms--Reproduction and
heredity in colonial protozoa--Conjugation--Specialization of
sex-cells--The fertilized ovum--Advancement seen in the Volvox
colony--Natural death--Specialization in higher organisms--Sexual
phenomena in higher forms--Cell-division--Chromosomes constant in
number and appearance--Significance of the chromosomes--Cleavage
of the egg--Chief processes operative in building the body--The
origin of the new germ-cells--Significance of the early setting
apart of the germ-cells--Individuality of chromosomes--Pairs of
chromosomes--Reduction of the number of chromosomes by one-half--
Maturation of the sperm-cell--Maturation of the egg-cell--Parallel
between the two processes--Fertilization--Significance of the
behavior of the chromosomes--A single set of chromosomes
sufficient for the production of an organism--The duality of the
body and the singleness of the germ--The cytoplasm in
inheritance--Chromosomes possibly responsible for the
distinctiveness of given characters--Sex and heredity--Many
theories of sex determination--The sex-chromosome--Sex-linked
characters in man--In lower forms.
III MENDELISM 67
New discoveries in the field of heredity--Mendel--Rediscovery of
Mendelian principles--Independence of inheritable characters--
Illustration in the Andalusian fowl--The cause of the ratio--
Verification of the hypothesis--Dominant and recessive--
Segregation in the next generation--Illustrated in guinea-pigs--
Terminology--The theory of presence and absence--Additional
terminology--Dominance not always complete--Modifications of
dominance--Mendel's own work--Dihybrids--Getting new combinations
of characters--Segregations of the determiners--Four kinds of
gametes in each sex--The 9:3:3:1 ratio--Phenotype and genotype--
The question of blended inheritance--Nilsson-Ehle's discoveries--
Such cases easily mistaken for true blends--Skin-color in man--
Questionable if real blends exist--The place of the Mendelian
factors in the germ-cell--Parallel between the behavior of
Mendelian factors and chromosomes--A single chromosome not
restricted to carrying a single determiner.
IV MENDELISM IN MAN 97
Probably applicable to many characters in man--Difficult to get
correct data--A generalized presence-absence formula--Indications
of incomplete dominance--Why after the first generation only half
the children may show the dominant character--Eye-color in man--
Hair-color--Hair-shape--Irregularities--Digital malformations--Eye
defects--Other defects inherited as dominants--Recessive
conditions more difficult to deal with--Albinism--Other recessive
conditions in man--Breeding out defects--Other inheritable
conditions in man.
V ARE MODIFICATIONS ACQUIRED DIRECTLY BY THE BODY INHERITED? 121
Which new characters are inherited?--Examples of somatic
modifications--Use and disuse--The problem stated--Special
conditions in mammals--Three fundamental questions--External
influences may directly affect the germ-cells--Such effects
improbable in warm-blooded animals--Poisons may affect the
germ-plasm--How can somatic modifications be registered in
germ-cells?--Persistence of Mendelian factors argues against such
a mode of inheritance--Experiments on insects--On plants--On
vertebrates--Epilepsy in guinea-pigs--Effects of mutilations not
inherited--Transplantation of gonads--Effects of body on germ,
general not specific--Certain characters inexplicable as inherited
somatic acquirements--Neuter insects--Origin of new characters in
germinal variation--Sexual reproduction in relation to new
characters--Many features of an organism characterized by
utility--Germinal variation a simpler and more inclusive
explanation--Analysis of cases--Effects of training--Instincts--
Disease--Reappearance not necessarily inheritance--Prenatal
infection not inheritance--Inheritance of a predisposition not
inheritance of a disease--Tuberculosis--Two individuals of
tubercular stock should not marry--Special susceptibility less of
a factor in many diseases--Deaf-mutism--Gout--Nervous and mental
diseases--Other disorders which have hereditary aspects--Induced
immunity not inherited--Social, ethical and educational
significance of non-inheritance of somatic modifications--No cause
for discouragement--Improved environment will help conserve
superior strains when they do appear.
VI PRENATAL INFLUENCES 151
All that a child possesses at birth not necessarily hereditary--
The myth of maternal impressions--Injurious prenatal influences--
Lead poisoning--The expectant mother should have rest--Too short
intervals between children--Expectant mothers neglected--
Alcoholism--Unreliability of most data--Alcohol a germinal and
fetal poison--Various views of specialists on the effects of
alcoholism on progeny--The affinity of alcohol for germinal
tissue--Innate degeneracy versus the effects of alcohol--
Experimental alcoholism in lower animals--Further remarks on the
situation in man--Much inebriety in man due to defective nervous
constitution--Factors to be reckoned with in the study of
alcoholism--Venereal diseases--The seriousness of the situation--
Infantile blindness--Syphilis--Some of the effects--A blood test--
Many syphilitics married--Why permit existing conditions to
continue?--Ante-nuptial medical inspection--The perils of venereal
disease must be prevented at any cost--Bad environment can wreck
good germ-plasm.
VII RESPONSIBILITY FOR CONDUCT 195
All mental process accompanied by neural process--Gradations in
nervous response from lower organisms to man--Behavior of many
animals often an automatic adjustment to simple external agents--
Tropisms--Certain apparently complex volitions probably only
tropisms--Complicating factors--Many tropic responses apparently
purposeful--Tropisms grade into reflex actions and instincts--
Adjustability of instincts opens the way for intelligent
behavior--Modification of habits possible in lower animals--Some
lower vertebrates profit by experience--Rational behavior--
Conceptual thought probably an outgrowth of simpler psychic
states--The capacity for alternative action in higher animals--The
elemental units of the nervous system are the same in lower and
higher animals--Neuron theory--Establishment of pathways through
the nervous system--Characteristic arrangements of nerve cells
subject to inheritance--Different parts of the cortex yield
different reactions--Skill acquired in one branch of learning
probably not transferred to another branch--Preponderance of
cortex in highest animals--Special fiber tracts in the spinal cord
of man and higher apes--Great complexity in associations and more
neurons in the brain of man--The nervous system in the main
already staged at the time of birth--Many pathways of conduction
not yet established--The extent of the modifiable zone unknown--
Various possibilities of reaction in the child--Probable origin of
altruistic human conduct--Training in motive necessary--Actual
practise in carrying out projects important--Interest and
difficulty both essential--The realization of certain
possibilities of the germ rather than others is subject to
control--We must afford the opportunity and provide the proper
stimuli for the development of good traits--Moral responsibility.
VIII MENTAL AND NERVOUS DEFECTS 228
Prevalence of insanity--Imperfect adjustments of the brain
mechanism inheritable--Many mental defectives married--
Disproportionate increase in number of mental defectives--Protests
voiced by alienists--Examples of hereditary feeble-mindedness--
Difficult to secure accurate data--Feeble-mindedness and insanity
not the same--Many types of insanity--Not all insanities of the
same eugenical significance--Difficulties of getting genealogies
of specific forms of insanity--Certain forms of insanity seem to
behave as Mendelian recessives--Grades of feeble-mindedness--About
two-thirds of feeble-mindedness inherited--Some results of
non-restraint of the feeble-minded--Not all cases of mental
deficiency inherited--Epileptics--Feeble-mindedness probably a
recessive--Many apparently normal people are carriers of
neuropathic defects--Tests for mental deficiency--The backward
child in school--The exceptionally able child--Cost of caring for
our mentally disordered--Importance of rigid segregation of the
feeble-minded--Importance of early diagnosis of insanity--Opinion
of competent psychiatrists essential--Some insanities not
hereditary--Importance of heredity in insanity not appreciated.
IX CRIME AND DELINQUENCY 263
Heredity and environment in this field--Feeble-mindedness often a
factor--Many delinquent girls mentally deficient--Institutional
figures misleading--Many prisoners mentally subnormal--Inhibitions
necessary to social welfare--The high-grade moron a difficult
problem--Degenerate strains--Intensification of defects by
inbreeding--Vicious surroundings not a sufficient explanation in
degenerate stocks--Not all delinquents defectives--No special
inheritable crime-factor--What is a born criminal?--Epileptic
criminal especially dangerous--The mental disorders most
frequently associated with crime--Bearing of immigration on crime
and delinquency--Sexual vice--School instruction in sex-hygiene--
Mere knowledge not the crux of the sex problem--Early training in
self-restraint an important preventive of crime and delinquency--
Multiplication of delinquent defectives must be prevented.
X RACE BETTERMENT THROUGH HEREDITY 289
Questionable charity--Past protests--An increasing flood of
defectives--Natural elimination of defectives done away with--Why
not prevent our social maladies?--Eugenics defined--Improved
environment alone will not cure racial degeneracy--Heredity and
environment--Inter-racial marriage--Human conservation--Kindness
in the long run--The problem has two phases--Constructive eugenics
must be based on education--Inferior increasing more rapidly than
superior stocks--An unselected population may contain much
valuable material--The lack of criteria for judging fitness--The
college graduate--Native ability, independence and energy
eugenically desirable--Four children to each marriage required to
maintain a stock--Factors contributing to low birth-rate in
desirable strains--The educated public must be made to realize the
situation--Utilization of family pride as a basis for constructive
eugenics--The tendency for like to marry like--Public opinion as
an incentive to action--Choosing a marriage mate means choosing a
parent--The best eugenic marriage also a love match--The
elimination of the grossly unfit urgent--Suggested remedies--
Inefficacy of laws which forbid marriage of mental defectives--
Systems of mating impracticable in the main--Corrective mating
presupposes knowledge of eugenics--Segregation has many
advocates--Sterilization as a eugenic measure--To what conditions
applicable--In insanity--In feeble-mindedness--In cases of
epilepsy--Sterilization laws--Social dangers in vasectomy--Our
present knowledge insufficient--Sterilization laws on trial--An
educated public sentiment the most valuable eugenic agent--The
question of personal liberty--Education of women in eugenics
needed--Much yet to be done--A working program--Which shall it be?
GLOSSARY 343
REFERENCES FOR FURTHER READING AND STUDY 355
INDEX 361
BEING WELL-BORN
CHAPTER I
HEREDITY
It is a commonplace fact that offspring tend to resemble their parents. So
commonplace, indeed, that few stop to wonder at it. No one misunderstands
us when we say that such and such a young man is "a chip off the old
block," for that is simply an emphatic way of stating that he resembles
one or the other of his parents. The same is true of such familiar
expressions as "what's bred in the bone," "blood will tell," and kindred
catch phrases. All are but recognitions of the same common fact that
offspring exhibit various characteristics similar to those of their
progenitors.
=Blood Heritage.--=To this phenomenon of resemblance in successive
generations based on ancestry the term heredity is applied. In man, for
instance, there is a marked tendency toward the reappearance in offspring
of structures, habits, features, and even personal mannerisms, minute
physical defects, and intimate mental peculiarities like those possessed
by their parents or more remote forebears. These personal characteristics
based on descent from a common source are what we may call the blood
heritage of the child to discriminate it from a wholly different kind of
inheritance, namely, the passing on from one generation to the next of
such material things as personal property or real estate.
=Kind Determined by Origin.--=It is inheritance in the sense of community
of origin that determines whether a given living creature shall be man,
beast, bird, fish, or what not. A given individual is human because his
ancestors were human. In addition to this stock supply of human qualities
he has certain well-marked features which we recognize as characteristics
of race. That is, if he is of Anglo-Saxon or Italian or Mongolian
parentage, naturally his various qualities will be Anglo-Saxon, Italian,
or Mongolian. Still further, he has many distinctive features of mind and
body that we recognize as family traits and lastly, his personal
characteristics such as designate him to us as Tom, Harry, or James must
be added. The latter would include such minutiæ as size and shape of ears,
nose or hands; complexion; perhaps even certain defects; voice; color of
eyes; and a thousand other particulars. Although we designate these
manifold items as individual, they are in reality largely more or less
duplicates of similar features that occur in one or the other of his
progenitors, features which he would not have in their existing form but
for the hereditary relation between him and them.
"O Damsel Dorothy! Dorothy Q.!
Strange is the gift that I owe to you;
* * * * *
What if a hundred years ago
Those close-shut lips had answered 'No,'
* * * * *
Should I be I, or would it be
One-tenth another, to nine-tenths me?"
"Soft is the breath of a maiden's yes;
Not the light gossamer stirs with less;
But never a cable that holds so fast
Through all the battles of wave and blast,
And never an echo of speech or song
That lives in the babbling air so long!
There were tones in the voice that whispered then
You may hear to-day in a hundred men."
When life steps into the world of matter there comes with it a sort of
physical immortality, so to speak; not of the individual, it is true, but
of the race. But the important thing to note is that the race is made up,
not of a succession of wholly unrelated forms, but a continuation of the
same kind of living organisms, and this sameness is due to the actual
physical descent of each new individual from a predecessor. In other
words, any living organism is the kind of organism it is in virtue of its
hereditary relation to its ancestors.
It is part of the biologist's task to seek a material basis, a continuity
of actual substance, for this continuity of life and form between an
organism and its offspring. Moreover, inasmuch as the offspring is never
precisely similar to its progenitors he must determine also what qualities
are susceptible of transmission and in what measure.
=Ancestry a Network.--=From the fact that each child has all of the
ancestors of its mother as well as of its father, arises the great
complications which are met with in determining the lineage of an
individual. A person has two parents, four grandparents, eight great
grandparents, and thus following out pedigree it is plain to be seen that
through this process of doubling in each generation, in the course of a
few centuries one's ancestry is apparently enormous. By actual
computation, according to Professor D. S. Jordan, if we count thirty
generations back to the Norman invasion of England in 1066, at this ratio
of duplication, the child of to-day would have had at that time an
ancestry of 8,598,094,592 persons. But we know that the total number of
inhabitants in England during the time of William the Conqueror was but a
small fraction of this enormous aggregate. This means that we shall have
to modify our inference that a child has twice as many ancestors as its
parents; a condition which at first sight seems evident, but which is not
literally true. The fact is that the parents of the child, in all
probability, have many ancestors in common--a state of affairs which is
brought about through the intermarriage of relatives, and this is
especially frequent among remoter descendants of common progenitors. Time
after time in genealogy strains of blood have crossed and recrossed until
it is not improbable that a man of to-day who is of English origin has the
blood in his veins from every inhabitant of England who lived during the
time of William the Conqueror and left fruitful descendants. Instead of
conceiving of ancestry as an ever branching and widening tree-like system
as it recedes into the past, it is more accurate, therefore, to regard it
in the light of an elaborate meshwork. The "family tree" in reality
becomes the family net.
=Ancestry in Royalty.--=The pedigrees of royal families have proved to be
of much importance in the study of human inheritance, not that royal
traits are any more heritable than any other, but simply because the
records have been carefully kept so that they are the most comprehensive
and easily followed pedigrees available. The netlike weave of ancestry is
particularly well exemplified in some of these families because of much
close intermarriage. Their heritage typifies on an intensified scale the
heritage of the mass of mankind. For example, if we go six generations
back in the ancestry of Frederick the Great instead of the expected
sixty-four individual ancestors we find only forty; or in a still more
closely woven stock, in the Spanish royal line of Don Carlos we find in
six generations instead of sixty-four individual ancestors, only
twenty-eight. While the present German emperor might have had four
thousand ninety-six ancestors in the twelfth generation back, it is
estimated that owing to intermarriage he probably had only five hundred
thirty-three.
=Offspring Derived from One Parent Only.--=So far in our reckoning of
heredity we have counted elements from both father and mother, and the
complications which arise from such a double ancestry are manifestly very
perplexing ones. If we could do away with the elements of sex and find
offspring that are derived from one parent only, it would seemingly
simplify our problem very much for we should thus have a direct line of
descent, free from intermingling. This, in fact, occurs to a greater or
less extent among lower animals in a number of instances. There may be
only female forms for a number of generations and the eggs which they
produce develop directly into new individuals. Moreover, many of the
simpler organisms have the power of dividing their bodies into two and
thus giving rise to two new forms, each of which resembles the parent.
This shows plainly that we may have inheritance without the appearance of
any male ancestor at all, hence sex is not always a necessary factor in
reproduction or heredity. The development of eggs asexually, that is,
without uniting first with a male cognate, is termed _parthenogenesis_.
The ordinary plant louse or aphid which is frequently found upon geraniums
is a familiar example of an animal which reproduces largely in this way.
During the summer only the females exist and they are so astonishingly
fertile that one such aphid and her progeny, supposing none dies, will
produce one hundred million in the course of five generations. In the last
broods of the fall, males and females appear and fertile eggs are produced
which lie dormant through the winter to start the cycle of the next year.
Again, the eggs of some kinds of animals which normally have to unite with
a male germ before they develop, can be made to develop by merely treating
them with chemical solutions. The difference between an offspring derived
in such a manner, and one which has developed from an egg fertilized by
the male is that it is made up of characteristics from only one source,
the maternal.
=Dual Ancestry an Aid in Studying Heredity.--=Although we have the factors
of heredity in a more simplified form in the case of asexual
transmission, as a matter of fact most of our insight into the problems
of heredity has been attained from a study of sexually reproducing forms,
because the very existence of two sets of more or less parallel features
offers a kind of checking up system by which we can follow a given
characteristic.
=Reversion.--=Occasionally, however, plants and animals do not develop the
complete individuality we might expect, but stop short at or re-attain
some ancestral stage along the line of descent, and thus come to resemble
some progenitor perhaps many generations back of their own time. Thus it
is well known that as regards one or more characteristics a child may
resemble a grandparent or often some remote ancestor much more closely
than it does its immediate parent. The reappearance of such ancestral
traits the student of heredity designates as _Reversion_ or _Atavism_.
Reversion may occur apparently in any class of plants or animals. It is
especially pronounced among domesticated forms, which through man's
selection have been produced under more or less artificial conditions. For
example, among fancy breeds of pigeons, there may be an occasional return
to the old slaty blue color of the ancestral rock-pigeon, with two dark
cross-bars on the wings, from which all modern breeds have been derived.
This is almost sure to happen if the fancy varieties are inter-crossed for
two or three generations. Another example of reversion frequently cited is
the occasional reappearance in domestic poultry of the reddish or brownish
color pattern of the ancestral jungle-fowl to which, among modern forms,
the Indian game seems most nearly related in color. Still another example
is the cross-bars or stripes occasionally to be seen on the forelegs of
colts, particularly mules, reminiscent of the extinct wild progenitors
which were supposedly striped.
Fig. 1, p. 9, is a picture of a hybrid between the common fowl and the
guinea-fowl. The chevron-like markings on certain feathers show a
reversion to a type of color pattern that is prevalent among both the
primitive pheasants (the domestic chicken is a pheasant) and the primitive
guinea-fowls. Although the common spotted guinea-fowl may be crossed with
a black chicken which shows no trace of barring, nevertheless the hybrid
offspring are likely to bear a chevron-like pattern such as that shown in
the picture.
There has been much quibbling over the relative meanings of reversion and
atavism. The general idea, whichever term we use, is that there is a
"throwing back" in a noticeable degree through inheritance to some
ancestral condition beyond the immediate parents. A few recent authors
have taken the term atavism in a restricted sense and use it to signify
specifically those not uncommon cases in which a particular character of
an offspring resembles the corresponding character of a grandparent
instead of a parent. Such, for example, as the blue eye-color of a child
with brown-eyed parents, each of whom in turn has had a blue-eyed parent.
The tendency of other authors is to abandon the term entirely because of
the diversity of meaning that has been attached to it in the past.
[Illustration: FIG. 1
Hybrid between the guinea-fowl and the common fowl, showing in many
feathers reversion to a primitive chevron-like barring.]
Certain classes of so-called reversions, such as the case of the eye-color
just cited, are readily explicable on Mendelian principles as we shall see
in a later chapter, but probably not all kinds of phenomena described as
reversion can be so explained. For example, some seem to be cases of
suppressed development. The word reversion, indeed, must be looked on as
a convenient descriptive term rather than as the name of a single specific
condition.
=Telegony.--=There is yet a wide-spread belief in the supposed influence
of an earlier sire on offspring born by the same mother to a later and
different sire. This alleged phenomenon is termed _telegony_. For example,
many dog-breeders assert that if a thoroughbred bitch has ever had pups by
a mongrel father, her later offspring, although sired by a thoroughbred,
will show taints of the former mongrel mating. In such cases the female is
believed to be ruined for breeding purposes. Other supposed instances of
such influences have been cited among horses, cattle, sheep, pigs, cats,
birds, pets of various kinds and even men. The historic case most
frequently quoted is that of Lord Morton's mare which bore a hybrid colt
when bred to a quagga, a striped zebra-like animal now extinct. In later
years the same mare bore two colts, sired by a black Arabian horse. Both
colts showed stripes on the neck and other parts of the body, particularly
on the legs. It was inferred that this striping was a sort of after effect
of the earlier breeding with the quagga. In recent times, however,
Professor Ewart has repeated the experiment a number of times with
different mares using a Burchell zebra as the test sire. Although his
experiments have been devised so as to conduce in every way possible to
telegony his results have been negative. Moreover, it has been pointed out
that the stripes on the legs of the two foals alleged to show telegony
could not have been derived from the quagga sire for, unlike zebras,
quaggas did not have their legs striped. Furthermore it is known that the
occurrence of dark brown stripes on the neck, withers and legs of ordinary
colts is not uncommon, some cases of which have exhibited more zebra-like
markings than those of the colts from Lord Morton's mare. It seems much
more probable, therefore, that the alleged instances are merely cases of
ordinary reversion to the striped ancestral color pattern which probably
characterized the wild progenitors of the domesticated horse.
Various experiments on guinea-pigs, horses, mice and other forms,
especially devised to test out this alleged after-influence of an earlier
sire, have all proved negative and the general belief of the biologist
to-day is that telegony is a myth.
=Prenatal Influences Apart from Heredity.--=In discussing the problems of
heredity it is necessary to consider also the possibilities of external
influences apart from lineage which may affect offspring through either
parent. Although modifications derived directly by the parent, and
prenatal influences in general, are of extremely doubtful value as of
permanent inheritable significance, nevertheless they must be reckoned
with in any inventory of a child's endowment at birth. Impaired vitality
on the part of the mother, bad nutrition and physical vicissitudes of
various kinds all enter as factors in the birthright of the child, who,
moreover, may bear in its veins slumbering poisons from some progenitor
who has handed on blood taints not properly attributable to heredity. Of
such importance is this kind of influence to the welfare of the immediate
child that it will be necessary to discuss it in considerable detail in a
later chapter.
=Parent Body and Germ Not Identical.--=Inasmuch as each new individual
appears to arise from material derived from its parent, taking the
evidence at its face value one might suppose that any peculiarity of
organization called forth in the living substance of the parent would
naturally be repeated in the offspring, but a closer study of the
developing organism from its first inception to maturity shows this to be
probably a wrong conclusion. The parent-body and the reproductive
substance contained in that body are by no means identical. It becomes an
important question to decide, in fact, how much effect, if any, either
permanent or temporary, the parent-body really has on the germ.
A given fertile germ (Fig. 2, p. 13) gives rise by a succession of
divisions to a body which we call the individual, but such a germ also
gives rise to a series of new germ-cells which reside in that individual,
and it is these germ-cells, not something derived from the body, that pass
on the determiners of distinguishing features or qualities from generation
to generation. It is only by grasping the significance of this fact that
we can understand how in certain cases a totally different set of
characters may appear in an offspring than those manifested in either
parent.
=An Hereditary Character Defined.--=By a _character_, in discussions in
heredity, is meant simply a trait, feature or other characteristic of an
organism. Where we can pick out a single definable characteristic which
acts as a unit in heredity, for greater accuracy we term it a
_unit-character_. Many traits are known to be inherited on a unit basis or
are capable of being analyzed into factors which are so inherited. These
unit-characters are in large measure inherited independently of one
another apparently, although cases of characters inherited as a unit along
with other characters are known.
=Hereditary Mingling a Mosaic Rather Than a Blend.--=The independence of
unit-characters in inheritance leads us to the important conclusion that
the mingling of two lines of ancestry into a new individual is in no sense
bringing them into the "melting pot," as it has been picturesquely
expressed, but it is rather to be regarded as the mingling of two mosaics,
each particle of which retains its own individuality, and which, even if
overshadowed in a given generation, may nevertheless manifest its
qualities undimmed in later generations when conditions favorable to its
expression transpire.
[Illustration: FIG. 2
Diagram illustrating germinal continuity. Through a series of divisions a
germ-cell gives rise to a body or a soma and to new germ-cells. The
latter, not the body, give rise in turn to the next generation.]
=Determiners of Characters, Not Characters Themselves, Transmitted.--=The
fact should be thoroughly understood that the actual thing which is
transmitted by means of the germ in inheritance is not the character
itself, but something which will _determine_ the character in the
offspring. It is important to remember this, for often these
_determiners_, as they are called, may lie unexpressed for one or more
generations and may become manifest only in later descendants. The truth
of the matter is, the child does not inherit its characters from
corresponding characters in the parent-body, but parent and child are
alike because they are both products of the same line of germ-plasm, both
are chips from the same old block.
METHODS OF STUDYING HEREDITY
Before entering into details it will be well to get some idea of the
methods which are commonly employed in arriving at conclusions in the
field of heredity. Some of these are extremely complex and all that we can
do in an elementary presentation is to get a glimpse of the procedures.
=Our Knowledge of Heredity Derived Along Three Lines.--=Our modern
conceptions of heredity have been derived mainly from three distinct lines
of investigation: First, from the study of embryology, in which the
biologist concerns himself with the genesis of the various parts of the
individual, and the mechanism of the germs which convey the actual
materials from which these parts spring; second, through experimental
breeding of plants and animals to compare particular traits or features in
successive generations; and third, through the statistical treatment of
observations or measurements of a large number of parents and their
offspring with reference to a given characteristic in order to determine
the average extent of resemblance between parents and children in that
particular respect.
=The Method of Experimental Breeding.--=A tremendous impetus was given to
the method of experimental breeding when it was realized that we can
itemize many of the parts or traits of an organism into entities which are
inherited independently one of another. Such traits, or as we have already
termed them, unit-characters, may be not only independently heritable but
independently variable as well. The experimental method seeks to isolate
and trace through successive generations the separate factors which
determine the individual unit-characters of the organism. In this attempt
cross-breeding is resorted to. Forms which differ in one or more respects
are mated and the progeny studied. Next these offspring are mated with
others of their own kind or mated back with the respective parent types.
In this way the behavior of a particular character may often be followed
and the germinal constitutions of the individuals concerned can be
formulated with reference to it. Inasmuch as we shall give much
consideration to this method in the chapter on Mendelism we need not
consider it further here.
=The Statistical Method.--=The statistical method seeks to obtain large
bodies of facts and to deal with evidence as it appears through
mathematical analysis of these facts. The attempt of its followers is to
treat quantitatively all biological processes with which it is concerned.
Historically Sir Francis Galton was the first to make any considerable
application of statistical methods to the problems of heredity and
variation. In his attempts to determine the extent of resemblance between
relatives of different degree as regards bodily, mental and temperamental
traits, he devised new methods of statistical analysis which constitute
the basis of modern statistical biology, or _biometry_ as it is termed by
its votaries. Professor Karl Pearson in particular has extended and
perfected the mathematical methods of this field and stands to-day as
perhaps its most representative exponent. The system is in the main based
on the calculus of probability. The methods often are highly specialized,
requiring the use of higher mathematics, and are therefore only at the
command of specially trained workers.
Just as insurance companies can tell us the probable length of human life
in a given social group, since although uncertain in any particular case,
it is reducible in mass to a predictable constant, so the biometrician
with even greater precision because of his improved methods can often,
when a large number of cases are concerned, give us the intensity of
ancestral influence with reference to particular characters.
For example, it is clear that by measuring a large number of adult human
beings one can compute the average height or determine the height which
will fit the greatest number. There will be some individuals below and
some above it, but the greater the divergence from this standard height
the fewer will be the individuals concerned.
Galton compared the heights of 204 normal English parents and their 928
adult offspring. In order to equalize the measurements of men and women he
found he had to multiply each female height by 1.08. Then, to take both
parents into account when comparing height of parents to that of children
he added the height of the father to the proportionately augmented height
of the mother and divided by two, thus securing the height of what he
termed the "mid-parent." He found that the mid-parental heights of his
subjects ranged from 64.5 to 72.5 inches, and that the general _mode_ was
about 68.5 inches. It should be mentioned that the _mode_, in a given
population, represents the group containing the largest number of
individuals of one kind; it may or may not coincide with the average. The
children of all mid-parents having a given height were measured next and
tabulated with reference to these mid-parents. The results of Galton's
measurements may be expressed simply as follows:
-----------------------------------------------------------------
|MODE|
----------------------------------------|----|-------------------
Height of mid-parent| | | | | | | | |
in inches |64.5|65.5|66.5|67.5|68.5|69.5|70.5|71.5|72.5
| | | | | | | | |
Average height of | | | | | | | | |
offspring |65.8|66.7|67.2|67.6|68.3|68.9|69.5|69.9|72.2
-----------------------------------------------------------------
=The Law of Regression.--=It is plain from this table that the offspring
of short mid-parents tend to be under average or modal height though not
so far below as their parents. Likewise children of tall parents tend to
be tall but less tall than their parents. This fact illustrates what is
known as Galton's _law of regression_; namely, that if parents in a given
population diverge a certain amount from the mode of the population as a
whole, their children, while tending to resemble them, will diverge less
from this mode. It is clear that the extent of regression is an inverse
measure of the intensity of inheritance from the immediate parents; if the
deviation of the offspring from the general mode were nearly as great as
that of their parents then the intensity of the inheritance must be high;
if but slight--that is, if the offspring regressed nearly to the
mode--then the intensity of the inheritance must be ranked as low. In the
example in question it must be ranked as relatively high. Computations
show that as regards stature the fraction two-thirds represents
approximately the amount of resemblance between the two generations where
both parents are considered.
=Correlations Between Parents and Offspring.--=In modern researches the
conception of mid-parent and mid-grandparent as utilized by Galton has
been largely abandoned. It has been found more convenient as well as more
accurate to keep the measurements of the two parents separate and to deal
with correlations between fathers and sons, fathers and daughters, mothers
and sons, mothers and daughters, brother and brother, etc. Professor
Pearson and his pupils have found for a number of characters that the
correlation between either parent and children, whether sons or daughters,
is relatively close. The correlation between brother and brother, sister
and sister, and brother and sister, usually ranges a little higher than
the corresponding relation between parents and children.
=The Biometrical Method, Statistical, Not Physiological.--=While biometry
may in certain cases go far toward showing us the average intensity of
the inheritance of certain characters it can not replace the method of
the experimental breeder which deals with particular characters in
individual pedigrees. It must be borne in mind that the biometrical method
is a statistical and not a physiological one and that it is applicable
only when large numbers of individuals are considered in mass. It is most
valuable in cases where we are unable sharply to define single characters,
due probably to the concurrent action of a number of independent causes,
or where experiment is impossible so that we have to depend solely on
numerical data gained by observation.
=Mental Qualities Inheritable.--=Galton showed by this method long ago,
and Pearson and his school have extended and more clearly established the
work, that exceptional mental qualities tend to be inherited. While on the
average the children of exceptional parents tend to be less exceptional
than their parents, still they are far more likely to be exceptional than
are the children of average parents. By this method Professor Pearson has
shown that such mental and temperamental attributes as ability, vivacity,
conscientiousness, temper, popularity, handwriting, etc., are as
essentially determined as are physical features through the hereditary
endowment.
CHAPTER II
THE BEARERS OF THE HERITAGE
Before we can make any detailed analysis of the inheritance of characters
we should have some general idea of the physical structure of animals and
particularly some familiarity with the development of an individual from
the egg, as well as some knowledge of the nature of the germ-cells.
=The Cell the Unit of Structure.--=If we examine one of the higher
animals, as, for example, the horse, the dog, or man, we find that it is
made up of a large number of constituents, such as bones, muscles, nervous
elements, blood and other tissues. Each kind of tissue is composed of a
number of living units, ordinarily microscopic in size, which are known as
cells. A careful examination of various cells reveals that although they
may differ greatly in size, shape and minor details, they all alike
possess certain well-marked characteristics. Each when reduced to its
fundamental form is seen to consist of a small mass of living matter
termed protoplasm in which may usually be distinguished two regions--the
cell-body or _cytoplasm_, and the _nucleus_ (Fig. 3, p. 21). Any cell,
whether it be of the brain, of the liver, or from any organ of an animal
or plant, has this same fundamental structure. In addition, a limiting
membrane or wall of some kind is generally present, although it is not a
necessary constituent of all cells.
[Illustration: FIG. 3
Diagram of a cell showing various parts.]
=Unicellular Organisms.--=While such a structure as a tree or a horse is
composed of countless millions of cells, on the other hand numerous
organisms, both plant and animal, exist which consist of only one cell.
Yet this cell is just as characteristically a cell as are the components
of a complex animal or plant. It has the necessary parts, the cell body
and the nucleus. Moreover it exhibits all of the fundamental activities of
life, though in a simplified form, that a complex higher organism does.
=Importance of Cell-Theory.--=This discovery that every living thing is a
single cell or an aggregation of cooperating cells and cell-products is
one of our most important biological generalizations because it has
brought such a wide range of phenomena under a common point of view. In
the first place, the structure of both plants and animals is reducible to
a common fundamental unit of organization. Moreover, both physiological
and pathological phenomena are more readily understood since we recognize
that the functions of the body in health or disease are in large measure
the result of the activities of the individual cells of the functioning
part. Then again, the problems of embryological development have become
much more sharply defined since it could be shown that the egg is a single
cell and that it is through a series of divisions of this cell and
subsequent changes in the new cells thus formed that the new organism is
built up. And lastly, the problem of hereditary transmission has been
rendered more definite and approachable by the discovery that the male
germ is likewise a single cell, that fertilization of the egg is therefore
the union of two cells, and that in consequence the mechanism of
inheritance must be stowed away somehow in these two cells.
=Heredity in Unicellular Forms.--=In unicellular animals one can readily
see how it is possible for an individual always to give rise to its own
kind. One of the simplest of the single-celled animals is the _Ameba_
(Fig. 4, p. 24).
The ameba eats and grows as do other animals. Sooner or later it reaches a
size beyond which it can not increase advantageously, yet it is
continuously taking in new food material which stimulates it to further
growth. Here then is a problem. The ameba solves this difficulty by
dividing to form two amebæ. Such a division is illustrated in Fig. 4, p.
24. First the nucleus divides, then the cell-body. When the two new amebæ
separate completely each renews the occupation of eating and growing. But
what has become of the parent? Here, where once existed a large adult
ameba are two young amebæ. The parent individual as such has disappeared,
yet there has been no death, for we have simply two bits of living jelly
in place of one. They will in turn repeat the same process, so will their
offspring, and thus, barring accident, this growth and reproduction, or
overgrowth as we may regard it, may go on forever, as far as we know. Here
the problem of heredity, or the resemblance of offspring to parent, is not
a very complicated one. The substance of the cell-body and cell-nucleus
divides into two similar halves, so that each descendant has the substance
of the parent in its own body, only it has but half as much. It differs
from the parent, not in quality or kind, but in size.
[Illustration: FIG. 4
Six successive stages in the division of _Ameba polypodia_ (after
Schulze). The nucleus is seen as a dark spot in the interior.]
=Reproduction and Heredity in Colonial Protozoa.--=There are enormous
numbers of these single-celled animals existing in all parts of the world.
Some are simple like the ameba, others are very complex in structure.
Many, after division, move apart and pursue wholly independent courses of
existence. On the other hand we find a modification appearing in some
which is of the greatest importance. After division instead of moving
apart the two cells may remain side by side and divide further to form
two more, these in turn may divide and thus the process goes on until
there is formed what is known as a colony. Each cell of such a colony
resembles the original ancestral cell because each is a part of the actual
substance of that cell. As in the ameba, the first two cells are the
ancestral cell done up in two separate packets, and thus finally the full
quota of cells must be so many separate packets of the same kind of
material. Inasmuch as each is but a repetition of its original ancestor,
it can, and at times does, produce a colony of the same kind as that
ancestor produced.
=Conjugation.--=At longer or shorter intervals, however, we find that two
individuals, on the disruption of the old colony, instead of continuing
the routine of establishing new colonies through a series of cell
divisions, very radically alter their behavior. They unite and fuse into a
single larger individual. This process is called _conjugation_. We find it
occurring even in some species of ameba. The conjugating cells in some
colonies are alike in size and appearance, in others different.
=Specialization of Sex-Cells.--=A beautiful sphere-shaped colony known as
_Volvox_ is to be found occasionally in roadside pools. Depending on the
species of _Volvox_ to which it belongs, the colony may be made up of from
a few hundred to several thousand individuals arranged in a single layer
about the fluid-filled center of the sphere and bound together by a clear
jelly-like inter-cellular substance. Each individual cell also connects
with its neighbors by means of thin threads of living matter. One of the
largest species is _Volvox globator_, one edge of which is represented in
Fig. 5, p. 27. Mutual pressure of the cells gives them a polygonal shape
when viewed from the surface. Each cell, with a few exceptions to be noted
immediately, bears two long flagella, whip-like structures which project
out into the water. The lashing of these flagella gives the ball a rotary
motion and thus it moves about. When the colony has reached its adult
condition and is ready to reproduce itself, certain cells without flagella
and somewhat larger than the ordinary cells become more rounded in outline
and increase considerably in size through the acquisition of food
materials. They are then known as egg cells or ova. Each ovum finally
enters on a series of cell-divisions forming a mass of smaller and smaller
cells which gradually assumes the form of a hollow sphere like the parent
colony. The young colonies thus formed drop into the interior of the
parent colony to escape later to the outside as independent swimming
organisms when the old colony dies and disintegrates.
=The Fertilized Ovum Termed a Zygote.--=After a number of generations of
such asexual reproduction, sexual reproduction occurs. The ova arise as
usual. Certain members of the colony, on the other hand, go to the other
extreme and divide up into bundles of from sixty-four to one hundred
twenty-eight minute slender cells, each provided with flagella for
locomotion. When mature these small flagellate cells, now known as
_spermatozoa_, escape into the interior of the parent colony and swim
about actively. Ultimately each ovum is penetrated by a spermatozoon, the
two cells fuse completely and thus form the single _fertilized ovum_ or
_zygote_. The body-cells of the mother colony finally disintegrate. After
a period of rest each zygote, through a series of cell-divisions, develops
into an adult Volvox. In some species of Volvox a still further advance is
seen, in that instead of both kinds of gametes being produced in the same
colony, the ova may be produced by one colony and the spermatozoa by
another. Here, then, we have the foreshadowings of two sexes as separate
individuals, a phenomenon of universal occurrence among the highest forms
of animal life.
[Illustration: FIG. 5
_Volvox globator_ (from Hegner after Oltmanns). Half of a sexually
reproducing colony: _o_, eggs; _s_, spermatozoa.]
=Advancement Seen in the Volvox Colony.--=In the Volvox colony there is a
distinct advance over the conditions met with in various lower protozoan
colonies in that only certain individuals of the colony take part in the
process of reproduction and these individuals are of two distinct types;
one is a larger, food-laden cell or egg and the other a small, active,
fertilizing cell. The motile forms are produced in much greater numbers
than the eggs, plainly because they have to seek the egg and many will
doubtless perish before this can be accomplished. This disparity in number
is only a means of insuring fertilization of the egg. The remaining cells
of the body carry on the ordinary activities of the colony such as
locomotion and nutrition and have ceased to take any part in the
production of new colonies.
=Natural Death Appears With the Establishment of a Body Distinct from the
Germ.--=Volvox is an organism of unusual interest because in it we see a
prophecy of what is to come. Although still regarded as a colony of
single-celled individuals, it represents in reality a transition between
the whole group of unicellular animals termed protozoa and the many celled
animals characterized by the possession of distinct tissues, known as
_Metazoa_. Moreover, it shows an interesting stage in the establishment of
a body or _soma_ distinct from special reproductive cells which have taken
on the function of reproducing the colony. In such colonial forms natural
death is found appearing for the first time, the reproductive cells alone
continuing to perpetuate the species. Then again Volvox represents an
important step in the establishment of sex in the animal kingdom for in
its sexual reproduction the conjugating cells known as _gametes_ are no
longer alike in appearance but have become differentiated into definite
ova and spermatozoa.
In Volvox as in the other organisms which we have studied we find that all
of the cells including the germ-cells are produced by the repeated
division of a parent cell, and consequently each must contain the
characteristic living substance of that parent. Many other forms might be
cited to illustrate reproduction in single-celled animals, whether free or
in colonies, but all such cases would be practically but repetitions or
modifications of those we have already examined.
=Specialization in Higher Organisms.--=If we pass on to the higher animals
and plants which are not single cells or colonies of similar cells but
organisms made up of many different kinds of cells, we find a pronounced
extension of the phenomenon met with in Volvox. Instead of each cell
executing independently all of the life relations, certain ones are set
apart for the performance of certain functions to the exclusion of other
functions which are carried on by other members of the aggregation. Thus
the organism as a whole has all the life relations carried on, but, as it
were, by specialists.
=Sexual Phenomena in Higher Forms.--=In the reproduction of multicellular
organisms, one sees likewise but a continuation of the phenomena exhibited
in Volvox. Ordinarily, each new form is produced by the successive
divisions of a single germ-cell which in the vast majority of cases has
conjugated with another germ-cell. In the development of the egg, as the
divisions proceed, groups of cells become modified for their particular
work until the entire organism is completed. During development certain
cells are set apart for reproduction of the form just as they were in
Volvox. These two kinds of reproductive cells in multicellular organisms
are derived ordinarily from two separate individuals known as male and
female, though there are some exceptions. The main difference between
these cells which will have to unite to form a single fertile germ-cell,
is that they have specialized in different directions; one is small and
active, the other large, food-laden and passive. But with two such
germ-cells coming as they do from two individuals, one the male, the other
the female, it is obvious that the actual living substance of which each
germ is composed will be distinctive of its own parental line and that
when the germs unite these distinctive factors commingle, hence the
complications of double ancestry arise.
=Structure of the Cell.--=Before we can understand certain necessary
details of the physical mechanism of inheritance we must inquire a little
further into the finer structure of the cell and into the nature of cell
division. A typical cell, as it would appear after treatment with various
stains which bring out the different parts more distinctly, is shown in
Fig. 3, p. 21. Typical, not that any particular kind of living cell
resembles it very closely in appearance, but because it shows in a
diagrammatic way the essential parts of a cell. In the diagram, there are
two well-marked regions; a central _nucleus_ and a peripheral cell-body or
_cytoplasm_. Other structures are pictured but only a few of them need
command our attention at present. At one side of the nucleus one observes
a small dot or granule surrounded by a denser area of cytoplasm. This body
is called the _centrosome_. The nucleus in this instance is bounded by a
well-marked nuclear membrane and within it are several substances. What
appear to be threads of a faintly staining material, the _linin_, traverse
it in every direction and form an apparent network. The parts on which we
wish particularly to rivet our attention are the densely stained
substances scattered along or embedded in the strands of this network in
irregular granules and patches. This substance is called _chromatin_. It
takes its name from the fact that it shows great affinity for certain
stains and becomes intensely colored by them. This deeply colored portion
of the cell, the chromatin, is by most biologists regarded as of great
importance from the standpoint of heredity. One or more larger masses of
chromatin or chromatin-like material, known as _chromatin nucleoli_, are
often present, and not infrequently a small spheroidal body, differing in
its staining reactions from the chromatin-nucleolus and sometimes called
the _true nucleolus_, exists.
=Cell-Division.--=In the simplest type of cell-division the nucleus first
constricts in the middle, and finally the two halves separate. This
separation is followed by a similar constriction and final division of the
entire cell-body, which results in the production of two new cells. This
form of cell-division is known as _simple_ or _direct division_. Such a
simple division, while found in higher animals, is less frequent and
apparently much less significant than another type of division which
involves profound changes and rearrangements of the nuclear contents. The
latter is termed _mitotic_ or _indirect_ cell-division. Fig. 6, p. 33,
illustrates some of the stages which are passed through in indirect
cell-division. The centrosome which lies passively at the side of the
nucleus in the typical cell (Fig. 6_a_, p. 33) awakens to activity,
divides and the two components come to lie at the ends of a fibrous
spindle. In the meantime, the interior of the nucleus is undergoing a
transformation. The granules and patches of chromatin begin to flow
together along the nuclear network and become more and more crowded until
they take on the appearance of one or more long deeply-stained threads
wound back and forth in a loose skein in the nucleus (Fig. 6_b_, p. 33).
If we examine this thread closely, in some forms it may be seen to consist
of a series of deeply-stained chromatin granules packed closely together
intermingled with the substance of the original nuclear network.
As the preparations for division go on the coil in the nucleus breaks up
into a number of segments which are designated as _chromosomes_ (Fig.
6_c_, p. 33). The nuclear membrane disappears. The chromosomes and the
spindle-fibers ultimately become related in such a way that the
chromosomes come to lie at the equator of the spindle as shown in Fig
6_d_, p. 33. Each chromosome splits lengthwise to form two daughter
chromosomes which then diverge to pass to the poles of the spindle (Figs.
6_e_ and _f_, p. 33). Thus each end of the spindle comes ultimately to be
occupied by a set of chromosomes. Moreover each set is a duplicate of the
other, because the substance of any individual chromosome in one group has
its counterpart in the other. In fact this whole complicated system of
indirect division is regarded by most biologists as a mechanism for
bringing about the precise halving of the chromosomes.
[Illustration: FIG. 6
Diagram showing representative stages in mitotic or indirect
cell-division: _a_, resting cell with reticular nucleus and single
centrosome; _b_, the two new centrosomes formed by division of the old one
are separating and the nucleus is in the spireme stage; _c_, the nuclear
wall has disappeared, the spireme has broken up into six separate
chromosomes, and the spindle is forming between the two centrosomes; _d_,
equatorial plate stage in which the chromosomes occupy the equator of the
spindle; _e_, _f_, each chromosome splits lengthwise and the daughter
chromosomes thus formed approach their respective poles; _g_,
reconstruction of the new nuclei and division of the cell body; _h_,
cell-division completed.]
The chromosomes of each group at the poles finally fuse and two new
nuclei, each similar to the original one, are constructed (Figs. 6_g_ and
_h_, p. 33). In the meantime a division of the cell-body is in progress
which, when completed, results in the formation of two complete new cells.
As all living matter if given suitable food, can convert it into living
matter of its own kind, there is no difficulty in conceiving how the new
cell or the chromatin material finally attains to the same bulk that was
characteristic of the parent cell. In the case of the chromatin, indeed,
it seems that there is at times a precocious doubling of the ordinary
amount of material before the actual division occurs.
=Chromosomes Constant in Number and Appearance.--=With some minor
exceptions, to be noted later, which increase rather than detract from the
significance of the facts, the chromosomes are always the same in number
and appearance in all individuals of a given species of plants or animals.
That is, every species has a fixed number which regularly recurs in all of
its cell-divisions. Thus the ordinary cells of the rat, when preparing to
divide, each display sixteen chromosomes, the frog or the mouse,
twenty-four, the lily twenty-four, and the maw-worm of the horse only
four. The chromosomes of different kinds of animals or plants may differ
very much in appearance. In some they are spherical, in others rod-like,
filamentous or perhaps of other forms. In some organisms the chromosomes
of the same nucleus may differ from one another in size, shape and
proportions, but if such differences appear at one division they appear at
others, thus showing that in such cases the differences are constant from
one generation to the next.
=Significance of the Chromosomes.--=The question naturally arises as to
what is the significance of the chromosomes. Why is the accurate
adjustment which we have noted for their division necessary? The very
existence of an elaborate mechanism so admirably adapted to their precise
halving, predisposes one toward the belief that the chromosomes have an
important function which necessitates the retention of their individuality
and their equal division. Many biologists accept this along with other
evidence as indicating that in chromatin we have a substance which is not
the same throughout, that different regions of the same chromosome have
different physiological values.
When the cell prepares for divisions, the granules, as we have seen,
arrange themselves serially into a definite number of strands which we
have termed chromosomes. Judging from all available evidence, the granules
are self-propagating units; that is, they can grow and reproduce
themselves. So that what really happens in mitosis in the splitting of the
chromosomes is a precise halving of the series of individual granules of
which each chromosome is constituted, or in other words each granule has
reproduced itself. Thus each of the two daughter cells presumably gets a
sample of every kind of chromosomal particle, hence, the two cells are
qualitatively alike. To use a homely illustration we may picture the
individual chromosomes to ourselves as so many separate trains of freight
cars, each car of which is loaded with different merchandise. Now, if
every one of the trains could split along its entire length and the
resulting halves each grow into a train similar to the original, so that
instead of one there would exist two identical trains, we should have a
phenomenon analogous to that of a dividing chromosome.
=Cleavage of the Egg.--=It is through a series of such divisions as these
that the zygote or fertilized egg-cell builds up the tissues and organs of
the new organism. The process is technically spoken of as _cleavage_.
Cleavage generally begins very shortly after fertilization. The fertile
egg-cell divides into two, the resulting cells divide again and thus the
process continues, with an ever-increasing number of cells.
=Chief Processes Operative in Building the Body.--=Although of much
interest, space will not permit of a discussion in detail of the building
up of the special organs and tissues of the body. It must suffice merely
to mention the four chief processes which are operative. These are, (1)
infoldings and outfoldings of the various cell complexes; (2)
multiplication of the component cells; (3) special changes (_histological
differentiation_) in groups of cells; and (4) occasionally resorption of
certain areas of parts.
=The Origin of the New Germ-Cells.--=On account of the unusual importance
from the standpoint of inheritance, which attaches to the germ-cells, a
final word must be said about their origin in the embryo. While the
evidence is conflicting in some cases, in others it has been well
established that the germ-cells are set apart very early from the cells
which are to differentiate into the ordinary body tissues. Fig. 7_A_, p.
38, shows a section through the eight-celled stage of _Miastor_, a fly, in
which a single large, primordial germ-cell (_p. g. c._) has already been
set apart at one end of the developing embryo. The nuclei of the rest of
the embryo still lie in a continuous protoplasmic mass which has not yet
divided up into separate cells. The densely stained nuclei at the opposite
end of the section are the remnants of nurse-cells which originally
nourished the egg. Fig. 7_B_, p. 38, is a longitudinal section through a
later stage in the development of _Miastor_; the primitive germ-cells
(oög) are plainly visible. Still other striking examples might be cited.
Even in vertebrates the germ-cells may often be detected at a very early
period.
=Significance of the Early Setting Apart of the Germ-Cells.--=It is of
great importance for the reader to grasp the significance of this early
setting apart of the germ-cells because so much in our future discussion
hinges on this fact. The truth of the statement made in a previous chapter
that the body of an individual and the reproductive substance in that body
are not identical now becomes obvious. For in such cases as those just
cited one sees the germinal substance which is to carry on the race set
aside at an early period in a given individual; it takes no part in the
formation of that individual's body, but remains a slumbering mass of
potentialities which must bide its time to awaken into expression in a
subsequent generation. Thus an egg does not develop into a body which in
turn makes new germ-cells, but body and germ-cells are established at the
same time, the body harboring and nourishing the germ-cells, but not
generating them (Fig. 2, p. 13). The same must be true also in many cases
where the earliest history of the germ-cells can not be visibly followed,
because in any event, in all higher animals, they appear long before the
embryo is mature and must therefore be descendants of the original
egg-cell and not of the functioning tissues of the mature individual. This
need not necessarily mean that the germ-cells have remained wholly
unmodified or that they continue uninfluenced by the conditions which
prevail in the body, especially in the nutritive blood and lymph stream,
although as a matter of fact most biologists are extremely skeptical as to
the probability that influences from the body beyond such general
indefinite effects as might result from under-nutrition or from poisons
carried in the blood, modify the intrinsic nature of the germinal
substances to any measurable extent.
[Illustration: FIG. 7
A--Germ-cell (_p. g. c._) set apart in the eight-celled stage of cleavage
in _Miastor americana_ (after Hegner). The walls of the remaining seven
somatic cells have not yet formed though the resting or the dividing (_M
p_) nuclei may be seen; _c R_, chromatin fragments cast off from the
somatic cells.
B--Section lengthwise of a later embryo of _Miastor_; the primordial
egg-cells (_oög__{3}) are conspicuous (after Hegner).]
=Germinal Continuity.--=The germ-cells are collectively termed the
_germinal protoplasm_ and it is obvious that as long as any race continues
to exist, although successive individuals die, some germinal protoplasm is
handed on from generation to generation without interruption. This is
known as the theory of _germinal continuity_. When the organism is ready
to reproduce its kind the germ-cells awaken to activity, usually
undergoing a period of multiplication to form more germ-cells before
finally passing through a process of what is known at _maturation_, which
makes them ready for fertilization. The maturation process proper, which
consists typically of two rapidly succeeding divisions, is preceded by a
marked growth in size of the individual cells.
=Individuality of Chromosomes.--=Before we can understand fully the
significance of the changes which go on during maturation we shall have to
know more about the conditions which prevail among the chromosomes of
cells. As already noted each kind of animal or plant has its own
characteristic number and types of chromosomes when these appear for
division by mitosis. In many organisms the chromosomes are so nearly of
one size as to make it difficult or impossible to be sure of the identity
of each individual chromosome, but on the other hand, there are some
organisms known in which the chromosomes of a single nucleus are not of
the same size and form (Fig. 8, p. 41). These latter cases enable us to
determine some very significant facts. Where such differences of shape and
proportion occur they are constant in each succeeding division so that
similar chromosomes may be identified each time. Moreover, in all ordinary
mitotic divisions where the conditions are accurately known, these
chromosomes of different types are found to be present as pairs of similar
elements; that is, there are two of each form or size.
=Pairs of Similar Chromosomes in the Nucleus Because One Chromosome Comes
from Each Parent.--=When we recall that the original fertilized egg from
which the individual develops is really formed by the union of two
gametes, ovum and spermatozoon, and that each gamete, being a true cell,
must carry its own set of chromosomes, the significance of the pairs of
similar chromosomes becomes evident; one of each kind has probably been
contributed by each gamete. This means that the zygote or fertile ovum
contains double the number of chromosomes possessed by either gamete, and
that, moreover, each tissue-cell of the new individual will contain this
dual number. For, as we have seen, the number of chromosomes is, with
possibly a few exceptions, constant in the tissue-cells and early
germ-cells in successive generations of individuals. For this to be true
it is obvious that in some way the nuclei of the conjugating gametes have
come to contain only half the usual number. Technically the tissue-cells
are said to contain the _diploid_ number of chromosomes, the gametes the
reduced or _haploid_ number.
[Illustration: FIG. 8
A--Chromosomes of the mosquito (_Culex_) after Stevens.
B--Chromosomes of the fruit-fly (_Drosophila_) after Metz.
Both of these forms have an unusually small number of chromosomes.]
=In Maturation the Number of Chromosomes Is Reduced by One-Half.--=This
halving, or as it is known, _reduction_ in the number of chromosomes is
the essential feature of the process of maturation. It is accomplished by
a modification in the mitotic division in which instead of each chromosome
splitting lengthwise, as in ordinary mitosis, the chromosomes unite in
pairs (Fig. 9_b_, p. 42), a process known technically as _synapsis_, and
then apparently one member of each pair passes entire into one new
daughter cell, the other member going to the other daughter cell (Fig.
9_c_, p. 42). In the pairing preliminary to this _reduction division_,
leaving out of account certain special cases to be considered later,
according to the best evidence at our command the union always takes place
between two chromosomes which match each other in size and appearance.
Since one of these is believed to be of maternal and the other of
paternal origin, the ensuing division separates corresponding mates and
insures that each gamete gets one of each kind of chromosome although it
appears to be a matter of mere chance whether or not a given cell gets the
paternal or the maternal representative of that kind.
[Illustration: FIG. 9
Diagram to illustrate spermatogenesis: _a_, showing the diploid number of
chromosomes (six is arbitrarily chosen) as they occur in divisions of
ordinary cells and spermatogonia; _b_, the pairing (synapsis) of
corresponding mates in the primary spermatocyte preparatory to reduction;
_c_, each secondary spermatocyte receives three, the haploid number of
chromosomes; _d_, division of the secondary spermatocytes to form _e_,
spermatids, which transform into _f_, spermatozoa.]
=Maturation of the Sperm-Cell.--=In the maturation of the male gamete the
germ-cell, now known as a _spermatogonium_, increases greatly in size to
become a _primary spermatocyte_. In each primary spermatocyte the pairing
of the chromosomes already alluded to occurs as indicated in Fig. 9_b_, p.
42, where six is taken arbitrarily to indicate the ordinary or _diploid_
number of chromosomes, and three the reduced or _haploid_ number. The
division of the primary spermatocyte gives rise to two _secondary
spermatocytes_ (_c_), the paired chromosomes separating in such a way that
a member of each pair goes to each secondary spermatocyte. Each secondary
spermatocyte (_d_) soon divides again into two _spermatids_ (_e_), but in
this second division the chromosomes each split lengthwise as in an
ordinary division so that there is no further reduction. In some forms the
reduction division occurs in the secondary spermatocytes instead of the
primary. Each spermatid transforms into a mature spermatozoon (_f_). The
spermatozoa of most animals are of linear form, each with a head, a
middle-piece and a long vibratile tail which is used for locomotion. The
head consists for the most part of the transformed nucleus and is
consequently the part which bears the chromosomes.
=Maturation of the Egg-Cell.--=As regards the behavior of the chromosomes
the maturation of the ovum parallels that of the sperm-cell. There are not
so many primordial germ-cells formed and only one out of four of the
ultimate cells becomes a functional egg. As in maturation of the
sperm-cell there is a growth period in which _oögonia_ enlarge to become
_primary oöcytes_ (Fig. 10_b_, p. 45). In each primary oöcyte as in the
primary spermatocyte the chromosomes pair and two rapidly succeeding
divisions follow in one of which the typical numerical reduction in the
chromosomes occurs. A peculiarity in the maturation of the ovum is that
there is a very unequal division of the cytoplasm in cell division so that
three of the resulting cells usually termed _polar bodies_ are very small
and appear like minute buds on the side of the fourth or egg-cell proper.
The scheme of this formation of the polar bodies is indicated in Fig. 10,
p. 45. In Fig. 10_b_ the chromosomes are seen paired and ready for the
first division; that is, for the formation of the first polar body. Figs.
10_c_, _d_, p. 45, show the giving off of this body. Note that while only
a small proportion of the cytoplasm passes into this tiny cell, its
chromatin content is as great as that of the ovum. A second polar body
(Figs. 10_e_, _f_, p. 45) is formed by the egg, but in this case each
chromosome splits lengthwise, as in ordinary mitosis, and there is no
further numerical reduction. In the meantime, typically, a third polar
body is formed by division of the first. (Stages _e_, _f_, _g_.)
=Parallel Between the Maturation of Sperm- and Egg-Cell.--=This rather
complex procedure of the germ-cells will be rendered more intelligible
through a careful study of Figs. 9 and 10, pp. 42 and 45, and Fig. 11, p.
46, which indicates the parallel conditions in spermotogenesis and
oögenesis.
[Illustration: FIG. 10
Diagram to illustrate oögenesis: _a_, showing the diploid number of
chromosomes (six is arbitrarily chosen) as they occur in ordinary cells
and oögonia; _b_, the pairing of corresponding mates preparatory to
reduction; _c_, _d_, reduction division, giving off of first polar body;
_e_, egg preparing to give off second polar body, first polar body ready
for division; _f_, _g_, second polar body given off, division of first
polar body completed. The egg nucleus, now known as the female pronucleus,
and each body contain the reduced or haploid number of chromosomes.]
The view now generally held regarding the polar bodies is that they are
really abortive eggs. They later disappear, taking no part in
embryo-formation. It can readily be seen how such an unequal division is
advantageous to the large cell, for it receives all of the rich store of
food material that would be distributed among the four cells if all were
of equal size. This increased amount of food is a favorable provision for
the forthcoming offspring whose nourishment is thus more thoroughly
insured.
[Illustration: FIG. 11
Diagram showing the parallel between maturation of the sperm-cell and
maturation of the ovum.]
On the other hand, all of the sperm-cells develop into complete active
forms, which, as aforesaid, usually become very much elongated and develop
a motile organ of some kind. In such cells an accumulation of food to any
large extent would hinder rather than help them, because it would
seriously interfere with their activity.
=Fertilization.--=In fertilization (Fig. 12, p. 48) the spermatozoon
penetrates the wall of the ovum and after undergoing considerable
alteration its nucleus fuses with the nucleus of the egg. In some forms
only the head (nucleus) and middle-piece enter, the tail being cut off by
a so-called fertilization membrane which forms at the surface of the egg
and effectually blocks the entrance of other spermatozoa. Thus normally
only one spermatozoon unites with an egg. In some forms while several may
enter the egg only one becomes functional. As soon as the nucleus of the
spermatozoon, now known as the male _pronucleus_, reaches the interior of
the egg, it enlarges and becomes similar in appearance to the female
_pronucleus_. It swings around in such a way (Fig. 12_b_, p. 48) that the
middle piece, now transformed into a centrosome, lies between it and the
female pronucleus. The two pronuclei (_c_, _d_, _e_), each containing the
reduced number of chromosomes, approach, the centrosome divides, the
nuclear walls disappear, the typical division spindle forms, and the
chromosomes of paternal and maternal origin respectively come to lie side
by side at the equator of the spindle ready for the first division or
cleavage (_f_, _g_). It will be noted that the individual chromosomes do
not intermingle their substance at this time, but that each apparently
retains its own individuality. There is considerable evidence which
indicates that throughout life the chromosomes contributed by the male
parent remain distinct from those of the female parent. Inasmuch as each
germ-cell, after maturation, contains only half the characteristic number
of chromosomes, the original number is restored in fertilization.
[Illustration: FIG. 12
Diagram to illustrate fertilization; [male], male pronucleus; [female],
female pronucleus; observe that the chromosomes of maternal and paternal
origin respectively do not fuse.]
=Significance of the Behavior of the Chromosomes.--=The question confronts
us as to what is the significance of this elaborate system which keeps the
chromosomes of constant size, shape and number; which partitions them so
accurately in ordinary cell-divisions; and which provides for a reduction
of their numbers by half in the germ-cell while yet securing that each
mature gamete gets one of each kind of chromosome. Most biologists look on
these facts as indicating that the chromosomes are specifically concerned
in inheritance.
In the first place it is recognized that as regards the definable
characters which separate individuals of the same species, offspring may
inherit equally from either parent. And it is a very significant fact that
while the ovum and spermatozoon are very unequal in size themselves, the
chromosomes of the two germ-cells are of the same size and number. This
parity in chromosomal contribution points clearly to the means by which an
equal number of character-determiners might be conveyed from each parent.
Moreover it is mainly the nucleus of the sperm-cell in some organisms
which enters the egg, hence the determiners from the male line must exist
wholly or largely somewhere in the nucleus. And the bulk of the nucleus in
the spermatozoon consists of the chromosomes or their products.
=A Single Set of Chromosomes Derived from One Parent Only Is Sufficient
for the Production of a Complete Organism.--=That a single or haploid set
of chromosomes as seen in the gametes is sufficient contribution of
chromatin for the production of a complete organism is proved by the fact
that the unfertilized eggs of various animals (many echinoderms, worms,
mollusks, and even the frog) may be artificially stimulated to development
without uniting at all with a spermatozoon. The resulting individual is
normal in every respect except that instead of the usual diploid number it
has only the single or haploid number of chromosomes. Its inheritance of
course is wholly of maternal origin. The converse experiment in
echinoderms in which a nucleus of male origin (that is, a spermatozoon)
has been introduced into an egg from which the original nucleus has been
removed shows that the single set of chromosomes carried by the male
gamete is also sufficient to cooperate with the egg-cytoplasm in
developing a complete individual.
=The Duality of the Body and the Singleness of the Germ.--=Since every
maternal chromosome in the ordinary cell has an equivalent mate derived
from the male parent, it follows therefore, supposing the chromosomes do
have the significance in inheritance attributed to them, that as regards
the measurable inheritable differences between two individuals, the
ordinary organism produced through the union of the two germ-cells is,
potentially at least, dual in nature. On the other hand through the
process of reduction the gametes are provided with only a single set of
such representatives. This duality of the body and singleness of the
mature germ is one of the most striking facts that come to light in
embryology. How well the facts fit in with the behavior of certain
hereditary characters will be seen later in our discussions of Mendelism.
=The Cytoplasm Not Negligible in Inheritance.--=Just what part is played
by the cytoplasm in inheritance is not clear, but it is probably by no
means a negligible one. The cytoplasm of a given organism is just as
distinctive of the species or of the individual of which it forms a part
as are the chromosomes. It is well established that neither nucleus nor
cytoplasm can fully function or even exist long without the other, and
neither can alone produce the other. They undoubtedly must cooperate in
building up the new individual, and the cytoplasm of the new individual is
predominantly of maternal origin. It is obvious that all of the more
fundamental characters which make up an organism, such, for instance, as
make it an animal of a certain order or family, as a human being or a dog
or a horse, are common to both parents, and there is no way of measuring
how much of this fundamental constitution comes from either parent, since
only closely related forms will interbreed. In some forms, moreover, the
broader fundamental features of embryogeny are already established before
the entrance of the spermatozoon. It is probable therefore that instead of
asserting that the entire quota of characters which go to make up a
complete individual are inherited from each parent equally, we are
justified only in maintaining that this equality is restricted to those
measurable differences which veneer or top off, as it were, the
individual. We may infer that in the development of the new being the
chromosomes of the egg together with those derived from the male work
jointly on or with the other germinal contents which are mostly
cytoplasmic materials of maternal origin.
=The Chromosomes Possibly Responsible for the Distinctiveness of Given
Characters.--=It seems probable that in the establishment of certain basic
features of the organism the cooperation of the cytoplasm with chromatin
of either maternal or paternal origin might accomplish the same end, but
that certain distinctive touches are added or come cumulatively into
expression through influences carried, predominantly at least, in the
chromatin from one as against the other parent. These last distinctive
characters of the plant or animal constitute the individual differences of
such organisms. In this connection it is a significant fact that in young
hybrids between two distinct species the early stages of development,
especially as regards symmetry and regional specifications, are
exclusively or predominantly maternal in character, but the male influence
becomes more and more apparent as development progresses until the final
degree of intermediacy is attained.
From the evidence at hand this much seems sure, that the paternal and
maternal chromosomes respectively carry substances, be they ferments,
nutritive materials or what not, that are instrumental in giving the final
parity of personal characters which we observe to be equally heritable
from either line of ancestry. It is clear that most of the characters of
an adult organism can not be merely the outcome of any unitary substance
of the germ. Each is the product of many cooperating factors and for the
final outcome any one cooperant is probably just as important in its way
as any other. The individual characters which we juggle to and fro in our
breeding experiments seem apexed, as it were, on more fundamental features
of organic chemical constitution, polarity, regional differentiation, and
physiological balance, but since such individual characters parallel so
closely the visible segregations and associations which go on among the
chromosomes of the germ-cells it would seem that they, at least, are
represented in the chromosomes by distinctive cooperants which give the
final touch of specificity to those hereditary characters which can be
shifted about as units of inheritance.
=Sex and Heredity.--=Whatever the origin of fertilization may have been in
the world of life, or whatever its earliest significance, the important
fact remains that to-day it is unquestionably of very great significance
in relation to the phenomena of heredity. For in all higher animals, at
least, offspring may possess some of the characteristics originally
present in either of two lines of ancestry, and this commingling of such
possessions is possible only through sexual reproduction. As has already
been seen, in the pairing of chromosomes previous to reduction, the
corresponding members of a pair always come together so that in the final
segregation each gamete is sure to have one of each kind although whether
a given chromosome of the haploid set is of maternal or paternal origin
seems to be merely a matter of chance. Thus, for instance, if we
arbitrarily represent the chromosomes of a given individual by _ABC_
_abc_, and regard _A_, _B_ and _C_ as of paternal and _a_, _b_ and _c_ as
of maternal origin, then in synapsis only _A_ and _a_ can pair together,
_B_ and _b_ and _C_ and _c_, but each pair operates independently of the
other so that in the ensuing reduction division either member of a pair
may get into a cell with either member of the other pairs. That is, the
line up for division at a given reduction might be any one of the
following, ABC/abc ABc/abC Abc/aBC AbC/aBc. This would yield the following
eight kinds of gametes, _ABC_, _abc_, _ABc_, _abC_, _Abc_, _aBC_, _AbC_,
_aBc_, each bearing one of each kind of chromosome required to cover the
entire field of characters necessary to a complete organism. And since
each sex would be equally likely to have these eight types of gametes and
any one of the eight in one individual might meet any one of the eight of
the other, the possible number of combinations in the production of a new
individual from such germ-cells would be 8x8, or 64. With the larger
numbers of chromosomes which exist in most animals it is readily seen that
the number of possible combinations becomes very great. Thus any
individual of a species with twenty chromosomes--and many animals,
including man, have more--would have ten pairs at the reduction period and
could therefore form (2)^{10}, or 1,024 different gametes in each sex. And
since any one of these in one sex would have an equal chance of meeting
with any one in the opposite sex, the total number of possible different
zygotes that might be produced would be (1,024)^{2}, or 1,048,576. Sex
therefore, through recombinations of ancestral materials, undoubtedly
means, among other things, the production of great diversity in
offspring.
DETERMINATION OF SEX
=Many Theories.--=From earliest times the problem of sex determination has
been one of keen interest, and needless to say hundreds of theories have
been propounded to explain it. Geddes and Thomson say that Drelincourt
recorded two hundred sixty-two so-called theories of sex production and
remark that since his time the number has at least been doubled. The
desirability of controlling sex has naturally appealed strongly to
breeders of domesticated animals.
A study of animals born in litters, or of twins, is enough in itself to
make us skeptical of theories of sex-determination based on nutritional or
external factors. In a litter of puppies, for example, there are usually
both males and females, although in their prenatal existence they have all
been subject to the same nutritional and environmental conditions.
Likewise in ordinary human twins one may be a boy, the other a girl,
whereas if the nutritional condition of the mother were the fact
determining sex, both should be boys or both girls. However, there are
twins known as _identical twins_ who are remarkably alike and who are
always of the same sex. But there is reason to suppose that identical
twins in reality come from the same zygote. Presumably in early
embryogeny, probably at the two-celled stage of cleavage, the two
blastomeres become separated and each gives rise to a complete individual
instead of only the half of one it would have produced had the two
blastomeres remained together. Such twins are monochorial; that is, they
grow inside the same fetal membrane, whereas each ordinary twin has its
own fetal membrane and has obviously originated from a separate ovum. It
has been established experimentally in several kinds of animals that early
cleavage blastomeres when isolated can each develop into a complete
individual. In man, ordinary twins are no more alike than ordinary
brothers and sisters, but identical twins are strikingly similar in
structure, appearance, habits, tastes, and even susceptibility to various
maladies. The fact that they are invariably of the same sex is a strong
reason for believing that sex was already developed in the fertile ovum
and consequently in the resulting blastomeres from that ovum.
The young of the nine-banded armadillo in a given litter are invariably of
the same sex and are closely similar in all features. Newman and Patterson
have shown that all the members of a litter come from the same egg.
Patterson has established the fact that cleavage of the egg takes place in
the usual manner, but later separate centers of development appear in the
early embryonic mass and give rise to the separate young individuals.
Again in certain insects where one egg indirectly gives rise to a chain of
embryos, or to a number of separate larvæ, possibly as many as a thousand,
all of the latter are of the same sex. Even in some plants researches have
shown that sex is already determined at the beginning of development.
Then, too, much evidence has come to light recently showing that
sex-characters in certain cases behave as heritable characters and are
independent of external conditions. Lastly there is visible and convincing
evidence obtainable through microscopical observations that sex is
determined by a mechanism in the germ-cells themselves. It is chiefly to
these latter facts that I wish to direct attention for the present.
=The Sex Chromosome.--=The evidence centers about a special chromosome or
chromosome-group commonly designated as the _sex-chromosome_ or
_X-element_, which has been found in various species of animals, including
man. In the males of such animals this chromosome is present in addition
to the regular number of pairs, thus giving rise to an _uneven_ instead of
the conventional even number of chromosomes. This element remains
undivided in one of the maturation divisions of the spermatocytes, in some
forms in the first in others in the second, and passes entire to one pole
of the spindle (Fig. 13, p. 58). This results in the production of two
classes of cells, one containing the _X_-element and one not. The outcome
is that two corresponding classes of spermatozoa are produced. The
phenomena involved are diagrammatically represented in Fig. 13. It has
been clearly demonstrated in several cases that eggs fertilized by
spermatozoa which possess this _X_-element, always become females, those
fertilized by spermatozoa which do not possess it always develop into
males.
[Illustration: FIG. 13
Diagram illustrating the behavior of the _x_-element or sex-chromosome in
the maturation of the sperm-cell. In one of the two maturation divisions
(represented here as in the first) it passes undivided to one pole (_a_,
_b_, _c_), in the other it divides. Since the cell without the _x_-element
also divides the result is that ultimately from the original primary
spermatocyte (_a_) four cells are formed (_f_), two with the _x_-element
and two without it. Half of the spermatozoa therefore will bear an
_x_-element, half will be without it. In _a_ the ordinary chromosomes,
arbitrarily indicated as 10, are supposed to have already paired for
reduction so that the original diploid number in spermatogonia and
body-cells of the male would be 20 plus the _x_-chromosome.]
It has been found, furthermore, that in species in which the males possess
this extra element the females have two of them. That is, if the original
number in the somatic cells of the male were twenty-three, twenty-two
ordinary and one _X_-element, the number in the somatic cells of the
female would be twenty-four, or twenty-two ordinary and two _X_-elements.
It has been found that when the chromosomes of the female pair for the
reduction division, each chromosome uniting with its corresponding fellow,
the two _X_-elements in the female pair in the usual way so that every
egg-cell possesses an _X_-element. Thus every mature egg has an
_X_-element, while only half of the spermatozoa have one. That is, if we
assume twenty-three as the diploid number present originally in the
somatic cells of the male and twenty-four as the number in the female,
then one-half the spermatozoa of the male would contain the haploid number
eleven, and the other half, the number twelve, whereas every mature ovum
would contain twelve. Since there are equal numbers of the spermatozoa
with the _X_-element and without it, and inasmuch as presumably under
ordinary conditions one kind is as likely to fertilize the egg as the
other, then there are equal chances at fertilization of producing a zygote
with two _X_-elements or with but one.
Thus, Spermatozoon + _X_ by Ovum + _X_ = Zygote + _XX_.
Spermatozoon (no _X_) by Ovum + _X_ = Zygote + _X_.
We have already seen that the former is always female, the latter male. It
thus becomes possible to distinguish the sex of an embryo by counting the
chromosomes of its cells. This has been accomplished in several cases.
In some instances[1] the conditions may be much more complex than the
ones indicated--too complex in fact to warrant detailed discussion in an
elementary exposition--but the principle remains the same throughout, the
very complexity when thoroughly understood, strengthening rather than
weakening the evidence. In a few forms an interesting reversal of
conditions has been found in that the eggs instead of the spermatozoa show
the characteristic dimorphism.
Just what the exact relationship between sex-differentiation and the
_X_-element is has never been clearly established. It is possible that
this element is an actual sex-determinant, in the ordinary cases one
_X_-element determining the male condition and two _X_-elements producing
the female condition. On the other hand it might be argued that it is not
the determining factor but the expression of other cell activities which
do determine sex; that is, a sex accompaniment. Or again, it may be one of
several essential factors which must cooperate to determine sex.
SEX-LINKED CHARACTERS
The discovery of the remarkable behavior of certain characters in heredity
which can only be plausibly explained by supposing that they are linked
with a sex-determining factor still further strengthens our belief in the
existence of such a definite factor. Such characters are commonly termed
sex-linked characters.
=Sex-Linked Characters in Man.--=Since there are a number of them in man
we may choose one of these, such as color-blindness, for illustration. The
common form of color-blindness known as Daltonism in which the subject
can not distinguish reds from greens, a condition which seems to be due to
the absence of something which is present in individuals of normal color
vision, is far commoner in men than in women. Its type of inheritance,
sometimes termed "crisscross" heredity, has been likened to the knight
moves in a game of chess. The condition is transmitted from a color-blind
man through his daughter to half of her sons. Or, to go more into detail,
a color-blind father and normal mother have only normal children whether
sons or daughters. The sons continue to have normal children but the
daughters, although of normal vision themselves, transmit color-blindness
to one-half of their own sons. If such a woman marries a color-blind man,
as might easily happen in a marriage between cousins, then as a rule
one-half her daughters as well as one-half her sons will be color-blind.
[Illustration: FIG. 14
Diagram illustrating the inheritance of a sex-limited character such as
color-blindness in man on the assumption that the factor in question is
located in the sex-chromosome (from Loeb after Wilson). The normal
sex-chromosome is indicated by a black =X=, the one lacking the factor for
color perception, by a light X. It is assumed that a normal female is
mated with a color-blind male.]
In such cases what appears to be a mysterious procedure becomes very
simple if we assume that the defective character is associated with the
sex-determining factor, or to make it concrete let us say with the
_X_-element. The chart shown in Fig. 14, p. 62, indicates what the
germinal condition would be under the circumstances. The column to the
right represents the maternal, the one to the left the paternal line.
Since two _X_ means female and one _X_ male, and inasmuch as we have
assumed that the physical basis of the defect to which color-blindness is
due is conveyed by the _X_-element, we may represent the defective single
_X_ of the male in outline only (see first row). It is obvious that after
the reduction divisions (second row) the mature sex-cells of the female
will each contain a single normal _X_, the corresponding sex cells of the
male will contain either no _X_ or a defective _X_. Since if any member of
the class of spermatozoa containing no _X_, fertilizes an egg the
resulting zygote (row three) will have but one _X_ and that a normal one,
the individual which develops from the zygote will be normal as regards
color vision and moreover will be male because the condition one _X_
always means maleness. On the other hand, if any member of the class of
spermatozoa containing the defective _X_ fertilizes an egg two
_X_-elements are brought together and this of itself means femaleness. In
this case one of the _X_-elements is defective but the single normal _X_
is sufficient in itself to produce normal color vision. But when it comes
to the maturation of the sex-cells of this female, the pair of
_X_-elements are separated in the usual way with the result that half of
the mature ova contain a normal _X_ and half a defective _X_ (row four).
Since in a normal male, however, the mature reproductive cells will
contain either a normal _X_ or no _X_ (fourth row), any one of four
different kinds of matings may result. A sex-cell carrying normal _X_ of
the male may combine with an ovum containing normal X producing a normal
female (row five). Or such a cell may combine with an ovum carrying the
defective _X_, also producing a female but one who although of normal
color vision herself, like her mother, is a carrier of the defect. On the
other hand, any one of the spermatozoa without an _X_ may combine with an
ovum containing the normal _X_, in which case a normal male is produced
and, moreover, one who, like his mother's brothers, is incapable of
transmitting the defect. However, the sperm-cell devoid of an _X_ is just
as likely to fertilize an ovum carrying the defective _X_, in which event
the resulting individual, a male, must be color-blind because he contains
the defective _X_ alone. In other words, the chances are that one-half the
sons of a woman whose father was color-blind will be color-blind, the
other half perfectly normal; and that all of the daughters will be of
normal color vision although one-half of them will probably transmit the
defect to one-half of their sons. From a glance at the diagram it is
readily seen also that a color-blind female could result from the union of
a color-blind man (see first row) and the daughter of a color-blind man
(see third row). For half of the gametes of such a female would bear the
defect as would also that half of the gametes of the male which carry _X_,
hence the expectation would be that half of the daughters of such a union
would be color-blind and half would be carriers of color-blindness; and
that half of the sons would be color-blind and half normal. All the sons
of a color-blind woman would be color-blind because she has only defective
_X_-elements to pass on.
The inheritance of various other conditions in man follows more or less
accurately the same course as color-blindness. Among these may be
mentioned: _hemophilia_, a serious condition in which the blood will not
clot properly, thus rendering the affected individual constantly liable to
severe or fatal hemorrhage; near-sightedness (_myopia_) in some cases; a
degenerative disease of the spinal cord known as _multiple sclerosis_;
progressive atrophy of the optic nerve (_neuritis optica_); Gower's
_muscular atrophy_; some forms of _night-blindness_; in some cases
_ichthyosis_, a peculiar scaly condition of the skin. In one of my own
tabulations of a case of inheritance of "webbed" digits or _syndactyly_, a
condition in which two or more fingers or toes are more or less united, a
sex-linked inheritance is clearly indicated (Fig. 15), although from the
pedigrees recorded by other investigators this condition usually appears
in some of both the sons and daughters of an affected individual.
[Illustration: FIG. 15
Chart showing the inheritance of a case of syndactyly after the manner of
a sex-linked character. The affected individuals are represented in black;
squares indicate males, circles females. The condition is seen to be
inherited by males through unaffected females.]
=The Occurrence of Sex-Linkage in Lower Forms Renders Experiments
Possible.--=The course followed by such characters in man can be inferred
only from the pedigrees we can obtain from family histories. Fortunately,
however, such sex-linkage also occurs in lower animals and we are able
therefore to verify and extend our observations by direct experiments in
breeding. Several sex-linked characters have been found to exist in a
small fruit-fly known as _Drosophila_. Extensive breeding experiments with
this fly by Professor T. H. Morgan and his pupils have borne out
remarkably the interpretation that the characters in question are really
linked with a sex-determining factor.
CHAPTER III
MENDELISM
=New Discoveries in the Field of Heredity.--=Writing in 1899, one of
America's well-known zoologists asserts that, "It is easier to weigh an
invisible planet than to measure the force of heredity in a single grain
of corn." And yet only two or three years later we find another prominent
naturalist saying regarding heredity that, "The experiments which led to
this advance in knowledge are worthy to rank with those that laid the
foundation of the atomic laws of chemistry." Again, "The breeding pen is
to us what the test-tube is to the chemist--an instrument whereby we
examine the nature of our organisms and determine empirically their
genetic properties." Here is a decided contrast of statement and yet both
were justifiable at the time of utterance. For even at the writing of the
first statement the investigations were in progress which, together with
the rediscovery of certain older work, were to transfer our knowledge of
heredity from the realm of speculation to that of experiment and disclose
certain definite principles of genetic transmission.
Through a knowledge of these principles in fact, the shifting of certain
characters is reducible to a series of definitely predictable proportions
and the skilled breeder may proceed to the building up of new and
permanent combinations of desirable characters according to mathematical
ratios and, what is of equal importance, he can secure the elimination of
undesirable qualities. While there are many limitations in the application
of these principles and while new facts and modifications are constantly
being discovered concerning them, nevertheless they represent the first
approximations to definite laws of hereditary transmission that we have
ever been able to make, and the practical fact confronts us that whatever
our theoretical interpretations may be, the principles are so definite
that through their application important improvements of crops and
domesticated animals have already actually been secured and one may
confidently expect still others to follow.
=Mendel.--=The principles involved are called the Mendelian principles
after their discoverer, Gregor Johann Mendel, abbot of a monastery at
Brünn, Austria. After eight years of patient experimenting in his cloister
garden with plants, chiefly edible peas, he published his results and
conclusions in 1866, in the _Proceedings of the Natural History Society of
Brünn_. While known to a few botanists of that day, the full importance of
the contribution was not recognized, and in the excitement of the
post-Darwinian controversy, the facts were lost sight of and ultimately
forgotten.
=Rediscovery of Mendelian Principles.--=In 1900 three men, Correns, De
Vries and Tschermak, working independently--in different countries, in
fact--rediscovered the principles and called attention anew to the
long-forgotten work of Mendel which they had come upon in looking over the
older literature on plant breeding. These investigators added other
examples from their own experiments. Since their rediscovery the
principles have been confirmed in essential features and extended by
numerous experimentalists with regard to a wide range of hereditary
characters in both animals and plants.
=Independence of Inheritable Characters.--=It has been found that many
truly heritable characteristics or traits of an individual, whether plant
or animal, are comparatively independent of one another and may be
inherited independently. Where there are contrasted characters in father
and mother, such as white plumage and black plumage in fowls, smooth coat
and wrinkled coat in seed, horns and hornlessness in cattle, long fur and
short fur in rabbits, beard and beardlessness in wheat, albino condition
and normal condition, etc., there is obviously a bringing together of the
determiners of the two traits in the resulting offspring. In the third
generation, however, in the progeny of these offspring, the two distinct
characters may be set apart again, thus showing that in the second
generation while perhaps one only was visible, the factors which determine
both were nevertheless present, and moreover, they were present in a
separable condition.
=Illustration of Mendelism in the Andalusian Fowl.--=Let us take as a
simple example the case of the Andalusian fowl. Although it is not a case
established by Mendel it illustrates certain of the essential conditions
underlying Mendelism in a more obvious way than the cases worked out by
Mendel himself. The so-called blue Andalusian fowl results from a cross of
a color variety of the fowl which is black with one which is white with
black-splashed feathers. The result is the same irrespective of which
parent is black. When bred with their like, whether from the same parents
or different parents, these blue fowls produce three kinds of progeny,
approximately one-fourth of which are black like the one grandparent,
one-fourth white like the other grandparent, and the remaining half, blue
like the parents (Fig. 16). Moreover, the black fowls obtained in this way
will, when interbred, produce only black offspring and the same is true of
the white fowls. To all appearances as far as color is concerned they are
of as pure type as the original grandparents. With the blue fowls,
however, the case is different, for when bred together they will produce
the same three kinds of progeny that their parents produced and in the
same proportions. Again the white and the black are true to type but the
blue will always yield the three classes of offspring and this through
generation after generation.
[Illustration: FIG. 16
Diagram showing the scheme of inheritance in the blue Andalusian fowl.]
These facts may be illustrated graphically as follows where the word
"black" indicates the original black parent, "white" the original white
(black splashed) parent and "blue" the hybrid offspring.
Parental
Generation (P) Black × White Black × White
| |
First Filial | |
Generation (F_{1}) Blue × Blue
|
+------------------------------------------+
| | |
Second Filial Black Blue White
Generation (F_{2}) (25%) (50%) (25%)
| | |
| +-------------------------+ |
| | | | |
Third Filial Black Black Blue White White
Generation (F_{3}) | (25%) (50%) (25%) |
| | | | |
| | +-------------+ | |
| | | | | | |
Fourth Filial Black Black Black Blue White White White
Generation (F_{4}) (25%) (50%) (25%)
=The Cause of the Mendelian Ratio.--=Concerning the cause of this peculiar
ratio of inheritance in crossed forms Mendel suggested a simple
explanation. Animals or plants that can be cross-bred, obviously must be
forms that produce a new individual from the union of two germ-cells, one
of which is provided by each parent. Mendel's idea was that there must be
some process of segregation going on in the developing germ-cells of each
hybrid whereby the factors for the two qualities are set apart in
different cells with the result that half of the germ-cells of a given
individual will contain the determiner of one character and half, the
determiner of the other. That is, a given germ-cell carries a factor for
one or the other of the two alternate characters but not the factors for
both. In a plant, for example, in the male line, half of the pollen grains
would bear germ-cells carrying the determiner of one character and half,
that of the other. Similarly, in the female line, half of the ovules would
contain the determiner of the one character and half, that of the other.
Likewise in animals as regards such pairs of characters there would be two
classes of germ-cells in the male and two in the female. In the case of
the blue Andalusian fowls under discussion this would mean that half of
the mature germ-cells of the male carry the black-producing factor, and
half carry the white-producing factor, and the same is true of the
germ-cells of the female. Thus when two such crossed forms are mated,
there are, by the laws of chance, four possible combinations, namely: (1)
white-determining sperm-cells and white-determining ovum; (2)
white-determining sperm-cells and black-determining ovum; (3)
black-determining sperm-cells and white-determining ovum; and (4)
black-determining sperm-cells and black-determining ovum. Manifestly, the
first combination can only give white offspring; the second, white and
black, gives blue (by such a cross the original blues were established);
likewise, the third, black and white, gives blue; and the fourth
combination can only give black offspring. This matter may be graphically
represented by the following formulæ in which B indicates the determiner
of Black in the germ-cell and W the determiner of White: [male] signifies
male; [female] female.
IN THE ORIGINAL PARENTS
W × B = WB = Blue
IN THE HYBRIDS
[male] [female]
germ- germ-
cells cells [male] [female]
W----W W × W = WW = White
\/ W × B = WB = Blue
/\ or B × W = BW = Blue
B----B B × B = BB = Black
Thus of the four possible combinations one only can produce white fowls,
two (WB or BW) can produce blue fowls, and one black fowls. That is, the
ratio is 1:2:1 or the 25, 50 and 25 per cent., respectively, of our
diagram. The black fowls or the white fowls will breed true in subsequent
generations when mated with those of their own color because the
determiner of the alternative character has been permanently eliminated
from their germ-plasm; but the blue fowls will always yield three types of
offspring because they still possess the two classes of germ-cells.
=Verification of the Hypothesis.--=The hypothesis that germ-cells of
crossed forms are of two classes with respect to a given pair of Mendelian
characters is further substantiated by the following facts. If in the case
of the fowls under discussion one of the blue fowls is mated with an
individual of the white variety, half of the progeny will be blue and
half white. For the hybrid has two kinds of germ-cells, black producing,
which we have designated by the letter B, and white producing (or W) in
equal number while the white parent has only one kind, white producing. It
is obvious that if half the germ-cells of the hybrid form are of the type
B then half the progeny will be of the BW type, which is blue, and the
other half will be of the WW type, which is white. In the same way if we
mate a hybrid and a black fowl, half of the progeny will be black and half
will be blue, that is, there could only be WB and BB types.
The fact must not be lost sight of that since the pairings are wholly
determined by the laws of chance the proportions are likely to be only
approximate. It is obvious that the greater the number of individuals, the
nearer the results will approach the expected ratio.
DOMINANT AND RECESSIVE
=One Character May Mask the Other.--=In a large number of cases, however,
the actual condition of affairs is not so evident as in the Andalusian
fowl, for instead of being intermediate or different in appearance, the
generation produced by crossing resembles one parent to the exclusion of
the other. Such an overshadowing is spoken of as _dominance_, and the two
characters are termed _dominant_ and _recessive_. Thus when brown
ring-doves and white ring-doves are mated the progeny are all brown, or if
wild gray mice are mated to white mice the progeny are all gray. So black
is dominant to white in rose-comb bantams; brown eyes to blue eyes in man;
beardlessness to beard in wheat, and likewise rough chaff to smooth, and
thick stem to thin; tallness to dwarfness in various plants; normal
condition to the peculiar waltzing condition in the Japanese waltzing
mouse. Numerous other cases might be cited but these are sufficient to
illustrate the condition.
=Segregation in the Next Generation.--=But now the question arises, what
do such crosses as show dominance transmit to the next generation?
Experiments show regarding any given pair of these alternate characters
that they are set apart again in the succeeding generation, returning in a
definite percentage to the respective grandparental types.
[Illustration: FIG. 17
Diagram showing the scheme of inheritance in guinea-pigs when black and
albino forms are crossed.]
=Dominance Illustrated in Guinea-Pigs.--=In guinea-pigs for example (Fig.
17), when an individual (either male or female) of a black variety, is
crossed with one of a white variety, the F_{1} generation are all black
like the black parent. When these are interbred or bred with other blacks
which have had one black and one white parent, only two visible types of
progeny appear, viz., black and white, and these approximately in the
ratio of three to one.
Analysis by further breeding shows, however, that there are in reality
three types, but since dominance is complete the pure extracted dominant
and the mixed dominant-and-recessive type are indistinguishable to our
eye. That is, while the blacks are three times as numerous as the whites,
two out of every three of these blacks are really hybrid and correspond to
the blue fowls of our former example.
The condition is readily comprehended when expressed diagrammatically
thus:
Generation P Black × White Black × White
| |
Generation F_{1} Black (White) × Black (White)
|
+-------------------------------------+
| | |
Generation F_{2} 1 Black 2 Black (White) 1 White
In other words, the germ-cells of the one original parent (Gen. P) would
contain only determiners for black and that of the other parent would
contain only determiners for white. The condition of the individuals
produced by the cross would be represented by the formula B(W). But these
determiners segregate in the germ-cells of the crossed form, whether it be
male or female, into B and W. Hence half the spermatozoa of the male
hybrid (generation F_{1}) would carry the B determiners and half the W
determiners. The same is true of the mature ova of the female hybrid.
Consequently, in mating there are always four equally possible
combinations, viz., BB, B(W), (W)B, and WW. Since B is always dominant
three out of the four matings would yield black individuals, or in other
words the ratio would be 3:1.
The pure blacks when mated together will breed true in subsequent
generations, likewise the whites, but the blacks carrying white as a
recessive will yield when interbred the same ratio of whites and black as
did their hybrid parents (Fig. 17, p. 75).
=Terminology.--=As work in the study of Mendelian inheritance has
progressed and expanded the need of a more precise terminology has become
evident and such is gradually being established. Thus Professor Bateson
has coined the term "allelomorph" (Gk. _one another_, and _form_) to
express more exactly what we have thus far been calling a pair of
alternate or opposite characters. In the blue Andalusian fowls discussed,
the white condition in the one parent is the allelomorph of the black
condition in the other. The term generally means one of the pair of
Mendelian characters themselves as expressed in the individual plants or
animals but when the germinal basis of such phenomena is under discussion,
it is sometimes used to refer to the determiners of such characters. And
by determiner is meant simply the condition which is necessary in the germ
to bring about the occurrence of a definite character. For example, when
we are studying a cross between a red flower and a white flower with
reference to the color factors, the difference between the two plants may
lie in the fact that one produces a red coloring matter and the other
does not. That is, the determiner for red is absent from the white
variety. What the exact relation of color production is to the parts of
the germ-cell we do not know. It could be the function of a single
definite body or the resultant of several cooperating bodies. The latter
is far more likely to be the case. We may suppose that a group of
cooperating substances function to produce red in the red flower but that
in the white flowers one of these bodies is absent or fails to perform its
red-producing function.
It is customary where practicable to refer to the determiner of a
character by the initial letter of the name of the character. The letter
when written as a capital indicates the determiner but when written as a
small letter the absence of the determiner. Thus R may be taken to
represent the determiner for red coloring matter and r its absence. It is
convenient also to have a brief symbol to denote a given generation and
for this purpose Bateson has introduced the symbol F_{1} for the hybrid
progeny of the first cross, the initial letter of the word "filial." F_{2}
would indicate the next generation, F_{3} the third and so on. Likewise P
denotes the original parent generation.
=The Theory of Presence and Absence.--=Many, if not all, allelomorphs
consist of the presence and absence respectively of a given determiner. In
such cases the character represented by the presence of the determiner is
dominant over the character represented by the absence of a determiner.
Thus in the crosses from the wild gray mice and albino mice the progeny
are all gray mice since one parent had the determiner or group of
determiners for grayness and the hybrid offspring must also possess it.
Likewise the presence of black in black guinea-pigs is dominant to its
absence in albino guinea-pigs and the resulting progeny are all black.
However, it has already been mentioned that beardlessness in wheat is
dominant to beard and that the absence of horns in cattle is dominant to
their presence, that is, the progeny of hornless by horned cattle are
without horns except for occasional traces of imperfect horns. Facts like
these would seem at first sight to contradict the assertion just made that
presence is dominant to absence, but it is fairly well established that in
such cases one is not dealing with true absences but with suppressions.
The polled breeds of cattle, for example, are hornless not because of the
absence of determiners for horns but because of the presence of an
additional inhibiting factor which prevents these determiners from
functioning. The horned breeds are without this inhibitor. When horned and
hornless individuals are crossed the presence of the inhibitor from one
line of ancestry is sufficient to suppress the development of horns in the
progeny. A similar explanation would, of course, apply to beardlessness in
wheat.
In writing double-lettered formulæ to denote the determiners of characters
in hybrids the condition is represented merely by the capital and small
letter. Thus Rr indicates that red is dominant to its absence.
=Additional Terminology.--=In pure breeds where the determiners are alike
as BB in black or bb in albino guinea-pigs, the individual is said to be a
_homozygote_ (like things united) with reference to that character, while
in those in which the determiners are unlike, as Bb, the individual is
termed a _heterozygote_ (unlike things united) with reference to the
character. Or to use the adjective forms, a pure black guinea-pig is
homozygous for black pigment, an albino guinea-pig is homozygous for
absence of pigment, while a cross between the two is heterozygous for
pigment. Also, where the determiner of a given character is present in
double quantity, that is, from both lines of ancestry, the individual is
said to be _duplex_, where represented in only the single form as in
heterozygous individuals, _simplex_, and where the determiner is absent
entirely, _nulliplex_, with reference to the character in question. Thus
black guinea-pigs of formula BB are duplex with regard to the determiner
for black color, individuals of formula Bb are simplex with reference to
this determiner, and those of formula bb are nulliplex.
A heterozygote in which dominance prevails can be identified with
certainty by breeding to a known recessive and noting the kind of
offspring produced. If the individual was really a heterozygote,
approximately fifty per cent. of the offspring should be of the recessive
type.
=Dominance Not Always Complete.--=As a matter of fact close inspection
shows that in numerous instances dominance is not absolute since traces of
the recessive character may be detectable. For example, in the cross
between smooth and bearded wheat while smoothness is regarded as the
dominant character and beardlessness as the recessive, nevertheless in the
hybrid offspring a slight tendency toward bearding is not infrequently
seen. Or again when horned breeds of cattle are crossed with hornless
ones, a small proportion of such progeny will show traces of imperfect
horns.
In some cases instead of either character dominating the other a form
intermediate between the two parents may result, as we have seen already
in the case of the Andalusian fowl. Thus, certain white-flowered plants
and certain red-flowered plants when crossed produce pink hybrids, and
longheaded and shortheaded wheats when crossed give offspring with heads
of intermediate length. Or again, crosses between white and red cattle may
yield red roans, and between black and white cattle, blue roans.
Thus, while for such pairs of alternative characters as have been studied,
dominance to some considerable degrees at least, seems to be the rule,
still we have gradations down to the intermediate condition, and in some
instances the hybrid with respect to a given character may be unlike
either parent. The things of chief importance in the Mendelian discovery
are the independent, unitary nature of the characters and their
segregation in the offspring of cross-bred forms.
=Modifications of Dominance.--=It should be noted also that there is such
a condition as _delayed dominance_. Davenport found, for example, that
chicks produced by crossing pure white with pure black Leghorn fowls are
speckled black and white, but later in the adult form white becomes
dominant. Likewise conditions of delayed dominance are known in man in
eye-color and notably in color of hair. Some few cases have been recorded
where a character is dominant at one time, recessive at another.
According to Davenport extra toe in fowls may behave in this way.
=Mendel's Own Work.--=Mendel[2] himself worked out his principles on seven
pairs of characters which he found in common culinary peas. Placing the
dominant characters first, these may be enumerated as follows: (1) Tall by
dwarf; (2) green pod (unripe) by yellow; (3) pod inflated by pod
constricted between the individual peas; (4) flowers arranged along the
axis of the plant by flowers bunched together at the top; (5) seed skin
colored by seed skin white; (6) cotyledons yellow by cotyledons green; (7)
seed rounded by seed wrinkled.
He found that each pair of characters followed the same law as any other
pair when more than one pair of the characters occurred in the same
plants, but that each pair behaved independently of the other. The meaning
of this is that we may get various combinations of characters not
associated in the original pure stocks, the number of such combinations
depending on the number of pairs of allelomorphs there are.
DIHYBRIDS
=Getting New Combinations of Characters.--=Since this principle is well
illustrated in peas, let us take two pairs of their characters, viz.,
greenness and yellowness (of the cotyledons) and roundness and angularity
to see exactly what happens when two pairs of allelomorphs are involved.
When a specific kind of yellow pea is crossed with a particular kind of
green pea the offspring are always yellow (Fig. 18, opposite p. 84). When
these hybrids (generation F_{1}) are self-fertilized there is the usual
Mendelian segregation; one-fourth the resulting offspring will be green,
one-fourth pure yellow, and one-half, although yellow in appearance, will
be of the mixed type. The exact numbers found by Mendel were 6,022 yellow
seeds to 2,001 green seeds. Now of the original peas (generation P) the
yellow ones are round and the green ones angular (really wrinkled).
Choosing this roundness and angularity respectively as a pair of
characters they are found to follow the same law that the colors follow
(Mendel obtained in the F_{2} generation 5,474 round and 1,850 wrinkled
seed), but independently of the latter. For while in the progeny of the
hybrids (Gen. F_{1}), twenty-five per cent. will be round and of pure type
as regards roundness, twenty-five per cent. angular, and fifty per cent.
round but containing hidden factors of angularity (i. e., roundness is
dominant), the roundness and the yellowness, or the angularity and the
greenness will not always go together as they did in the original
grandparental strains, but there will be in addition some new types of
round green peas and some of angular yellow ones. That is, the factors of
color and of shape have been inherited independently of one another, so
that instead of the two original kinds of peas, four have been produced,
viz., (1) round-yellow (one of the original types); (2) round-green (new
type); (3) angular-yellow (new type); and (4) angular-green (one of the
original types). Furthermore, these will be found to stand in the ratio of
9:3:3:1 respectively.
=Segregations of the Determiners.--=How these combinations come about in
this definite proportion is easily understood if the matter is expressed
in terms of determiners and the possible matings tabulated (Fig. 18). If
we represent the yellow determiner by Y and the green determiner by y, and
likewise the determiners of roundness and angularity by R and r
respectively, then the formulæ for the determiners of these two pairs of
characters in the body cells (that is, in the unreduced condition) of the
pure forms and of the F_{1} generation hybrids respectively are as
follows:
In pure round yellow peas RR YY
In pure angular green peas rr yy
In the hybrid Rr Yy
But now in the segregation of these determiners in the germ-cells of the
hybrids (generation F_{1}) the pair of determiners Rr and the pair Yy
operate entirely independently of one another. Their only compulsion is
that each pair be separated into the single determiners, R and r in the
one case and Y and y in the other. So in the separating division which
brings about this divorcement R separates from r irrespective of whether
it is accompanying Y or y into the resulting daughter cell. Thus in some
cases R and Y would pass into one germ-cell, in others R and y, in others
r and Y, and in still others r and y, depending entirely upon the
chance relations of the respective pairs to the plane of division. That
is, the segregation is equally likely to be RY/ry giving gametes RY and
ry, or Ry/rY giving gametes Ry and rY.
[Illustration:
\[Female]
[Male]\ RY Ry rY ry
+-------+--------+--------+--------+
RY | RRYY | RRYy | RRYY | RrYy |
+-------+--------+--------+--------+
Ry | RRYy | RRyy | RrYy | Rryy |
+-------+--------+--------+--------+
rY | RrYY | RrYy | rrYY | rrYy |
+-------+--------+--------+--------+
ry | RrYy | Rryy | rrYy | rryy |
+-------+--------+--------+--------+
(1) 1 RRYY (4) 2 RrYY (7) 1 rrYY
(2) 2 RRYy (5) 4 RrYy (8) 2 rrYy
(3) 1 RRyy (6) 2 Rryy (9) 1 rrYy
9:3:3:1
FIG. 18
Diagram showing the possible combinations arising in the second filial
generation (F_{2}) following a cross between yellow, round (YYRR) and
green, angular or wrinkled (yyrr) peas. Y, presence of factor for yellow;
y, absence of such a factor; R, presence of factor for smoothness or
roundness; r, absence of such a factor; [male] male; [female] female.]
=Four Kinds of Gametes in Each Sex Means Sixteen Possible
Combinations.--=There are, therefore, with reference to the two pairs of
characters under consideration, four kinds of gametes (or mature
germ-cells) produced in equal numbers in each hybrid, viz., RY, Ry, rY,
and ry. That is, in the first type roundness and yellowness are
associated, in the second roundness and greenness, in the third angularity
(lack of roundness) and yellowness, and in the fourth angularity and
greenness.
But since both males and females have these four kinds of gametes, when
they are mated there will be sixteen possible combinations. These may be
tabulated as in Fig. 18, opposite p. 84.
=The 9:3:3:1 Ratio.--=While there are sixteen possible and equally
probable combinations, these will give only nine distinct kinds because
some of the matings are alike. The numbers of the various kinds of matings
are as follows:
(1) 1 RRYY (4) 2 RrYY (7) 1 rrYY
(2) 2 RRYy (5) 4 RrYy (8) 2 rrYy
(3) 1 RRyy (6) 2 Rryy (9) 1 rrYy
Since roundness (R) and yellowness (Y) are dominant to angularity (r) and
greenness (y) in all combinations containing R or Y, the alternative
determiners r or y would be obscured, with the result that individuals
having certain of the combinations would look alike to our eye. For
example, the individuals represented by numbers 1, 2, 4 and 5, since they
contain dominant R and Y, would all appear round and yellow, although in
reality No. 1 would be the only one of pure type (both elements
homozygous) and hence the only one that would breed true in subsequent
generations. The two individuals represented in No. 2 would breed true as
regards shape (RR) but not color (Yy). Just the reverse is true of No. 4
since shape is heterozygous (Rr) and color homozygous (YY). The four
individuals represented in No. 5 are heterozygous with regard to both
elements. Thus nine individuals (1 plus 2 plus 2 plus 4 = 9) represented
in Nos. 1, 2, 4 and 5 would be round and yellow, three individuals (Nos. 3
and 6) would be round and green, three (Nos. 7 and 8) would be angular and
yellow, and only one (No. 9) would be angular and green. That is to say,
the four classes discernible to the eye in generation F_{2} would be
present in the ratio of 9:3:3:1.
=Phenotype and Genotype.--=Forms such as those represented in Nos. 1, 2, 4
and 5 which to the eye appear to be alike, regardless of their germinal
constitution, are said to be of the same _phenotype_. Those of the same
hereditary constitution, as the two individuals represented in No. 8, or
the four individuals in No. 5, are said to be of the same _genotype_, that
is, they are of identical gametic constitution.
As we have seen, it is from the genotypical not the phenotypical
constitution that an offspring is derived and what a given form will bring
forth depends then on its genotype.
=Crosses With More Than Two Pairs of Characters.--=In crosses in which
more than two pairs of contrasted characters are involved the underlying
principles are in no way different, only with each pair of additional
characters there is, of course, a greater number of possible combinations.
Thus with three pairs of characters there will be eight different classes
of gametes in each sex and consequently sixty-four possible combinations
in mating, giving eight different phenotypes in the proportion of
27:9:9:9:3:3:3:1. The largest class manifests the three dominant
characters; the smallest class, the three recessives; the three classes in
the proportion of 9 each exhibit two dominant and one recessive
characters; and those in the proportion of 3 each display two recessive
and one dominant characters.
THE QUESTION OF BLENDED INHERITANCE
We come now to certain types of inheritance in which there seems to be a
true fusion or blend of the contributions from the two parents, the
intermediate condition apparently persisting in subsequent generations
without segregation. Numerous cases of blended inheritance have been cited
in earlier literature of heredity, but as our knowledge of genetics has
progressed many experimental breeders have come to believe that the
blends in such cases are apparent rather than real and that the phenomena
can be best explained on a non-blending unit-character basis, just as we
would explain ordinary Mendelian phenomena.
=Nilsson-Ehle's Discoveries.--=To get their point of view we may review
certain experiments on wheat made by Nilsson-Ehle, together with their
Mendelian interpretation. Nilsson-Ehle found that a certain brown-chaffed
wheat when crossed with a white-chaffed strain yielded a brown-chaffed
hybrid, apparently in accordance with the simple principle of Mendelian
dominance. But these heterozygous brown-chaffed individuals did not in
turn give the expected ratio of 3:1 in the F_{2} generation but a ratio of
15 brown to 1 white, and furthermore the browns were not all of the same
degree of brownness. To be exact, from fifteen different crosses of the
strains he obtained 1,410 brown-chaffed and 94 white-chaffed plants.
This apparent anomaly in segregation was easily explained, however, when
it was finally figured out that there were really two independent
determiners for brown color, either of which alone could produce a brown
individual, but when combined produced individuals of correspondingly
deeper shades of brown. In such a case then Nilsson-Ehle discovered that
he was dealing merely with a Mendelian dihybrid where two different
determiners B and B´ and their respective absences b and b´ are involved.
The original brown wheat had both B and B´ and the original white b and
b´. The formula for the F_{1} heterozygote was therefore BbB´b´. The four
possible types of gametes for male and female are BB´, Bb´, bB´, bb´, and
the tabulation would be as follows:
+-----------------------------------
| BB´ | Bb´ | bB´ | bb´
-----+--------+--------+--------+--------
BB´ | BBB´B´ | BBB´b´ | BbB´B´ | BbB´b´
-----+--------+--------+--------+--------
Bb´ | BBB´b´ | Bb´Bb´ | BbB´b´ | Bbb´b´
-----+--------+--------+--------+--------
bB´ | BbB´B´ | BbB´b´ | bbB´B´ | bbB´b´
-----+--------+--------+--------+--------
bb´ | BbB´b´ | Bbb´b´ | bbB´b´ | bbb´b´
-----------------------------------------
It will be observed that there are more brown determiners in some
combinations than others. For instance one of the sixteen contains four
such determiners, viz., B, B´, B, B´, four contain three determiners, six
contain two, four contain only one, and one contains none. Thus all but
one of the sixteen contain at least one determiner and will therefore be
brown in color but the depth of color will depend on the number of brown
determiners in a given individual. This is more graphically represented in
Fig. 19, p. 90. The largest number of similar individuals, six in all,
contain two determiners each and represent an intermediate "blend" between
the original brown-chaffed and white-chaffed strains. The deeper and the
lighter browns due to more or fewer determinants in an individual would if
one did not know the units in this case look like the fluctuations around
this average which we might expect in a blend.
[Illustration: FIG. 19
Diagram illustrating the proportionate distribution of determiners where
either of two different determiners produces the same character, the
degree of expression of the character depending on the number of the
determiners present. The numerals indicate the number of brown determiners
present in an individual.]
Nilsson-Ehle found another significant case in wheat where one particular
red-grained strain of Swedish wheat when crossed with white-grained
strains produced red-grained offspring, but when these were interbred the
F_{2} generation gave approximately sixty-three red to one white-grained
individual. Here it was found that in the original red wheat there are
three separate determiners which act independently of one another in
heredity, any one of which would make red color; and that they together
with their absences simply follow the Mendelian laws for a trihybrid.
=Such Cases Easily Mistaken for True Blends.--=If we should tabulate the
possible combinations as we did the dihybrid we should see that we would
get individuals having varying numbers of red determiners. Only one of the
sixty-four possible combinations would be without a factor for red. Of the
sixty-four, one would have six determiners for red, six would have five,
fifteen would have four, twenty would have three, fifteen would have two,
six would have one, and one would have none. Since here every additional
red factor means deeper redness in the individual there would be varying
degrees of redness in the F_{2} generation with those having three
determiners, the largest group, standing apparently intermediate. Not
knowing the factors involved we might easily mistake such a case for a
true blend with fluctuations about an average intermediate form.
Nilsson-Ehle finally proved his interpretation by rearing an F_{3}
generation from isolated and self-fertilized plants of this F_{2}
generation.
This same principle of cumulative determiners has also been established in
America by East with field corn.
As the number of duplicate determiners increases it can be readily seen
that the number of apparent blends of different degrees of intermediacy
between the two extremes would rapidly increase.
=Skin-Color in Man.--=In man, the skin-color of the hybrids between
negroes and whites is often cited as a case of blended inheritance in
contradistinction to Mendelian inheritance. The skin-color of the mulatto
of the F_{1} generation is intermediate between that of the white and
black parent. This same degree of intermediacy is commonly supposed to
persist in subsequent generations, but as a matter of fact, careful
investigation has shown that while mulattoes rarely produce pure white or
pure black children, there is considerably greater range in the shades of
color in the F_{2} generation and subsequent generations than in the F_{1}
generation. This is exactly what one would expect of a Mendelian character
in which several cooperating factors were involved. Indeed, Davenport who
has made extensive studies[3] on the inheritance of skin-color in man has
come to the conclusion that the case is really one of Mendelian
inheritance in which several factors for skin-color are concerned. Even
the skin of a white man is pigmented in some degree under normal
conditions. Davenport has shown in the skin of both whites and blacks that
there is a mixture of black, yellow and red pigments. He concludes that
"there are two double factors (AABB) for black pigmentation in the
full-blooded negro of the west coast of Africa and these are separably
inheritable." Since these factors are lacking in white persons the
intermediate color of an F_{1} mulatto would therefore be heterozygous for
pigmentation, and subsequent generations, following the laws for
segregation where a number of factors are concerned, would show different
degrees of color because of the varying combinations of factors.
=Some Investigators Would Question the Existence of Real Blends.--=Still
other reputed blends such as ear length in rabbits and the like have been
shown to be analyzable into Mendelian behavior if one will but postulate
numerous or multiple factors. Just how far we are justified in so
accounting for blends has not yet been established. Some of our most
careful experimentalists in heredity still believe that real blends exist,
particularly where the character is quantitatively expressed--that is, as
more or less of a given size or amount--while others would maintain that
all alleged blends will probably be found to be resolvable into factors
which follow Mendelian rule. It must be left for future investigations to
demonstrate which school is correct.
THE PLACE OF THE MENDELIAN FACTORS IN THE GERM-CELLS
=Parallel Between the Behavior of Mendelian Factors and Chromosomes.--=The
question arises as to whether there is any evidence from the study of
germ-cells themselves to bear out the Mendelian conception of separation
of contrasted characters in the gametes of the F_{1} generation. In the
discussion of the maturation of germ-cells (Chap. II) it has already been
seen that the chromosomes of the germ-cells are in all probability
arranged in homologous pairs, one member being of maternal and the other
of paternal origin, and that furthermore they are closely associated with
the phenomena of heredity. And since in maturation there is an actual
segregation of the chromosomes into two sets, half going to one cell and
half to its mate, a physical basis adequate to the necessities of the case
is really at hand. It will be recalled that the individuals of a pair
separate in such a way at the reduction division that the paternal member
goes to one cell and the maternal member to the other, although each pair
seemingly acts independently of the others with the result that any mature
germ-cell may contain chromosomes from each of the original parents but
never the two chromosomes which earlier made up a pair. The close parallel
between the behavior of chromosomes and the behavior of Mendelian factors,
although the two sets of phenomena were discovered wholly independently of
each other, is obvious. If we suppose that each chromosome bears the
determiner of a Mendelian character and that chromosomes bearing
allelomorphic characters make up the various pairs which are seen in the
early germ-cells of an individual before reduction occurs, then the
segregation of the individuals of an allelomorphic pair into different
gametes must result in consequence of the passing of the corresponding
chromosomes into separate gametes. Fig. 20, p. 95, from Professor Wilson
represents equally well the segregations of pairs of chromosomes or pairs
of Mendelian characters.
[Illustration: FIG. 20
Diagram showing union of factors from the two separate parents in
fertilization and their segregation in the formation of germ-cells (after
Wilson). With four pairs of factors (_Aa_, _Bb_, _Cc_, _Dd_), sixteen
types of gametes are possible, as shown in the series of small circles at
the right. The same diagram equally well represents the pairings and
segregations of chromosomes.]
=A Single Chromosome not Restricted to Carrying a Single Determiner.--=It
has been objected that there may be more pairs of independently heritable
allelomorphic characters than there are pairs of chromosomes. It is true
that there are more pairs of characters than pairs of chromosomes but
there is no reason for supposing that a given chromosome is restricted to
carrying a single unit-determiner. On the contrary it probably carries
several or many. Some workers have pointed out that certain units might be
interchanged during the pairing of chromosomes before the reduction
division, others that inasmuch as the chromosomes become diffuse and
granulated during the intervals between divisions it is not improbable
that the individual units may become separated from their original system
during such times and that it is a matter of chance into which of the
homologous chromosomes, A or a, they enter with the re-establishment of
the chromosomes. On the other hand, cases are known where two or more
separate characters are permanently associated in inheritance, that is, if
they enter a crossed form together they come out together in the
grandchildren as if they were carried in the same unit-body in the
germ-cell. The only observable unit-bodies that fulfil the necessities of
such cases are the chromosomes. This tendency of characters to exist in
groups which are inherited independently of one another is coming more and
more into evidence as we penetrate farther into the intricacies of
inheritance, and it is exactly what we would expect on the supposition
that each chromosome carries the determiners of a number of characters
instead of a single one.
CHAPTER IV
MENDELISM IN MAN
=The Mendelian Principles Probably Applicable to Many Characters of
Man.--=We are really just beginning to make the proper observations and
collect the necessary data with reference to the application of Mendelian
principles to the traits of man. Yet brief as has been our study we have
disclosed much significant evidence which makes it seem highly probable
that many of his characters, good and bad, of mind and body are as
subservient to these laws as are the traits and features of lower forms.
Davenport and Plate record over sixty human characters or defects which
are seemingly inherited in Mendelian fashion. Although about fifty of
these are pathological or abnormal conditions, this does not mean that
such conditions are more prone to follow Mendelian inheritance but merely
that being relatively conspicuous or isolated they are easier to follow
and tabulate.
=Difficult to get Correct Data.--=While it must be said that in many cases
no simple form of Mendelian tabulation has been unequivocally established,
yet the general behavior of the various inheritable traits in question is
so obviously related to the conventional Mendelian course that there seems
little reason for doubting that they are at bottom the same. Failure to
obtain exact proportions may be attributable in part to the probability
that what we loosely regard as a character should in reality be analyzed
into more elemental components, and above all to the fact that from the
very nature of the conditions under which human records must be obtained,
there is considerable chance of inaccuracy or error in such accounts. How
many human traits follow Mendelian rules remains largely for future
investigators to establish.
We are handicapped at the outset in man by the many difficulties of
getting correct data from the genealogies on which we must depend, or in
fact of getting any genealogy at all, for in this country at least, most
families keep imperfect records of births and deaths and many of the
institutions for the various kinds of defectives have little in their
records that will help us in following out hereditary conditions. Then in
matters of disease we meet with the fact that many former diagnoses were
erroneous. In yet other cases, and this is particularly true among mental
and moral defectives, we are often not sure of the paternity of a given
child. Furthermore, one is likely to be misled by the proportions which
may occur in the very limited number of children of any given couple.
Still other difficulties exist. Among these is the fact, for example, that
in many cases of defect or susceptibility to disease, a given individual
in the stock may have the trait in an expressible and transmissible form,
yet it never comes to expression because that individual has been
fortunate enough to escape the environmental stimulus which would call it
forth. Thus one highly susceptible to tuberculosis might escape infection,
or persons hovering on the verge of insanity might never receive the
precipitating stimulus which would topple them into actual insanity; yet
each would be wrongfully recorded in a genealogy looking to such traits as
perfectly normal. Or again if it be a question of intellectual brilliancy
as shown by accomplishment in the realm of scholarship, or of worldly
affairs, the ones who although possessing them have had no chance to
display unusual talents would be tabulated as average whereas in fact they
should be recorded as of high rank. That this is particularly likely to
happen in the case of women is evident.
=A Generalized Presence-Absence Formula for Man.--=In man as in lower
forms some characters or traits are due presumably to the presence of
determiners or to their absence. Likewise, dominance and recessiveness are
as much in evidence, for in tracing back pedigrees of various traits we
find the same forms of tabulation that obtain for these conditions in
plants and lower animals hold good. For typical cases in man let us use a
generalized presence-absence formula and the arbitrary symbol A for the
presence of the determiner of the character (double in the individual,
single in the germ) and a for its absence. Thus AA represents a condition
in which similar determiners have been derived from both parents and the
individual is _duplex_ as regards the character in question; each mature
germ-cell will have the determiner. Aa represents a condition in which the
individual has received the determiner from only one parent and is
therefore _simplex_ with regard to the character; half of the gametes of
such an individual will have the determiner and half will lack it. Lastly,
aa represents total absence of the determiner. Such an individual is
_nulliplex_. He or she will not have the determiner represented in any of
the gametes, and can not, of course, transmit a trait represented by the
determiner.
It is evident that six kinds of gametic matings are possible among
individuals representing these various formulæ. These matings are as
follows:
Possible
couplings
Matings of gametes Product
1. Nulliplex x Nulliplex (aa x aa) == a------a == all nulliplex
\/
/\
a------a
2. Nulliplex x Simplex (aa x Aa) == a------A == 50 per cent.
\/ with character
/\ nulliplex and
a------a 50 per cent.
with it
simplex.
3. Nulliplex x Duplex (aa x AA) == a------A == all with characters
\/ simplex
/\
a------A
4. Simplex x Simplex (Aa x Aa) == A------A == 25 per cent.
\/ with characters
/\ duplex, 50 per
a------a cent. with it
simplex and 25
per cent. with
it nulliplex.
5. Simplex x Duplex (Aa x AA) == A-------A == 50 per cent.
\/ with character
/\ duplex and 50
a-------A per cent. with
it simplex.
6. Duplex x Duplex (AA x AA) == A-------A == all duplex.
\/
/\
A-------A
=Indications of Incomplete Dominance.--=While in cases of strict Mendelian
dominance it is not possible to distinguish directly the simplex from the
duplex condition, as a matter of fact the individual of simplex
constitution sometimes has the character represented in the single
determiner less perfectly developed than in the corresponding character of
duplex origin. In studying defects in man due to the absence of a
determiner, where theoretically presence of the determiner (normality) is
dominant over its absence in individuals of simplex constitution, one
finds it recorded with increasing frequency that such individuals are more
or less "intermediate" or are "tainted" with the defect; thus showing that
the defect though obscured is not wholly in abeyance. Thus individuals
carrying epilepsy or feeble-mindedness which are regarded as recessive
traits, while not showing specific feeble-mindedness or epilepsy, may
nevertheless apparently show a neuropathic taint in the form of migraine,
alcoholism or other lapse from normality. The condition is seemingly more
akin in some cases to that found in the offspring of certain red flowers
crossbred with white flowers, which though red do not show the same
intensity of color as the original red parent. Just as here the single
determiner or single "dose" of redness is insufficient to produce the
intensity of color that appears when the offspring receive two determiners
for red, one from each parent, so in man a single determiner for normality
of a specific character is inadequate in some cases to make the individual
wholly normal. Or possibly some cases are more of the type of those in
which the character in question, for instance the red color of some wheats
and corn, may be produced by any one of two or three determiners, the
intensity of the characters (red color, e. g.) depending on whether one,
two or three determiners are present.
=Why After the First Generation Only Half the Children May Show the
Dominant Character.--=If the trait is a simple dominant one it is clear
that it will appear in each generation and always spring from an affected
individual. By referring back to our tabulation of possible matings on
page 100 where the dominant character is represented by the letter A, this
can be seen at a glance. If the trait is present in the duplex condition
in one parent and absent from the other, then formula 3 applies; all
children will show the trait, but in the simplex form (Aa). If the trait
is present in the simplex form in one parent and absent in the other,
formula 2 applies. Fifty per cent. of the children will have the character
in the simplex form (Aa) which means also an even chance of transmitting
it to their offspring; fifty per cent. will not inherit it and will be
incapable, furthermore, of transmitting it, since they have become
nulliplex (aa). In human genealogies if an individual having an unusual
trait which is inherited as a dominant marries a normal person and half of
the offspring show the trait (and this is common), this means that the
parent manifesting the trait had it represented only in the simplex
condition, otherwise all of the children would have shown it. Even though
the original ancestor who first developed the condition or structure may
have had it in a duplex form, it would after the first mating, if this
were with an individual lacking the trait, be represented only in the
simplex form (see formula 5) and could never become duplex again unless
two individuals both having the character married, and then only in
twenty-five per cent. of the offspring (see formula 3). If the trait is a
defect all the children showing it, even though marrying normal
(nulliplex) individuals, will pass it on again to half their children, but
those who do not show it may ordinarily marry with impunity since its
non-expression in their make-up means, as far as we know at present, that
their germ-plasm has been purged of the defect and that they are therefore
nulliplex with reference to it.
=Eye-Color in Man.--=Of normal characters in man which follow the
Mendelian formula perhaps eye-color is the best established. Brown or
black eye-color is due to a _melanin_ pigment absent from the blue or gray
eye. That is, a brown eye is practically a blue eye plus an additional
layer of pigment on the outer surface of the iris. The different shades of
brown and the black are due to the relative abundance of this pigment.
Gray color and the shades of blue seem to be a modification of an original
dark blue, due to structural differences in the fibrous tissues of the
iris.
In inheritance brown or black is dominant to blue or gray, or in other
words the _presence_ and _absence_ of a pigment P constitutes a pair of
allelomorphs. Hence two brown-eyed parents, if P is duplex in both (or
duplex in one and simplex in the other) can have only brown-eyed children.
Thus,
1. PP × PP = PP, or all duplex brown.
2. PP × Pp = PP and Pp, half duplex brown and half simplex brown.
If each parent has brown eyes but in simplex condition, then one-fourth
of children will have blue or gray eyes; for example,
Mating Gametic Product
couplings
Pp × Pp = P--P = PP, Pp, pP, and pp, or one-fourth
\/ duplex brown, one-half simplex
/\ brown, and one-fourth blue or
p--p gray.
If both parents have blue or gray eyes they can not have children with
black or brown eyes, since the recessive condition in each parent means
total absence of brown pigment in both.
If one pair is duplex brown and the other blue, then all children will
have brown eyes but of simplex type.
If one parent has simplex brown eyes (type Pp) and one blue (pp) then
one-half of the children will have brown eyes of simplex type and one-half
will have blue eyes.
Occasional objections have been raised against the Mendelian
interpretation of inheritance in eye-color, but the cases cited in
evidence against the theory usually narrow down to those in which the
color is so diluted as to render classification uncertain. For example,
hazel eyes are sometimes called gray; they belong however to the melanic
pigmented type although the brown pigment may be much diluted and occur
mainly around the pupil. So-called green eyes are due to yellow pigment on
a blue background. In the rare cases where in the same individual one eye
is brown and the other blue, the individual should probably be rated as
brown-eyed on the supposition that in the one eye the development of brown
pigment has in some way been suppressed.
=Hair-Color.--=The inheritance of hair-color has also been the subject of
considerable study and while the conditions are not so simple as in the
case of eye-color, there is little doubt that it belongs in the Mendelian
category. In human hair, color has as its foundation apparently two
pigments, black and red. Absence of one or both or various combinations or
dilutions of these seemingly account for the prevailing colors in human
hair. In general dark hair is dominant to light, although because of the
delay sometimes in the darkening of the hair in children this fact is
often obscured. Black is dominant to red. People with glossy black hair,
according to Davenport, are probably simplex for black, the glossiness
being due usually to recessive red. The expectation would be for some of
the children of such a pair to have red hair.
In man occasionally a congenital white lock contrasting strikingly with
the remaining normally pigmented hair occurs. It behaves as a simple
dominant in heredity.
=Hair-Shape.--=Again, straight and curly hair seem to be distinct
inheritable characters. Curly is incompletely dominant to straight, the
simplex condition yielding wavy hair.
Not to enter into details of the matings, statistics gathered by Mr. and
Mrs. Davenport show that, two flaxen-haired parents have flaxen-haired
children; two golden-haired parents have only golden-haired children; two
parents with light brown hair have children with hair of that color or
lighter, but never darker; two parents each with dark brown or black hair
may have children with all the varieties of hair-color. Summing together
a series of recessives Davenport points out that two blue-eyed, flaxen or
golden and straight-haired parents will have only children like
themselves.
[Illustration: FIG. 21
Diagram showing descent of brachydactyly through five generations; black
symbols indicate affected individuals; [male], male; [female], female
(after Farabee).]
=Irregularities.--=If a dominant trait or defect depends on more than a
single factor, as is sometimes the case, or if it is modified by sex or
other conditions, as is true of certain characters, some of which, such as
color-blindness, have already been examined, then we shall find some
apparently non-affected individuals having affected offspring. Certain
diseases, for example, are generally transmitted by affected members of
the family to their children in the expected Mendelian ratio for a
dominant, yet an occasional skip of a generation may appear in which an
apparently perfectly normal individual transmits to his children what,
except for the omission in his own case, appears to be an ordinary
dominant character. This occasional lapse in the appearance of a
character when theoretically it should appear is doubtless due in some
instances to the fact that what is really inherited is a _tendency_, and
although this is present in the apparently normal individual, for some
reason the condition itself has not appeared. This might especially be
true in the case of a disease which does not manifest itself until late in
life. In other cases there are undoubtedly complicating accessory
conditions which modify the behavior of the trait somewhat.
OTHER CASES OF DOMINANCE IN MAN
Among other normal characters in man, as far as available evidence goes,
dark skin is dominant to light skin; normally pigmented condition to
albino; and nervous temperament to phlegmatic.
=Digital Malformations.--=An interesting and easily followed defect is a
condition known as _brachydactylism_, in which the digits are shortened
because of the absence or rudimentary condition of one segment. The
fingers, therefore, appear to be only two-jointed like the thumb. Several
families showing this defect have been charted and it appears to behave as
a typical dominant. In looking over such a chart (Fig. 21, p. 106) one is
struck by the fact that only half of the children from most of the matings
show the defect, but when we recall that the affected parent, after the
first generation, probably carried the condition in only the simplex form
and married a normal individual, such a result is just what would be
expected (see formula 2).
_Polydactylism_ (Figs. 22, 23, pp. 109, 110) is a condition in which there
are extra digits on hands or feet. The character, with apparently slight
exceptions in a few records, behaves as a typical dominant. Among other
digital defects which are inherited as a dominant is a condition known as
_syndactylism_ (Fig. 24, p. 111), in which two or more digits are fused
side by side. For an example of syndactyly which seems to be in the class
of sex-linked characters, see Fig. 15, p. 65.
=Eye Defects.--=_Congenital cataract_ is another not uncommon defect in
man which is transmitted as a dominant (Fig. 25, p. 112) with occasional
irregularities. It is a condition of opacity of the lens of the eye which
produces partial or total blindness. In a paper on _Hereditary Blindness
and Its Prevention_, Clarence Loeb (1909) mentions 304 families of which
pedigrees have been published. Of the 1,012 children in these families
589, or 58 per cent., were affected. It is obvious that this is near the
expected percentage in the case of a dominant trait where matings of
affected with normal individuals prevailed. An unfortunate circumstance
about this malady from the eugenic standpoint is the fact that it is
frequently of the presenile form which comes on late in life so that it is
usually impossible to predict whether an individual of marriageable age is
immune or will later become affected.
[Illustration: FIG. 22
Radiograph (Courtesy of Dr. W. B. Helm) showing polydactyly in a child's
hand. For genealogy of this see Fig. 23, p. 110.]
[Illustration: FIG. 23
Chart showing a history of polydactylism through five generations in the
B---- family. The individual whose hand is pictured in Fig. 22, p. 109, is
of the fifth generation. Squares represent males, circles females.]
Another defect of the eye following the course of a dominant in heredity
is a pigmentary degeneration of the retina known as _retinitis
pigmentosa_. Atrophy of the optic nerve is also involved and the final
result is blindness. Still another example frequently cited is that of
hereditary night blindness (_hemeralopia_), a disease in which the
affected person can not see by any but the brightest light. In most
affected families the final outcome is usually total blindness. One of the
most remarkable pedigrees of defects in man ever collected is one of this
disease published by Nettleship. He succeeded in tracing the defect
through nine generations, back to the seventeenth century. The genealogy
includes 2,116 persons. The character behaves as a single dominant in
males, but frequently, though not always, females may be carriers of the
defect in transmissible form though not exhibiting it themselves. That is,
males in which the condition is simplex (Aa) develop the defect but
females of similar simplex constitution (Aa) frequently do not. It
follows, therefore, that normal males of such strains will have normal
offspring but normal females may have affected children.
[Illustration: FIG. 24
Radiograph (Courtesy of Dr. W. B. Helm) showing a partial syndactyly in
each hand of an individual. Some degree of webbing between the more distal
portions of the affected parts is usual.]
[Illustration: FIG. 25
Pedigree of a family with presenile cataract (black symbols); numbers in
circles indicate unaffected individuals (after Davenport).]
=Other Defects Inherited as Dominants.--=Not to go into details other
defects which behave as dominants or modified dominants in human
inheritance may be mentioned. The following list is not complete and it
must be understood that in some cases the statistics are insufficient to
justify us in making anything but a tentative decision. We may thus
enumerate as dominant over normality: _Achondroplasy_ (abnormally short
limbs with normal head and body); _Keratosis_ (thickening of epidermis);
_Epidermolysis_ (excessive formation of blisters); _Hypotrichosis_
(hairless, toothless condition); _Diabetes insipidus_; _Diabetes
mellitus_; ordinary (not Gower's) _muscular atrophy_; _Glaucoma_ (internal
swelling and pressure of eye-ball); displaced lens; _Coloboma_ (open
suture in iris); spottedness of hair-coat; and corneal opacity.
As a final illustration of a serious malady in man which acts as a
dominant in inheritance, let us take _Huntington's chorea_. Ordinary
_chorea_, or St. Vitus' dance, a disorder characterized by involuntary
muscular movements, is commonly though not always confined to children and
usually ends in recovery, but _Huntington's chorea_ appears typically in
middle life and is a much more dangerous malady. Fig. 26, p. 114,
represents the family history of one of five cases which have been studied
by Doctor Lorenz in the Mendota Hospital for the Insane. All charts which
have been platted of this malady show it to be inherited as a dominant.
This means that half of the children of an individual who carried the
malady in the simplex condition, and all the children of one who carries
it in the duplex condition, are probably marked for this terrible end. And
the true horror of it can only be appreciated by one who has seen the last
stages of the malady. The victim once in its grasp gradually becomes
wrecked in mind and body; the muscular twitchings and disorders of
movement continually increase and dementia progresses until at last death
ensues. Fig. 27, p. 115, is another chart showing inheritance of
_Huntington's chorea_. In still a third case at the Mendota Hospital, the
gravity of the situation can be appreciated when one realizes that the
patient is the father of ten children, ranging in age from one to
seventeen and one-half years. The calamitous fact that this disease does
not manifest itself usually until middle life makes it likely that these
children will all reach maturity, marry and in turn probably produce
offspring before the doomed members of the family realize their fate.
[Illustration: FIG. 26
Chart showing descent of _Huntington's chorea_ in the P---- family
(courtesy of Dr. W. F. Lorenz). Squares represent male, circles female;
shaded figures are choreic members of the family; partially shaded
figures, slightly affected or very "nervous" members. The members of the
last generation are for the most part still too young to show their
condition. The cross indicates the individual in the asylum from whom the
record was traced back.]
CASES OF RECESSIVENESS IN MAN
=Recessive Conditions More Difficult to Deal With Because They Are
Frequently Masked.--=Coming now to the question of recessive conditions in
man, we find that defects are more likely to be of recessive than of
dominant type. Apparently normality usually means the presence of normal
determiners and abnormality, the absence of some essential determiner. In
the latter case, a unit-factor has seemingly been lost out in some way in
the germ-plasm, and the product of such germ-plasm is therefore
incomplete. As long as the loss is counterbalanced by the presence of a
single determiner from the other line of ancestry, that is, as long as the
simplex (Aa) condition prevails, the loss may not be in evidence, except
in cases of incomplete dominance (taints, etc.), but any mating which
permits of the production of the nulliplex condition will bring the defect
to expression again.
[Illustration: FIG. 27
Chart showing inheritance of _Huntington's chorea_ in the R---- family
(courtesy of Dr. W. F. Lorenz); 1, 2 have been patients at Mendota
Hospital for the Insane; 3, died of "paralysis"; the fourth or last
generation indicated by the cross, ranging in age from 6 to 14, are too
young yet to show their condition as regards this malady.]
The obscure nature of recessives makes such conditions more difficult to
deal with than dominant defects. For as regards the latter we have seen
that marriage of unaffected members of the family as far as that
particular trait is concerned, is perfectly safe, even to a cousin, for
once the germ-plasm is purged of such a positive factor, it, in so far as
we know, remains pure. But in the case of a recessive character due to the
absence of some necessary determiner a normal offspring of simplex
constitution (Aa) will probably transmit to half of his children the
capacity for handing on the defect, or if mated to another normal
individual of simplex constitution (Aa) is likely to have the actual
defect revealed again in one-fourth of his children and latent in
two-thirds of the remainder.
=Albinism a Recessive.--=As an easily understood illustration of this type
of case we may take human albinism, a condition which is due to the
absence of a pigment-developing determiner. According to Davenport the
albinic condition is recessive to normal condition. If albino (aa) is
mated with albino (aa) nothing but albino children may be expected. An
albino (aa) mated with a normal individual will have normal offspring
(Aa), but they will have the capacity for transmitting albinism to their
descendants. Thus the normal offspring (Aa) of an albino (aa) and a normal
parent (AA) if mated to another normal individual (Aa) who has also had an
albino parent will probably transmit actual albinism to one-fourth of his
children and the same capacity that he himself has of producing albinos,
to one-half of his children, although the latter will appear to the eye to
be normal.
=Other Recessive Conditions in Man.--=If for albinism we substitute
certain forms of insanity, hereditary feeble-mindedness (Fig. 28, p. 118),
or hereditary epilepsy, all of which apparently follow the same law, we
can readily understand how unfit such matings are where both strains are
affected. Marriage with similarly defective stock will result in the
affection appearing in one-fourth of the progeny, and one-half of them,
though apparently normal themselves, will have the capacity for
transmitting the imperfection. It is in the existence of such hidden
factors that the chief danger in the marriage of cousins, or in fact any
consanguineous marriage lies.
A few of the various defects which seem to be inherited as recessives when
mated with normality are: susceptibility to cancer; _chorea_ (St. Vitus'
dance); true dwarfism (all parts proportionately reduced); _Alkaptonuria_
(urine darkens after passage); alcoholism and criminality, where based on
mental deficiency; hereditary _hysteria_; _multiple sclerosis_ (diffuse
degeneration of nervous tissue); _Friedreich's disease_ (degeneration of
upper part of the spinal cord); _Merriere's disease_ (dizziness and
roaring in ears); _Thomsen's disease_ (lack of muscular tone); hereditary
_ataxia_; possibly the tendency to become hard of hearing with increased
age; and possibly, non-resistance to tuberculosis.
Of non-pathological conditions in man which are inherited as recessives,
apparently either very great or very small intellectual ability are
examples.
[Illustration: FIG. 28
Chart showing descent of feeble-mindedness as a typical recessive (after
Goddard). Squares represent males, circles females; DD, homozygous
dominant; DR, heterozygous dominant (i. e. normal although a carrier); RR,
pure recessive; N, normal; F, feeble-minded; A, alcoholic.]
=Breeding Out Defects.--=Even though recessive defects occur in a stock,
there is the possibility of diluting out the imperfection in successive
generations if care is taken always to marry into a stock wholly free from
it. For example, a normal individual carrying a recessive defect will bear
the abnormality in half of his or her germ-cells. This means that when
such an individual marries a normal, non-carrier, half of their children
will be wholly normal (AA) and half will be carriers; normal but of
simplex constitution (Aa). If now this generation, carriers and
non-carriers, marry only into normal strains of duplex constitution, then
their combined issue will be likewise normal with only one-fourth of them
carriers of the imperfections. This means that even if all of this last
generation were married to persons having the defect only one out of four
would have children showing it although the remaining children would be
carriers. On the other hand if mated to normals only one-eight of the next
generation would be carriers. Thus by continually marrying into strong
strains liability to manifest any recessive defect can be diminished in a
few generations until the descendants are no more likely to have defective
children than are members of our ordinary population.
The proportion in which the recessive defect would appear in successive
generations if all persons in a given generation married only normal
individuals who were non-carriers is indicated in the following table
where AA indicates a normal individual, Aa one who is normal but a
carrier, and aa an individual with the imperfection expressed; to indicate
proportions simply after the first generation, four is arbitrarily chosen
as the number of children which results from each marriage:
Matings Children
Generation 1 aa × AA = Aa
Generation 2 Aa × AA = 2AA + 2Aa
Generation 3 AA × AA = 4AA
AA × AA = 4AA
Aa × AA = 2AA + 2Aa
Aa × AA = 2AA + 2Aa
----------
12AA + 4Aa
=Other Inheritable Conditions in Man.--=While many pedigrees show beyond
dispute that such qualities as musical ability, literary ability, memory,
calculating ability, mechanical skill, longevity, peculiarities of
handwriting, obesity and muscular strength, for example, are inherited,
their modes of inheritance have not yet been sufficiently analyzed to
express them exactly.
CHAPTER V
ARE MODIFICATIONS ACQUIRED DIRECTLY BY THE BODY INHERITED?
=Which New Characters Are Inherited?--=Any new feature which appears in a
given organism may have had its origin in some change which has come about
in the germ from which it sprang, or it may be merely the product of some
unusual stimulus operating on the body. While the outcome, as far as the
present individual is concerned, is in each case a definite modification,
the matter of inheritance is a very different question. On the first
alternative where the new character is the outcome of germinal change, it
is obvious that the altered germ-plasm will find expression in a similar
way in succeeding generations as long as the new germinal combinations
persist. On the other hand, if the new character has resulted merely from
some influence operating on the body of the individual, then to be
inherited it would also have in some way to be transferred to and
incorporated in the germ-plasm. Inasmuch as the body or soma of any
individual is highly plastic and since various of its ultimate features
may be mere somatic modifications, it is important to decide if possible
whether or not somatic variations which are not of germinal origin can be
inherited.
=Examples of Somatic Modifications.--=For example, the small foot of the
Chinese woman of certain caste is the result of inherent germinal factor
for the production of a foot plus the effects of binding which are in no
wise germinal. The hand of the skilled pianist is a normal hand of
germinal origin and normal environment plus the effects of special
training. Again, the head of the Flathead Indian is a normal head of
germinal origin and environment plus the effects of flattening. Similarly,
almost any malformation of extrinsic origin may be cited, ranging from
mutilations and amputations, scars and the like to monstrosities such as
one-eyed fish which may be produced by subjecting a developing embryo to
adverse conditions of development.
=Use and Disuse.--=Even reactions set up through the organism's own
activities must produce changes. For example, a muscle has a certain
average of normal development in the average man; it comes to this through
the innate nature of its component cells plus a certain average amount of
exercise. It may, however, be developed far beyond this average by
excessive exercise. On the other hand, it is a well-known fact that an
unused organ weakens or may remain but partially developed. Thus either
use or disuse may play an important part in the molding of a given
individual. But whether or not in doing this it similarly affects the germ
is a very different matter.
=The Problem Stated.--=The question is can such enhanced or suppressed
development, or can new or modified characters, produced in an individual
by external agencies be so reflected on the germ-cell of the individual
that they tend to reappear _as such_ in its offspring without requiring
the same external factors for their production?
=Special Conditions Prevail in Mammals.--=Before proceeding further we
must recognize clearly the very special conditions which exist in most
mammals. With them environment is in part an intra-maternal environment
and in part independent of parental influences. Thus the formula for most
non-mammalia would be--
Individual == egg + non-parental environment; but
for most mammals, including man--
Individual == egg + intra-maternal environment + non-parental
environment.
This condition in mammals introduces a complicating factor which is likely
to obscure the whole issue unless we bear it constantly in mind. In other
words, we must discriminate sharply, in the discussion of inheritance in
man, for instance, between two classes of influences which may exist in
the infant at birth, that is, which are _congenital_; namely, those which
were truly inherent--were in the germ-cells--at the very inception of the
young individual, and (2) those which might later have been derived from
either parent by the yet unborn offspring. The latter are not regarded as
truly hereditary. Since certain diseases or their effects belong here we
occasionally find a physician using the term inheritance for such prenatal
influences, but the more careful ones now employ the term _transmission_
to discriminate between such conditions and true inheritance. In its
biological usage inheritance always refers to germinal constitution and
never to any condition that may be thrust on a developing organism before
birth. It is clear, then, that congenital conditions are not all
necessarily cases of inheritance.
=Three Fundamental Questions.--=To get at the question of the inheritance
of body modifications with the least confusion, let us examine it in the
form of three fundamental questions, as follows:
1. Can external influences directly affect the germ-cells?
2. Can external influences, operating through the intermediation of the
parental body, affect the germ-cells? If so, is the effect a specific and
a permanent one which persists in succeeding generations independently of
external influences similar to those which originally produced it? Only
such a condition as this would rank as the inheritance of a somatic
modification.
3. Can the appearance of new characters be explained on any other ground,
or on any more inclusive basis, than through the transmission of somatic
acquirements, or do organisms possess heritable characters which are
inexplicable as inheritance of such modifications?
Obviously the only way the question can be settled is through careful
experimentation in which all possible sources of error have been foreseen
and guarded against. Much experimental work has been undertaken for the
solution of this problem as the goal and we may therefore select typical
ones of these experiments and apply the results toward answering our three
questions.
=External Influences May Directly Affect the Germ-Cells.--=There is
evidence that under special conditions external influences may in certain
organisms affect the germ-cells, but that this occurs commonly is
extremely doubtful. For example, Professor MacDougal, by treating the
germ-cells of the evening primrose with various solutions, such as sugar,
zinc sulphate and calcium nitrate, has apparently succeeded in producing
definite germinal mutations. He injected the solution into the ovary of
the flower the forenoon of the day at the close of which pollination would
occur. He reports that in this way changes were produced in the germ which
found expression in new and permanent characters.
Professor Tower has experimented for a number of years with various
species of _Leptinotarsa_, the potato beetle. By varying the conditions of
temperature, humidity and atmospheric pressure when females were laying
their eggs, he reports having produced variations in the young which came
from these eggs although the mothers themselves were not changed.
According to Professor Tower slight increase or decrease in these
environmental factors stimulated the activity of the color producing
ferments, giving rise to melanic or darker individuals. Greater increase
or decrease, inhibited them and produced albinos. He found also that at
times the same stimulus might show different results in different eggs.
The effect, therefore, is a general and not a specific one. Ordinarily the
eggs of these beetles are laid in batches. When one of these batches was
laid and left under normal conditions, the usual form of young hatched
from it, but other batches from the same female under abnormal conditions
resulted in the production of atypical forms. For example, a normal
two-brooded form became five-brooded. The commonest modification was the
production of various color types. These once established, according to
Professor Tower, behave as independent, inheritable units.
The experiments of Doctor Bardeen with X-rays and of others with X-rays,
radium and other agents on the sperm and ova of amphibia show that these
are very susceptible to injurious influence at or near the time of
fertilization.
=Such Effects Improbable in Warm-Blooded Animals.--=However possible it
may be to bring about germinal changes in invertebrata or lower vertebrata
by such external agents as temperature and the like it is obvious that the
probability of such extrinsic influences affecting the germ-cells of
warm-blooded animals is very remote indeed. In the latter the germ-cells
are more or less distant from the exterior and are at practically a
constant temperature. Such experiments, therefore, beyond showing the
possibility of producing changes in germ-cells, do not have very direct
bearing on the problem of how inheritable variations are produced in man.
In his case about the only avenue of approach through which germ-cells
might be influenced is the blood or lymph.
=Poisons in the Blood May Affect the Germ-Cells.--=Any poisonous material
in the latter might injuriously affect the gametes. We know, in fact, that
such poisons as alcohol, lead and various drugs, and also the toxins of
various diseases, do so affect germ-cells. It seems plausible to suppose
that changing conditions of nutrition may affect the constitution of the
germ-cells and thus induce changes in the organism which arise from these
cells, but such nutritional effect is not yet a matter of established
fact.
=Difficulty of Explaining How Somatic Modifications Could be Registered in
Germ-Cells.--=As to our second query concerning the possibility of
affecting the germ-cells through the intermediation of parental tissues,
it is evident at a glance that since the germ-cells are built up along
with the body and are not a product of it (Fig. 2, p. 13), if such effects
are possible they must take place through the agency of some transporting
medium. The germ-cells, being lineal descendants of the original fertile
germ or zygote, already have the same possibilities of developing into an
adult that the zygote had, and so the problem becomes one of modifying a
complete germ already organized rather than of establishing a new germ by
getting together samples of every part of the body. This is all the more
evident when one realizes that usually the germ-cells are set apart long
before the body becomes adult, that is, before the body has developed most
of its characteristics. Moreover, among lower animals many instances are
known where the immature young or even larvæ will produce offspring which
nevertheless ultimately manifest all the structures of the adult
condition.
But supposing specific modifications of the germinal mechanism were
possible, it is difficult to comprehend how an influence at a distant
point of the body could reach the germ-cell, to say nothing of the even
greater difficulty of understanding how it could become registered in the
germ in a specific way as affecting a particular part. For it must be
remembered that the organs of the adult do not exist as such in the germ
but are present there only as potentialities. How, for example, can a
change in the biceps muscle of one's arm be registered in a germ-cell in
which there is no biceps muscle, but merely the possibilities of
developing one? Or how can increased mental ability which is contingent on
the elaboration of certain brain-cells be impressed on a germ which has no
brain-cells but only the capacity under certain conditions of producing
such cells? For the brain of a child is not descended from the brain of
his parent, but from a germ-cell carried by that parent.
=Persistence of Mendelian Factors Argues Against Such a Mode of
Inheritance.--=On the face of things, the apparent inviolability of
Mendelian factors which may remain unexpressed in the germ for one or many
generations--indeed the whole matter of genotypical differences in the
gametes of the same individual--shows the improbability of somatic
interference with the germ-plasm. But notwithstanding this, because of the
great importance of the issue, it is well to review in some considerable
detail the various phases and possibilities of the question.
=Experiments on Insects.--=Some of the attempts to secure evidence of the
transmission of personally acquired parental modifications in insects are
very interesting. Many insects in the larval stages, particularly just
after pupation seem to be especially susceptible to external influences.
They have been much used, therefore, for purposes of experiment. It has
long been known that differences in size, in color and even in the shape
of wings can be produced by various agents if applied at this period of
development. From the standpoint of heredity, however, the important
consideration is to determine if these experimentally induced changes have
been reflected on to the germ-cells so that they reappear in the offspring
of the modified individuals.
It has been found that in some cases where male and female are of
different color, the color of the female can be changed to that of the
male by altering the conditions of temperature. In certain cases types can
be changed by cold so that they resemble varieties of the same species
found farther north, and by heat, varieties found farther south. But not
all individuals of a given lot are affected, and often different
individuals of the same kind show different effects. Moreover, in some
cases the same aberrations were produced by heat as by cold. This
indicates that it is not so much a question of specific effects as a
general physiological change, apparently mainly a matter of direct
influence of temperature on the chemical composition of the pigments. The
Countess von Linden in fact has shown that the extracted pigments can be
made to undergo the same changes of color in a test-tube by heat and cold
as in the pupæ. But there is no evidence that the germ-cells of the living
insect were affected in a specific way. In a small fraction of the
offspring of such modified individuals abnormalities appeared, but these
were not always of the same kind as those which had been produced in the
parent. That is, there was no evidence of a trait or character having been
acquired by the body and handed on to the germ-cell. Where an effect was
produced on the germ-cell it was probably produced directly as in the
first cases discussed.
Size, colors and markings of butterflies have also been altered by
subjecting the caterpillars or the pupæ to such influences as strong
light, electricity, various chemical substances, centrifuging, diminished
oxygen supply, etc., but the results were in the main confined to the
immediate generations. In the few cases where permanent inheritable
changes were seemingly produced they were more reasonably interpreted as
the effects of direct action on the germ-cells than as examples of
inherited somatic modifications.
Starvation experiments which resulted in the dwarfing of adult individuals
have been performed on various insects, and while the dwarf condition may
persist through one or two generations due to a diminished food supply in
the eggs of the dwarf, the stock in question when returned to normal food
conditions soon resumes its original characteristic size.
=Experiments on Plants.--=Many experiments have been performed with
plants, inasmuch as they are particularly prone to become modified by
changes of food supply, or climate. For example, plants which grow
luxuriantly in a warm moist climate or a rich soil may become stunted and
markedly changed if transplanted to a cold climate or a poor soil.
Naturally, their progeny will exhibit the same behavior as long as they
are kept under the new conditions. Experiments carried on through numerous
generations, however, practically all show that the germinal constitution
of the plants remains unchanged, for when their seeds are planted under
the original favorable conditions of soil or climate, the plants resume
their former habits of growth. Naegeli, for instance, who made a study of
many varieties of Alpine plants, and who carried on experiments with many
of them for years in the Garden of Munich, concluded that no permanent
effects had been produced by the Alpine climate and conditions in plants
from other regions which had come under its influence. A few botanists
have claimed to have found that the changes produced by the Alpine climate
have persisted for a generation or two and have then worn off. More recent
experiments on various of our field grains which have been stunted and cut
down in productivity by growing for a number of generations under adverse
conditions show that they have not been permanently modified by such
treatment, for they resume normal productivity and size when grown again
under favorable conditions.
On the other hand, Lederbaur found that a common weed, _Capsella_, when
transplanted from an Alpine habitat to the lowlands did not return to the
lowland type of the weed, but retained certain of its Alpine
characteristics. It is not clear, however, that this particular species
during its long sojourn of many generations in Alpine conditions may not
have undergone a series of germinal variations and have developed into a
new variety or species quite independently of changes wrought in the germ
by reflected somatic effects. Indeed, in face of the preponderance of
other cases to the contrary, this interpretation would seem to be the more
plausible one.
=Experiments on Vertebrates.--=In the vertebrates we may also find
examples of various somatic modifications experimentally produced, but
evidence of their inheritance is as difficult to establish as in the
invertebrates. Let us examine a few of the more significant of these which
are alleged by some to bear evidence of such inheritance.
By decreasing the amount of water in an aquarium Marie von Chauvin was
able to transform the aquatic, gill-breathing salamander _Axolotl_ into
the gill-less land form _Ambystoma_, heretofore regarded by systematists
as a different species. Either of these forms when sexually mature
produces its like. The salamanders in question have both lungs and gills,
but after a time the ones which are to be land forms lose their gills and
become exclusively lung-breathers. What seems to have been accomplished
then is the accelerating or forcing of normal natural tendencies already
inherent in the organism instead of introducing something new into the
inheritance by way of the soma. _Axolotl_ is in all probability merely a
larval form of _Ambystoma_ which with high temperature and an abundance of
water reproduces without advancing to the final possible stage of its life
cycle.
=Epilepsy in Guinea-Pigs.--=Perhaps the most frequently cited case and the
one in which the defenders of the idea of somatic inheritance usually take
final refuge is that of Doctor Brown-Sequard's guinea-pigs,
notwithstanding the fact that no one has had convincing success in
repeating the experiments and that the original results are apparently
open to more than one interpretation. This experimenter rendered
guinea-pigs epileptic by certain injuries to the nervous system. Epilepsy
appeared in some of the offspring of these operated animals. He regarded
this as an example of the inheritance of an artificially induced epilepsy.
An indirect loss of toes occurred in some of the parents as a result of
the operations on the nervous system. Some of their young also had missing
toes. However, as has been pointed out by various critics, guinea-pigs are
strongly predisposed toward epileptic-like seizures, and the epilepsy in
the young may have been merely a coincidence. Voison and Peron believe
they have shown that in epilepsy a toxin is produced that may affect the
unborn fetus. That is, the result might have been due to a poison derived
directly from the mother. The experiments in fact show that it was mainly
in the offspring of affected mothers that the condition appeared. Others
maintain that we do not know the exact nature of epilepsy, that in some
cases it may be the result of infection by disease-germs, and that
Brown-Sequard's cases may, therefore, have been merely the communication
of a disease from parent to child. As to the disappearance of toes it is a
well-known fact that rodents in particular are likely to gnaw off the toes
of their young very soon after birth, and little credence can be put in a
lack of toes in such young as cases of inheritance except under conditions
of much more careful observation than existed in Brown-Sequard's
experiments. A fuller account of these experiments will be found in
Romanes' _Darwin and After Darwin_, Vol. II, Chap. 6.
=Effects of Mutilations Not Inherited.--=Many experiments have been
performed by investigators to determine whether or not the results of
mutilation are transferred to succeeding generations, but so far only with
negative results. Many such experiments have been unwittingly carried on
for many generations, in fact, by breeders and fanciers, in the docking of
horses, dogs and sheep, the dehorning of cattle and the like, yet no
satisfactory evidence of the transmission of such conditions in any degree
has ever been forthcoming. The mutilations or distortions of the human
body through various rites or social customs also fails to yield any
convincing examples. Foot-binding, head-binding, or waist-binding must be
repeated in each successive generation to produce the particular type of
"beauty" that results from such deformities. And lucky it is for man that
injuries do not persist in subsequent generations, otherwise the modern
human being would be but a maimed relic of past misfortunes.
=Transplantation of Gonads.--=An interesting experimental test regarding
the effect of the body on the germ was made recently by Castle and
Phillips with guinea-pigs. It will be recalled from the discussion on
Mendelism that when a black guinea-pig is mated with a white one the
offspring are always black. These experimenters transplanted the ovaries
from a young black guinea-pig to a young white female whose own ovaries
had been previously removed. This white female was later mated to a white
male. Although she produced three different litters of young, six
individuals in all, the latter were all black. That is, not a trace of
coat-color of the white father or of the white foster-mother was impressed
on the transplanted germ-cells or the developing young. Later experiments
of the same kind by Castle and Phillips, with other varieties of
guinea-pigs, have yielded the same results. The body of the mother,
indeed, seems to serve merely as a protective envelope and a source of
nutrition.
=Effects of Body on Germ-Cells General, Not Specific.--=As far as the
evidence regarding the modification of the germ-plasm by the body is
concerned, we must conclude then that while under special circumstances
the germ-cells may be affected, the effect is general rather than specific
and the result as seen in the offspring has no discoverable correlation
with any particular part or structure of the parental soma. The effect is
presumably of much the same nature as where the germ is directly affected
by external agents. Where a new character or a modification of one already
existing is produced by a given condition of environment, in our
experience so far to have the same repeated in the offspring, a similar
evocative condition must prevail in the environment of the latter. Or in
other words the new character is not a permanent one which persists in
succeeding generations independently of external influences similar to
those which originally produced it.
=Certain Characters Inexplicable as Inherited Somatic Acquirements.--=It
would require remarkable credulity, in fact, to believe that some of the
most striking features about certain plants or animals could have been
developed by means of the inheritance of somatic modifications. For
example, many animals such as the quail, the rabbit, or the leaf-butterfly
are protectively colored. That is, they harmonize in color-pattern with
their surroundings so closely that they are overlooked by their enemies.
But how can this oversight on the part of an enemy so affect the bodies
and through them the germ-cells of such individuals as to develop so high
a degree of protective coloration? Or how, indeed, could any of numerous
adaptive structures which one can think of, such as the color or scent of
flowers to lure insects for cross-pollenation, the various grappling
devices on many seeds to secure wide distribution by animals, or the like,
have been directly produced by use or disuse or by any variation produced
in them by the agents to which they are adapted?
=The Case of Neuter Insects.--=A very instructive example of the
improbability that great skill, highly specialized structures, or certain
instincts are first developed in the parental body as the result of use
and then passed on to the offspring, is seen in the case of neuter
insects. In bees, for example, there are three classes of individuals: the
drones or males; the queens or functional females; and the workers, which
are neuter, that is, take no part in reproduction. The latter are really
sexually undeveloped females. The queen can lay either fertilized or
unfertilized eggs. The latter always give rise to males. The workers
gather the food, attend the queen, wait on the young, construct the comb,
and in short perform all the ordinary functions of the colony except the
reproductive. They have many highly specialized structures on various
parts of their bodies for carrying on their many activities, as well as
the very highly specialized instincts necessary to the maintenance of the
colony. But now, complex and highly developed as these workers are, since
they do not give rise to offspring, no matter how much experience or
structural modifications they may acquire during their lifetime, it can
not be handed on to another generation. Nor can they have come to their
present highly organized state through such a form of transmission since
they are not the descendants of workers but of a queen. Any new
modifications that appear in the workers of a colony must therefore have
their origin in changes which have taken place in the germ-cells of the
queen, and not in the soma of some other worker. It has been argued that
the worker has not always been infertile; that at a more primitive stage
of the evolution of the bee colony every female was both worker and
mother, and that individual somatic acquirements might therefore have been
transmitted, but this argument can not hold for many of the instincts or
features of the modern bee because these have to do only with the
conditions of life which exist in the colony in its present form. It is
obviously absurd to maintain, for instance, that all the highly
specialized instincts incident to queen production, queen attendance and
the like were functionally produced through usage before there was any
queen to produce or attend, while on the other hand, the very necessity of
queen production and maintenance is the outcome of the infertility of the
workers. Some workers have been known to lay eggs, but as these are few in
number and are never fertilized, which means if they develop they can only
produce males, they can play no considerable part in inheritance.
ORIGIN OF NEW CHARACTERS
=Origin of New Characters in Germinal Variation.--=This brings us to our
last query as to whether the appearance of new characters can be explained
on any other or any more inclusive ground than that which infers that
changes undergone by the parent-body are in some way registered in the
germ-cells so as to be repeated in a certain measure in the body of the
offspring. The answer to the question of how inheritable variations do
come to appear in offspring if not through changes produced in the body of
the parent, is uncertain; nevertheless most biologists believe that they
do not have such a somatic origin but arise directly as germinal
variations. Some would attribute them to the fluctuating nature of living
substance in general. The instability of protoplasm is one of its striking
characteristics. It is constantly being broken down and built up, or, in
other words, undergoing waste and repair. Like all other protoplasm, that
of the germ-cells must also undergo these metabolic changes and it is
possible though not proved that in this give and take of substances small
changes occur in their constitution which find expression in the offspring
as variations. As already seen, substances in the blood other than food
may also affect the constitution of the germ-cells.
=Sexual Reproduction in Relation to New Characters.--=Some biologists
attribute great importance to sexual reproduction as a basis of variation
and the origin of new characters. They argue that the mingling of
determiners from two different lines must produce many new combinations
and expressions of germinal potentialities. Plausible as the argument
seems at first sight no one has succeeded as yet in securing proof that
absolutely new characters can be originated in this way. What seems to
occur under such circumstances is merely a reshuffling or sorting of old
unit-characters. Although innumerable permutations and combinations of
these may be made which find new expression outwardly, this is obviously
not creating determiners of new unit-characters in the germ-plasm. While
many biologists would not deny the possibility or even the probability
that the determiners of unit-characters may sometimes combine or influence
one another so as to form actual permanent new characters, the proof of
such performance is wholly lacking. On the other hand, there are not a few
biologists who argue that sexual reproduction accomplishes just the
reverse of increasing the extent of variation or creating new characters;
according to them it tends to annul exceptional peculiarities of either
parent by throwing the offspring back to the average racial type. It is
thus looked on by these advocates as a stabilizer which reduces the
amplitude of variations instead of increasing them. As a matter of fact
the two ideas are not mutually exclusive; sexual reproduction may
accomplish both of these ends. A limited number of observations and
experiments have been made to test out the correlation between sexual
reproduction and variation, but they have so far been too few or too
inconclusive to enable us to come to a satisfactory conclusion.
While we are uncertain about the method of origin of new characters the
fact remains that they do arise in abundance as abrupt mutations or
otherwise and become a part of the permanent heritage of a stock. It is
clear that sexual reproduction may be one important means by which a given
new character which has arisen in one or a few individuals may become
incorporated in the species at large. Through Mendelian combinations and
segregations it would by cross-breeding be spread and gradually introduced
into more and more strains of the general population.
=Why So Many Features of an Organism Are Characterized by
Utility.--=Germinal variations are seemingly at first more or less hit or
miss affairs as far as utility to the organism is concerned. Useless
variations, so long as they are not actually harmful, may persist and
apparently be indefinitely inherited. However, a special premium is put on
variations which happen to be useful for they help the organism to succeed
in its struggle for life and since success in the world of life means not
only mere individual survival but also the production of progeny, through
this very means insured transmission to subsequent generations. It is
probable that the very many useful features of any organism, that is, its
_adaptations_, have thus been established. It is possible also that many
variations which at their inception are indifferent may wax in strength in
successive generations until they reach a point where they must become
either useful or harmful. In the former case they would mean increased
insurance of survival for their possessors, in the latter, elimination.
With such an automatic process as this operative in nature it is not
astonishing that the main features of any organism are characterized by
their utility to it.
=Germinal Variation a Simpler and More Inclusive Explanation.--=The gist
of the whole matter regarding the source of new characters in offspring
seems to be that the explanation based on the idea of germinal variation
is in last analysis the simpler and more inclusive, and there is no
alleged case of inheritance of parental modification, which can not be
equally well explained as the result of a germinal variation. There are
numerous cases which can not be explained as transmissions of somatic
acquirements even if this transmission could be established in certain
cases. So, many biologists argue, why have two explanations when one is
sufficient, especially when the other has never been conclusively
established as true in any case and is obviously untrue in certain test
cases? The attitude of most investigators is that of the open mind. While
feeling that the weight of probability is very decidedly against the
theory of the inheritance of somatic modifications, they still stand ready
and willing to accept any evidence in its favor which when weighed in the
balance is not found wanting.
ANALYSIS OF CASES
While space will not permit extended discussion, in order further to fix
the nature of the problem in mind as well as to exemplify the conditions
that must be satisfied to form convincing evidence of inherited somatic
acquirements, it will be well perhaps to analyze a few typical cases as
they are frequently cited.
=Are the Effects of Training Inherited?--=Breeders and trainers very
commonly believe that the offspring of trained animals inherit in some
measure the effects of the training. Thus the increased speed of the
American trotting horse is often pointed to as strong evidence of such
transmission. According to W. H. Brewer, the earliest authentic record of
a mile in three minutes was made in 1818. The improvement, approximately
by decades, from that time was as follows:
During 1st decade after 1818, improved to 2:34
2nd " " " " " 2:31-1/2
3rd " " " " " 2:29-1/2
4th " " " " " 2:24-1/2
5th " " " " " 2:17-1/2
6th " " " " " 2:13-1/2
7th " " " " " 2:08-1/2
By 1892, the date of Professor Brewer's publications (See _Agricultural
Science_, Vol. 4, 1892) the record had reached 2:08-1/2. Since then it has
been lowered still further.
On the face of it this looks like a good case of inheritance of training,
and Brewer himself believed it such. If so this would mean that colts of a
highly trained trotter would be faster than they would have been if their
parent had remained untrained. It is impossible to get positive proof in
the case of any trained horse since there is no way of establishing just
how speedy the progeny would have been had the parent remained untrained.
If it could be shown that colts sired by a trotter late in life were on
the whole faster than those sired by the same father when younger and as
yet not highly exercised in trotting, then the facts might give some
evidence of value, but unfortunately no such records are available.
On the other hand, even ignoring the fact that improvement in track and
sulky are probably the biggest items in the shortening of records in
recent times, _selection_ instead of inheritance of the effects of
training will equally well account for any innate progress in trotting.
And since, as pointed out by Professor Ritter, there are even more
striking cases of similar improvements in other fields, such as college
athletics, where the factor of use-inheritance is entirely precluded, it
is wholly unnecessary to postulate it in the case of the trotter.
For example an inspection of the records of college athletics for the last
thirty-five years in running, hurdling, pole-vaulting, jumping, putting
the shot, etc., shows on the whole a steady advance year by year.
Moreover, the greatest improvement has occurred in those events in which
skill and practise count for most together with selection of the
inherently ablest candidate for the events. But in the case of athletics
the improvements shown in thirty-five years have all come within a single
generation and hence the inheritance of the effects of training is ruled
out as a factor. Selection and improved training are the only factors
operative.
In the case of the trotter inheritance undoubtedly has also been a factor,
but inheritance based on selection of what the race-track has shown to be
the speediest individual, not inheritance of the effects of training. In
other words, horses which have shown the capacity for being trained to the
highest degree of speed have naturally been selected as sires and dams
and so through selection generation after generation a speedier strain has
gradually been established.
=Instincts.--=When we turn to the realm of mental traits, particularly of
instincts, we meet with a whole host of activities which are frequently
pointed to by transmissionists as examples of inherited acquirements. Thus
according to them, habits at first acquired through special effort
ultimately become instinctive, or according to some, instinct is "lapsed
intelligence." Instances often cited are the pointing of the bird-dog, the
extraordinary crop-inflation of the pouter-pigeon, or the tumbling of the
tumbler pigeon. We can not stop to discuss these cases beyond pointing out
as many others have done that practically all dogs have more or less of an
impulse to halt suddenly, crouch slightly and lift up one fore-foot when
they scent danger or prey, that all pigeons pout more or less, and that
practically all show more or less instincts of tumbling when pursued by a
hawk. Thus in all of these cases the fundamental germinal tendency is
already at hand for the fancier to base his choice on and thus through
selection build up the type desired. Just as in the fan-tailed pigeon, by
repeatedly selecting for breeding purposes individuals which showed an
unusual number of tail-feathers he has built up a type with an upright,
fan-like tail having many more feathers than the twelve found in the tail
of the ordinary pigeon, so by similar procedure in the case of other forms
he has markedly enhanced certain features. The idea of instincts being
"lapsed intelligence" is so clearly and concisely criticized in an
article by the late Professor Whitman[4] that I can not do better than
quote an excerpt. His views to the contrary are as follows:
"The view here taken places the primary roots of instinct in the
constitutional activities of protoplasm and regards instinct in every
stage of its evolution as action depending essentially upon
organization. It places instinct before intelligence in order of
development, and is thus in accord with the broad facts of the present
distribution and relations of instinct and intelligence, instinct
becoming more general as we descend the scale, while intelligence
emerges to view more and more as we ascend to the higher orders of
animal life. It relieves us of the great inconsistencies involved in
the theory of instinct as "lapsed intelligence." Instincts are
universal among animals, and that can not be said of intelligence. It
ill accords with any theory of evolution, or with known facts, to make
instinct depend upon intelligence for its origin; for if that were so,
we should expect to find the lowest animals free from instinct and
possessed of pure intelligence. In the higher forms we should expect
to see intelligence lapsing more and more into pure instinct. As a
matter of fact, we see nothing of the kind. The lowest forms act by
instinct so exclusively that we fail to get decided evidence of
intelligence. In higher forms not a single case of intelligence
lapsing into instinct is known. In forms that give indubitable
evidence of intelligence we do not see conscious reflection
crystallizing into instinct, but we do find instinct coming more and
more under the sway of intelligence. In the human race instinctive
actions characterize the life of the savage, while they fall more and
more into the background in the more intellectual races."
For further discussion of this field the reader is referred to an
excellent chapter on "Are Acquired Habits Inherited?" in C. Lloyd Morgan's
book, _Habit and Instinct_.
=Disease.--=Perhaps in the realm of disease more than in any other has an
interest in the inheritance of somatic acquirements been manifested. The
problem arising here is not essentially different from other questions of
inheritance but since it is a matter of such practical importance to man,
we may well give it special attention. We have to deal simply with the old
questions of what is constitutionally in the germ, what is acquired by the
body, and lastly, whether the somatically acquired is inherited. While we
all know in a general way what is meant by disease, especially if some
specific disorder such as scarlet fever, malaria or tuberculosis is
mentioned, an attempt to give an accurate definition is much like trying
to define a weed, inasmuch as what is functionally all right at one time
or place may be all wrong at another, or what is normal in one animal may
be abnormal in another. In general we may say that disease is derangement
or failure of physiological function.
=Reappearance of a Disorder in Successive Generations Not Necessarily
Inheritance.--=In attempting to study the inheritance of diseases we must
recognize clearly at the outset that reappearance of a disease in
successive generations by no means necessarily signifies inheritance.
Before it can be pronounced such we must make sure that it is not a case
of reimpressing similar modifications on the individuals of successive
generations. For example, in England there is a well-recognized condition
known as collier's lung which results from constant working in coal mines.
And while both father and son may exhibit it, because of their similar
occupations, there is nothing hereditary about the malady. Likewise there
is what is known as emery grinder's lung, and practically every large
manufacturing city with soot-laden atmosphere leaves its impress on the
lungs of the inhabitants. This will occur, of course, generation after
generation, as long as such pollutions of the atmosphere continue to
exist. It is clear that any unhealthy occupation is likely to cause the
reappearance of an associated typical disease generation after generation
as long as the children follow the calling of their parents. The common
misconception that deformities or postures associated with a trade, such
as a shoemaker's or tailor's, is genetically stamped on offspring by the
end of the third or fourth generation results from failure to discriminate
between real inheritance and mere reappearances under similar conditions
of environment.
=Prenatal Infection Not Inheritance.--=Again, we must recognize that
prenatal infection is not inheritance. We have already seen that the young
mammal undergoes a certain period of intra-maternal development, but
influences operating on it during this period of gestation must be
reckoned with as environmental, not germinal. For example, it is said that
an unborn child may take smallpox from its mother but this and all similar
occurrences are cases of contagion. We find the great pathologist,
Virchow, who with many others of his time was a believer in the
inheritance of acquired characters, saying nevertheless regarding such
instances that, "What operates on the germ after the fusion of the
sex-nuclei, modifying the embryo, or even inducing an actual deviation in
the development, can not be spoken of as inherited. It belongs to the
category of early acquired deviations which are therefore frequently
congenital."
=Inheritance of a Predisposition Not Inheritance of a Disease.--=We must
discriminate sharply also between the inheritance of a predisposition and
the inheritance of a disease itself.
We often hear the statement made that tuberculosis is inherited and have
cited in evidence certain consumptive families or strains. But
tuberculosis is a bacterial disease and children of tuberculous parents
are never born with the disease except in the rarest of instances.
=Tuberculosis.--=What is really inherited is a constitutional
susceptibility to this particular germ. While almost any individual may
contract tuberculosis when in a state of depressed vitality, or under
stress of adverse surroundings, there is no doubt that certain families
are more easily infected than others and much less resistant to the
ravages of the disease when once it gains a foothold. However, a
predisposition is a vastly different thing from the inheritance of the
actual disease. For just as we are born with a nose well adapted to
eye-glasses but not with eye-glasses on our nose, so many of us are born
tuberculizable though not tuberculous, and every sanitary advance we make
toward lessening the chances of infection is just so much more insurance
for the susceptible.
The whole problem of tuberculosis is an extremely complex one. We do not
know just the measure of the inheritance of the predisposition. Some
writers in the past have maintained that tuberculosis is mainly a question
of infection and not of inherent susceptibility, but steadily increasing
evidence all points the other way.
Where the predisposition exists the chances of infection are still, even
under the conditions of present-day sanitation, very great. The close
association between a consumptive and other members of the family through
a prolonged period of time, of course, renders the latter likely to
infection unless unusual care is exercised. Very often where a parent is
consumptive a child contracts the malady shortly after birth and is
particularly likely to do so if the mother, who nurses it and cares for it
most intimately, is the tubercular member of the family. Where the mother
is tubercular, indeed, the probabilities are that the child has already
before birth had its vitality lowered through the toxins circulating in
her blood or through defective nutrition, and in consequence does not
resist well any diseases.
Undoubtedly a large proportion of our infant mortality is of tubercular
origin. It is now a well-established fact that much tuberculosis in
children is attributable to drinking milk from tuberculous cows, yet we
find individuals so uninformed and dairymen so mercenary that they fight
all attempts of the commonwealth to test out cattle for tuberculosis so as
to condemn the infected individuals and thus save our babies. Recent
investigations made in some of our large pork-packing establishments also
indicate that hogs, especially such as have been around tubercular
cattle, are often shot through and through with tuberculosis and that such
flesh when used as food, if not thoroughly cooked, may become a serious
menace to our health.
With the wide prevalence of bovine and human tuberculosis it is little
wonder that nearly every human being becomes more or less infected at some
period of life. Autopsies on large numbers of individuals in some of our
great hospitals have shown that as many as ninety-nine per cent. of the
subjects show tubercular lesions of some kind. While it is true that the
class of people who would come to autopsy in such public hospitals would
perhaps be more likely to be tubercular than the average of the community,
still it can not be denied that a very large degree of infection exists.
Pearson, from statistics gathered in Europe, has shown that about eighty
to ninety per cent. of the population have tubercular lesions before the
age of eighteen. Hamburger found that in Vienna ninety-five per cent. of
the children of the poor, between twelve and thirteen years of age, were
infected with tubercular bacilli and he estimates that all would be before
maturity. According to Doctor Mott, pathologist to the London County
Asylums, the insane between the ages of fifteen and thirty-five are about
fifteen times as likely to acquire tuberculosis as the sane are.
Yet the mortality from tuberculosis, great though it be, is obviously not
in proportion to the enormous degree of infection. The crux of the
situation is mainly the matter of resistance. From the standpoint of
heredity, therefore, the question largely resolves itself into one of the
inheritance or non-inheritance of constitutional resistance. Some are
predisposed to be non-resistant and hence succumb.
The work of Karl Pearson[5] and other recent researches forcibly indicate
that hereditary constitutional predisposition is one of the chief factors
concerned in subjects who develop well defined attacks of the disease. Yet
we must not forget that there are degrees of susceptibility and that
therefore a constitutional predisposition which might be of little
significance under good average conditions of nutrition and sanitation
might be insufficient under unfavorable conditions.
Before we can make any relatively accurate estimate of the exact degree to
which the malady is based on inheritance we must have more data. Many
difficulties beset the path of the investigator. In the first place, when
one gets back a generation or two he finds that diagnosis was crude and
uncertain; a given malady may or may not have been tuberculosis. The main
error however was probably on the side of not recognizing it in mild or
obscure cases. Then again the questions of virulence of the infection, of
size and frequency of the dose, etc., are also complicating factors.
Moreover, in very many cases the infection is a mixed one and hence we are
dealing with other factors than straight tuberculosis.
=Two Individuals of Tubercular Stocks Should Not Marry.--=However,
sufficient is now known of the inheritance of susceptibility to the
disease that we can have little conscience toward the welfare of the race
if we in any way countenance the marriage of two individuals who come each
of tubercular strains, and marriage of even a normal person into a badly
tainted strain, where the one married is tubercular, is extremely
hazardous looked at from the standpoint of the children likely to be born
of such a union. The Supreme Court of New York recently held that the
fraudulent concealment of tuberculosis by a person entering into a
marriage relation is ground for the annulment of the marriage.
=Special Susceptibility Less of a Factor in Many Diseases.--=With some
diseases such as leprosy, typhoid fever, smallpox and cholera there seems
to be less a question of special susceptibility since nearly all persons
are vulnerable. Yet in cases of typhoid, at least, there are some
indications that certain families are more likely to take the disease than
others under similar exposure. We know of no inherited effects of such
diseases, however. For instance, children of lepers do not inherit leprosy
and if kept out of leper districts remain normal.
=Deaf-Mutism.--=In certain abnormal states there is danger of confusing
similar conditions which may have two entirely different sources of
origin. Deafness, for example, may be strictly inborn as the outcome of a
germinal variation or it may result from extraneous influences such as
accidents, infective diseases, neglected tonsils and the like. The former
is inheritable, the latter not. Bell in 1906 in a special census report to
the United States government showed that deaf-mutism is markedly
hereditary, particularly where deaf-mutes intermarry as they are prone to
do. Fay's extensive studies on _Marriage of the Deaf in America_ also
demonstrate the hereditary nature of the congenital forms of deafness. Cut
off as such individuals are from communication with normal people, the
association of the two sexes in special schools and institutions is of
course highly conducive to such marriages. The defect seems to behave in
the manner of a Mendelian recessive. Two deaf-mutes should not have
children and yet such marriages are occurring every day. Even if two
persons marry from families which tend to become hard of hearing the
evidence indicates that their children are likely also to develop this
partial deafness as they grow older, although it seems safe for a person
of such tendency to marry into a family without it.
=Gout.--=In such disorders as gout there is little question but that a
tendency to it runs in families. On the other hand it may also be acquired
without special susceptibility. There is no evidence, however, that
because a father has gout the effect of the gout is reflected on his
germ-cells and the son has gout as a result. Indeed, often a son who
becomes gouty was born long before the father became gouty. Son and father
both have gout then, because each has innate germinal tendencies which
when subjected to certain evocative stimuli become expressed as gout.
=Nervous and Mental Diseases.--=Inasmuch as the question of nervous and
mental diseases has become one of such overshadowing importance at the
present day, a discussion of the subject at some length will be presented
in a separate chapter. I shall merely point out here that the general
verdict of experts in nervous and mental disorders is to the effect that
externally induced mental disorders are of rare occurrence except as the
result of general poisoning or enfeeblement of the system in some way, or
by traumatic conditions such as a blow on the head, and that there is no
evidence of the transmission of the effects of such conditions. In most
cases of insanity, supposedly caused by fright or worry, a close study of
the family stock will reveal nervous instability of some kind. The
supposed cause has been merely the precipitating stimulus which has
brought to expression a dormant weakness of germinal origin. The stress
and strain of modern life is particularly likely to test out and reveal
such neurally unstable individuals.
=Other Disorders Which Have Hereditary Aspects.--=Space will not permit
discussion of various other specific disorders which are known to have
important hereditary aspects, although none shows any convincing evidence
of having become hereditary in nature through first affecting the soma.
Some of these, such as epilepsy and other nervous affections,
tuberculosis, color-blindness, cataract and various malformations, have
already been mentioned. Others that may be listed are cancer,
arterio-sclerosis, obesity and certain forms of rheumatism, and of heart
and kidney diseases. In practically all of these cases in which heredity
enters as a factor the condition is one of inheriting a special
susceptibility and not the disease itself. Which means simply that the
disorder in question is much more easily called forth in such persons by
appropriate bacterial or other stimulus, than in the case of the normal
individual.
=Induced Immunity Not Inherited.--=Lastly, it is well known that various
animals, including man, after recovery from an attack of any one of
certain diseases, become more or less immune from further attacks of the
same disease. Moreover in some instances as in inoculation against typhoid
or diphtheria, immunity may be artificially induced by means of
anti-toxins. The question arises as to whether such immunity is
transmitted to offspring. Experiments have been made (see _Bulletin No.
30, U. S. Hygienic Laboratory_) to test this and it has been found that
the condition is not inherited. Young guinea-pigs, for instance, born of
mothers immunized during pregnancy are immune at birth but they lose their
immunity in the course of a few weeks. The effect is clearly one of direct
transference from the blood of the mother. The same temporary immunity can
be produced in the young, in fact, by merely having them nurse from an
immunized mother.
=Non-Inheritance of Parental Modifications Has Social, Ethical and
Educational Significance.--=Like many other biological conclusions these
relative to the non-inheritance of parental modifications are of extreme
importance to humanity. It is clear that they have not only physical but
social, ethical and educational significance. For if the education which
we give our children of to-day, or the desirable moral conduct which we
inculcate does not affect the offspring of succeeding generations through
inheritance, then the actual progress of the race is much slower than is
commonly supposed, and the advance of modern over ancient times lies more
in an improvement in extraneous conditions through invention and the
accumulation and rendering accessible of knowledge, than in an actual
innate individual superiority. And when we face the issue squarely we have
to admit that there is no more indication of the inheritance of parentally
acquired characters as regards customs, knowledge, habits and moral
traditions than there is of physical features. In fact, if such
acquirements were inherited then we should soon have a race which would
naturally, spontaneously as it were, do what its ancestors did with
effort. Yet we do not find the children in our schools reading, doing sums
and developing proper social relations without ceaseless prompting and
urging on the part of the teacher. Indeed I can testify that this
necessity carries over even into a university. In short, the habits and
standards of each generation have to be instilled into the succeeding
generation.
=No Cause for Discouragement.--=At first glance when we realize that
notwithstanding our individual advancement, that in spite of all our
painstaking efforts toward self-improvement, we can not add one jot or
tittle to the native ability of our children, that, aside from possible
advantageous germinal variations, they will have to start in at
approximately the same level as we did, and like us will have to struggle,
or be coaxed, pulled or spurred up to the higher reaches of attainments,
we are apt to feel discouraged and to look on heredity as the hand of fate
which irrevocably bars progress. But there is another side to the picture.
This very fact of heredity which can not be altered at will is the
conservative factor which maintains the excellence of our standard strains
of plants and animals, and sustains man himself at his present level of
accomplishment. While we are denied advancement through the efforts of the
flesh, we are also largely protected from our misfortunes and follies, as
witness the non-inheritance of mutilations, of various maladies of
extrinsic origin, or of personally acquired bad habits.
=Improved Environment Will Help Conserve the Superior Strains When They Do
Appear.--=If we can not hand on to our descendants a personally enhanced
blood heritage, we at least can do our share toward building up a social
heritage of established truth, of efficient institutions and of
stimulating ideals, through which their dormant capacities may be led to
expand more surely and more effectively to their uttermost limits. Each
advance in such social heritage will tend more and more to create an
atmosphere which will make it sure that the occasional real progressive
and permanent variations which occur from time to time will find adequate
expression and preservation in future lines of descendants. It will reduce
the numbers of our "mute, inglorious Miltons" by more certainly disclosing
the individual of exceptional talents and insuring for him an opportunity
of revealing them to the best advantage. Above all, since surrounding
influences are especially powerful on young and developing organisms, we
should realize that great care must be exercised in behalf of the young
child to secure an environment which is saturated with wholesome
influences. For it is a rule of development that if the environment is
faulty the organism is impaired.
CHAPTER VI
PRENATAL INFLUENCES
=All That a Child Possesses at Birth Not Necessarily Hereditary.--=We come
now to the more specific discussion of what may happen to offspring of
mammals, and particularly man, in the interval between fertilization and
birth; that is, during the intra-maternal period. We have already seen
that anything affecting the offspring during this period has to be
reckoned as environmental, our formula reading, Mammal = germ +
intra-maternal environment + external environment. It is evident, then,
that all that a child possesses at birth is not necessarily hereditary,
since the unborn child may be influenced by conditions prevailing in
either parent.
=The Myth of Maternal Impressions.--=In order to clear the way for more
urgent matters let us first inquire into the question of the production of
changes in the unborn child as a result of "maternal impressions." As the
tale generally goes, structural changes are produced in the unborn child
corresponding to some mental experience of the mother, usually a vivid
impression of strong emotion, but when a given individual is pinned down
to sources, it is usually a case of hearsay.
Stock examples are: The mother sees a mouse with the result that a
mouse-shaped birthmark occurs on the child; or she sees a crushed hand
and in consequence bears a child later with some of the bones of the hand
missing; the mother touches her body when frightened and thus marks the
unborn child on the corresponding part of the body; or she produces beauty
in the child by long contemplation of a picture of a beautiful child; and
so on almost endlessly. The favorite is usually the production of a red
birthmark or marks on the child's body by strong desire on the part of the
mother for strawberries, tomatoes, etc.--the fruit must be red since the
mark is red--or by fright from seeing a fire. As a matter of fact it is
not uncommon for the capillary blood vessels of the skin of a new-born
infant to remain dilated in spots instead of contracting as they normally
should do. The result is more or less of a red or "flame" spot. It is easy
to see, therefore, why such birthmarks are so frequently referred back by
the credulous mother to her desire for or fear of some red object.
An analysis of the case of a child shuddering at the sight of peaches is
of interest in this connection. The child showed the greatest aversion to
peaches, particularly to the fuzzy covering. The mother's explanation was
that peaches were unusually plentiful the year the child was born and that
she had worked hour after hour at peeling and canning peaches shortly
before his birth until she had become thoroughly sick of them. This
acquired aversion on her part she believed had been transferred to the
child. A few questions revealed the fact, however, that the mother,
herself, had never liked peaches and when asked if they were distasteful
to any other member of her own family she exclaimed, "Oh, yes, my mother
would shudder and shake if a peach were brought near her." And there we
have it. The idiosyncrasy was an inherited one as many similar
peculiarities are. The mental impression produced in the mother by her own
experience with peaches had nothing to do with its occurrence in the
child.
Very frequently also one encounters the mother who is sure she has
engendered musical ability in her child by constant practise and study of
music during pregnancy. The child is musical; what better evidence does
one want! It seems never to occur to such a mother that the child is
musically inclined because she herself is, as is evinced by her own desire
in the matter even if she is not a skillful performer.
When we take into account the extreme credulity of many people, the
unconscious tendency of mankind to give a dramatic interpretation to
events where causes are not certainly known, the hosts of coincidences
that occur in life, and the multitude of cases where something should
happen but nothing does, we are compelled to believe that the whole matter
of direct specific influence of the mother's mind on the developing fetus
is a myth. After seeing the conditions which prevail in Mendelism, for
example, it will take strong faith to believe that a mother with duplex
brown eyes can "think" or "will" blue eyes on her baby, yet this would be
a mild procedure compared to some we are asked to accept by believers in
the transmission of maternal impressions. Most of all, however, when we
recall the actual relation between the embryo and the mother--a narrow
umbilical cord is the sole means of communication between the two--the
physical impossibility of a connection between some particular mental
happening of the mother and a corresponding specific modification in the
fetus becomes evident. For there are no nerves in the umbilical cord, the
only path of communication between mother and fetus being the indirect one
by way of the blood stream. Even this method of communication is limited
inasmuch as the mother's blood does not circulate through the blood
vessels of the fetus. Gaseous and dissolved substances are merely
interchanged through the thin walls of the capillary blood vessels in the
placenta.
=Injurious Prenatal Influences.--=However, the denial that a particular
mental impression of the mother is associated with a particular structural
defect in a child does not carry with it the implication that prenatal
influences of all kinds are negligible factors. On the contrary any
deleterious effect which can reach the fetus through absorption from the
blood of the mother may be of grave consequence. There is not the least
doubt that malnutrition or serious ill-health on the part of the mother
often has a prejudicial effect on the unborn offspring. Severe shock or
grief, worry, nervous exhaustion, the influence of certain diseases,
poisons in the blood or tissues of the parent, such as lead, mercury,
phosphorus, alcohol and the like, may all act detrimentally, but they
operate either by rendering nutrition defective, by direct poisoning, or
by generating toxins in the blood of the parent which then poison the
fetus. Among the latter may be mentioned the toxic products of
tuberculosis and certain other bacterial diseases. Such factors operating
on the unborn young or even on the germ-cells may cause malformations,
arrests of development, instabilities of the nervous system, and general
physical or mental weakness. The effects are general, however, and not
specific.
To distinguish certain of these prenatal effects, particularly those of
certain diseases or poisons, from true hereditary influences they are
frequently spoken of as cases of _transmission_ rather than inheritance
from parents. Some writers use the technical term _blastophthoria_, or
false-heredity, extending the meaning so as to include also any damage
that might be inflicted on the germ-cells.
=Lead Poisoning.--=By way of illustration of how certain cumulative
poisons may act we may examine a tabulation of eighty-one cases of lead
poisoning as reported by Constantin Paul (Fig. 29, p. 164).
The table requires little comment. The disastrous effects of such
poisoning are apparent in every class of cases. The sixth class where the
husband alone was exposed to lead shows that the poison can operate
directly through the germ-cell. Other observers note that in the children
of workers in lead, there is a distressing frequency of feeble-mindedness
and epilepsy.
That lead poisoning operating through the germ-cells of the father can
affect the development of the young harmfully is well shown in Fig. 30, p.
165, which is a photograph of two young rabbits from the same litter The
white young one is from a normal albino mother mated to an albino father
which had received lead treatment. The pigmented young one is from the
same albino mother by a normal pigmented father. Although the white
father was considerably larger than the pigmented father, nevertheless the
young of the former, because of the harmful effects of the lead, is
distinctly smaller and less lively. A number of litters, each from the
same mother but in part from a lead-poisoned father and in part from a
normal father, have been secured. All show more or less the same results.
The experiments are still in progress in the department of experimental
breeding at the University of Wisconsin.
--------------------------------------------------------------------
|Number of cases.
| +----------------------------------------
| |Number of pregnancies.
| | +---------------------------------
| | |Abortions, premature labor, and
| | | stillbirths.
| | | +---------------------------
| | | |Infants born living.
| | | | +--------------------
| | | | |Remarks.
---------------------|-----|------|-----|------|--------------------
1. Mother showing | | | | |One infant died
symptoms of plubism | 4 | 15 | 13 | 2 | within 24 hours.
| | | | |
2. Mother working in | | | | |
type foundry, all | | | | |
of whose previous | | | | |
pregnancies had | | | | |Four of these died
been normal | 5 | 36 | 29 | 7 | in first year.
| | | | |
3. Mother who during | | | | |
period of work in | | | | |After ceasing to
type foundry had | | | | | work had
five pregnancies | 1 | 5 | 5 | 0 | healthy child.
| | | | |
4. Mother working | | | | |When away from
intermittently in | | | | | work for some
type foundry; | | | | | period of time
while working | | | | | gave birth to
there | 3 | 3 | 3 | 0 | healthy children.
| | | | |
5. Mother in whom | | | | |
blue line on gum | | | | |
the only sign of | | | | |
lead poisoning | 6 | 29 | 21 | 8 |
| | | | |Of these, eight died
6. Husband alone | | | | | in first year,
exposed to lead | ? | 32 | 12 | 20 | four in second,
| | | | | five in third.
--------------------------------------------------------------------
FIG. 29
Tabulation of eighty-one cases of lead poisoning recorded by Constantin
Paul (from Adami).
[Illustration: Fig. 30
Photograph of young rabbits from the same litter, the smaller one stunted
by lead-poisoning of its father (Courtesy of Professor L. J. Cole).]
=The Expectant Mother Should Have Rest.--=The mere matter of rest on the
part of the pregnant mother is, judging from the work of Pinard, a
Frenchman, and his pupils, an important one. In a number of detailed
investigations they have shown that rest on the part of the working mother
during the last three months before the child is born results in the
production of markedly larger and more robust children than those born of
mothers equally healthy but who have not had such rest. Moreover the
danger of premature birth is considerably lessened.
=Too Short Intervals Between Children.--=Too short an interval between
childbirths would also seem to be an infringement on the rights of the
child as well as of the mother. Thus Doctor R. J. Ewart ("The Influence of
Parental Age on Offspring," _Eugenic Review_, October, 1911) finds that
children born at intervals of less than two years after the birth of the
previous child still show at the age of six a notable deficiency in
height, weight and intelligence, when compared with the children born
after a longer interval, or even with first-born children.
=Our Duty to Safeguard Motherhood.--=Doubtless the unventilated factory
and tenement also do their share, even though we can give no exact
quantitative measure of it. Obviously, it becomes a civic duty to protect
as much as possible all members of our social system from such injurious
factors as have just been discussed. It is particularly necessary to
safeguard mothers before confinement, especially working mothers.
=Expectant Mothers Neglected.--=According to the claims of life insurance
men, expectant mothers are the most neglected members of our population.
Doctor Van Ingen, of New York City, estimates that ninety per cent. of
women in this country are wholly without prenatal care. Yet every
prospective mother should be taught the probable meaning of such symptoms
as headache, hemorrhages, swelling of the feet and disturbed vision. She
should realize the importance of submitting a sample of urine for analysis
at least once a month before childbirth and twice a month for a while
thereafter. She should be specially informed regarding work, exercise,
diet and dress. A recent government bulletin written by Mrs. Max West
which may be had free by writing to the Children's Bureau, Department of
Labor, Washington, D. C., gives much useful information on this subject.
ALCOHOLISM
=Unreliability of Much of the Data.--=One of the most important poisons
that plays a prominent part among ante-natal influences is alcohol. But
when it comes to a study of the problem of alcoholism from the standpoint
of heredity and parental influences we meet with many difficulties,
prominent among which are the inaccuracy and unreliability of many of the
statistics brought forward in this connection. Many of the results are
vitiated by the prejudices of propagandists who propose to make a case
either for or against alcohol as a beverage whether or not the facts
justify their conclusions. When one tries to view the matter with an open
mind he finds that there is a deplorable lack of statistics which are not
susceptible to more than one interpretation. However, using as much as
possible what seems to be unbiased data, the evidence is almost wholly
against alcohol as a beverage, at least to any immoderate extent.
=Alcohol a Germinal or Fetal Poison.--=The bad effects as far as offspring
are concerned reveal themselves in the main under the category of "false
heredity," i. e., germinal or fetal poisonings rather than of heritable
changes induced in the germ-cells. Most investigators feel that there are
too many criminal, imbecile, insane and unhealthy persons among the
offspring of drunkards to dismiss the matter as a coincidence. In an
investigation of Imbault, for example, we find recorded of one hundred
tuberculous children that while forty-one were of tuberculous parentage,
thirty-six per cent, were the offspring of inebriates. Furthermore Imbault
cites the observations of Arrivé on 1,506 cases of juvenile meningitis to
the effect that this malady is twice as frequent in the children of
alcoholic as in those of tuberculous parentage. It has been proved by
Nicloux (_L'Obstetrique_, Vol. 99, 1900) that in dogs and guinea-pigs
alcohol passes through the placenta and may be detected in fetal tissues;
hence it is in position to influence the fetus. He found that in a very
short time the amount of alcohol in the blood of the fetus about
paralleled that in the blood of the mother.
=Progressive Increase in Death-Rate of Offspring of Inebriate Women.--=In
an investigation on the effects of parental alcoholism on the offspring,
Sullivan (_Journal of Mental Science_, Vol. 45, 1899) gives some
important figures. To avoid other complications he chose female drunkards
in whom no other degenerative features were evident. He found that among
these the percentage of abortions, still-births and deaths of infants
before their third year was 55.8 per cent. as against 23.9 per cent. in
sober mothers. In answer to the objection that this high percentage may be
due merely to neglect, and not to impairment of the fetus by alcoholism,
he points out the fact based on the history of the successive births, that
there was a progressive increase in the death-rate of offspring in
proportion to the length of time the mother had been an inebriate, thus:
-------------------------------------------------------------
|No. of|Per cent.|Per cent. dying| Total
|cases |born dead| before 3 |percentage
-----------------|------|---------|---------------|----------
First births | 80 | 6.2 | 27.5 | 33.7
Second births | 80 | 11.2 | 40.8 | 50.0
Third births | 80 | 7.6 | 45.0 | 52.6
Fourth and fifth | 111 | 10.8 | 54.9 | 65.7
Sixth to tenth | 93 | 17.2 | 54.8 | 72.0
-------------------------------------------------------------
=Views of a Psychiatrist on Alcohol.--=Forel, who for years was the
psychiatrist at the head of a large insane asylum at Zurich, Switzerland,
has this to say about the effects of narcotic poisons and alcohol in
particular:
"The offspring tainted with alcoholic blastophthoria suffer various
bodily and physical anomalies, among which are dwarfism, rickets, a
predisposition to tuberculosis and epilepsy, moral idiocy, and idiocy
in general, a predisposition to crime and mental diseases, sexual
perversions, loss of suckling in women, and many other misfortunes."
In another passage he[6] remarks as follows:
"But what is of much greater importance is the fact that acute and
chronic alcoholic intoxication deteriorates the germinal protoplasm of
the procreators.... The recent researches of Bezzola seem to prove
that the old belief in the bad quality of children conceived during
drunkenness is not without foundation. Relying on the Swiss census of
1900, in which there figure nine thousand idiots, and after careful
examination of the bulletins concerning them, this author has proved
that there are two acute annual maximum periods for the conception of
idiots (calculated from nine months before birth); the periods of
carnival and vintage, when the people drink most. In the wine-growing
districts the maximum conception of idiots is enormous, while it is
almost nil at other periods. Moreover, these two maximum periods come
at the time of year when conception is at a minimum among the rest of
the population, the maximum of normal conceptions occurring at the
beginning of summer."
Another interpretation of Bezzola's results has been suggested to the
effect that the license of these periods enables the defective members of
the community, such as the feeble-minded, an opportunity of mating more
readily and that consequently the result is direct inheritance of idiocy
and allied defects instead of idiocy produced through alcoholic poisoning
of the parental germ-cell.
=Other Views.--=There are indeed many competent investigators who believe
that alcoholism in parents has little or no part in the direct production
of mental defects in children. For instance, Tredgold quotes Doctor
Ireland's observations that although at New Year, when the fishermen
return, the whole population of certain villages in Scotland gets drunk,
there is no noticeable excess of defectives born nine months later, and
remarks further that, "I have histories of idiots conceived under such
circumstances, but so I have of normal children, and my opinion is, that
while this may be a cause in some cases, the number of instances in this
country at any rate is exceedingly small." Again, Goddard, one of our best
known American students of feeble-mindedness, who has made careful study
of this point under especially favorable conditions, feels that his data
do not prove that alcoholism of either the father or the mother causes
feeble-mindedness in the child. He concludes, "Everything seems to
indicate that alcoholism itself is only a symptom; that it for the most
part occurs in families where there is some form of neurotic taint,
especially feeble-mindedness." Goddard, however, in common with many other
observers, notes that miscarriages and deaths in infancy are far higher
among inebriates than among abstainers.
Doctor Mjöen cites an interesting parallel between the increase of
feeble-mindedness in Norway and a period from 1816 to 1835, when every one
was permitted to distil brandy. In some districts many of the farmers
distilled brandy from corn and potatoes, and in such regions during this
period feeble-mindedness increased nearly one hundred per cent. Later the
home distillation of brandy was stopped. According to Doctor Mjöen, "The
enormous increase in idiots came and went with the brandy." He is
inclined to believe, however, that the alcohol operated injuriously mainly
on stocks already defective.
=The Affinity of Alcohol for Germinal Tissue.--=Nicloux and Renault have
shown that alcohol has a decided affinity for the reproductive glands. In
individuals who have recently taken alcohol the proportion of alcohol in
the gonads is soon almost equal to the amount found in the blood. Thus in
experiments on mammals it was found that the proportion of alcohol in the
ovary to that in the blood was as three to five, and in the testis as two
to three. This would afford abundant opportunity for alcohol to act
directly on the spermatozoon or the ovum.
A number of different investigators concur in finding that the germ-glands
of the male human inebriate in many cases show more or less atrophy and
other degenerative changes. In guinea-pigs which have been repeatedly
intoxicated with alcohol, Stockard found that while he could detect no
visible abnormality in the gonad, nevertheless their defective and
weakened progeny showed that the germ-cells had been affected.
=Innate Degeneracy Versus the Effects of Alcohol.--=Many observations on
human beings have been brought forward which at first sight seem to
indicate that noticeable defects, particularly mental and nervous, occur
with appalling frequency in children resulting from conception during
intoxication, although, unfortunately, the evidence is rarely clear as to
whether the defects are really due to the effects of the alcohol or to the
fact that the parent or parents were degenerate to begin with.
A very interesting human case cited by Forel on the authority of
Schweighofer is that of a normal woman who had three sound children when
married to a normal man. After the death of this husband she married an
inebriate by whom she had three other children. One of these suffered from
infantilism, one turned out to be a drunkard, and the third became a
social degenerate and drunkard. Moreover the first two contracted
tuberculosis, although hitherto the family stock had been free from this
malady. Ultimately the woman married again and by this third husband, who
was normal, she again had sound children. Similar cases might be cited,
as, for example, a record of eighty-three epileptics, of whom sixty had
drunken parents, but it can be urged against all of them, of course, that
the defective offspring were due to an innate degeneracy of the drunken
parent which made him a drunkard rather than to the effects of the alcohol
he took. While one is skeptical as to the validity of this objection in
all of the many cases which occur with such monotonous frequency in man,
there is no way of escaping such an interpretation with the evidence at
hand. It must be admitted, moreover, that there are many families with one
or both parents alcoholic in which the children are not mentally
defective.
=Experimental Alcoholism in Lower Animals.--=Many of the objections that
exist in the case of man, however, do not apply in that of lower animals.
If normal animals are experimentally alcoholized and are shown to produce
defective offspring under such conditions, then in their cases at least,
the disorders in the offspring must be due to the effects of alcohol and
not to an innately degenerate condition of the parent. Disorders similar
to some of those seen in the children of alcoholics do actually result in
alcoholized animals of one kind or another.
Against the earlier experiments on animals it has been urged that too few
individuals were used to give conclusive results, but this objection can
not be brought against the recent experiments of Stockard. While he has
published accounts of his work in various scientific periodicals lately,
the reader will find a full statement of his own experiments, together
with a review of the whole subject of experimental alcoholism in animals
and the effects on progeny in _The American Naturalist_, Vol. XLVII,
November, 1913, together with a useful bibliography.
Before taking up Stockard's results we may select a few of the more
significant experiments made earlier by other investigators.
Laitinen alcoholized rabbits and guinea-pigs. He found that the treated
individuals had more still-born young than the control, and also that
growth of the living young was retarded. His alcoholized rabbits and
guinea-pigs produced more young than did the normal individuals used as a
control. Laitinen's studies on man, together with three other studies of
the Eugenics Laboratory in London, show that in man also more children are
born to alcoholics than to normal parents. Goddard's investigations in
America corroborate this fact.
Ceni found that only 43 per cent. of the eggs from alcoholized fowls
developed normally, as against 77 per cent. of normal development in the
controls. Moreover the eggs of alcoholic fowls were shown to be less
resistant to adverse conditions than normal eggs from the fact that
fluctuations of temperature at the beginning of incubation kept all the
alcoholic eggs from developing perfectly, while 27 per cent. of the
control eggs developed normally under the same adverse circumstances.
Hodge made a pair of dogs alcoholic. Of 23 pups obtained from the pair, 8
were deformed and 9 were dead; 4 alone were viable. From a control pair of
dogs 45 pups were obtained, of which 4 were deformed, none were born dead,
and 41 were viable.
=Stockard's Experiments on Guinea-Pigs.--=Stockard's experiments
demonstrate that the offspring of mammals may be injured or modified in
their development by treating either parent repeatedly with alcohol. The
guinea-pigs used in the experiment were all first tested by normal matings
and found to yield normal offspring. The alcohol was given to them by
inhalation. It was found to be readily taken into the animals' blood and
to produce intoxication. While guinea-pigs alcoholized in this way as
often as six times a week for two and one-half years would maintain their
own bodily vigor and health apparently, the deleterious effects on their
progeny were marked. The defects were general rather than specific,
although the central nervous system and special sense organs were
apparently affected most.
Out of 119 total young produced by the alcoholic animals, only 52, or less
than 44 per cent., survived, whereas out of 64 young produced from normal
parents used as a control for the experiment, 56, or over 87 per cent.,
survived. In some cases alcoholic males were mated with normal females, in
other, alcoholic females with normal males. In still other instances both
parents were alcoholic.
The results are summarized in the accompanying table (Fig. 31), taken from
Stockard's paper:
CONDITION OF THE OFFSPRING FROM GUINEA-PIGS TREATED WITH ALCOHOL
-----------------------------------------------------------------
|Number of Matings
| +--------------------------------------
| |Negative Result or Early Abortion
| | +---------------------------------
| | |Stillborn Litters
| | | +----------------------------
| | | |Number Stillborn Young
| | | | +---------------------
| | | | |Living Litters
| | | | | +----------------
| | | | | |Young Dying Soon
| | | | | | After Birth
| | | | | | +---------
Condition of | | | | | | |Surviving
the Animals | | | | | | | Young
--------------------|-----|----|----|------|----|------|---------
Alcoholic [male] by | | | | | | |
normal [female] | 59 | 25 | 8 | 15 | 26 | 21 | 33
Normal [male] by | | | | | | |
alcoholic [female]| 15 | 3 | 3 | 9 | 9 | 9 | 10
Alcoholic [male] by | | | | | | |
alcoholic [female]| 29 | 15 | 3 | 6 | 11 | 7 | 9
SUMMARY | 103 | 43 | 14 | 30 | 46 | 37 | 52
Normal [male] by | | | | | | |
normal [female] | 35 | 2 | 1 | 4 | 32 | 4 | 56
2d generation | | | | | | |
by normal | 3 | 0 | 0 | 0 | 3 | 0 | 4
2d generation | | | | | | |
by alcoholic | 3 | 0 | 2 | 5 | 1 | 0 | 2
| | | |1 def.| | |
2d generation | | | | | | |
by 2d generation | 19 | 7 | 0 | 0 | 12 | 6 | 13
| | | | | |1 def.|
Female treated | | | | | | |
during pregnancy | 4 | 0 | 0 | 0 | 4 | 1 | 7
-----------------------------------------------------------------
FIG. 31
Table showing condition of the offspring from guinea-pigs treated with
alcohol (after Stockard).
Lines four and five give a comparison between the 103 total matings of all
treated individuals and 35 normal matings. In the first case almost 42 per
cent. of the matings gave negative results or early abortions, whereas in
the normal control matings, failure to yield a full-term litter occurred
in only two cases. The 103 matings of alcoholic animals gave only 46
living litters, or about 45 per cent. On the other hand the 35 control
matings produced 32 living litters, or 91-1/2 per cent. It will be
observed also that from such of the 103 matings of alcoholics as produced
young there were 30 still-born, 37 which died soon after birth, and only
52 surviving young, whereas from the 35 matings of normal individuals
there were only 4 still-born young, 4 which died soon after birth, and 56
surviving young.
The bottom line of the table, although, as Stockard points out, containing
too few cases to prove wholly convincing, indicates that alcoholizing
erstwhile normal females during pregnancy was not particularly harmful to
the embryos _in utero_.
Some of the most interesting results were obtained when offspring termed
second generation animals, derived from alcoholic parents though not
themselves treated with alcohol, were mated in various ways. When such
individuals were mated with normal individuals, although the litters were
small, the results were normal, the normal mate having seemingly
counteracted any defects which might have lurked in the second generation
animal. On the other hand, out of three matings of second generation
animals with alcoholic individuals, two produced still-born young, of
which one was markedly deformed, while the third yielded two living young.
However, the most striking results were obtained when two second
generation individuals, the offspring of alcoholic parents, were bred
together. Although themselves untreated, these individuals, of which 19
matings were made, produced as many or more defective young than did their
alcoholic parents. Seven of the matings were unfruitful. The remaining 12
matings gave living litters consisting of 19 individuals in all. Six of
these showed various nerve disorders (spasms, epileptic-like seizures,
etc.) soon after birth; one was eyeless and otherwise deformed.
=Stockard's Interpretation.--=Stockard's interpretation of his experiments
is as follows: "Mammals treated with injurious substances, such as
alcohol, ether, lead, etc., suffer from the treatments by having the
tissues of their bodies injured. When the reproductive glands and
germ-cells become injured in this way they give rise to offspring showing
weak and degenerative conditions of a general nature, and every cell of
these offspring having been derived from the injured egg or sperm-cell are
necessarily similarly injured and can only give rise to other injured
cells and thus the next generation of offspring are equally weak and
injured and so on. The only hope for such a line of individuals is that it
can be crossed by normal stock, in which case the vigor of the normal
germ-cell in the combination may counteract, or at any rate reduce, the
extent of injury in the body cells of the resulting animal."
He also believes that various deformities and developmental arrests such
as harelip and cleft-palate may similarly be cases of transmission rather
than true inheritance, due to the weakening of the germ-cells in some way,
or to some lack of full vigor in the uterine environment.
=Further Remarks on the Situation in Man.--=Returning now to the question
of alcoholism in man, it seems in view of the strong circumstantial
evidence in the case of man himself, together with the result of
experiments on animals, that little doubt remains that excessive
alcoholism might result in the production of defective offspring. On the
other hand an antecedent degeneracy or neural instability undoubtedly
plays an important part in many cases, in the original production of
drunkards, and when such occurs, it, as well as the direct effects of
alcoholic poisoning, must be reckoned with in the effects on progeny.
Studies carried on by Pearson, Elderton and Barrington of the Eugenic
Laboratory in London lead these investigators to the conclusion that
extreme alcoholism is a _result_ not a _cause_ of degeneracy. That is, the
degeneracy is due to the defective stock, not to alcohol. They cite in
evidence their records of four thousand school children of alcoholic and
of sober parents, which fail to show any unfavorable effect of alcohol on
offspring. Some of their critics, however, maintain that they did not
choose subjects who were sufficiently alcoholic to give the injurious
results that might legitimately be expected among the offspring of
excessive drinkers or habitual drunkards.
Where children show a hereditary inclination toward drink, unquestionably
one of the strongest factors is the inheritance of the same disposition,
the same unstable nervous constitution and its accompanying lack of
self-control which led the parent to drink, rather than the inheritance of
the effects of the drink on the parent. For in many cases a parent may not
become a drunkard until after the children who also become drunkards are
born. That the tendency to drink immoderately is frequently due to a
strain of feeble-mindedness or epilepsy becomes more evident every day.
In many of the so-called "periodical" drunkards, the accompanying features
of their periodic attacks of drink-craving, such as clouding of memory,
restlessness and depression, are those commonly associated with ordinary
epileptic attacks.
=Probably Over Fifty Per Cent. of Inebriety in Man Due to Defective
Nervous Constitution.--=Branthwaite, an English authority on drunkenness,
finds that about sixty-three per cent. of the inebriates who come to his
notice are mentally defective. In alcoholic insanities heredity is a
potent factor. It is coming to be realized more and more that pronounced
alcoholism is due in a large percentage of cases, perhaps over half, to a
defective nervous make-up. While it is true that many drunkards would not
develop without free access to alcohol, on the other hand many would never
develop without a bad heredity back of them, which gives them a peculiar
nervous constitution that renders alcohol an undue stimulus. In a recent
report of the New York State Hospital Commission it is stated that in
fifty-four per cent. of the cases of alcoholic insanity, a family history
of insanity, epilepsy or nervous disease exists. Thus in the presence of
alcohol most of these unfortunates are helpless pawns of a hereditary
weakness.
So when the question of alcoholism is viewed from all angles, the children
of the human drunkard would seem to run a double menace of misfortune,
since they may be subject both to the direct poisoning effects of alcohol
and the results of an inheritable degeneracy.
=Factors to Be Reckoned With in the Study of Alcoholism.--=In any
thoroughgoing study of alcoholism in man many factors will have to be
reckoned with. First of all there is the question of inherent lack of
control. This is probably the principal thing inherited where heredity
truly enters as a factor. That example and social environment are
important factors in addition to or in place of heredity is clear, too,
when we observe that often it is the boys only who take after a drunken
father, for there is no evidence that the inherited tendency when it
really exists is at all sex-linked. Again, in certain occupations carried
on under unwholesome influences relief is frequently sought in alcoholic
stimulants, and such custom may easily crystallize into habit.
Furthermore, the accustoming young children to doses of alcohol, or the
unborn young to alcohol through the body of a drunken mother, may be
strongly contributory toward establishing inebriety in certain cases. As
we have seen from an abundance of experimental data on animals, moreover,
the nurture effects on germ-cells may result in the production of weakened
offspring. Such offspring in the case of man are probably less able to
withstand temptations of all kinds and hence readily succumb to the
habit-forming effects of alcohol if once its use is begun. Lastly, it must
not be forgotten that alcoholism in the father usually means poverty and
the subsequent accompaniment of malnutrition and neglect of the children,
and this in itself may not only account for poor development of the
latter, but may also be strongly contributory toward establishing the
habit of alcoholism in them.
An inherent bias plus most of the other conditions just enumerated is the
not unusual lot of the offspring of drunkards.
=Venereal Diseases.--=There is yet another very considerable class of
maritally unfit who in any conscientious discussion of unfitness for
marriage or of racial improvement must be considered. I refer to those who
are afflicted with the diseases which are inseparably associated with the
so-called "social evil." To _gonorrhea_, one of the most prevalent of
these diseases, more than one-fourth of our total one hundred and ten
thousand blind in the United States are said to owe their affliction.
Milder types of eye disease may also result from such infections. As much
as eighty per cent., or some say practically all blindness in children
born blind is caused by it, the infection occurring at the time of birth
or within a few days thereafter. The terrible consequences of this disease
to the innocent wife would alone make its discussion imperative.
=The Seriousness of the Situation.--=Unfortunately the insidious nature of
gonorrheal infections is unknown to most persons. A cure is apparently
effected, yet as a matter of fact the germs may live for years and, if in
the male, later be transmitted to the wife, subjecting her to a future of
invalidism and misery. Reliable statistics from various medical
authorities reveal the appalling fact that seventy-five per cent. or more
of the surgical operations for inflammatory pelvic disorders peculiar to
women, such as pus tubes and peritonitis, are attributable to this
disease, as is also the involuntary sterility of forty-five per cent. of
childless women. Unwelcome as the fact is there is an abundance of
evidence to show that a large percentage of men in particular have at
some period of their life been infected with venereal disease. Of our
fourteen million males in the United States under the age of thirty we
find estimates by some specialists in venereal diseases to the effect that
five million of them, that is, one out of three, suffer from some one of
the social diseases or their consequences. Doctor Hugh Cabot, one of the
chief surgeons of the Massachusetts General Hospital at Boston, a member
of the faculty of the Harvard Medical School and president of the American
Association of Genito-Urinary Surgeons, has this to say about the
situation: "We have of late years heard much about the frequency and
serious consequences of tuberculosis; it has been dubbed the 'white
plague,' and so active has been the campaign that a wide-spread
understanding of this serious disease has resulted. It may safely be
averred that in the urban population at least there are two, and perhaps
three, individuals with syphilis to every one with tuberculosis. The
frequency of gonococcus infection is much higher." He believes that over
half the male population acquire a gonococcus infection at some period of
their career. While as a layman, one can not but feel that a specialist's
estimate may run unduly high because of the fact that he is encountering
an inordinate proportion of such maladies every day, still such
specialists are in position to get at the truth as no other person can and
their calculations are probably not grossly in error. In any event any one
who has progressed in worldly knowledge beyond the naïveté of a child must
recognize the appalling prevalence of these maladies.
=Infantile Blindness.--=So serious has the matter of infantile blindness
become that some state boards of health and some city health departments
supply all physicians and midwives with specially prepared packages
containing cotton and nitrate of silver solution for preventive or
curative treatment of the eyes of all new-born children. At the time of
the first bath each eye is carefully washed with a separate pledget of
cotton saturated with boric acid solution. Each then receives a drop of
the silver solution, which is made just strong enough to kill any
gonococci that might be present without itself inflaming the eye. Water
used in bathing the baby's body of course is not allowed to come in
contact with its eyes. Such treatment should be given every child no
matter how unsuspicious the circumstances may be. German authorities who
have been following this method now for some years assure us that
nineteen-twentieths of the blindness of infancy can thus be prevented.
=Syphilis.--=As to _syphilis_, another and even more terrible of these
diseases, we have before us the absurd fact that while thousands upon
thousands of dollars are being spent to establish a rigid inspection and
preventive measures against the spread of a very similar disease in the
horse, this malady in man is allowed to pass unchallenged and we are
confronted by the gruesome certainty that there are hundreds of these
diseased persons about us to-day who, on their mere affirmation that they
are unmarried and of age, will be given the right to marry and thus
produce families of infected children irrevocably doomed to early death or
to lifelong misery.
While syphilis is most commonly spread through relations between the
sexes, it may be acquired in various other ways, as for example, through a
cut in shaving with the same razor an infected individual has used. It is
commonly transmitted from parent to child. Practically every prostitute is
a center of dissemination. Katherine Bement Davis has shown in her studies
made at the New York State Reformatory for Women that while ordinary
clinical tests show that apparently only twenty-one per cent. of these
women are infected with venereal disease, more careful laboratory tests
showed at least ninety per cent. to be infected.
Syphilis is caused by _Treponema pallidum_, a small unicellular animal
parasite. Given access to the blood by any means whatever, possibly even
through an abrasion in the lip by means of a kiss, it multiplies rapidly
and any part or organ of the body may be attacked. Usually a small sore
occurs at the point of entrance to the body, but often it heals up readily
with little indication of the seriousness of the infection.
The development of the malady is insidious and long continued. As a matter
of clinical convenience physicians divide its progress into successive
stages although in reality the transitions are frequently variable and ill
marked. The symptoms that arise within the first few months or even years
are readily controlled by appropriate treatment, but to insure a cure
prolonged and most thoroughgoing treatment is imperative. The symptoms
disappear so completely after a short period of treatment that it is very
difficult to persuade the average patient that he is not yet cured. Two
years at least are none too short a period of treatment, yet the majority
of patients, fully convinced that they are merely being exploited by the
physician as a source of revenue, drift away at the end of a few months.
As a matter of fact, however, the germs usually persist long after the
obvious symptoms of the disease have disappeared, and in consequence many
of the most serious results of syphilis may not manifest themselves for a
period of perhaps ten, twenty or thirty years.
=Some of the Effects.--=It is now known that _paresis_, also termed
general paralysis or softening of the brain, is probably invariably due to
syphilis. The work of Flexner and Noguchi on _paresis_ and _tabes
dorsalis_ show that always in such afflictions the tissues of the central
nervous system have been invaded by the parasite. The original infection,
however, may have occurred so long before as to have been almost forgotten
by the patient. Thus many an apparently robust man is stricken down in the
prime of life. Earlier and prolonged treatment would in all probability
have eradicated the germs and thus prevented the mental breakdown, which
can not be cured by any known treatment. Postmortem examination always
shows that the _Treponema_ has wrought wide-spread damage in the brain.
The frequency of paresis may be realized when one learns that in some
regions it is responsible for about one-fifth of all cases of insanity
sent to hospitals for the insane. It ranks next to the highest as a cause
of insanity. Statistics show that in the state of New York more deaths
result annually from paresis than from smallpox, tetanus, malaria,
dysentery and rabies all combined.
In some cases the disease attacks the membranes of the brain and the small
blood vessels giving rise to a still different type of mental disorder.
Practically all patients with _locomotor ataxia_ owe their condition to an
antecedent syphilis. Moreover it is one of the important causes of
_arterio-sclerosis_, or hardening of the blood vessels, and is also a
prominent factor in certain forms of heart-disease, as well as by no means
an unimportant cause of blindness in children.
As to specific cases of the effects of this disease on descendants the
literature of the subject is crowded full. While it is needless to conduct
the reader through a chamber of horrors by reviewing clinical cases, it is
desirable to point out in a general way some of the effects. Doctor George
H. Kirby, director of Clinical Psychiatry, Manhattan State Hospital, says:
"We find that when either the father or the mother suffers from
paresis that many other members of the family may be infected with
syphilis, and furthermore, we find that a large number of children in
these families are feeble-minded, nervous, or in other ways abnormal.
Doctor Plant examined a group of 100 children, the offspring of cases
of paresis, and found that 45 per cent. were plainly damaged mentally
or physically, or in both fields; the blood test showed that one-third
of these 100 children had the syphilitic poison in their systems.
"Another investigator found in a group of 139 children, the
descendants of parents who had syphilitic nervous disease, that over
25 per cent. were definitely feeble-minded or affected with some
serious nervous disorders.
"Other studies indicate that there exists a close relation between
syphilis and many of the hitherto unexplained cases of
feeble-mindedness, including idiocy, imbecility, infantile paralysis,
and some forms of epilepsy. While the question is not yet settled, it
appears that syphilis is the real cause of many of these cases of
mental defect in children."
Still other investigators give details of physical afflictions and
distortions, of suppressed development, of inordinate percentages of
stillbirths--perhaps the most merciful lot for the little victims--but
sufficient has been said to indicate the full horror of the situation.
Goddard,[7] although not minimizing the terrible nature of the disease,
finds little evidence in his studies that syphilis in parents is a
specific cause of feeble-mindedness.
=A Blood Test.--=Fortunately a delicate blood test known as the Wasserman
test has been discovered by means of which, through an examination of a
few drops of blood, any trace of syphilitic poison which exists in the
body may usually be detected. This is true even though the individual may
at the time show no visible symptoms of syphilis. The test is therefore of
great value in detecting the latent germs of syphilis in individuals who
have apparently been cured, and also often in making an early diagnosis of
paresis. The Wasserman test, however, is reliable only in the hands of a
skilled operator. It may occasionally give a positive reaction when
syphilis does not exist and on the contrary a negative when it is present.
The _luetin_ test is also now applied by some specialists, but is too new
a test to have come into general use. It works on the same principle as
the tuberculin test for tuberculosis. Some army physicians now also give
what is termed a provocative Wasserman. That is, in a suspicious case
which gives only negative results by an ordinary Wasserman, they can get,
if syphilis really exists, a positive reaction after giving small doses of
potassium iodide or salvarsan.
It should be well understood by every one that syphilis is usually curable
provided the patient is given modern scientific treatment by a _competent_
physician. I emphasize competent because there are so many quacks in this
field that one undergoing treatment can not be too careful in assuring
himself of the competency of the physician. In even a case of long
standing, where the symptoms have been in abeyance for a number of years,
the disease can be cured provided it has not developed into an active
cerebro-spinal type, and even the latter can be much benefited by proper
treatment. The great danger of the cerebro-spinal type is that it will
result in paresis or locomotor ataxia.
As long as the blood of a patient shows a _positive_ Wasserman reaction,
marriage should certainly not be consummated. If after a proper course of
treatment by a well-informed physician, the patient shows a _negative_
Wasserman when tested by a competent examiner, he probably would not
infect his wife or offspring, although prudence would require that he wait
at least six months or a year before marriage, and marrying then only if
later tests remain negative.
The only way for a patient to be sure that he is not harboring the
cerebro-spinal form would be to have a spinal puncture made and the
cerebro-spinal fluid examined. While the cerebro-spinal phase often does
not occur until long after the primary infection, cases are known in which
it has appeared within a few weeks. Evidence that the central nervous
system is frequently invaded early in the course of the disease is
increasing. Marriage of an individual suffering from the cerebro-spinal
form should not take place, since such a one is almost sure to become a
burden on the family or the state.
=Many Syphilitics Are Married.--=It may seem to some that in a treatise on
being well-born the subject of syphilis might be ignored as not being
especially pertinent, but the supposition that no considerable percentage
of syphilitics marry is not borne out by the facts. Seventy-five per cent.
of men with insanity due to syphilis who are admitted to hospitals are
married. The insanity in such cases is mainly the result of infections in
earlier years, often long before marriage. While syphilis, strictly
speaking, is not inherited, that is, does not become part and parcel of
the germ-plasm, still the frequency of its direct transmission to
offspring is so appalling that the outcome, as far as the immediate child
is concerned, is quite as disastrous as the most thoroughgoing real
inheritance could be.
=Why Permit Conditions to Continue as They Are?--=When one faces the
easily ascertained facts regarding venereal disease, it seems incredible
that we, an intelligent people, can go on complacently handing our
daughters and sisters over to the surgeon's knife and a life of personal
misery, and even in not a few instances to become mothers of incurably
defective children, yet the dire fact confronts us that we do. We can no
longer excuse ourselves on the plea of ignorance, for the grisly record
may now be read in many medical and not a few popular treatises, and we
find the theme entering even into the modern drama, as witness Brieux's
_Damaged Goods_. Further indifference to these conditions can only be
attributed to culpable apathy or prudery.
The extreme dangers to which parents are subjecting their daughters if
they do not demand a clean bill of health on the part of their prospective
husbands are obvious. Fathers and mothers perfectly willing to inquire
into their future son-in-law's social connections, his income, securities,
or business chances become strangely "modest" when it comes to determining
whether he is physically fit for marriage.
One great cause of ignorance in the past was the prudish taboo against
frank discussions of venereal diseases which has thrown the veil of
silence about the subject. To-day, however, it is coming to be recognized
that these maladies are diseases and not a standard of social propriety,
and that like most other diseases the surest way to secure prevention and
gradual eradication is through the enlightenment of the public. They are
prevalent in all classes of society. Moreover, it must not be forgotten
that there is no form of venereal disease which may not be innocently
acquired. Even where acquired through transgression of moral law an
ignorant attitude toward the sexual instinct is often at the bottom of the
difficulty.
=Medical Inspection Before Marriage.--=Ante-nuptial medical inspection is
certainly as necessary to the welfare of society as the certification of
age and of the single state now required by law. No one objects to a
medical examination pertaining to venereal and other diseases when it
comes to taking out a life insurance policy, and why there should be any
more objection to it as a preliminary to marriage is a mystery. A few
states already have compulsory ante-nuptial medical inspection. The laws
have been enacted too recently to judge adequately of their working. There
has been much debate in Wisconsin as to whether their law (Chapter 738,
Laws of 1913), which went into effect January 1, 1914, is constitutional
and whether it requires a Wasserman test. The Wisconsin law applies to
males only. The Supreme Court of the state has declared it constitutional
and that its requirement of "the application of the recognized clinical
and laboratory tests of scientific search" involves only such examination
as the ordinary licensed physician is equipped to make and can reasonably
be expected to make for three dollars, the maximum fee specified in the
law.
A number of the physicians of the state are still dissatisfied with the
wording, although most do not oppose the principle of the law. Many
believe that it should apply to the women as well as to the men, and
others feel that the law should be extended to cover still other kinds of
marital unfitness. Most of the practitioners with whom I have discussed
the matter appreciate the motive underlying the law and are endeavoring to
make it successful.
The general public of the state as a whole seems to be in favor of the
provision. At least one hears much favorable comment and little
dissension among those who understand its purpose. The very controversy
over it which sprang up after its passage proved to be of great benefit in
the education of the public regarding the necessity of such measures. Such
physicians as I have been able to question report that the candidates for
marriage rarely object to the requirement, but on the contrary strongly
favor it. Especially where they have suffered from venereal disease
earlier in life most are eager to know their condition and to have medical
advice. To my own mind this last fact is the most significant of all, as
it will give every candidate for marriage a chance to know the truth. Most
men are not so much brutal or vicious as ignorant in such matters. The
vast majority of those unfit for marriage as a consequence of venereal
disease will, when they realize the danger their condition imposes on wife
and children, take every possible means to put themselves into proper
condition.
Desirable as the Wasserman test may be, it requires special laboratory
facilities and equipment as well as a specially trained examiner to make
it a reliable test. Moreover it can not be given by the general
practitioner for the very moderate fee that must obtain in a pre-nuptial
examination compelled by law. If it or the serum test for gonorrhea are to
be applied then the legislative body of the state will find it necessary
to establish a special public laboratory or laboratories for their
application. This, however, is not a matter of particular difficulty and
would be capital well invested in any state.
=The Perils of Venereal Disease Must Be Prevented at Any Cost.--=However,
no matter what the cost may be to the state, no matter what the exaction
from the individual, the grave perils of venereal disease to society
_must_ be prevented. We owe it to the cause of humanity that there be
fewer victims born into a world of eternal night, that from a parentage of
polluted blood there spring no longer hosts of children with feeble
misshapen bodies or with tarnished intellects, death-marked at the door of
life.
=Bad Environment Can Wreck Good Germ-Plasm.--=In conclusion it is evident
from our discussion of prenatal influences that not all of being well-born
is concerned with heredity in its proper sense, since the unborn young may
be influenced either directly or indirectly by environmental conditions
which are in no sense products of heredity, although as far as the
immediate child is concerned the result may be quite as disastrous where
the influence is a baneful one. As to the production of beneficial
prenatal effects, while parents can do nothing toward modifying favorably
such qualities as are predetermined in their germ-plasm, nevertheless they
must come to realize that bad environment can wreck good germ-plasm. They
can see to it that they keep themselves in good physical condition by
wholesome temperate living, and thereby insure as far as possible healthy
germ-cells for the conception and good nutrition for the sustenance of
their progeny. Their one sacred obligation to the immortal germ-plasm of
which they are the trustees is to see that they hand it on with its
maximal possibilities undimmed by innutrition, poisons or vice.
CHAPTER VII
RESPONSIBILITY FOR CONDUCT
Since both physical and mental attributes are unquestionably inherited, it
becomes a matter of importance to inquire into the nature of the entity we
call personality. To what extent is human conduct a product of parentage?
Although apparently free agents are we in reality only by infinitely
subtle indirections making the responses, forming the habits, establishing
the characters which result merely from the blind impulsions of an
inherent constitution? If so, who is praiseworthy, who blameworthy? Are
men
"But helpless pieces of the Game He plays
Upon this chequer-board of Nights and Days."
=All Mental Process Accompanied by Neural Process.--=Whatever the ultimate
decision of psychologists may be regarding the relation of mind to the
sensory and nervous mechanism of man it is certain that there is so close
an association between them that the least alteration in the mechanism
means a parallel effect in the mind, or in the words of Huxley, "every
psychosis is definitely correlated with a neurosis." The rind or _cortex_
of gray matter which constitutes the surface of the large cerebral
hemispheres of the human brain is regarded as the seat of consciousness.
The development of the mental powers in the infant is dependent on the
development of the elements of this cortical substance and the waning of
the mental faculties in old age goes hand in hand with its atrophy.
Abnormal arrangements, injuries or omissions in it mean mental
unsoundness. How the activity of the structural mechanism gives a reaction
in consciousness is not understood, but we know that in the living being
the two phenomena are inseparably linked. Whether we accept the hypothesis
that consciousness is an actual product of the structural mechanism or the
hypothesis that the latter is only an instrument for the manifestations as
consciousness of an outside force or entity, just as the telegraphic
instrument manifests the existence of electricity, is neither here nor
there for our purposes. On either supposition the degree and manner of
expression are determined by the structure of the mechanism. Our main
problem is to decide as nearly as possible how much of the mechanism is
rigidly inherited, how much is at birth largely undestined, so that its
ultimate outcome is in part a product of the forces which play upon it, or
in other words of education and training.
=Gradation in Nervous Response from Lower Organisms to Man.--=To
comprehend fully the basic nature of human neural responses one must seek
the roots in the behavior of lower organisms. For there is found in a
simpler form many of the fundamental activities and the first dim gropings
which emerge in man as memory, reason and will. As we ascend the scale of
animal life we find a continuous advance in neural complexity and nervous
response that in many respects grades up closely to the human type.
A windmill or a weather-vane points toward the source of the wind,
obviously not because either exercises any special choice in the matter,
but because it is constructed on such lines of symmetry that when the wind
strikes it, if it slants the slightest to left or right, the more exposed
surface receives the greatest pressure and thus swings the body back into
the line of least resistance.
=Behavior of Many Animals Often an Automatic Adjustment to Simple External
Agents.--=It is a far cry, of course, from the responses of such a machine
as a windmill to the responses of even the simplest living thing, but in
spite of the broad gap between the two, there is much reason to believe
that the behavior of many living organisms is due in a marked degree to
the directive effects of comparatively simple external factors rather than
to the complex internal volitions the casual observer is likely to
attribute to them.
=Tropisms.--=It is a marked characteristic of all living protoplasm that
it has the power of responding to external stimuli. This power of response
is termed _excitability_ or _irritability_. In describing the motor
responses of living organisms to stimuli resulting from a change in
surroundings the term _tropism_ (Gr. _Trope_, turning) is frequently used
and the kind of stimulus is indicated by a prefix. Thus the term
phototropism means a turning or _orientation_ brought about by means of
light. An organism which reacts by a movement toward the source of light
is said to be _positively phototropic_, one which moves away from it,
_negatively phototropic_. By using such a neutral terminology the
physiologist avoids implying that necessarily "likes" or "dislikes" or any
other psychic reaction enter into the movements.
Several kinds of tropisms are recognized, such as _phototropism_ or
_heliotropism_, reaction to light; _thermotropism_, reaction to heat;
_electrotropism_ or _galvanotropism_, to electric current; _geotropism_,
to gravity; _chemotropism_, to a chemical; _rheotropism_, to current;
_thigmotropism_ or _stereotropism_, to contact; and _chromotropism_, to
color.
=Many Animals Show Tropic Responses.--=Many of the lower animals seem to
have their movements determined more or less mechanically by the action of
such external factors, some being positively, others negatively responsive
to a given kind of stimulus, or the same individual may be at one time
positive, at another negative, according to modifying conditions to be
mentioned presently.
In plants and in simpler lower animals there is no special nervous system.
The responses of these organisms depend on the general irritability of
their constituent protoplasm. In other animals a nervous system is
developed, crude and diffuse in lower forms, extremely delicate, complex
and definitely ordered in higher forms. But it should be borne in mind
that nerve protoplasm possesses only in high degree a capacity for
irritability, conduction, etc., that is common to all living substance. In
keeping with other "physiological divisions of labor" or specialization
which mark the increasing complexity of animals, this enormously enhanced
sensitivity and conductivity of certain tissues have come about, and they
have become set apart for these special functions. In higher animals,
therefore, the tropisms where operative must act more or less through the
agency of the nervous system instead of directly through the general
protoplasm of the organism.
=Certain Apparently Complex Volitions Probably Only Tropisms.--=Where
nervous systems enter into tropic responses there must be specific
sensibility of certain nerve terminations (i. e., sense organs) at the
surface of the body. These sensory or receiving nerves connect through the
central system with corresponding motor nerves which in turn supply
certain specific muscles through the contraction of which the organism is
as surely and as mechanically oriented as in the simpler cases. For
example, if light is the stimulating agent, when it strikes a positively
phototropic animal, if the latter is not already oriented, the eyes or
other nerve terminations sensitive to light transmit an impulse through
the central nervous system to certain muscles causing them to increase
their tension and thereby swing the animal around with its head toward the
light. Progressive movements which the organism then makes must carry it
toward the source of light. Thus it is not "love of light" that draws the
moth into the flame but the mechanical steering of the body toward the
source of light through the stimulations produced by the light waves. It
is chemotropism, not solicitude for its offspring, which drives the flesh
fly to lay its eggs on decaying meat. And it is stereotropism and not a
desire for concealment which impels certain animals such as many worms
and insects to get into a close contact with solid bodies, or in other
words to "hide" themselves in burrows and crevices.
=Complicating Factors.--=However, beautifully as these theories of
tropisms work out in a broad general way, there are various additional
factors entering which must be reckoned with, and these become more
numerous and of more consequence as the organism becomes more complex. In
the first place certain internal conditions must be considered. Living
matter is characterized by its instability. There are continual synthetic
and disruptive processes in progress which the physiologist terms
metabolic changes. The very "life" of such matter seems to be the
manifestation of such changes. Concerning what the ultimate source of
these changes is, whether or not indirectly they may be referred to
external conditions as seems probable to many biologists, no one so far
has ever given a convincing, positive answer. It is sufficient for our
purposes to know that they may have set up certain internal stimuli which
may modify the behavior of the organism in which they reside, and that the
"physiological state" of the organism at the time of external or internal
stimulation will condition the response. This physiological condition may
be dependent on the general metabolic equilibrium of the animal, or on the
extent of previous stimulation by means of the same or different agents.
Thus the organism may not always react in the same way to the same
stimulus.
The intensity of the stimulation and change in the intensity of the
stimulation, are also factors to be reckoned with. Moreover, it must be
taken into account that a given organism is often operating under the
control of more than one external influence. For example, swarm spores in
a dish of water which at a given temperature are positively phototropic,
that is, gather at the side of the dish toward the light, may, if the
temperature of the water is raised or in case of marine forms if the
salinity is increased, become negatively phototropic. Sometimes two or
more forms of stimuli may cooperate in bringing about certain behavior as,
for instance, in the reaction of the earthworm to a suitable habitat,
through a combination of chemical and contact stimuli. On the other hand,
two different stimuli may interfere with each other; for example, the
usual phototropic responses of certain animals do not manifest themselves
when they are mating or feeding. In short, anything that alters the
physiological state of the organism may cause it to react in a different
manner. And thus with the interplay of shifting external agents and
variable internal state the bounds of behavior on these purely mechanical
bases become considerably extended.
=Many Tropic Responses Apparently Purposeful.--=The query arises as to why
if these responses are mechanical they are so often apparently purposive;
that is, why do they so often subserve some useful end for the animal?
While they do not always work out to the animal's benefit, as for instance
in the case of the moth and the light or under many other conditions that
can be devised experimentally, as a matter of fact under normal natural
conditions they are on the whole useful to the organism, carrying it
into suitable surroundings of food, lessened danger, temperature, and the
like.
The probabilities are that in their first origin the reactions were not
purposive. However, if any proved harmful they would result in the
extermination of their possessors and hence of that particular strain of
individuals. Those types that happened to have useful reactions would be
left and in course of time as the process of eliminating the others went
on, would become the prevailing types. Any organism which the useful
reaction had preserved would tend to hand it down to the succeeding
generation where again it would be the conserver of those individuals
which possessed it in sufficient degree.
=Authorities Not Agreed on Details of Tropic Responses.--=Although all the
foremost modern students of animal behavior accept as facts the more or
less mechanical orienting effects of external stimuli, there is by no
means unanimity of opinion regarding details. Some stress as the directive
factor the continuous action of the stimulating agent on sensitive tissues
symmetrically situated. Others would maintain that it is the time rate of
change in the intensity of the stimulating agent, or that the factor is
different in different cases. Some make much of an automatic sort of
"trial and error" system by which certain organisms test out an inimical
environment until the path of least irritation is hit upon as the way to
safety. The field is a broad one and to get at the finer shades of
distinction the reader will have to refer to the works of such
authorities as Loeb, Jennings, Holmes and Mast.
=Tropisms Grade Into Reflex Actions and Instincts.--=The tropisms in many
cases become indistinguishable from _reflex actions_ and these in turn
grade up into the _instincts_ of animals. The latter may be looked on as
but subtler and more involved reactions made possible through a more
intricate structural organization. As might be expected of instincts, the
feature of utility is more in evidence than in simpler tropisms because
they have become of proportionately greater magnitude, but the same
fundamental mechanism is apparently at bottom of both. It has already been
seen how the "instinct" of the blow-fly to lay its egg on meat is
interpretable as a chemotropic response. Thus no elaborate psychic
mechanism is necessary in such behavior.
=Instincts.--=In the typical instinct there is a series of "chain
reflexes" in which one step determines the next until mechanically the
whole gamut of changes is run to the last step. It is characteristic of a
purely instinctive act that an animal performs it without practise,
without instruction, and without reason. Moreover, all of the same kind of
animals tend to perform the act in the same way. But with instincts, as
with tropisms, the physiological state of the organism must be regarded.
For instance, the instinctive reactions of an animal sated with food or
hungry will be different.
=Adjustability of Instincts Opens the Way for Intelligent Behavior.--=As
we progress in the scale of animal life this adjustability of instincts
to new conditions comes more into evidence. While prescribed in the main
by internal impulse the carrying out of the action is capable of some
adaptability to circumstances. And in proportion as this adaptability
releases the organism from a blind rigid working-out of a predetermined
end, there is opened up the possibility of intelligent behavior; that is,
of modification of the instinctive behavior by individually acquired
experience.
While the generation of instinctive impulses still occurs it is left more
for individual experience to teach discrimination between ends. But we can
not escape a fundamental structural mechanism, for with this new capacity
of educability must come new structural mechanisms in the nervous system
and this must be as faithfully reproduced in each individual as is the
basis for any other nervous response. How low in the scale of animal life
animals can profit from their experiences to the extent that their future
conduct is conditioned thereby is not known. Some would place it as far
back as the protozoa, others would not. Where such modification of
behavior is possible there must be some mechanism for the storage of
impressions in the form of what we term _memory_.
=Modification of Habits Possible in Lower Animals.--=Among invertebrates
such animals as crayfish will acquire new habits, or rather will modify
old ones. Even as lowly an organism as the starfish can have changes of
habit thrust on it. When a starfish is placed upon its back it rights
itself by means of its arms or rays. Professor Jennings found that in a
given individual the tendency was always to employ certain rays for this
rather than others. However, by preventing the use of the rays customarily
employed, he found that the animal would use a different pair and that
ultimately in this way it could be trained into the habit of using this
pair of rays even when restrained in no way. One starfish which was given
one hundred eighty such lessons in eighteen days after an interval of
seven days still retained the new habit; young individuals were found to
be more easily trained than old ones.
=Some Lower Vertebrates Profit by Experience.--=Among vertebrates it is
known that those as low in organization as fish will profit by experience.
They will learn to come for food at a regular time and apparently learn
more or less to appreciate the presence of certain obstacles with which
they have had unsatisfactory experiences. Professor Sanford sums up what
he believes are the limitations of the piscine mental organization as
follows: "No fish is ever conscious of himself; he never thinks of himself
as doing this or that, or feeling in this way or that way. The whole
direction of the mind is outward. He has no language and so can not think
in verbal terms; he never names anything; he never talks to himself; as
Huxley says of the crayfish, he 'has nothing to say to himself or any one
else.' He does not reflect; he makes no generalizations. All his thinking
is in the present and in concrete terms. He has no voluntary attention, no
volition in the true sense, no self-control."
=Rational Behavior.--=Finally, however, out of these first dull
glimmerings of intelligence as exemplified in the higher invertebrates
and the lower vertebrates, which can modify behavior as the result of
experience, come the still higher factors so dominant in man, of
_rational_ behavior. This higher mental process can realize the end to be
reached and can deliberate on the means to be employed. By means of his
_reason_ man can overcome difficulties in advance by "thinking" out
suitable schemes of action. Some naturalists believe that man stands alone
in possessing the power to reason, although others believe that some of
the other mammals, notably the other primates, possess the same attribute
although in a much less degree.
=Conceptual Thought Probably an Outgrowth of Simpler Psychic States.--=Is
the capacity for such conceptual thought, however, which appears as the
final efflorescence of complex neural activity something entirely new?
Most students of comparative psychology maintain that it is not. Just as
one kind of an instinct frequently grows out of another, so has this grown
out of the complex of _psychic_ states which preceded it. It apparently is
the product of the increasing awareness on the part of animals of their
neural processes and the outcome of these processes, which becomes more
and more prominent as we ascend the scale of animal life. With the advent
of associative memory the mind comes more and more to deal with attributes
of objects instead of merely with each single concrete object as it
presents itself, and these attributes being common to many objects, come
to represent definite ideas which can be manipulated by the mind.
Language, of course, has been an indispensable aid to man in this regard,
for words become descriptions of facts and symbols of concepts, and
thereby allow of abstract thought.
=The Capacity for Alternative Action in High Animals Renders Possible More
Than One Form of Behavior.--=With this modification of instinct by
experience made possible, there comes at the same time, of course, the
capacity for a rational instead of a purely instinctive behavior. This
very capacity for alternative action opens up many new possibilities of
behavior and together with the well-known fixative effects of habit, also
the opportunity of permanently establishing certain ones. Thus it is
obvious that a behavior toward which in a strict sense there can not be
said to have been an original specific tendency, can be developed. What
was present in the first place was only a general possibility of the
development of any one of several types of behavior. The final choice of
the alternatives together with repetition makes it the habitual behavior
of the individual. Of course it can be urged that if the selection of the
type of behavior is left to the individual then the latter will operate
automatically toward the various impulsions of its neural make-up and one
path will be followed because of stronger inclination in that direction,
so that the whole procedure is in the end the mere operation of an
automaton. But however this may be in the individual left to itself, the
fact is in man that the young individual is never left to itself and in
the nature of things can not be, so that without entering into this
troubled pool of controversy regarding freedom of the will, I wish merely
to point out that the possibility of more than one form of behavior
exists and that if one is more desirable than the others then this one can
be chosen by the ones responsible for the training of the young individual
and clenched fast by the agency of habit.
Intelligence, reason and habits, however, no less than instincts and
tropism must have neural as well as psychical existence and we can not
escape therefore the underlying mechanism.
=The Elemental Units of the Nervous System Are the Same in Lower and
Higher Animals.--=It is interesting to note that the fundamental neural
mechanism which underlies the mental processes of higher animals is not
essentially different from that which serves in lower forms. Although as
animals become more complex their nervous systems have become
proportionately larger and incomparably more intricate, still all the
changes have been rung on the same basic neural unit, the _neuron_ or
nerve-cell (Fig. 32_A_, p. 209). The higher nervous system differs from
the lower in the number, in the specializations and in the associations of
these units rather than in possessing something of entirely different
elemental structure.
=Neuron Theory.--=According to the prevailing modern conception the entire
nervous system is made up of a series of units called _neurons_. Each
neuron is a single cell with all its processes. The latter consists
typically of short branching processes on the one hand, known as
_dendrites_, and of a single process on the other, known as the _axon_,
which extends from the cell to become a nerve fiber (Fig. 32, p. 209). The
various neurons, with possibly a few exceptions, are not anatomically
continuous but contiguous. They communicate with one another apparently by
contact only. The axon of each neuron ends in an elaborate series of fine
branchings which lie in contact with the dendrites of another neuron, or
in some cases with the body of the other cell (Fig. 32, p. 209). Thus the
nervous impulse passes from one neuron to the other at these points of
contact. An impulse is supposed to travel normally only in one direction
through a neuron, the dendrites being the receiving and the axon the
discharging terminals. There are various types of neurons. Some,
particularly within the brain, have their main processes so provided with
branches and brushes that they may come into physiological connection with
a number of other neurons.
[Illustration: FIG. 32
A--Diagram to illustrate neurons and their method of connection; _a_,
axon; _d_, dendrite; _s_, synapse. To simplify the diagram the medullary
sheathes of such fibers as would have them have been omitted. The arrows
indicate the direction in which the impulse travels. The lower series
shows diagrammatically how from the same neuron in the cortex two
subordinate neurons may be affected, the one excited to cause contraction
of a certain group of muscle fibers, the other inhibited so that the
antagonistic fibers may relax and thus not hinder the movement of a given
part.
B--Section of a region of the cerebral cortex (after Cajal). The cells
have been blackened with chrome-silver and are much less highly magnified
than the diagrams in A. The numerals refer to certain characteristic
layers of the cortex in this region.]
=Establishment of Pathways Through the Nervous System.--=It is believed
that more or less resistance to transmission of stimuli prevails at the
point of contact (_synapse_) between two neurons but that this resistance
is lessened by repetition of conduction. The frequent traversing of a
given pathway by similar impulses finally results in an automatic
occurrence of the transmission, or, in other words, the action becomes
habitual. Education consists largely in establishing such routes through
the nervous tissue. Because of the greater plasticity of the neural
mechanism in youth it is easier to open up and fix pathways of conduction
than in later years. Moreover the earlier established lines of conduction
become the more permanent.
=Characteristic Arrangements of Nerve Cells Are as Subject to Inheritance
as Other Structures of the Body.--=That the main features of the nervous
system are inherited becomes obvious when we see that each kind of animal
has its own distinctive numbers, arrangements and proportions of the
various neural units. In man, for example, there are certain
characteristics, types and groupings of nerve-cells which are reproduced
generation after generation with remarkable fidelity. This means that in
so far as these represent the mental make-up of the individual, his
mentality is continuously linked with others which have gone before. The
new-born child has all the nerve-cells in its brain that it will ever have
but the ultimate linkages of the finer connectives between them, or at
least the pathways of travel, remain in large measure to be made.
As we have already seen, the cerebral cortex is the seat of the chief
mental faculties of man or at least of the highest of these. Professor
Lloyd Morgan, one of our greatest authorities on comparative psychology,
is inclined to believe that the instincts are located in the subcortical
material. In any event, the inheritance of mental ability resolves itself
into the inheritance of a certain cerebral mechanism.
=Different Parts of the Cortex Yield Different Reactions.--=The cerebral
cortex, however, is not functionally homogeneous throughout. Certain
regions have been shown to be motor, others sensory, and moreover, these
regions are apparently further specialized so that a given one of them is
associated with a specific type of sensory or motor response, not merely
with responses in general. Thus by injuring one of the sensory areas we
might destroy vision but not other sensations, or by stimulating one of
the motor centers we would get a response in a corresponding motor organ
but not in all such organs. Likewise, it is probable that still different
areas, the so-called "association areas," relatively of much greater
development in man than in any other animal, are the regions in which
various perceptions and conceptions are synthesized and formed into
organized knowledge. Here also are engendered the volitions which when
flashed through the motor centers become expressed in activity or
behavior.
It seems highly probable that just as the sensory and motor areas differ
in kind from one another, so we must suppose there are qualitative
differences in various parts of the association areas so that the
different parts give different reactions in consciousness; that is, each
special mental ability of the individual is more or less centered in a
special part of the cortex. And just as there may be variations in other
structures of the organism so there may be variations in these areas. The
"gifted" person in some one direction, whether it be in mathematics,
music, painting, or what not, is on this hypothesis one who has that
particular area of his brain which forms the basis for the talent in
question more highly developed than it is in the average individual. And
since such talents are handed down to descendants, this can only mean that
a similar grouping of the neurons in the region in question has occurred.
=Skill Acquired in One Special Branch of Learning Probably Not Transferred
to Another Branch.--=Such a differential arrangement of the
brain-mechanism which presumably underlies the various mental abilities
would lead to the inference that skill in one special branch of learning,
in so far as it involves only certain centers of the cortex, would not be
transferred to another branch based on different neural pathways and
centers. Development of historical knowledge, for example, would not
enhance one's mathematical ability, or vice versa. The testimony of
various psychologists bears out this idea. In so far as certain factors of
training, such as habits of industry, concentration, etc., are common to
the study of either mathematics or history, the good effects of either
discipline will probably be much the same, but the identity of effect
vanishes as soon as the intrinsic characteristics of the subjects
themselves are involved.
Just how far we are warranted, however, in carrying this idea of localized
functions as regards the association areas is a moot question. Our present
attitude regarding the specificity of such localizations is largely a
matter of inference based on analogy to conditions which obtain in other
and better known parts of the brain, together with the indubitable
differences in inborn abilities which exist between individuals. Some few
brain physiologists maintain that the whole cortex operates more or less
as a unit in all of the higher psychical activities.
=Preponderance of Cortex in Highest Animals.--=One of the most interesting
conditions in the nervous system of the highest types of animals is the
way in which the cortex has outrun the other parts of the brain in size
and complexity and has come to dominate the organism more and more both
directly and indirectly. Aside from the proportionately greater increase
in size of the cortex, there is an abundance of anatomical evidence of
this altered and probably altering system of control in man and the higher
apes. This is well illustrated in the fiber tracts (nerve bundles) of the
spinal cord.
=More Long Fiber Tracts in the Spinal Cord of Man.--=The spinal cord
although having many nerve centers of its own is also in great part a
large cable for conducting enormous numbers of fibers from one part of the
cord to another, or to and from the brain. In man and the higher apes a
considerably larger percentage of the total area of the cord is given up
to the long fiber tracts from the brain to the body than in lower
vertebrates. This progressive increase in long fiber tracts in the higher
anthropoids probably marks more and more domination of the body by the
higher brain centers and correspondingly less by the direct activity of
the cord and by the lower brain centers. However, even in man, many of the
simpler reflexes of the body still have their centers in the spinal cord.
=Special Fiber Tracts in the Cord of Man and Higher Apes.--=There are
certain special tracts of the cord that are particularly interesting in
connection with the increasing domination of the brain over the body,
namely, the _pyramidal tracts_. These were the latest tracts to appear in
the animal kingdom and are apparently the latest to become functional in
the individual. It is believed that the development of the medullary
substance (an enveloping sheath) of the common medullated nerve fiber
marks the time of entrance of the fiber into activity and it is a
significant fact that the formation of this sheath occurs last of all in
the fibers of the pyramidal tracts, where it does not appear till after
birth. These tracts convey impulses from the brain to the body. They
consist of two sets of tracts, in fact, one the crossed, the other the
direct. As an anomaly, probably arising most frequently from instrumental
injury at birth, the pyramidal tracts fail to develop normally, with the
distressing result that the infant, although possessing perfectly normal
brain activity and normal spinal cord reflexes, is unable to exercise
voluntary control of the body. In other words the condition, like
hare-lip, is one of suppressed development. At least this seems to be the
most plausible explanation of what is known as _Little's disease_. Such
unfortunates usually die early although they may survive for a few years.
The direct pyramidal tracts occur only in man and man-like apes. They vary
considerably in extent in different individuals. They originate in nests
of characteristic large cells located in the cerebral cortex and are
regarded as paths, though not the only ones, through which volitional
impulses are conveyed from the brain. They seem to control certain of the
finer and more delicate movements of the body.
=Great Complexity in Associations and More Neurons in the Brain of Man
Than of Other Animals.--=It has already been noted that as animals stand
higher in the scale of life while the general plan of their neural
elements remain the same, there is increasing complexity in the number and
connections of the neurons. The number of processes on individual
nerve-cells is also greater. There is in fact much greater complexity in
the number of processes and the inter-connections of the neural cells
than in the numbers of the cells themselves. This would seem to indicate
that the greater mental activities of higher animals depend more on
richness in complex associations than on mere increase in number of
neurons. The latter, however, is by no means unimportant as may be seen in
man, for instance, in whom it is estimated that the cerebral cortex, that
is, that part of his brain in which his more complex mental processes
transpire, contains some nine billion more nerve cells than does the
corresponding region of the brain of an anthropoid ape.
Of especial significance in the psychic make-up of man is his vastly
increased capacity for inhibition. Although not possessed by all men in
equal measure and not entirely wanting in lower animals it is a
distinctive feature in all human conduct. Much of any child's education,
particularly as it pertains to behavior, must be concerned with training
in the exercise of proper inhibitions. He must learn to suppress certain
primitive types of reaction in favor of higher ones. This applies not only
to motor activities but to trains of thought as well. The essence of
self-control consists mainly in ability to substitute for one impulse or
idea other compensating ones. And the secret of concentration lies in
being able to banish irrelevant ideas and focus on the central thought.
=The Nervous System in the Main Already Staged at the Time of Birth for
the Part It Must Play.--=It is clear from what is known of its anatomy
that in the main the central nervous system is framed to respond in
certain set ways, that there are determinative elements in it which
control or determine the responses, and therefore the behavior of the
body. The same evidence shows also, however, in the incompleteness of many
of the associations, that while the stage is all set and some of the main
features of the performance are determined at the time of birth,
considerable yet remains to be done toward fitting the parts together and
working up the detail. Just exactly what and how much is rigidly
determined no one knows.
=Many Pathways of Conduction Not Established at Birth.--=As we have
already seen the evidence is that many of the neural pathways are not yet
fully established at birth, and there is some indication that routes once
opened may be altered. To what degree this has bearing on behavior is
still unknown, but since neurologists attribute so much importance to the
richness and the associations of the cell-outgrowths, it is evident that
this increase in the number of pathways after birth with possible
alternatives of connections may be a very important factor in the
modification of behavior. Yet, on the other hand, we are completely in the
dark as to what extent these later associations are predetermined in the
earlier cells.
=The Extent of the Zone That Can Be Modified Is Unknown.--=There is little
doubt that many of the paths of action are already firmly established.
Others, although not irrevocably fixed, offer the least resistance and
would "naturally" be taken if not counteracted or modified by the more or
less artificial development and fixation of other paths through
cultivation and habit. Yet others perhaps are largely neutral; they still
await the initial decisive push which "choice" or external environment may
mete out to them. As trainers of youth all that is left that we can do is
to attempt to develop in certain ways the elements of this indefinite,
impressible zone. Unfortunately, we must labor in the dark to a great
extent as we have all too little indication of which the malleable factors
of intellect and conduct are. We can only infer from long, intelligent and
sympathetic observation of children in successive stages of their
development. It is only by having clearly in mind the nature of our
problem that our conclusions will finally come to be of enhanced practical
value in the training of children. Observation to the present time clearly
indicates that many children are strongly predisposed this way or that "as
the sparks fly upward."
This is a point too frequently overlooked by educators. They are often
unduly actuated by the other piece of the truth that, "as the twig is bent
the tree inclines." They sometimes fail to realize that after all the tree
remains the same kind of a tree. If an apple tree, while it may be bent
from the normal path of development, it can not produce other fruit than
apples. Just how much the destiny of man can be influenced by training and
the exercise of his own will power is the fundamental question not only of
pedagogy but of ethics as well. For if man's rational judgments are
markedly conditioned by his neural make-up then the volitional judgments
which underlie conduct are likewise conditioned since they are
inextricably intermingled with his reason. We must believe that to a
considerable extent emotional expression, as well as other mental
functions, is due to hereditary dispositions of the neurons in the
various parts of the brain.
=Various Possibilities of Reaction in the Child.--=Despite the innate
predeterminations of the tree, it is nevertheless our province to see that
the twig _is_ bent, but our work can only be done with due intelligence
when we recognize something of the limitations of our material. Of the
various possibilities of reaction we must see that certain desirable ones
are realized, even, in some cases, if only to have others thereby
excluded. It is a commonplace of psychology that all cerebral excitations,
no matter what the origin, must vent themselves in some way and if this
expression is not directed into proper channels it will very likely find
improper ones. We must see that the young wearer of the coat of
undetermined capacities gets it set by repeated performance into the
habitual wrinkles of normal social conduct. For it is a trite observation
that when habits are once well established it requires tremendous efforts
to do otherwise than as they dictate. There is not the least doubt that
some of our subjects will respond much more readily to training in certain
directions of habitual reactions than others, but we have always the
consolatory knowledge that no matter how difficult the art may be at
first, repetition reduces the difficulty.
While much of any youth's character must be determined by external forces
brought to bear upon it, the ultimate climax of our effort and measure of
our success will be the extent to which we have engendered in him the
capacity for initiating and carrying out through his own volition those
impulsions and inhibitions which tend to the highest good of humanity.
=Probable Origin of Altruistic Human Conduct.--=Those phases of human
conduct which find expression in consideration for others seem no less
than other mental attributes to have their origin in certain fundamental
instincts. Altruistic conduct, in last analysis, apparently resolves
itself back largely to certain very fundamental impulsions, namely those
which arise out of certain obligations for the welfare of others which are
necessarily associated with the marital, parental and filial relations
that must exist where the young require post-natal care. Looked at from
the standpoint of natural selection, this would come about as a mere
matter of survival value. Where the young, as in man, are helpless for a
long period of time, more opportunity would be afforded for the
development of both conjugal and filial affection. The sympathetic
emotions once established in such family relations would partly through
habit, partly through community of interest, readily become extended to
clan or tribe and as a final consummation to all mankind.
=Training in Motive Necessary.--=In the training of children, then, we
must recognize first of all that there are decided inclinations or bents
which, as long as they are not anti-social in nature, must be respected if
not always encouraged. While it is necessary to utilize these as much as
possible in their training still we must bear in mind that although it is
natural for a child to follow certain interests, the fact remains that as
regards social worth these natural interests may not be the most valuable.
When this is true we must strive to develop others which will compel
attention and thus become impelling factors in conduct. Where certain
fundamental impulsions run contrary to the common welfare it is necessary
to practise the child in the setting up of inhibitions or counter-impulses
until this becomes habitual. He must be led to construct a protective
mantle of appropriate scruples, doubts and fears. It is all important to
get the proper motives for action to prevail in his mind.
=Actual Practise in Carrying Out Projects Is All Important.--=But on the
other hand it is equally important to see that the action is effectively
carried out. In the matter of self-discipline, particularly, we may have
many ideal impulses and realize that they should prevail over certain of
our natural propensities, but unless we put forth effort to overcome the
propensities our ideal impulses are of no avail. The world has many such
moral paralytics to-day who can not seize their "languor as it were a
curling snake and cast it off." It is training in this very overcoming of
reluctance, in this putting forth of actual effort toward worthy ends
instead of merely memorizing precepts about the desirability of such
accomplishments, that is so sadly lacking in our school and home life
to-day. We prate of the importance of self-control, we say with our lips
that the way to learn to do is by doing, we proclaim that it is more vital
to instil good mental and physical habits into our pupils than to stock
them with information, we preach that mere fact training is as conducive
to making a first-class rascal as an upright man, yet we jog on
complacently in the well-beaten ruts of memory routine which require the
memorizing of symbols rather than real understanding. We seldom require
that our protégés make intelligent judgments based on evidence, we rarely
exact of them decisions in matters of ethics, and almost never demand that
they put their knowledge into efficient accomplishment. It can not be too
strongly urged that we need less of formulæ learned by heart, less dead
erudition pigeonholed in the brain like so many foreign bodies, and vastly
more assimilation of knowledge into the living personality of the
individual.
Where in school or home to-day do we find provision for such training? Our
tendency is, in fact, just the opposite. According to the modern code, as
it works out in many instances at least, the child must be taught through
play. Though it is a truism that he who has not learned obedience can
never be master of himself, the child of to-day must not be made to obey
but be wheedled into changing his mind. If a given subject of study proves
distasteful to him, the fault is the teacher's for not making it
interesting, for he must always be led on by the thrill of fascination. In
other words, the child must not only be allowed but be encouraged to take
the path of least resistance. His own pleasure is to be the standard of
his actions. Let no stern demands of duty interfere!
Is it any wonder that the products of such tutelage come into the
activities of life self-indulgent and undisciplined, and although often
recognizing our private and public shame in business, politics and
conduct, still remain supine, evasive of the unpleasantness or hardships
of reform, or inefficient or unwilling in accomplishing unselfish ends?
=Interest and Difficulty Both Essential.--=The writer does not wish to be
understood as minimizing the importance of interest on the part of the
child in what he is doing. Interest is undeniably the open sesame to
desirable mental development; but what he does protest against is that not
uncommon interpretation of interest which deems it necessary to eschew
most serious consideration of a subject and evade such parts as present
difficulties. Certainly if there is any fact that stands out prominently
in human experience it is the fact that nothing conduces to the
development of moral stamina so much as the overcoming of difficulties,
particularly distasteful difficulties.
=Conduct Developed Through Actual Performance.--=Self-control and the will
to do can be trained and crystallized into habit as well as can any other
activity. It is a fact that one well grounded in morals by habit will
successfully resist subconscious impulsions to wrongdoing even when
suggested in the hypnotic state. Conduct is largely a matter of growth
through actual performance. For proper guidance of this growth there must,
of course, be high ideals around which the feelings are led to cluster and
by which they gradually come to be controlled.
=Construction of Ideals.--=The construction of such ideals through
example, through precept, through appeal and through actual practise in
self-denial and self-control on the part of the child, should be the
foremost duty of the parent or teacher. Above all it should be remembered
that imitation of teacher, of parents, of companions, is more of a factor
than intellect in the moral action of children. At present educationally
we are in a fever for vocational training, for "practical" work, and in
general for all things conducive to coaching our pupils in how to make a
living, yet commendable as all this may be, is it not of even more
fundamental importance to train them how to live?
=The Realization of Certain Possibilities of the Germ Rather Than Others
Is Subject to Control.--=It may be said in a sense that there exists
potentially in any germ all the things that can possibly come out of it
under any obtainable conditions of environment. The very initiation of a
given mode of expression by some environmental factor, however, often
mutually excludes many of the others. We get a given average result
ordinarily because development normally takes place in a given average
environment.
As may be easily shown by experiment, this is manifest even in the
instincts of lower animals. In the young the various instincts do not come
into expression at the same time, and it not infrequently happens that if
one of the earlier instincts becomes operative toward certain objects or
situations, later instincts will have a wholly different relation toward
these objects or situations than they would otherwise have had. As a
result the whole life conduct of the animal is markedly modified. For
example, young animals immediately after birth have no instinct of fear.
They do, however, have a strong instinct to attach themselves to some
moving thing and follow it. The utility of such an instinct, as for
instance in the case of young chickens, is obvious. The object of
attachment is usually the parent, but man may take the place of a parent
and the young animal will fearlessly follow him about. However if the
young animal has had no experience with man during its earliest infancy a
later instinct, that of fear or wildness, will have come into play and it
will flee from him. It is clear, therefore, that by familiarizing the
young animal with man before its instinct of fear has come to expression,
certain habitual reactions are set up in it which inhibit or limit the
application of its instinct of wildness as regards man. In other words,
the whole course of its life has been altered by this simple experience.
The same principle applies in even greater degree to the young of man.
We have seen in a former chapter that what in the ordinary course of
nature was "predestined" to become one individual nevertheless contained
the possibility of becoming four or more if the environing conditions were
made such as to bring about a separation of the cleavage blastomeres. Or a
fish egg that contained the possibility of becoming a normal two-eyed form
also contained the possibility of becoming a one-eyed form and could be
made to do so by certain unusual modifications of the conditions under
which it develops. However we must not be led so far by the plausibility
of this comparison that we are misled, for the fact is that we are not
creating anything new by these environmental upheavals, but are mainly
altering features that already exist. Beyond doubt the nature of the
material is of greater import in the specificity of the outcome than are
the external forces brought to play on it. The only point I wish to make
is that even what seem ordinarily to be predestined ends can be altered
by environment, and that the probabilities are that certain features are
relatively indifferent at their inception, the environmental factor adding
the final touch of specificity. And our common experience in education
would indicate that the same is true of mental conditions, including
behavior. The actual appearance of a particular trait is not necessarily
always a matter of an initial trend, but may be due merely to the fact
that its development is possible under certain conditions of environment
and that these conditions have prevailed in the given instance. And even
where there is a specific bent it may be arrested through the awakening of
a contrary impulse, or, on the other hand, its exercise may prevent the
engendering of the opposite impulse.
=Our Duty to Afford the Opportunity and Provide the Proper Stimuli for the
Development of Good Traits.--=It is clearly our duty to see that the
expression of good traits is made possible. We must throw a sheltering
screen of social environment around the young individual which will fend
off wrong forms of incitement and chances for harmful expression, and we
must provide proper stimuli and afford opportunity for development of
proper modes of expression. We must not forget that a normal instinct
denied a legitimate outlet will not infrequently find an illegitimate one.
Above all we must not forget the vital importance of establishing correct
habits nor the possibility of even replacing undesirable ones by good
ones. If training can redirect the machine-like behavior of as lowly a
creature as the starfish into new courses, why should we be so willing as
some of our genetists would seem to be to throw up our hands and admit
failure in the case of man before we have even made a rational attempt to
correct the evils in question? Even in lowly organisms we have seen that
behavior is not only the result of an innate constitution but also of the
degree and kind of stimulations to which it has been subjected.
If the individual himself has not the initiative or will to make the
attempt to set up proper or corrective habits, or to cultivate the
necessary specific inhibitors, then all the more is it our duty to see
that he is led by suggestion and drill into the proper routine of
activities for their establishment. For if the individual with
propensities toward moral obliquity is to be saved to society it must be
through the stereotyping effects of good habits.
=Moral Responsibility.--=Beyond question different men have different
degrees of capacity for mental and moral training. All can not be held
equally responsible ethically, but the lowermost limit of obligatory
response to social and ethical demands necessary to rank one as within the
pale of normal conduct is at such a level that any one not an actual
defective can in a reasonably wholesome environment surmount it. All
normal men are responsible for their conduct.
CHAPTER VIII
MENTAL AND NERVOUS DEFECTS
Some of the most important and serious problems which confront humanity
to-day lie in the realm of mental and neural maladjustments. For human
progress and social welfare are in last analysis based fundamentally on
the results of normal reactions of human nervous systems. Any serious
derangement of the latter may, and in certain cases must, lead to more or
less disaster for the individual and disorder for society of which he is a
unit. So appalling has the number of neuropathic subjects become in modern
times that the matter may well cause even the most thoughtless citizen to
pause and consider.
=Prevalence of Insanity.--=As to the prevalence of insanity, one learns
from recent charts prepared by a member of the National Committee for
Mental Hygiene that in 1910 we had more insane (187,454) in our
institutions than there were students (184,712) in all our colleges and
universities in the United States, or officers and enlisted men (142,695)
in our combined United States army, navy and marine corps; further, the
yearly cost ($32,804,450) of caring for these insane is greater than the
annual cost of construction ($32,520,100) on such a stupendous undertaking
as the Panama Canal. In New York over twenty per cent. of the revenues of
the state go to support the insane. Doctor Lewellys F. Barker, President
of the National Committee for Mental Hygiene, says: "It is calculated that
some 250,000 people in the United States are insane. One of every five men
discharged from the United States army for disability is discharged
because of insanity, 60 per cent. of the cases being _dementia precox_."
Even in individual states with exceptionally large university populations
we still find these outnumbered by those of the insane. Thus in Wisconsin
by 1914 the state university had attained a population of about 4,700
students resident at the university during the regular school year, and of
approximately 6,000 attending during some part of the year, but the number
of insane under restraint in public institutions in the state June 20,
1912, was 6,851, with an additional 1,284 on parole. This does not include
the insane in various private sanatoria, and moreover a considerable
greater number of patients had been treated in these public institutions
than were resident there June twentieth.
To make such comparisons complete one should, of course, know the average
length of residence of students in college, and of insane patients in
institutions. No accurate data on this point are at hand. The average
period of residence in hospitals for the acutely insane is doubtless
considerably shorter than the average period of attendance of students in
college, while on the other hand the average period of residence of
inmates in asylums for chronic insane is probably considerably longer. For
example, the Wisconsin State Hospital for the Insane reports a total of
1,224 patients under treatment, but an average population at any one time
of only 622 during the year 1911, and the Northern Hospital for the
Insane, a total of 1,194, with a daily average of 613 during the same
period. The combined thirty-four county asylums in Wisconsin, for chronic
insane, had a total population of 5,384 during the year 1911, with a loss
of 517, or approximately 10 per cent. During 1912 the figures for these
same institutions run 5,758 and 742 respectively, or a loss of over 12.5
per cent. The conditions in other states are probably much the same.
In other representative states we find the number of insane in public
institutions as follows: California, 7,909; Michigan, 7,703; Minnesota,
5,329; Pennsylvania, 16,992. Epileptics are estimated by alienists to be
about equal in number to the insane, feeble-minded to be more numerous.
The estimate that in the United States there are 300,000 feeble-minded is
probably a minimal figure.
=Imperfect Adjustments of the Brain Mechanism Often Inheritable.--=The
outside layer or "cortex" of the brain is the region in which the more
complicated adjustments occur, especially such as pertain to human
behavior, and inasmuch as this portion of the brain is extremely complex
and delicate in its mechanism, it is peculiarly liable to derangements
which, even when slight, may have far-reaching effects.
This brain-mechanism is as much a product of ancestry as is any other
structure of the body, and it is obvious therefore that imperfect
adjustments of its structure must be as subject to the laws of
inheritance as are other malformations of the body. And just as with
other defects, mental disorders may thus flow from pre-existing ancestral
maladjustment of the nervous system or from immediate causes thrust upon
it, such as syphilis, alcoholism, degeneration of the blood vessels and
traumata. Or, in other words, the mechanism of mentality may be faulty
from the beginning, or it may be made faulty by bad environmental
conditions.
The records of the inheritance of insanity, imbecility, feeble-mindedness
and other forms of nervous and mental defects are truly startling. Active
researches in this field have been in progress now for several years, and
as each new set of investigations comes in the tale is always the same. It
is questionable if there is a single genuine case on record where a normal
child has been born from a union of two imbeciles. Yet the universal
tendency is for defective to mate with defective. Davenport gives a list
of examples, beginning with such a one as this: "A feeble-minded man of
thirty-eight has a delicate wife who in twenty years has borne him
nineteen defective children." Little wonder, in the light of such facts as
these, that the number of degenerates is rapidly increasing in what are
called civilized countries.
=Many Mental Defectives Married.--=But, it may be urged, these are
exceptional cases, there is surely no considerable number of mental
defectives who are married. Let us look at the available facts. In Great
Britain in 1901, of 60,000 known feeble-minded, imbeciles and idiots,
19,000 were married, and in the same year, of 117,000 lunatics, 47,000
were married; that is, a sum-total of 66,000 mentally defective
individuals were legally multiplying, or had had the opportunity to
multiply their kind, to say nothing of the unmarried who were known to
have produced children.
In the state of Wisconsin I note from the tenth biennial report of the
Board of Control that of 574 patients admitted to the Northern Hospital
for the Insane during the year from July 1, 1908, to June 30, 1909, 274
were married and 29 others were known to have been married; this is a
total of 303 out of 574, considerably over half. At the Wisconsin State
Hospital for the Insane we find the conditions are no better, for out of
499 admitted in the year 1909-10, 208 were married and 65 others had at
some time been married, or a total of 273 out of 499. There is every
reason to believe that conditions are approximately similar in other
states.
=Disproportionate Increase in the Number of Mental Defectives.--=Writing
of conditions in England the Commissioners in Lunacy state in their
fifty-fourth report that now (1901) there is one officially known lunatic
to 301.32 individuals of population, whereas in 1859 there was only one to
536 individuals of population. In Great Britain, taking into account
mental defectives of all kinds, the 1901 census showed a total of 485,507,
or 1:85 of total population. Rentoul estimates that 1:50 would be nearer
the truth because of the fact that the number of officially known mental
defectives is much less than the actual number. The conditions in Ireland
are even more impressive, for in 1851 there was one known lunatic to 657
individuals of population; in 1871, one to 328, and in 1901 one to 178.
When all allowance is made in these statistics for the greater accuracy of
recent enumeration, and for other modifying influences, such as migration,
we are still forced to believe that an alarming increase in insanity is in
progress and that society is woefully derelict in permitting the marriage
of such unfortunates.
A census of the insane under public care in Wisconsin June 30, 1910, not
counting the paroled, shows 6,537, or one to each 357 of population, since
the population of the state was then 2,333,860. If, however, we should add
the number of insane in private sanatoria and the number unconfined the
proportion of normal individuals would be very much reduced.
In the United States as a whole, while I know of no data giving the number
of married insane, it is estimated that at least one-fourth of the insane
are not in asylums or hospitals. In all states the number of insane in
state institutions (there are no available records of most private
institutions) is rapidly increasing. According to the special census of
1903 covering a period of fourteen years, during which the general
population increased thirty per cent., the number of insane in
institutions increased one hundred per cent. This is due doubtless in part
to the fact that because of better facilities for keeping them a
proportionately greater number of insane are being sent to state hospitals
than in former years. Moreover, improved sanitation has cut down the
death-rate in asylums. The increase is in such vastly greater proportion
than the increase in general population, however, that it seems impossible
to attribute it wholly to the greater accuracy of recent enumerations and
the increasing custom of confining the insane in asylums. This is a matter
that demands our gravest attention and one that should be investigated
with the greatest thoroughness. One of the most disquieting facts in the
situation in most states is that many patients--an average of
approximately one thousand a year, in Wisconsin for example--are on parole
subject to recall. This means that although it is recognized that these
patients are likely to have to be returned to the asylum or hospital,
little or no restraint in the meantime is placed on their marital
relations.[8]
=Protests Voiced by Alienists.--=Is it any wonder under the circumstances
that we find Doctor Charles Gorst, superintendent at the Mendota Hospital,
voicing in his 1910 report the following vigorous protest--and certainly
such men as he are in the best position to know. He says: "No one doubts
for a moment that defective mental conditions are transmitted from parent
to child as surely as the physical defects and deformities. Every one
knows that it is common for defectives to be attracted to each other and
marry, and that the defects of both parents are liable to be transmitted
to the children. It is also true that there are more children born in such
families; and for that reason the percentage of defectives is continually
on the increase. The report of the state of Illinois shows the increase to
be alarming, and many other states are no better. It is absolutely wicked
that the persons suffering from periodical insanity should be allowed to
return to their homes to propagate and scatter their children about the
state as dependents."
=Examples of Hereditary Feeble-Mindedness.--=No one can look at the
remarkable series of charts and records brought together by Doctor Goddard
of the institution at Vineland, New Jersey, and by other directors of
similar institutions, and doubt for an instant the inheritability of
feeble-mindedness and allied defects. In some instances the family history
has been followed back as far as five generations, and it is always the
same dire sequence of insanity, idiocy, epilepsy or feeble-mindedness,
from generation to generation. For example, Fig. 33, p. 236, is one of
Doctor Goddard's charts. It shows thirteen descendants of a supposedly
normal father (possibly a carrier) and a feeble-minded mother, of whom
seven were feeble-minded, the others dying in infancy. The mother herself
was one of seven feeble-minded children, who were in turn the descendants
of feeble-minded parents, of whom the woman had five feeble-minded
brothers and sisters. In Fig. 34, p. 237, he shows mental defects running
through four generations. Fig. 35, p. 238, is a remarkable exhibit which,
starting in the fifth generation back with a feeble-minded, alcoholic
man--the mental condition of his wife being unknown--shows that in every
generation down to and including the present there has been nothing but
feeble-minded (or worse) offspring, leaving out of account two unknown
and a number who died in infancy without revealing their mental condition.
This is true notwithstanding the fact that in the course of the various
generations there had been several matings with apparently normal
individuals. The new blood, however, instead of redeeming the tainted
stock, itself became vitiated. The numerous specific cases of inheritance
of family traits reviewed in recent books or in special reports of trained
workers give us abundant confirmatory evidence of the inevitable
inheritance of various nervous and mental defects.
[Illustration: FIG. 33
Inheritance of feeble-mindedness (after Goddard): squares represent males,
circles females; F, feeble-minded; N, normal; E, epileptic; I, insane; C,
criminal; T, tuberculous; d. inf., died in infancy; the hand shows the
individual from whom the record was traced back; small black circle
indicates miscarriage.]
=Difficult to Secure Accurate Data.--=It is obvious, of course, that in
tabulations such as these there may lurk considerable margins of error.
Notwithstanding our Binet-Simon and other tests for feeble-mindedness, for
example, there is yet much to be desired in the way of accuracy. Many
cases just bordering normality are by no means easy to decide. Then again
in most human records, when one gets back beyond the third or, at most,
the fourth generation, the investigator has to depend on the hearsay
evidence of relatives, friends or neighbors, and how vague this generally
is can only be appreciated by those who have themselves tried to collect
such data. But in spite of all the difficulties, there is little doubt
that the more carefully prepared records are sufficiently accurate to
establish the fact beyond dispute that defective tends in large measure to
breed defective.
[Illustration: FIG. 34
Inheritance of feeble-mindedness (after Goddard); symbols same as in Fig.
33, p. 236.]
One serious drawback in making a study of the inheritability of insanity
and other nervous disorders is that so far we have dealt mainly with mass
effects rather than specific neuroses. But even when the latter is
attempted we are confronted by the fact that there are various
intergradations of the recognized types of defect, that because of
varying degrees of defect in the same type a standard is hard to
establish, and above all that what appears as a specific mental malady in
one individual may crop out in his descendants in an entirely different
guise. Moreover, not only the predisposition of the individual, but age
and precipitative cause enter as factors in determining the ultimate
symptoms.
[Illustration: FIG. 35
Inheritance of feeble-mindedness (after Goddard); symbols same as in Fig.
33, p. 236.]
=Feeble-Mindedness and Insanity Not the Same.--=Authorities make a sharp
distinction between insanities on the one hand and feeble-mindedness on
the other. According to Goddard, not only is there no close relationship
between the two conditions, but in reality they stand at opposite ends of
the psychical scale. In general, insanity is a degenerative process,
whereas feeble-mindedness is an arrest of development. In the first case
the victim loses part of the mentality he once had, in the second he stops
short of normal development.
=Many Types of Insanity.--=The commonest manifestations of insanity are
undue depression, apathy, excitement, instability, obsessions,
hallucinations and delusions. Some mental disorders are associated with
recognizable structural changes in the nervous system, but the structural
basis of many is not known.
In general there is more doubt about the inheritability of some of the
insanities than about cases of mental deficiency. The term insanity is
merely a loose descriptive one, and we shall gain little definite
knowledge about the inheritance of such maladies until we study each
separate insane diathesis specifically. Psychiatrists recognize many
different forms of insanity, some of them very distinct from others and
the product of unrelated underlying causes. Often it is only a question of
degree or sometimes a matter of chance as to whether a given individual is
certified as insane or not. A neuropathic person who manifests certain
anti-social activities is sure to be classed as insane, whereas another
individual with the same diathesis in a less degree might pass
unrecognized. It is almost impossible in some instances to tell just where
the border-line between a neuropathic and a normal constitution lies. Many
of the idiosyncrasies of the insane, indeed, are merely exaggerations of
characteristics seen in normal people. Recent studies of the psychology of
the insane show that most of their hallucinations and delusions are
closely related to some previous mental experience they had before
becoming insane. And it has been found that the surest means toward
removing the obsessions of the patient in curable cases is to ferret out
these earlier experiences and correct the wrong impressions regarding
them. Again, certain forms of insanity do not become manifest except as
special reactions to particular environmental conditions, and if these
conditions do not happen to occur, then the neuropathic constitution
though existing would not be revealed. Certain critical periods of life
such as puberty, pregnancy and the close of sexual life are particularly
likely to test out the mentally unstable, although such individuals may
have maintained normal mental balance up to the crisis in question.
=Not All Insanities of the Same Eugenical Significance.--=Of the various
kinds of insanity some seem to be of much greater eugenical significance
than others, not only because they are strongly heritable, but also
because of the periodicity of the attacks. The patient may be repeatedly
in and out of the asylum and in his sane intervals wholly unrestrained as
far as propagating his kind is concerned. _Manic depressive_ psychoses and
_dementia precox_ in the order named represented the largest number of
admissions to the Wisconsin State Hospital for the Insane in 1911 and
1912, and both of these very frequently have a hereditary basis. Fig. 36,
a chart showing the insanity in a local family as worked out by one of my
pupils, is a good example of a recurrent type. The father (Fig. 36, p.
241) was about eighty-two years old when the record was made. His memory
was poor and he could not talk connectedly, although this was possibly
attributable to old age rather than to insanity. His brother, written to
in Ireland, stated that to his knowledge there had never been insanity in
his side of the family. The mother (2) was insane at nine, again at
twenty-nine and again at thirty-six. In her later life she has been in the
Mendota Hospital for the Insane five times and in the County Asylum twice.
The eldest daughter (3) has been in the State Asylum five times and is now
at home. The next daughter (4) spent five months in the asylum in 1885.
Another daughter (5) likewise spent a short period in the asylum. Two sons
(6, 7) have each spent two periods in the asylum, and a third son (8) has
had an attack of insanity. The youngest child died at the age of three.
Thus of the eight adult children six have been insane at some time. The
cases in this family seem all to be instances of manic-depressive
insanity.
[Illustration: FIG. 36
Inheritance of insanity in the L---- family. See text for description.]
=A Neuropathic Constitution May Express Itself Differently Under Different
Conditions.--=Some of the difficulties of getting genealogies of specific
forms of insanity are obvious from the following quotations chosen from
the works of eminent psychiatrists. Kraepelin, for instance, expresses the
opinion that: "The psychopathic charge of a family may reveal itself not
only by the appearance of mental disorders but also by other forms of
manifestation. Here belong before all, those diverse slighter deviations
from mental health which go to make up the borderland of insanity:
nervousness, states of anxiety and compulsion, constitutional depressions,
slight hysterical disorders and forms of feeble-mindedness, tics; also odd
characters, peculiarities in mode of living, criminal tendencies, lack of
self-control, intemperance, love of adventure, mendacity, suicide on an
inner basis."
From the volume of Church and Peterson on _Nervous and Mental Diseases_ a
further confirmatory opinion may be cited: "In determining the factor of
heredity we must not be content with ascertaining the existence of
psychoses in the ascendants, but must seek, by careful interrogation of
various members of the family, for some of the hereditary equivalents,
such as epilepsy, chorea, hysteria, neurasthenia, somnambulism, migraine,
organic diseases of the central nervous system, criminal tendencies,
eccentricities of character, drunkenness, etc., for these equivalents are
interchangeable from one generation to another, and are simply evidence of
instability of the nervous system. It is the unstable nervous organization
that is inherited, not a particular neurosis or psychosis, and it must be
our aim in the investigation of the progenitors to discover the evidence
of this."
=Certain Forms of Insanity, But Not All, Seem to Behave as Mendelian
Recessives.--=A number of psychiatrists and investigators of the
inheritance of insanities (Rudin, Lunborg, Davenport, Rosanoff, Jolly),
although working independently and in different countries, concur in the
opinion that manic-depressive insanity, dementia precox and allied
psychopathic conditions tend to occur after the manner of a Mendelian
recessive. On the other hand such maladies as Huntington's chorea are
transmitted as a dominant and in all probability at least half of the
children of an afflicted individual will inherit and manifest the defect.
As to inheritance of various other psychoses we have too few accurately
charted pedigrees for most types to make very positive statements about
their degree or manner of inheritance. Little can be said beyond the
statement that there is a decided tendency for various forms to recur in
offspring. Where more than one case of insanity occurs in a given family
or stock it is strong presumptive evidence that a hereditary defect is at
the bottom of it. As Doctor Wilmarth says, "Mental accident may occur in
any family, but it is rarely a second case occurs unless there is a
tendency to nerve degeneracy." For example, of 818 insane at the Wisconsin
State Hospital for the Insane during the biennium 1909-10, 187, or
practically one-fourth were positively known to have insane relatives. Of
these, 24 had insane fathers, 31 insane mothers, 30 insane brothers, 23
insane sisters, 25 insane uncles, 21 insane aunts, and 21 insane cousins.
Where definite information could be obtained it was found that of the
5,700 admissions of insane patients to the New York state hospitals
during the year ending September 30, 1911, 27.7 per cent. of the cases
showed a history of insanity in the family and an additional 22.9 per
cent. showed a history of alcoholism, nervous diseases and the like.
=Grades of Feeble-Mindedness.--=As to the various grades of
feeble-mindedness, while no sharp lines of demarcation can be drawn, a
rough and ready test usually applied is the relative ability of such
subnormal individuals to take care of themselves. In all, the conditions
exist from birth or shortly after. _Idiots_ are such defective individuals
as are unable to take care of themselves even to the matter of guarding
against common physical dangers. Their mentality does not progress beyond
that of a two-year-old child. _Imbeciles_ can take care of themselves in
the cruder physical ways, but are unable to earn their living. Their
mental age ranges from three to seven years inclusive. _Morons_, or the
"feeble-minded" in a more specific usage of the term, can under proper
direction become more or less self-supporting but they are as a rule
incapable of undertaking affairs which demand judgment or involve
unrestricted competition with normal individuals. Their intelligence
ranges with that of normal children from seven to twelve years of age. The
last class grades up insensibly into the shiftless, ne'er-do-well types
which exist in every community. It is the hordes of the feeble-minded in
the restricted sense that afford our most serious problems to-day. The
idiot and the imbecile are usually early and easily recognized and are
kept more or less under restraint, but the higher grades of feeble-minded,
the so-called moron type, can be detected often only by carefully devised
tests.
=About Two-Thirds of the Feeble-Minded Have Inherited Their
Condition.--=Concerning the various types of feeble-mindedness there is
strong evidence that heredity is a factor of greater magnitude than in
most insanities. All facts point to the conclusion that most mental
deficiency is strongly inheritable and that the majority of our defectives
of this type come from degenerate stocks. Practically all specialists at
the heads of asylums and homes for the mentally deficient concur in the
opinion that about two-thirds of the cases are hereditary. For example,
Doctor Alfred Wilmarth, superintendent of the Wisconsin Home for
Feeble-minded, says: "My own observations, and those of others in this
country and Europe, would indicate that at least two-thirds of the
feeble-minded have defective relatives."
In his study of two thousand children tested by the Binet measuring scale
for intelligence, Doctor Henry H. Goddard, director of the Department of
Research at the Training School for Feeble-minded at Vineland, N. J.,
remarks concerning heredity of feeble-mindedness: "But we now know that
sixty-five per cent. of these children have inherited the condition, and
that if they grow up and marry they will transmit the same condition to
their offspring. Indeed, we know that this class of people is increasing
at an enormous rate in every community and unless we do something to stop
this great stream of bad protoplasm we shall some day be swamped in a sea
of degeneracy."
E. R. Johnstone, superintendent of the training school at Vineland, N.
J., in a recent bulletin remarks concerning feeble-minded and epileptics,
"We are now convinced that from sixty to eighty per cent. of the cases are
hereditary."
Again, we find Doctor A. C. Rogers, superintendent of a school for
feeble-minded in Minnesota, saying, "We have no survey of mentality in
this country except in very small areas, but probably about sixty-five per
cent. of the feeble-minded children that we know of are feeble-minded from
heredity; that is, they come from families in which there is much
feeble-mindedness, usually associated with various neuroses or psychosis.
There are about thirty-five per cent. approximately that are acquired
cases. These cases develop from various things. Full development may be
prevented during gestation, or early childhood, or early adolescence, but
these acquired cases are entirely distinct from the hereditary ones."
In a recent paper Doctor Martin W. Barr, chief physician for the
Pennsylvania Training School for Feeble-minded Children, says: "In my
individual study of 4,050 cases of imbecility, I find 2,651, or 65.34 per
cent., caused by malign heredities; and of these 1,030, or 25.43 per
cent., are due to direct inheritance of idiocy; and 280, or 6.91 per
cent., to insanity." From these figures it will be seen that Doctors Barr,
Goddard, Wilmarth, Johnstone and Rogers all agree in their estimates;
namely, that two-thirds of our imbeciles are so through inheritance.
=Some Results of Non-Restraint of the Feeble-minded.--=The following
excerpt from a paper by Doctor Barr, is a fair sample of what happens
when such defective individuals are not restrained from propagating their
kind:
"My own study and observation alone, of over 4,000 degenerates, shows
such examples as: A man 38 years of age, the father of 19 defective
children, all living, he and his wife both under par mentally; as was
another couple, with 9 imbecile children; an idiot woman with 7 idiot
children. A forcible instance is that of a man with two daughters and
one illegitimate grandchild, all feeble-minded.... I could name a
family, one of the proudest in the land, where there are five
children, an aunt and two uncles, all feeble-minded.
"Yet another, which in seven generations numbering some 138
individuals, records 10 still-born children (premature births), 16
insane, 7 imbeciles, 3 epileptics and 32 with mental peculiarities so
pronounced as to occasion remark. Of the 138 there remain 80
apparently normal, who are nevertheless hopeless slaves of a neurotic
heredity, direct or collateral.
"In a study of 15 imbecile girls, 3 were recognized prostitutes, 9 had
each 1 illegitimate child (2 being the result of incestuous
intercourse with brothers); 1 had 2; 2 epileptics had, the one 3, and
the other 4 idiot children.
"Four feeble-minded women had 40 illegitimate children.
"A feeble-minded woman living in an almshouse since early childhood,
allowed to go out to service periodically, had given birth to six
illegitimate children, all inheriting her defect.
"An imbecile drunkard is the father of three feeble-minded children.
The daughter, seduced before the age of sixteen, gave birth to an
idiot child; one son is a harmless imbecile, but the other is a moral
imbecile, a sexual pervert, a thief on the streets, and a pyromaniac,
firing in sheer wantonness a large mill property.
"Another shows the entire family for three generations below normal.
Father, mother, mother's sister, and father's uncle, all imbecile.
Five children feeble-minded. One girl had a proposal of marriage, and
one boy is married to a feeble-minded girl.
"One insane woman, whose brother and sister committed suicide, had
five sons. The oldest, feeble-minded, a drunkard and hobo, had one
son, a criminal. The second son, insane, had three imbecile children.
The third, an insane epileptic, had three imbecile sons, one of whom
was an epileptic. The fourth son was insane. The fifth, apparently
normal, had a morally imbecile son and an epileptic daughter."
Yet striking as is the inheritance of these maladies, Doctor Barr points
out that of the 10,000 known cases of feeble-mindedness in Pennsylvania,
only 3,500 are sequestrated. This leaves a balance in that state of 6,500
totally irresponsible individuals to work havoc in society by producing
their kind.
=Inheritance Not a Factor in Some Cases of Mental Deficiency.--=On the
other hand as our data show, there remain about one-third of the mentally
deficient type to be accounted for on other than a basis of heredity. As
already noted, some of these are doubtless the product of suppressions of
normal development by various extraneous factors operating before or
shortly after birth. There is one class particularly, estimated by some
authorities as constituting as high as thirty per cent. of the
feeble-minded which is unusually puzzling. These are the so-called
mongolians. The name is given because the features of such individuals
bear more or less resemblance to those of some of the Mongolian races. The
defect does not seem to be hereditary although it is usually congenital.
It appears to be due to something which interferes with prenatal
development. Whatever the conditions, whether lack of nutrition in the
mother, alcoholic or other poisoning, the cases seem to be as hopelessly
incurable as are the hereditary forms. From the social standpoint, of
course, such individuals are in their immediate generation, as incompetent
or as dangerous to society as those suffering from the more surely known
hereditary forms of mental defect.
=Epileptics.--=Although epileptics are not classed as imbeciles
ordinarily, as a matter of fact no sharp distinction can be drawn between
the two classes. Doctor Wilmarth says, "Epilepsy and mental deficiency are
as closely related as branches on the same tree.... Over one-half and
perhaps two-thirds of all feeble-minded are subject to convulsive seizures
at some period of their lives, and we are never surprised at the
appearance of epilepsy in any feeble-minded person. On the other hand, so
small a percentage of epileptics maintain normal mental actions as hardly
to be worth consideration ... even those who retain a normal mind in the
early stages of the diseases almost infallibly become imperfect later."
How slight a chance the epileptic has of ever becoming normal may be
inferred from a statement made by Doctor Frank Billings in a paper read
before the Illinois State Medical Society in 1909 to the effect that "ten
per cent. or more can be cured by proper care."
According to the estimates of "The Committee of Fifty" in the state of
Illinois, who have been agitating for the establishment of a colony for
epileptics, there are 10,000 of these unfortunates in that state. The
consensus of opinion of experienced workers in various states is that
there is about one epileptic to each three hundred fifty to five hundred
inhabitants.
=In Heredity Conditions of Feeble-Mindedness Are Probably Recessive to
Normal Condition.--=As to the mode of inheritance of the various forms of
feeble-mindedness, the evidence points to such defects in the main as
being recessive. However, no particular grade can be picked out and shown
to be a pure recessive. For instance, the children of two epileptics will
be defective but it is impossible to predict always whether the defect
will appear as epilepsy or feeble-mindedness. This is doubtless due to the
fact that mental deficiencies even of the inheritable type are not all due
to the same specific cause, and in many cases the individual is defective
in more than one direction. If one or more of a great number of units
which are necessary for complete mental development are lacking, obviously
mental deficiency will result. In other words, feeble-mindedness and
allied disorders may not be definite characters, but simply evidences of
the fact that the nervous system has not developed all factors necessary
for normal mental coordination. Goddard, however, one of our best
authorities on the heredity of feeble-mindedness, is inclined to regard
the condition as a unit character, "due either to the presence of
something which acts as an inhibitor, or due to the absence of some
stimulus which sends the normal brain on to further development."
Supposing nervous defects finding expression in feeble-mindedness,
epilepsy and related conditions, to act as a Mendelian recessive, then the
marriage of one such defective with another should yield only mentally
enfeebled offspring. How nearly this expectation may be realized is seen
from the following examples.
In an extensive study[9] of feeble-mindedness, just from the press, Doctor
Henry H. Goddard points out that of 482 children with both parents
feeble-minded all but six were feeble-minded. Even the exceptions may be
apparent rather than real as there is possibility of mistake in judging
the condition of the parents or of the children themselves. Moreover, with
the feeble-minded one is not always sure of the paternity of a child, as
is instanced by Doctor Goddard in a case quoted from Doctor Emerick in
which of twelve children in a white family with both father and mother
feeble-minded ten were feeble-minded and two were not, but these two were
_mulatto_ children.
In a paper by Weeks (_The Inheritance of Epilepsy_), in part an extension
of an earlier joint paper by Davenport and Weeks, is recorded among others
a study of twenty-seven fraternities in which both parents were either
epileptic or feeble-minded. Of the 28 progeny, 19 lived long enough to
reveal their mental state. Of these 3 were feeble-minded, 8 epileptic and
8, from parents who developed epilepsy late in life, were what Doctor
Weeks terms "tainted." In 15 fraternities in which one parent was
epileptic and the other feeble-minded he found there had been 81
conceptions. Of these 7 were too young to classify and 19 had died before
fourteen years of age. Of the remaining 55, 28 were epileptic, 26
feeble-minded, and 1 insane. Again, in 9 families in which the parents
were both feeble-minded, of the 38 surviving offspring who were old enough
to classify, 7 were epileptic, 29 feeble-minded, and 2 drunkards. In 5
families where one parent was insane and the other epileptic or
feeble-minded, 5 children died before the age of fourteen, the condition
of 2 was unknown, 2 were epileptic, 4 feeble-minded, 1 insane, 8 tainted,
and 7 seemingly normal. Regarding the latter Doctor Weeks says they came
from two families where in one case the father's insanity seemed to be
traumatic and in the other alcoholic.
In a few cases where the defect in one parent has apparently been of a
type different from the defect of the other parent a "normal" child was
produced. That is, presumably each parent carried normality in the trait
defective in the other so that the child became simplex with reference to
each defect. Davenport points out that not infrequently two deaf-mutes
whose defects are due to different causes may have normal children.
In general, however, the reasonable expectation is that where two
feeble-minded individuals marry, a very common occurrence, the children
will all show mental deficiency. A mating between a feeble-minded person
and one of perfectly normal stock will apparently result in normal
children although they will be carriers. There is some evidence, however,
that such carriers may occasionally show "taints" of abnormality in the
form of migraine (nervous sick headache), alcoholism, queerness, violent
temper, etc. Thus according to the studies of Doctor Weeks, "In 50 matings
where at least one parent is migrainous, there were 350 conceptions, of
which number enough is known of 212 to classify 55, or 26 per cent., as
epileptic; 12, or 6 per cent., as feeble-minded, with the others tainted
or normal. In the 131 matings where at least one parent is alcoholic,
there were 845 conceptions. Of the 494 classified, 151, or 31 per cent.,
were epileptic; 54, or 11 per cent., feeble-minded, with the balance
tainted or normal." Marriage between two carriers will cause the defect to
reappear in active form in approximately 25 per cent. of the offspring and
50 per cent. will continue to be carriers.
=Many Apparently Normal People Really Carriers of Neuropathic
Defects.--=There is considerable evidence that many apparently normal
individuals of our average population are in reality carriers of some form
of neuropathic defect, some authorities placing the proportion
provisionally at over thirty per cent. This being true, then it is easy to
explain the apparently unaccountable appearance of epilepsy,
feeble-mindedness, or similar defects among the children of what pass for
normal stocks. The probabilities are that in many cases it means simply
that the parents of the defective children have been carriers.
As to the contention that in preventing the propagation of the
feeble-minded we may be depriving the world of geniuses, Doctor Goddard
remarks: "It is a significant fact that in our three hundred family
histories totaling 11,389 individuals not a single genius has been found.
Not only are there no geniuses but the fact can not be too strongly
emphasized that even the people who are considered normal ... are not as a
rule people of average intelligence...." However, between insanity and
genius he finds more kindred spirit.
=Tests for Mental Deficiency.--=As to tests for mental deficiency, the one
commonly meted out to victims in the every-day world is the
social-economic one of survival in the competitions of life. The mentally
deficient fail. Although often unrecognized as feeble-minded they drift
through life social and economical derelicts who have to be supported by
the community.
Of laboratory tests many have been devised. While all yet leave much to be
desired, still through their application the majority of mental defectives
can be detected. Fairly accurate standards of normality have been
established from which the relative degree of "backwardness" can be
determined. We have just awakened to the importance of detecting
defectives early in life, hence many of our tests have been planned with
reference to children. They are based not so much on training or conscious
learning as on fundamental processes which develop at certain ages in
children. Another impetus toward securing adequate criteria of mental
deficiency has been the crying need of having some easily applied standard
for detecting the very large numbers of defective immigrants who are
continually seeking to enter the United States.
Most of the methods consist of "performance" tests which are planned to
test the powers of perception, concentration, application, ingenuity and
education of the subject. Previous environment, education and the
difficulties under which the subject may be laboring at the time of the
test must, of course, be taken into account. It is particularly difficult
to get adequate tests for the immigrant which will enable one to
distinguish between ignorance, stupidity, fear and temporary psychic
depression on the one hand, and congenital mental deficiency on the other.
Perhaps the most successful single set of tests for mental deficiency is
that known as the Binet-Simon Scale. From an examination of large numbers
of French school children Binet constructed a scale of tests of increasing
complexity accurately graded to age and previous training of the average
normal child. In the Binet-Simon system tests are given for each age from
three years to thirteen. When a child successfully passes the tests for
his age he is classed as normal. If he succeeds only in tests which
normally are those given for a child a year younger then he is backward to
the extent of one year. Similarly he may show by these graded tests that
he is backward to the extent of two years, three years and so on. If a
child is more than three years backward according to the test he is
regarded as mentally defective. Various corrections and adjustments of the
original scale have been worked out to allow for unevenness in mental
development. On the whole the scheme works out satisfactorily when applied
by one skilled in its use. The attitude of the examiner, however, is of so
great importance that the tests are of less value in the hand of
inexperienced workers. A revision of the scale to adapt it better to
American children has recently been made by Doctor Goddard.[10] Besides
the Binet-Simon tests various performance tests, standardized for children
of different ages, such as Seguin's form board, Healy's pictorial
completion test, Fernald's construction puzzle, the Rossolimo test, De
Sanctis test, etc., are used by different investigators. Questions
designed to reveal moral tone are also employed. Doctor Howard A. Knox,
assistant surgeon United States Public Health Service, in a recent
article[11] gives an interesting account of the tests applied to determine
the exact mentality of immigrants entering the United States together with
a brief review of various tests. A full account and discussion of the
various tests for the mentally subnormal will be found in a recent
publication by Doctor William Healy,[12] director of the Juvenile
Psychopathic Institute, Chicago.
=The Backward Child in School.--=It is only in recent times that we have
come to realize the seriousness of the problem which the backward child
presents in our schools. It is of the utmost importance to discover early
in school life which of the backward children owe their condition to
adenoids, defective sight or hearing, poor nutrition, imperfect
circulation, or other remediable defects, and which are the victims of
innate mental deficiency. The treatment of the individual must be very
different in the two cases. In the one the condition can be cured by
proper manipulations or other treatments; in the other it can only be
ameliorated. All school children who are two or three years below grade
should be rigidly inspected by the medical examiner.
From a study of about two thousand children comprising the first five
grades of an entire public school system Goddard found that eighteen per
cent. were definitely "backward." Of these between two and three per cent.
were actually feeble-minded, the condition in the remaining fifteen per
cent. being presumably capable of correction. Other similar surveys have
given practically the same results.
=The Exceptionally Able Child Likely to Be Neglected.--=However, while we
must not forget that it is important to recognize backward children and to
see that they are segregated into small groups which are not required to
do the full amount of work in regular time, it is equally urgent to see
that the unusually bright individual is also given opportunity to advance
more rapidly than the rank and file. Only too often the holding back of a
child in school leads to lack of interest and habits of mental laziness,
and sometimes to truancy and incorrigibility. The general attempt in our
graded schools to keep all children close to the average is to be strongly
condemned.
=Cost of Caring for Our Mentally Disordered.--=Doctor Charles L. Dana,
member of the National Committee for Mental Hygiene, estimated in 1904
that the actual cost of caring for feeble-minded and insane in the
United States amounted to sixty million dollars, to which should be added
the corresponding loss in industrial activity on the part of the
afflicted,--at least twenty million dollars more, and he figures that the
amount was increasing at the rate of four per cent. per annum. Many
investigators concur in the opinion that our insane and feeble-minded
alone cost us far above one hundred million dollars. Adding to this
economic burden the cost of our delinquents and criminals the total
expense becomes stupendous. And when we consider still further the even
greater burden of suffering of the unfortunates themselves and the sorrows
of those to whom they are dear, a burden not measurable in money, the
feeling that something must be done to relieve the situation becomes
overpowering.
=Importance of Rigid Segregation of Feeble-Minded.--=As regards the really
feeble-minded little can be done beyond making them as happy as possible
and developing the limited gifts they have been given by nature. Their
teaching must be in the main concrete and simple. At the age of puberty it
is imperative to see that the sexes are separated and kept under
sufficient permanent supervision to prevent all possibility of
procreation. There is neither economic nor common sense in even allowing
the remotest chance of such occurrences as the following: "This is the
case of a feeble-minded and epileptic woman who had six children by
various persons while an inmate of a county poor house. One child at the
age of eighteen died in the almshouse, two died in infancy, one was
epileptic (the son of a man with a criminal record) and two who are now
living in the almshouse are feeble-minded, one being the son of a negro."
Again, we find a superintendent of an English almshouse reporting that one
hundred and two out of one hundred and five children born there in five
years were feeble-minded.
As conditions are to-day every institution for the feeble-minded has a
long waiting list and the same is true of most asylums for the insane.
Instead of providing the prolonged care necessary for such patients,
institutions are forced to discharge many prematurely in order to make
room for more urgent cases.
=Importance of Early Diagnosis of Insanity.--=In insanities, even when of
hereditary origin, there is much hope in certain cases of greatly
benefiting the individual, though a permanent cure, or at least the
establishment of procreative fitness may be impossible. It is extremely
important that the public realize how much can be done through early
examination and advice in such mental afflictions. Most of the insane who
recover usually do so within a few months of their first alienation, hence
the importance of losing no time in detecting the condition and securing
early treatment. It is now well known that many cases of chronic insanity
may be measurably improved under the care of a psychiatrist by systematic
re-education, especially in industrial lines. But how little of this may
be expected at the hands of the untrained custodians who "feed" the
inmates of our county almshouses, to which in many states the chronic
insane are entrusted, is obvious.
=All Insane Should Be Passed Upon by Competent Psychiatrists.--=The
atrocious system of turning the chronic insane over to county poorhouses
manned by supervisors whose chief qualification for the position has not
infrequently been the lowness of their bid for boarding and caring for the
inmates, can not be too strongly condemned. Incredible as it may seem, in
some states the court can on its own judgment send patients directly to
these institutions without first submitting them to the study of expert
physicians in the state hospital for the insane. The viciousness of such
procedure is evident when one realizes that often careful scrutiny on the
part of the very best experts, extending over a considerable period of
time, is required before the true condition of the patient can be
determined. Recently a psychiatrist of high standing, who was gathering
data on county asylums for a national organization, informed the writer
that beyond the shadow of a doubt he had come across case after case in
county asylums which would have been curable under proper treatment.
Here again the responsibility in last analysis must rest upon us as
citizens, for it is largely through our intelligent demands as voters that
conditions will be improved and competent experts be put in charge of
county asylums as well as of the state hospitals for the acutely insane.
=Some Insanities Not of Hereditary Origin.--=Some alienists believe that
self-poisoning known as _auto-intoxication_, due to improper elimination
of poisons generated through faulty digestion or metabolism, if of long
standing, may be not only a contributory but a more or less direct cause
of insanity. About twenty per cent. of insanities of men living in cities
and about fifteen per cent. of those living in the country seem to be
directly related to the intemperate use of alcohol. The corresponding
figures for women are seven per cent. and one per cent. respectively.
General paresis or softening of the brain is probably invariably preceded
by syphilis. About twenty-two and five-tenths per cent. of the first
admissions to hospitals for the insane from city-dwelling men, and eight
per cent. from men living in the country in the state of New York are
cases of this kind of insanity. The corresponding figures for women are
five and five-tenths per cent. and two and five-tenths per cent.
respectively.
=Importance of Heredity in Insanity Not Appreciated.--=We have already
seen that heredity plays an important part in insanities. There can be
little doubt that the tendency is to under-estimate rather than
over-estimate its importance. Many cases said to be "caused" by mental
strain such as those occasioned by domestic infelicities, business
reverses and the like should in all probability be fundamentally
attributed to something far more deep-seated than the more obvious cause.
In many such instances there is little doubt that an inherent weakness in
mental make-up exists which predisposes the individual toward mental
breakdown. This is more apparent when one recalls that there are thousands
of other individuals who undergo equally great or greater calamities
without loss of mental balance. There are well-recognized types of mental
disposition which later contribute to corresponding forms of insanity. In
many instances the final catastrophe may be averted if the "peculiar"
individual can be kept in good health and guided into right habits of
thought. Undoubtedly certain infectious diseases, arterio sclerosis,
various poisons in the blood, child-birth, and similar influences often
enter as important contributory factors. In all cases of cure, however, we
must face the fact that under existing conditions these mentally restored
individuals are released into society without let or hindrance as regards
their marital relations.
CHAPTER IX
CRIME AND DELINQUENCY
=The Relative Importance of Heredity and Environment in This Field
Uncertain.--=The whole question of crime and delinquency is a highly
complex one. Here, perhaps, more than in any other phase of race
betterment we find the greatest difficulty in separating the effects of
hereditary predisposition from the results of unfavorable environment.
While there is no longer a reasonable doubt about such nervous disorders
as epilepsy, feeble-mindedness and certain forms of insanity being rooted
largely in ancestral taints, the degree to which crime or delinquency is
based on heredity is far more questionable. Every student of genetics
knows that we may have dwarf plants because the constitution of the germ
is of a nature to produce only such individuals, or we may have dwarfed
plants because of adverse conditions of soil and lack of an opportunity to
climb or rise to their full capacity. Bateson pertinently remarks, "The
stick will not make the dwarf pea climb, though without it the tall can
never rise. Education, sanitation, and the rest are but the giving or
withholding of opportunity." The important sociological question for us to
determine is which of these lowly peas of the human family are really
dwarfs and which are dwarfed simply because the stick of opportunity on
which to climb is lacking.
Beyond doubt a considerable portion of crime and degeneracy is due in
large measure to innate inclination, but with just as little doubt much is
the effect mainly of vicious habits acquired through an unwholesome
environment. A normal appetite or impulse may be given a pathological
trend by bad influences. And one has to reckon, moreover, with degrees of
hereditary aptitude to crime. Just what is the measure of normality? To
what extent by developing to their highest point certain inhibitive or
opposing tendencies, can we counteract certain inherent proclivities for
wrong-doing? By what means shall we sift the congenital defectives from
the victims of suppressed opportunities? These and kindred questions
confront us at the very outset of our studies of crime and delinquency. It
is obvious that although we may institute the strictest elimination of the
socially unfit, unless we can provide a wholesome environment for the fit,
lapses into unfitness are sure to recur.
=Feeble-Mindedness Often a Factor.--=The conviction is steadily growing
among students of human heredity that a considerable amount of crime,
gross immorality and degeneracy is due at bottom to feeble-mindedness and
that, therefore, if we can once eliminate feeble-mindedness, these vicious
accompaniments will at the same time in equal measure disappear. Goddard,
for example, one of our authorities on the inheritance of
feeble-mindedness, is convinced that a large proportion of the delinquent
girls who fill our reformatories are actually feeble-minded. They are
often the higher grade or moron type, and their mental condition remains
unsuspected because they have never been thoroughly tested in this
respect.
=Many Delinquent Girls Mentally Deficient.--=According to Havelock Ellis,
2,500 of some 15,000 women who passed through Magdalen homes in England
were definitely feeble-minded and were known to have added a thousand
illegitimate children to the population.
The preliminary reports of the so-called white slave investigations now in
progress in New York City classes 25 per cent. of these unfortunate women
as mentally incapable of taking care of themselves. Other investigations
indicate that from 40 to 60 per cent. of this class of women are
defectives. For example, from the report of the Massachusetts "Commission
for the Investigation of the White Slave Traffic, So-Called," one reads:
"Of 300 prostitutes, 154, or 51 per cent., were feeble-minded. All
doubtful cases were recorded as normal. The mental defect of these 154
women was so pronounced and evident as to warrant the legal commitment of
each one as a feeble-minded person or as a defective delinquent.... The
135 women designated as normal, as a class were of distinctly inferior
intelligence. More time for study of these women, more complete histories
of their life in the community, and opportunity for more elaborate
psychological tests might verify the belief of the examiners that many of
them were also feeble-minded or insane."
The data from some of our public reformatories, industrial schools and
state homes for delinquent girls, are very instructive in this respect.
Reports from a number of such institutions show that many of their inmates
are mentally subnormal. The proportions range from thirty-three per cent.
in the New Jersey Reformatory at Rahway to eighty-nine per cent. in the
institution at Geneva, Illinois.
=Institutional Figures Misleading.--=However, significant as are these
figures from institutions for delinquents, one should not be misled by
them. They are undoubtedly not representative of offenders in general, but
of a selected group of the most hopeless cases. In the first place the
more capable individuals escape the dragnet which lands the defective
delinquents in an institution, and furthermore, because of liberal systems
of probation, only the more incorrigible or the very stupid make up the
bulk of the population of such places. Miss Augusta F. Bronner, assistant
director of the Psychopathic Institute of the Juvenile Court of Chicago,
from a careful study of five hundred and five cases of delinquent boys and
girls in the Detention Home, chosen with as little selection as possible,
finds the proportion of mentally subnormal among them to be less than ten
per cent.
=Many Prisoners Mentally Subnormal.--=Doctor Walter S. Fernald, of the
Massachusetts School for Feeble-minded, estimates that "at least 25 per
cent. of the inmates of our penal institutions are mentally defective."
Among the various available estimates at hand this seems to be a fairly
conservative approximation. Hastings H. Hart points out that this
calculation of 25 per cent. means that there are 20,000 adult defective
delinquents in prison, and 6,000 youths in juvenile reformatories, or a
total of 26,000 in custody in the United States.
=The Inhibitions Necessary to Social Welfare Not Well Established in
All.--=But let us look at this matter of delinquency a little more in
detail. In common with other living creatures mankind has two strongly
predominating instincts without which there can be no prolonged individual
or racial existence, namely, the self-preservative and the reproductive.
Says Schiller: "While philosophers are disputing about the government of
the world, Hunger and Love are performing the task." Under
self-preservative would be included everything pertaining to food,
property and self-protection. In addition, however, man, together with
certain other social animals, has developed a third set of activities or
instincts--an impulsion toward the preservation of the community to which
he belongs--and so far has this evolved in his case that it outranks in
importance the other two. For the highest accomplishments and ideals of
the race are in last analysis expressions of this social instinct. But
with this system of mutual help comes the necessity of certain restraints,
because for society to exist its members must impose upon themselves, or
have imposed upon them, certain inhibitions of their self-preservative and
reproductive instincts.
Being a late acquisition of the race and less firmly ingrained, the social
instinct is not well established in all individuals. Some have it
sufficiently strong to exercise of their own accord the necessary
inhibitions of other instincts. Experience has shown that others, either
through a lack or through a wrong cultivation of it, can not or will not
do so unaided. For the latter, society has instituted certain conventions
and the criminal law whereby through a system of restraints and
punishments such an individual is held in check either by actual physical
restraint of his property or person or through the powerfully inhibitive
factors of shame or fear. Man as a normal member of society must
constantly take heed of the physical, intellectual or moral danger the
exercise of a given feeling, action or procedure on his part will bring to
humanity, and govern himself accordingly.
But it is in just these very inhibitions that mental defectives are
lacking. They are almost invariably anti-social types because they are
unable to establish the personal abstentions which are necessary for the
good of the community. While in the individual of innate normal mentality
anti-social traits may have developed because of improper training or
surroundings, in mentally defective types some factor or factors necessary
to normality have been left out of their make-up and as a result they are
often wholly lacking in social instincts or have these so feebly developed
that education and exhortations toward social ideals are fruitless. We can
not appeal successfully if there is nothing to appeal to; we can not
develop something out of nothing.
=The High-Grade Moron a Difficult Problem.--=One great difficulty in
identifying the high-grade morons who are a bountiful source of our
criminals is our almost universal failure to recognize that a memory test
alone is not sufficient to determine the mental responsibility of an
individual. Not only memory, but judgment, will-power and perhaps, also,
to a lesser degree, the powers of attention and concentration are all
indispensable elements in the make-up of a normal individual. There are
cases on record of imbeciles with prodigious memories, yet hopelessly
incapable of caring for themselves or of respecting the rights of others.
In fact certain types of morons, usually cunning, often prepossessing and
superficially clever, are characterized by good memories and will
_moralize_ volubly, although their wills are too weak to inhibit impulses
when they face temptation. It is obvious that just in proportion as the
intelligence of the high-grade degenerate approaches normality and yet
remains abnormal, the more dangerous he may become to society.
=Degenerate Strains.--=A number of family records are now available which
show convincing evidence of the hereditary nature of a degeneracy which
finds expression in pauperism, immorality and crime.
As has already been pointed out, there is reason to believe that much of
this is based in some degree on feeble-mindedness. One of the most
remarkable of these is the recent study on degeneracy by Goddard as set
forth in his book called _The Kallikak Family_. The record is that of six
generations of descendants from an original progenitor to whom the
fictitious name of Kallikak has been assigned. This individual, descended
from good stock, before his marriage met a feeble-minded girl by whom he
became the father of a feeble-minded son. Later he married a normal woman
by whom he had normal children. Thus from one normal father have sprung
two lines of progeny, one vitiated with feeble-mindedness, the other
normal. The comparison may be readily made by drawing up in parallel
columns the data as follows:
LINE A LINE B
In five generations 480 direct In five generations 496 descendants
descendants from a normal father from the same normal father as in
father and a feeble-minded Line A and a normal mother have the
mother have been accounted for following record:
as follows:
143 known to be feeble-minded. All but one of normal mentality.
291 mental status unknown or Two men known to be alcoholic.
doubtful.
36 illegitimate. One case of religious mania.
33 sexually immoral, mostly Among the rest have been found
prostitutes. nothing but good representative
citizenship, numbering doctors,
24 confirmed alcoholics. lawyers, educators, judges,
traders, etc.
3 epileptics. No epileptics or criminals.
82 died in infancy. Only fifteen children died in
infancy.
3 criminals.
8 keepers of disreputable houses.
46 only ones known to ben ormal.
Certainly there is abundant food for thought in these two records.
If we take still other families of criminal or degenerate antecedents the
same multiplication of viciousness, as a rule, is in evidence. Thus,
_Margaret, the Mother of Criminals_, has left a progeny of some 700
paupers, prostitutes and criminals, some of the women bearing as many as
twenty children. The famous Jukes family, so often cited, with its 310
professional paupers, 300 deaths in infancy, 440 physical wrecks from
debauchery, 50 prostitutes, 60 habitual thieves, 7 murderers, and 130
other convicts out of a total 1,200 descendants who have been identified,
has alone cost the state of New York $1,250,000 in the care of its
criminal, defective and immoral progeny.
Another family record, the Zeros, reported by Poellman, of Bonn, starts
with a female confirmed drunkard. In six generations of her descendants,
totaling 800 people, Poellman found 102 professional beggars, 107
illegitimates, 181 prostitutes, 54 in almshouse, 76 convicted of serious
crime, 7 of murder, and costing some $1,206,000. Or we might cite the
so-called _Tribe of Ishmael_, the progeny of a neurotic man and a
half-breed woman. They have spread their ill-favored spawn over various of
the central states in a veritable flood of imbecility and petty crime. And
to these families may be added the records of _The Hill Folk_, _The
Pineys_, or others of the several recent studies of degenerate strains.
All bear the same message of rapidly multiplying degeneracy.
=Intensification of Defects by Inbreeding.--=Most of these regional
surveys that are now in progress show that there is particular danger in a
population becoming broken up into small communities and isolated. Under
such conditions there is a pronounced tendency to intermarry, and if
deterioration is already present in the stock such communities become
centers of marked degeneracy. The situation is well exemplified in the
following excerpt from Davenport:
"I have been going over the records of one family in New York, the
so-called Nam family. There were 55 per cent. consanguineous matings,
marriage between cousins, in one generation, and, owing to the fact
that the strain was already loaded with defects, we can see how these
defects were concentrated by these cousin marriages, so that about 90
per cent. of the strain is feeble-minded. There were fully 90 per
cent. of the men who are unable to resist the lure of liquor.
One-fourth of the children are born illegitimates. Infanticides,
incest, murder, harlotry, are all over the chart. This is a highly
inbred community, keeping a nearly pure strain of social defects, and
the cost to the community has been a million and a half on a fair way
of figuring, not directly in the care, but indirectly in the damage
they have done. These constitute a rural community. Out of this
community we can trace those who have gone to the cities and become
murderers, prostitutes and thieves. They are not confined to one
state; they spread out over the country. One branch of the family came
to the state of Minnesota. We sent to one of Doctor Rogers' trained
field workers to learn whether she had ever heard of this family, and
received a reply that the family was well known to social workers in
the state of Minnesota. These strains of degenerates are not local
matters at all; they are matters of national interest."
Concerning crime and delinquency, we find that all evidence tends to show
that an alarming increase is in progress although satisfactory data are
hard to obtain. It is certain that there is a tremendously
disproportionate increase in the number of prisoners in recent years
compared with general population, for while the total population has
increased three and one-half fold, the prison element has increased
fifteen fold. According to Wier, in this country there are four and
one-half times as many murders for every million of our population to-day
as there were twenty years ago.
It may be urged that this increase in prison population is not a
disproportionate increase in the number of defectives or criminals, but
only an increase in the number sent to prison, and this is probably a
partial truth--but when we recall such pedigree as those of the Nams, the
defective line of Kallikaks and other known unsound strains, he must be
hopeful indeed who can find much consolation in this supposition. In any
event, no such uncertainty exists regarding the number of murders and
homicides, since these have in all probability been as fully recorded in
the past as at present.
=Vicious Surroundings Not a Sufficient Explanation in Degenerate
Stocks.--=It is sometimes urged that we are not dealing in such cases with
degenerate strains, but merely with unfortunate individuals who have been
subjected to pernicious surroundings from the beginning. And it can not be
denied that parents who are mentally defective, dissipated or syphilitic
afford most noxious developmental and environmental conditions for their
children. But when one notes how intimately the moral degeneracy in such
stocks is bound up with some degree of feeble-mindedness, he is strongly
skeptical toward the sufficiency of such an interpretation, although
environment undoubtedly intensifies the results. Concerning this point
Davenport says:
"We have certain methods of testing whether it is bad environment or
bad breeding which produced these people. Some of the children have
been taken at an early age and 'placed out'. We have traced their
subsequent history. In most cases they have turned out quite as bad as
those who have remained at home. In a few cases they have turned out
well, but it is also true that some of the children who remained at
home in bad environment have turned out well."
And to Davenport's testimony may we add that of Doctor Wilmarth, who,
speaking of children at the home for feeble-minded, says:
"In no place is this subject of the power of heredity in relation to
environment so easily studied as among our children. A group of many
little children came to us from the state school, being untrainable
there. They have had with us the same teaching and the same
companionship. Each one has lived, eaten and slept among the others,
and, so far as we know, with but one exception, those of vicious
parentage have turned instinctively to vicious traits by preference,
while those of simple but honest stock do evil things only under
strong temptation, and do not persist in them after the wrong is
pointed out."
=By No Means All Delinquents Are Defectives.--=One must not overlook the
fact, however, that _delinquent_ and _defective_ are by no means
synonymous terms, and that many delinquents are with little doubt the
product of adverse social circumstances.
The recent careful work of Doctor William Healy[13] in connection with the
juvenile delinquents of Chicago shows convincingly that the underlying
causations of delinquency are many. Such factors as immorality or constant
quarreling of parents, bad companions, lack of parental control, defective
sense organs, debilitating habits, lack of healthy mental interests and a
host of other environmental factors are not infrequently sufficient in
themselves to develop delinquency in the absence of inherited deficiency.
The present-day efforts of the student of heredity should not be
misunderstood. They are not attempts to make all delinquents out
defectives, but rather to determine what percentage of delinquents may be
legitimately reckoned as defective and to make the facts known. Since
there is no longer any reasonable doubt that, to express it in the mildest
terms, an amount of delinquency far from negligible is due in great
measure to congenital omissions or propensities, then the sooner the
public learns this the better, for we may then set about supplementing our
present efforts at race betterment through external improvement by
devising means of cleansing the fountain source as well.
It can scarcely be doubted that the average man differs little if any in
inherent personality and capacity from many a criminal who is such by
occasion rather than by undue predisposition. Who can truthfully answer
how many individuals there are who are not potentially criminals to some
extent, given sufficient evocative conditions of ignorance, vice, adverse
economic pressure and undue temptation?
"Virtue itself turns vice, being misapplied."
=No Special Inheritable Crime-Factor.--=The main difficulty in trying to
find a hereditary basis for crime lies in the multiplicity of things crime
may be. The individual impulsions which lead to certain offenses may be
utterly different from those which conduce to others. Undoubtedly many
inborn tendencies which are perfectly normal or neutral in themselves may
be warped by circumstances into the commission of what are classified as
crimes. The moral man may have the same desire for a thing that the
criminal does, but when he finds that this desire can only be gratified by
injury to others, he inhibits it because of his repugnance to such injury.
The criminal makes no such inhibition.
In general, crime means an offense of some kind against person, property
or state. But a biological analysis of it, could it be made, would require
among other things knowledge of crime in terms of motive or lack of
motive, whether the act was intended to benefit the perpetrator, some
other person, or even the race or state; whether the offense was one of
dishonesty, of cupidity, of lust, or of violence against another.
As a matter of fact no satisfactory classification of crime can be made
since so many factors enter and in such varying degrees. Most
classifications made in our legal codes are a hodge-podge based on a
mixture of motive on the part of the participant, degree of turpitude
involved, nature and extent of the injury inflicted, and the object
against which the offense was perpetrated, whether an individual, society
or the state. Moreover, it must not be forgotten that in many instances
what was crime in the past is no longer so, and vice versa many things
which are regarded as criminal to-day were not considered so in the past.
So the futility of seeking a specific inherent propensity for "crime" is
manifest. How, for instance, in terms of hereditary determiners shall we
draw the fine lines of distinction among those who bribe legislators and
legal officials, those who are avaricious and dishonest in the world of
trade, and those who are wilfully obtuse in providing proper safeguards
for employees?
=What Is Meant by a Born Criminal?--=All we can do is to fall back on the
assurance that any act directly or indirectly injurious to society is an
offense, and that those offenders who are congenitally unable to
distinguish between what is generally accepted as right and wrong, or who
if recognizing this are nevertheless uncontrollably impelled toward or are
unable to refrain from anti-social acts because of some inherent condition
of intellectual or volitional make-up, may be legitimately classed as
individuals born with an aptitude for crime and social transgressions. In
such individuals the natural mental make-up is lacking in some of its
necessary elements so that memory, judgment, or will-power are not up to
the minimum that is necessary for the establishment of proper conduct. In
some cases, apparently, this lack finds expression in almost any kind of
vice or crime into which circumstances happen to lead the individual. In
others, however, there seem to be tendencies toward the commission of
certain types of crime or vice. Certain family strains are characterized
by petty thieving, others by deeds of violence, and still others by sexual
offenses. Certain types of mental defect are closely associated with
certain crimes. Thus sufferers from incipient paresis seem particularly
prone to commit assaults and larceny; epileptics, crimes of brutality and
violence.
=The Epileptic Criminal Especially Dangerous.--=One of the characteristics
of epilepsy, indeed, emphasized by various psychiatrists, is that
frequently it leads to loss of those forms of self-restraint which are
absolutely indispensable to morality and the safety of society. Cruelty,
atrocious sexual offenses and other vicious crimes are the result. It is a
noteworthy fact, moreover, that often in the milder forms of affliction,
where instead of well-marked convulsions only momentary lapses of
consciousness occur, the greatest amount of mental and moral deterioration
and fluctuation is sometimes found.
The situation as regards the epileptic is well presented by Doctor William
Healy, Director of the Juvenile Psycopathic Institute of Chicago, in an
article entitled "Epilepsy and Crime; the Cost", in the _Illinois Medical
Journal_, November, 1912. He says:
"In the work of our institute,[14] which represents the most
thoroughgoing research into the genetics of criminalism ever
undertaken in this country, we have with the help of parents and
others carefully studied nearly 1,000 young repeated offenders. We
have found that no less than 7-1/2 per cent. of these are ordinary
epileptics, and we have reason to suspect others. This by no means
represents the total number of epileptics seen in connection with
juvenile court work, where, of course, first offenders as well as
large numbers of dependents are seen. In addition to my above
enumeration, other cases seen by the Detention Home physicians and
myself amount up to many scores of cases. If one remembers that it is
ordinarily calculated that one person in every 500 is epileptic, the
significance of this high criminal percentage is clear, and the
practical bearing of it is still further accentuated by the fact that
some of the worst repeaters are epileptics, and that many of the
gravest crimes are committed by those unfortunates. The connection
between epilepsy and crime has everywhere been recognized by students
of the subject, but it apparently needs constant emphasis in order
that common sense steps may be taken toward guardianship of these who
suffer from a disease which wreaks such extravagant vengeance on
society."
=Mental Disorders Most Frequently Associated With Crime.--=Doctor Charles
Mercier, an English authority on crime and insanity, in enumerating the
mental disorders most frequently associated with crime, places the
insanity of drunkenness first. Any one who will take the trouble to verify
the facts in his own community will find that a large percentage,
frequently considerably over half, of the arrests made by the police are
for acts committed while the offender was more or less under the influence
of alcohol. Next to drunkenness among mental disorders which lead to crime
Doctor Mercier places feeble-mindedness. Next to feeble-mindedness comes
epilepsy; then paranoia or systematized delusion; next paresis; and lastly
melancholia.
Paranoics are peculiar in that they are particularly apt to attack persons
of prominence. Highly egotistical, they almost invariably believe
themselves or some one or some cause dear to them, the subject of a plot,
perhaps to rob them, to torture them, to steal their inventions or
literary productions, or to persecute them in some way. Two if not three
of our murdered presidents owe their assassinations to paranoics. Many
rulers have been attacked and some killed by such insane individuals. Most
of the "cranks" who write threatening letters are lunatics of this type.
Of the kinds of mental unsoundness known to be inheritable which are of
special significance from the standpoint of crime and delinquency
undoubtedly feeble-mindedness ranks first. We have already seen that as
our methods for detecting the higher grades of feeble-mindedness become
more accurate we disclose in border-line cases a veritable hot-bed of
mental incapacity suitable for the engendering of the criminal and the
vicious. Here in addition to some of the more pronounced criminal types
belong hosts of our chronic petty offenders, our sexually vicious and our
"won't-works". One interesting outcome of a recent investigation into the
army of unemployed in England was the discovery of the general unfitness
of these unemployed. In our own country the habitually unemployed are so
not because of lack of work, but largely because it is unprofitable to
employ them.
=The Bearing of Immigration on Crime and Delinquency.--=Perhaps in no
field more than this of crime and delinquency, especially in so far as it
is based on innate deficiency, does the gravity of the immigration
question impress itself on us. How stupendous this problem[15] has become
may be realized from the fact that according to the census of 1910,
13,345,545, or one out of seven of the inhabitants of the United States,
were foreign born. And if we add to these the 18,897,837 of whom one or
both parents were of foreign birth, we reach the astonishing total of over
32,000,000, or more than one-third of our total population, who are
foreign born, or who have one or both parents of foreign birth.
During the decade from 1900 to 1910, 8,500,000 foreigners came to the
United States, of whom 5,250,000 remained to make a permanent home. This
shows how rapidly our whole population might be radically changed. In
recent years the source of our immigrants has shifted proportionately from
northwestern Europe to southern and eastern Europe (Italy, Austria-Hungary
and Russia), and whether for weal or woe this new blood must inevitably
leave its impress upon us. Does it not behoove us then to seek with
anxious eyes some knowledge of these invading hordes with whom we are to
mingle our life-blood?
Even the most superficial examination may well cause us grave concern. We
find that in one year (1908) at Ellis Island alone, 3,741 paupers, 2,900
persons with contagious disease, 184 insane, 121 feeble-minded, 136
criminals, 124 prostitutes and 65 idiots were denied entrance, and yet,
according to the estimate of Doctor F. K. Sprague, of the United States
Public Health Service, probably only about 5 per cent of the mentally
deficient and 25 per cent. of those who will become insane have been
detected. When confronted by such data we can begin to realize what we are
facing. Others estimate that from 6 to 7 per cent. of the immigrants who
are now arriving are feeble-minded. We learn further that recently while
the foreign-born population of New York state was about 30 per cent., the
foreign-born population of the insane hospitals of the state was over 43
per cent., and at one time approximately 65 per cent. for New York City.
In one year (1908) 84 per cent. of the patients in Bellevue Hospital, New
York City, were of foreign parentage. Paresis, which probably always has
syphilis as its antecedent, is proportionately twice as prevalent among
foreigners as among natives in New York City.
But from the standpoint of inheritance, however great the danger may be
from classifiable defectives, it is probably far greater from that much
larger class of aliens we are now receiving with open arms who are below
the mental and physical average of their own countries. Moreover, with our
present system of inspection there is no way of detecting the grades of
feeble-mindedness above idiocy and imbecility in the great numbers of
foreign children under five when brought in, who are beginning to show up
in alarming numbers in the schools of some of our larger cities. About
thirty per cent. of the annual increment of our population is due to
immigration and not to births; and once in our country the alien far
outbreeds the native stock, with relatively little increase in death-rate,
thus making a double contribution to the increase of population. When we
take all these facts into consideration it certainly is high time that we
arouse from our self-complacent attitude and consider the whole question
of immigration most earnestly.
In spite of the fact that many individuals are caught in the net of
inspection at our portals, it is clear that still more rigid rejection[16]
is imperative. The inspectors at our various ports are doing the best
they can under the circumstances, but there are at present too few of them
and they are too restricted in their powers to meet the situation
satisfactorily. Moreover, when at one of our ports in one year (1910), of
1,483 immigrants certified by the inspecting surgeons as unfit to land
because of serious mental or physical defects, 1,370 were landed anyway,
it is evident that there is a strong and reprehensible pull somewhere to
evade the obvious intent of the law.
It remains for us as a people to decide whether we shall continue to let
the large employers of cheap labor, the railroad and steamship agents and
brokers, who care nothing about the innate fitness of the immigrants they
bring, determine the character of our future population, or whether we
shall insist on a proper regulation of this flood so that we may receive
only an honest, intelligent, industrious and healthy stock. To continue to
absorb these aliens with as little selection as we now do is nothing short
of criminal carelessness. Let us not be deceived by the promptings of a
misguided sentiment, "The voice is Jacob's voice, but the hands are the
hands of Esau." The voice is Jacob's voice, nor should this voice of the
easily persuaded, the sentimentalist, the interested organization to which
the relatives of the defective alien belong, or any other pressure move us
from our obvious duty of refusing to fasten upon this country an incubus
of degeneracy for which we as a nation are in no way responsible.
To render us safe we should not only have more carefully drawn laws and
more rigid selection at our ports of entry, but we should if possible
also know the stock from which our future citizens come. This is
peculiarly desirable for such defects as feeble-mindedness and various
other mental imperfections, some of which require prolonged observation
for detection. Davenport estimates that it is wholly within the realm of
possibility and good business sense to maintain a corps of trained
inspectors abroad in the chief centers from which our immigrants come who
shall certify the desirable applicants. He makes the point that the
national expense would be far less than the cost of maintaining the army
of defectives we are now admitting to our own country, many of whom almost
immediately become public charges, to say nothing of the hordes of
carriers who though normal themselves, will transmit undesirable traits.
=Sexual Vice.--=As to sexual vice, the skein is indeed a tangled one.
Since nine-tenths of the difficulty centers in a lack of self-restraint,
and inasmuch as the mating instinct is one of the strongest that tugs at
the flesh of humanity, it is obvious that those by nature deficient in
volitional control will almost without exception give way to the call. So
as might be expected the hordes of our feeble-minded and epileptic are
always a source of grave danger in this respect. However, the mentally
enfeebled are by no means the only offenders; indeed, they are probably
not the majority. The true situation is finally dawning on society and the
reformer's call for instruction in "sex-hygiene" resounds through the
land. The whole matter is one of the most perplexing and momentous that
confronts us to-day.
=The Question of School Instruction in Sex-Hygiene.--=While the writer
does not for an instant underestimate the gravity of the situation, and
has only contempt for the nonsense that is palmed off on children about
their origin, or the indelicate self-consciousness which puts under the
ban the discussion of so serious a problem by adults, still he is not
convinced that the universal teaching of the subject to children in
schools by the average teacher, as advocated by some, is to be the
solution of the matter or is even a wise attempt at solution. Yet he
freely admits that he is possibly overfearful of the effects of the
undesirable features of such instruction. True it is that all children do
learn, frequently at an astonishingly early age, about sex, and their
knowledge is usually of an undesirable kind from unreliable and often
vicious sources, and it is equally true that parents, either through
ignorance or prudery, generally can not be depended on to give the child
necessary instruction. But before entering on a wide-spread campaign of
undiluted sex-instruction in schools might it not be more prudent to make
an attempt toward reaching fathers and mothers and convincing them of the
necessity of dealing more frankly and intelligently with their children
regarding sex?
Even to the novice in psychology the powerful nature of suggestion is
known, and with this knowledge before us, is it not wiser to strive in the
main to keep the child's mind off of sex rather than specifically to focus
it on it by special convocations and discourse? If our psychology means
anything, then the worst possible thing we can do for a child is to make
him unduly sex-conscious. Something might be done profitably perhaps in
schools in an unobtrusive way by specially gifted persons, but the
self-conscious way in which most teachers go about topics of sex is
certainly not reassuring to the thoughtful observer as regards the benefit
derived from such instruction. The one evident method of accomplishing
wholesome sex-instruction in schools, devoid of all possibility of
undesirable suggestion and sex-consciousness, is in the form of biological
work where plants and animals are studied in all their relations, the
subject of propagation being taken up in as matter-of-fact a way as the
functioning of any other organ system of plants or animals. In such a
course, long before the subject of sex in higher animals need be
approached the pupil will have developed an attitude of mind which will
lead him to see nothing unusual or suggestive in the function of sex no
matter where it may be found. Incidentally, inasmuch as the manner in
which germs affect living organisms should be studied in such a course
anyway, it would be a simple matter to give all necessary information
about the dangers of infection from venereal diseases.
=Mere Knowledge Not the Crux of the Sex Problem.--=However, desirable as
correct knowledge about sex is, knowledge alone is not the crux of the sex
problem. The moral dangers and abuses that we are trying to circumvent lie
rather in the realm of the emotions than that of the intellect. The
problem must be solved from a broader foundation than mere information.
The all-important consideration is the early establishment of general
habits of self-control so that these may become incorporated in the
nervous organization of the child and become inhibitory anchors against
passions and temptation. Children must be taught to suppress the present
impulse, to sacrifice the immediate pleasure for the more distant or
permanent good. They must be practised in calling up feelings that will
counteract other promptings which if followed blindly are inimical to
social welfare. Their control must come from within not as a matter of
external compulsion. That way character lies.
So in viewing the problem of sexual hygiene the writer feels that our
attempts toward damming the torrents in the adolescent by a belated effort
at verbal instruction on sex-hygiene is at best only a palliative or an
attempt to cure the symptoms of a more deeply-seated, organic, social
malady. The treatment should have been in progress long before in the form
of training in self-control, and in the inculcation of the sense of
dignity and self-respect which springs from the individual's consciousness
of being, not a slave to his desires, but his own master. This, together
with the judicious schooling of boys in a greater chivalry and respect for
womanhood, and of girls in the necessity of meriting such esteem, will, in
my estimation, carry us further than formal courses in sex-hygiene.
=Early Training in Self-Restraint an Important Preventive of Crime and
Delinquency.--=As to crime and delinquency in general, it is evident that
the same early training in self-restraint is a most important factor of
prevention. A wise warden in charge of a large prison says, "Most of these
men are here because they have not learned sufficiently the lesson of
self-control." This is the age of preventive medicine, why not also of
preventive crime and delinquency? Instead of confining our practise to
punishing offenders, necessary as this may be under the present
conditions, why not strive more to prevent the commission of offenses? As
far as normal individuals are concerned much can be done by early
cultivation in self-discipline and through the establishment of moral
backbone by training in the overcoming of difficulties. Much, very much,
also remains to be done in the correction of wrong social conditions.
=Unpardonable to Permit Delinquent Defectives to Multiply Their Kind.--=As
for our mental defectives and moral imbeciles, knowing now how strongly
hereditary the underlying factors of these conditions are, and with no
preventive or curative agents in sight, to let them produce progeny, is
clearly unpardonable.
CHAPTER X
RACE BETTERMENT THROUGH HEREDITY
Most of us have heard in one form or another the fairy story of the youth
on adventure bent, who was captured by the giant and under dire penalty in
case of failure was set the task of sweeping out the giant's stable before
sundown. The peculiarity of this stable, it will be recalled, was that, as
fast as the refuse was swept out at the door an even greater quantity
poured in through the windows so that the sweeper, just in proportion to
his zeal, became more and more encumbered with his burden.
=A Questionable Form of Charity.--=Though we smile at the childishness of
this legend, are we not as a civilized people attempting through our
charities a feat parallel to that of this unfortunate youth? We foster and
favor our social wastage with the inevitable result that it runs riot
under our sheltering hand and deluges us with an ever accumulating flood
of its like. For are we not constantly building more asylums, sanitaria
and prisons, to preserve more unfit, to produce more defectives, to
require still greater numbers of asylums, sanitaria and prisons, to
preserve more unfit, and so on in unending progression?
At nearly every period of history there have been certain individuals who
have seen the necessity of a state eliminating its supply of defectives.
=Past Protests.--=For instance, we find the importance of this strongly
urged by Plato. After pointing out the fact that the shepherd, in order to
maintain the standard of his flocks, bred only from the best individuals,
as did likewise the huntsman with his dogs and horses, and the fancier
with his various pets, Plato went on to show the danger to the state of
allowing the constantly increasing body of defectives and degenerates to
multiply their kind. Repeated expression of the same idea has occurred
from time to time during the succeeding centuries.
Little heed was paid to these remonstrances, however, with the result that
is known to us all. To-day, "the glory that was Greece and the grandeur
that was Rome" is still sung by the poet, but the original nations
themselves have long since passed into the night.
=An Increasing Flood of Defectives.--=Strive to ignore the unpleasant
facts as we may, we have to admit that the same problem of what the human
harvest shall be is with us in grave form to-day. The alarming phase of
the situation, however, lies in the fact that we are facing an ever
increasing flood of social wastage.
But _why_ this increase of defectives? It can not be attributed to
oppression, to grinding poverty, or to decline in attention to our sick
and needy, for never was prosperity greater, never were charities more
flourishing, never such activity in the search for palliatives and cures.
The simple fact is that we are breeding our defectives. The human harvest
like the grain harvest is based fundamentally on heritage. And to get a
better crop of human beings, we must, as with other crops, weed out bad
strains.
To whatever source of information we turn the facts are essentially the
same. Abroad we find that in England, for example, the ratio of defectives
to normals more than doubled between 1764 and 1896. At home, from the
investigation of Davenport and Weeks we learn that in the state of New
Jersey the number of epileptics doubles every thirty years. And other
investigators estimate that the fecundity of mental defectives in general
is about twice as great as that of the average of our population. In a
recent report of the New York State Board of Charities we read, "There are
about thirty thousand feeble-minded persons in the state of New York, of
whom four thousand are intermittently sequestered while twenty-six
thousand who are a menace to society are at liberty and may produce the
unfit." And a passage from the last Massachusetts report reads as follows:
"We have been obliged to refuse a very large number of applicants for the
admission of feeble-minded women--many of whom have given birth to one or
more children. The prolific progeny of these women almost without
exception are public charges from the date of their birth."
How fertile defective types may be is shown by a passage in one of Doctor
Wilmarth's papers which runs as follows: "One feeble-minded woman, now
removed from this state, had by different men eighteen children in
nineteen years, she alleges." In a letter Doctor Wilmarth tells me that
the birth of the twenty-third child of this woman has just been
announced! In one English workhouse Potts reports sixteen feeble-minded
women who have produced one hundred sixteen mentally defective children,
and Branthwaite ninety-two female habitual drunkards who have had eight
hundred fifty babies. If we include the two million individuals cared for
annually in various institutional homes, hospitals and dispensaries as
dependents, the estimated total of insane, feeble-minded, epileptic, deaf
and dumb, criminals, juvenile delinquents, paupers and other dependents in
the United States in 1910 was approximately three million, or one in every
thirty of our population! With the higher fertility of certain of these
classes and with only a small percentage under custodial care where will
it all end? Is it not time for us to waken from our lethargy and stem this
tide of national deterioration?
=Natural Elimination of Defectives Done Away With.--=With our improved
methods of sanitation and care of the sick, the pauper and the defective,
these classes have been freed from the stress of an environment that under
natural conditions would have resulted in their premature death and
consequent infertility. Or in the terminology of the biologist, we have
done away with the factor of _natural selection_, the factor which in
state of nature keeps all races purged of the unfit, the ill-adapted. With
this restraining, and purifying influence removed, however, the weakling,
the defective, may arrive at maturity and commingle his blood with that of
the strong, with the inevitable result that the general vigor of the
progeny from generation to generation is sapped and progressively
undermined. Thus we are confronted by the stubborn fact that through
present humanitarian methods we are driving the race toward decadence.
=Why Not Prevent Our Social Maladies?--=Now there is no reasonable person,
I think, who will not admit that the motives underlying our modern
altruistic practises are the noblest fruitage of our slow upward struggle
from the brute to man. As humane beings, we can not cast aside these
principles and return to the painful and pitiless method of nature which
would leave the sick and the defective alone to perish miserably; the
sacrifice would be too great.
Is there then no escape from this dilemma? To this query the modern
student of heredity answers yes; let us but add more wisdom to our charity
and the enigma is solved. We need no sacrifice of pity but rather an
expansion of it. Let us but extend our vision from immediate suffering to
the prospective suffering of the countless unborn descendants of our
present unfit and ask ourselves the question, why should they be born? Why
not prevent our social maladies instead of waiting to cure them? This is
the province of eugenics.
=Eugenics Defined.--=The term Eugenics was coined in 1883 by Francis
Galton in his book entitled _Inquiries Into Human Faculties_, and we may
therefore look to him for a satisfactory definition. He says, "Eugenics is
the study of the agencies under social control, that may improve or impair
the racial qualities of future generations, either physically or
mentally." And again, "I take Eugenics very seriously, feeling that its
principles ought to become one of the dominant motives in a civilized
nation, much as if they were one of its religious tenets.... Man is gifted
with pity and other kindly feelings, but he also has the power of
preventing many kinds of suffering. I conceive it to fall well within his
province to replace natural selection by other processes that are more
merciful and not less effective. This is precisely the aim of Eugenics.
Its first object is to check the birth-rate of the unfit instead of
allowing them to come into being, though doomed in large numbers to perish
prematurely. The second object is the improvement of the race by
furthering the productivity of the fit, by early marriages and the
healthful rearing of their children."
=Improved Environment Alone Will Not Cure Racial Degeneracy.--=While many
an enthusiastic humanitarian is laboring under the assumption that if we
can improve external conditions human deficiencies will disappear, the
student of heredity realizes that this is in large part a delusion unless
we can secure an accompanying improvement in intrinsic qualities of the
human species itself through the suitable mating of individuals. Just as
the intelligent farmer to-day demands selected seed as well as good soil
and proper cultivation, so one with the facts of heredity at hand would,
as he views social problems, urge the fundamental importance of having
selected stock with which to start. No shifts or shapings of environment
will ever enable men to "gather grapes of thorns or figs of thistles."
=Heredity and Environment.--=To wrangle over the question of which is the
more important, heredity or environment, is about as idle a proceeding as
to argue which is the more important, the stomach or something to put in
the stomach. Man would soon come to grief without either. So, too, the
question of human development is not one of heredity alone nor of
environment alone; both are necessary and must work hand in hand. Dormant
capacities must have proper environment to call them forth, but on the
other hand no kind of environment can evoke responses if some degree of
aptitude is not present.
Professor Thorndike undertook experiments with groups of school children
of high and of low initial ability respectively to determine whether equal
opportunity or equal special training would produce an equalizing effect
in easily alterable traits such as rapidity in addition and the like.
Without exception he found that at the end of such experiments, although
both groups had improved, the superior individuals were farther ahead than
ever, that equality of opportunity and training had widened rather than
narrowed the gap between the two classes. Others who have made special
studies on the causes of individual differences have come to the same
conclusion; namely, that individuals differ widely by original nature and
that similarity in conditions of nurture and training will not avail in
deleting these differences.
Galton and others, from extensive studies based on English sources, have
shown that notable achievements have run in certain families to a degree
that is inexplicable on the basis of opportunity alone; it can be fully
accounted for only by attributing much to superior inborn capacity. Doctor
Woods has shown much the same thing for certain families in America.
Schuster and Elderton have proved that there is a high degree of
similarity in scholastic standing between fathers and sons in Oxford.
Professor Pearson's measurements of mental characters in brothers and
sisters while at school show a high degree of innate resemblance in many
cases and certain cases of decided contrast. Where contrasts exist in
certain families they remain unreduced in spite of the similarity of
environment, thus proving that environment is less operative in the final
intellectual establishment of such individuals than are their inborn
aptitudes. Even in twins, as both Galton and Thorndike have shown, there
is no tendency for similar education, home life and the like to render
those originally different any more similar with advancing years.
Professor Karl Pearson has done more perhaps than any other individual
toward attempting actually to measure the relative strength of heredity
and environment. Numerous statistical measurements lead him to conclude
that it is a conservative estimate to regard heredity as at least five or
ten times as important as environment in the development of the
individual. A vigorous defense by him of this position will be found in
_Biometrika_ for April, 1914.
=Inter-Racial Marriage.--=Some of the dangers of racial deterioration
which threaten us because of our laxity regarding immigration have already
been indicated. It is high time that we give this whole question the most
serious consideration of which we are capable. From the rate at which
immigrants are increasing it is obvious that our very life-blood is at
stake. For our own protection we must face the question of what types or
races should be ruled out. Aside from the dangers which lie in the
defective or unsuccessful types already discussed in Chapter IX, many
students of heredity feel that there is great hazard in the mongrelizing
of distinctly unrelated races no matter how superior the original strains
may be. Unfortunately there is a great lack of reliable data on this
point. The mulatto of our own country, the Eurasians in India and the
mixed races of South America are, according to the testimony of many
observers, eloquent arguments against such hybridization. Agassiz remarked
on this point as follows:
"Let any one who doubts the evil of the mixture of races and who is
inclined from mistaken philanthropy to break down all barriers between
them come to Brazil. He can not deny the deterioration consequent upon
the amalgamation of races, more wide-spread here than in any other
country in the world, and which is rapidly effacing the best qualities
of the white man, the Indian, and the negro, leaving a mongrel
nondescript type deficient in physical and mental energy."
Of the American mulatto one not infrequently meets with the assertion that
he is on the average inferior mentally, morally and physically to either
the white or the negro race. Thus Doctor J. B. Taylor[17] states that,
"It is demonstrated by well-attested facts that these hybrids of black and
white are vastly more susceptible to certain infections; their moral as
well as physical stamina is lower than that of either original race."
Others would deny that conclusive evidence to this effect exists. However,
it is certain that under existing social conditions in our own country
only the most worthless and vicious of the white race will tend in any
considerable numbers to mate with the negro and the result can not but
mean deterioration on the whole for either race.
There is certainly not one iota of evidence that the crossing of any two
widely different human races will yield superior offspring in any respect
and there are many indications that such intermixture lowers the average
of the population. Our evidence derived from plant and animal breeding is
also against pronounced crosses. The inferiority of the mongrel is
universally recognized. No sane farmer, for example, would seek to improve
his Jerseys or his Herefords by crossing one with the other. It is true
that in pure breeds of plants and animals we sometimes venture on a cross
to introduce some new desirable character but we follow up such mixture by
a rigid selection in which is eliminated all but the rare individuals
having the desired characteristics, and we continue this elimination
generation after generation to fix our characters again. It is obvious
that no such selection as this would be possible among the progeny of
human crosses.
It clearly becomes our duty then to determine as accurately as possible
the degree of non-relationship between races it is inadvisable to
transcend in inter-racial marriages. We are certainly taking great risks
in accepting in any considerable numbers those races we can not assimilate
to advantage into our own stock.
=War.--=The deteriorating effect of war on national physique and vigor has
been so frequently cited by eugenists[18] and is so obvious as scarcely to
require further comment. It should be pointed out, however, that where, as
is the case at present in Great Britain, armies are assembled from
volunteers, instead of by conscription, there is the greatest danger from
the eugenic standpoint, since not only physical but moral qualities are
involved. For it is the brave, the generous, the individual with a high
sense of duty who goes forward to the slaughter leaving the cowardly, the
selfish or the indifferent to father the race. With the awful deadliness
of modern warfare upon exhibition before our very eyes to-day, the extreme
seriousness of such selective action must be evident to every thoughtful
person.
=Human Conservation.--=We talk much in recent years of _conservation_; but
what are our forests and frontiers, our minerals and our waterways,
compared with our national health and life-blood? No farmer would think of
setting aside a diseased or physically defective _animal_ for breeding
purposes, yet the same man together with the majority of mankind is wholly
oblivious to similar faults when it comes to the mating of human beings.
But is it not as important to look to fitness in man as in Poland China
hogs or Holstein cows? Certainly the various strains are as marked and
breed as true in the human family as in our live stock. Why face
complacently in our own families what we would not tolerate in our
piggery?
From the expenditure of comparatively small sums in studying the
inheritance of various qualities in wheat, corn and other grain,
improvements based on the laws of genetics have been secured which are
enormously increasing our agricultural output and thereby adding to our
national wealth. But if it costs relatively little to discover and
conserve millions of dollars' worth of hereditary qualities in our plants
and animals, what are we to think of ourselves, an intelligent people who,
knowing that "every good tree bringeth forth good fruit, but a corrupt
tree bringeth forth evil fruit," still go on placidly permitting the
production of defectives and delinquents? Can we continue to drink the
sluggish blood of the pauper and the imbecile into our veins and hope to
escape unscathed?
We are all familiar with the fate of Babylon, Assyria, Persia, Egypt and
Rome. Why not America? Certainly we have no pledge of special immunity
from Divine Powers. If so, what then is the meaning of our 366 hospitals
for insane which cost us annually $21,000,000; our 63 institutions for
feeble-minded costing us over $5,000,000; our 1,300 prisons maintained at
a cost of more than $13,000,000; our 1,500 hospitals whose annual
maintenance requires at least $30,000,000; our 115 schools or homes for
deaf and dumb; our 2,500 almshouses with an annual expense account of
$20,000,000 and our 1,200 refuge homes costing annually several millions
of dollars more? To say that we spend annually over $100,000,000 on the
custody of insane, feeble-minded, paupers, epileptics, deaf, blind and
other charges is expressing the situation very conservatively.
=Kindness in the Long Run.--=There is no one I think who will not admit
that the sympathy and charity of the human heart are its noblest virtues.
But we must face the problem of what is kindness in the long run. Havelock
Ellis well says, "The superficially sympathetic man flings a coin to the
beggar; the more deeply sympathetic man builds an almshouse for him so
that he need no longer beg; but perhaps the most radically sympathetic of
all is the man who arranges that the beggar shall not be born."
What shall we do?
=The Problem Has Two Phases.--=For an intelligent consideration of the
problem one must recognize at the outset that it has two distinct phases;
namely, (1) a selective union of the fittest, or in other words, a
conscious attempt to breed a superior race; and (2) the elimination of the
obviously unfit by preventing their reproduction, with the purpose of
purifying the present race. It is evident at a glance that these are two
essentially distinct problems although the practise of either method could
result in racial improvement. The first is sometimes spoken of as
_positive_ or _constructive eugenics_, the second as _negative_ or
_restrictive eugenics_.
=Constructive Eugenics Must Be Based on Education.--=As to the first
phase, direct selection for superiority, the campaign must, in the very
nature of things, be one of education. With the necessary knowledge of the
facts in mind, the awakening conscience of the individual together with
an enlightened public opinion will form the safest guide. Increasing
popular comprehension of the inevitable nature of human inheritance must
engender a sense of responsibility as to the positive eugenic fitness of a
contemplated marriage. The growth of this sentiment will doubtless be
slow, and properly so, for as yet we have but half-lights on what are the
most desirable types of humanity. No one can say what the highest type of
man should be, but almost any one can readily pick out types which
certainly should _not_ be.
=Inferior Increasing More Rapidly Than Superior Stocks.--=Modern
eugenists, although realizing that the constructive phase is of great
importance, are making no attempt to map out any fixed mode of procedure
for it beyond pointing out the desirability of larger families among the
better classes. The need for individuals of superior physical, mental and
moral qualities to multiply is so obvious as scarcely to require comment.
Yet the fact is that judging from all appearances these are the very ones
who have the lowest birth-rate. Eugenics is mainly concerned with the
relative rates of increase of the various classes, not with mere fertility
in itself. And the actual increase must be measured in terms of the extent
to which birth-rate exceeds death-rate. If a high birth-rate is
accompanied by a high death-rate then it is not especially significant in
increasing a given class as a whole. All available evidence points to the
fact that to-day the lower strata of society are far outbreeding the
middle and higher, with an almost negligible difference in death-rate, and
just in the measure that these lower strata are innately inferior just in
that degree must the race deteriorate. The seriousness of the whole
situation as it exists to-day hinges, therefore, on the extent to which
the lower strata are inferior to those above them.
=An Unselected Population May Contain Much Valuable Material.--=In
evaluating these lower strata a matter of very great importance is whether
the population is a selected or an unselected one. If the population has
been long resident in a given region and has had fairly good opportunity
for education then we will find in the lower reaches a larger percentage
of sedimentation made up of the worthless and inferior stocks. If,
however, a continual fomentation and geographical shifting of the
population is in progress as in parts of America, or if adequate
educational opportunities are lacking, as in some parts of Russia, the
poor and less well-to-do classes may contain, no one can tell how much,
relatively valuable stock.
Forel remarks on this point as follows:
"If we compare the nature of delinquents, abandoned children,
vagabonds, etc., in a country where little or nothing has been done
for the people (Russia, Galicia, Vienna, etc.), with that of the same
individuals in Switzerland, for example, where much has already been
done for the poor, we find this result: In Switzerland, these
individuals are nearly all tainted with alcoholism, or pathological
heredity; they consist of alcoholics, incorrigibles, and congenital
decadents, and education can do little for them because nearly all
those who have a better hereditary foundation have been able to earn
their living by honest work. In Russia, Galicia, and even in Vienna,
we are, on the contrary, astonished to see how many honest natures
there are among the disinherited when they are provided with work and
education."
=The Lack of Criteria for Judging Fitness.--=Barring the untold hordes of
actual defectives who have gravitated into this lower stratum, there are
few positive criteria by which we can measure the real fitness of the
remainder. Before we can set out on a campaign of positive eugenics we
must have some standard by which to steer, and it would be a rash advocate
indeed who would assert that class distinction alone, or even success as
measured by public opinion to-day should be our whole criterion of
fitness. Shall we measure fitness in terms of how successfully one can
acquire worldly goods, or in other words, by the property test, or what
shall be our standard?
=The College Graduate.--=Many of our modern critiques of the birth-rate
situation make much of the fact that our college graduates as a group are
scarcely reproducing themselves. According to Davenport, Bryn Mawr College
between 1888 and 1913 has graduated 1,193 bachelors of arts, but these
women have produced up to January, 1913, only 263 girls to take their
place in the next generation. He also points out that statistics on some
of the graduate classes of Harvard of twenty years ago or earlier show
that they are little more than maintaining themselves; thus one class of
328 graduates twenty years later had produced 195 sons, and in another
case a class of 278 individuals had produced, twenty-five years later, 141
sons. Relatively similar statistics can be cited for other eastern
colleges.
All such cases of college graduates cited as especially deplorable
declines in birth-rate are based on the assumption that these individuals
are a particularly superior stock.[19] But one might question this premise
as a generalization. It may or may not be true. Are they superior or have
they had mainly a combination of luck and incentive, luck in that their
parents had sufficient means, acquired possibly through their own
superiority, possibly not, to send them to college, and incentive derived
from a fortunate environment which awakened a desire in them--or in their
parents for them--for college education? Is the woolly-witted son of
opulence, so abundant in our colleges to-day, who is boosted through by
hook or by crook, of superior eugenical value to the alert eager boy--and
his name is legion--destined for economic reasons to go to work at or
before the completion of his high-school course, perhaps because of the
very fact of an unlimited fecundity in his own family which necessitates
his help for the general support?
When one first learns of the declining birth-rate among college women and
men he feels appalled, but immediately the question flashes up, if this is
_the_ superior stock, and up to date it has died out or is dying out
rapidly, whence then this ever augmenting rush of young folk who fairly
deluge our universities and colleges to-day? Does it not rather point to
the fact that in our own country at least, the man who will and can take
a college education successfully is not so much the product of breeding
from college men, but of a prosperity which leaves a sufficient surplus in
the family exchequer to enable sons and daughters to go to college, and is
it not reasonable to suppose that there is yet an abundant stock back of
these who similarly await but the golden touch of opportunity? When we
consider such men as Carlyle, Lincoln and a host of others who were not
the sons of collegians, although we may be university pedigreed ourselves
we can not but feel doubtful of the validity of a premise which takes a
college stock unqualifiedly as having any considerable monopoly of innate
superiority. After all, college can mean little more than opportunity, and
the obtaining of such opportunity in this world of economic maladjustments
and accidents of social position is too largely a matter of chance, at
least in America, to stamp the possessors of these advantages, on this
criterion alone, as of inborn superiority. Undoubtedly much that is
intrinsically good now slumbers in the lower strata of society because of
lack of favorable environment to call forth the latent possibilities.
=Native Ability, Independence and Energy Eugenically Desirable.--=Although
we can not sift out with certainty the superior from the inferior in our
normal population by the property test or the educational standard alone,
it is undoubtedly true that, on the whole, native ability, independence
and energy are present to a higher degree in our well-to-do and prosperous
families than in the stocks which merely hold their own or which
gradually decline, and there is no gainsaying the fact that in so far as
the lower classes are where they are through actual deficiency--and there
are enormous numbers in this category--they threaten our very existence as
a race. It is imperative that the great middle class in particular
establish in some way a selective birth-rate, by increased fertility on
their own part, and diminished fecundity on the part of inferior stocks,
which will offset or more than offset the disproportionate increase of the
socially unfit.
=Four Children to Each Marriage Required to Maintain a Stock.--=It is
estimated that under present conditions an average of at least four
children should be born to each marriage if a stock is to maintain its
numbers undiminished. Some of our most valuable strains are falling far
short of this average. In a statistical table on the relative fertility of
different stocks, prepared by Pearson, we find the mentally defective,
criminal, deaf-mute and degenerate stocks heading the list with averages
ranging from five to seven children per family, while the American
graduate (based on Harvard statistics) and the English intellectual types
average less than two children per marriage. While the death-rate is
higher in the undesirable classes mentioned, it is by no means enough
higher to compensate for the difference in birth-rates. Thus while certain
very desirable types are not maintaining themselves genetically, other
extremely undesirable ones are rapidly more than replacing themselves.
Investigations made by Heron in London show that this condition as regards
English desirables did not exist sixty years ago; then the richer a
community was in professional men and well-to-do families, the higher was
the birth-rate.
=Factors Contributing to Low Birth-Rate in Desirable Strains.--=Most
students of the subject believe that the fecundity of much of the best
blood in our country has reached such a low ebb as to threaten the whole
fabric of our commonwealth. How to correct this is the pressing problem to
which no one has found a solution. However much one may deplore it the
fact remains that always in the history of the civilized world with the
rise of material conditions in any class of a population there has come an
accompanying limitation of child-birth. Explain this as we may in modern
times--whether as an awakened individualism which looks only to the
immediate interest of the individual as against the ultimate interest of
the race, or a desire for luxuries or for a better opportunity for smaller
numbers of children, or as a determined effort of the wage earner to
better his conditions, or to the feminist movement with its accompaniment
of a greater personal freedom of married women and the recognition of the
fact that marriage and child-bearing are often bars to employment, or to
general increasing pressure of economic burdens--in brief whatever the
cause or causes, there is no denying the fact of a diminishing birth-rate
among our abler men and women. Moreover, no amount of coaxing, cajoling or
dire prophecy seems to avail in altering the conditions. Various partial
remedies, many of them of questionable practicability, have been proposed,
but so far there has been no far-reaching effort made to put any of them
into effect. It has been suggested that society return to the simple life
so that our young folk may marry earlier and live more easily on limited
means, but so far few volunteers have appeared to lead the procession.
While there is no doubt that present economic conditions tend to penalize
parenthood, the simple life will not return for the mere asking. It has
been pointed out that the father is in unfair competition with the
bachelor and is also unfairly taxed in comparison, and some would
therefore tax unmarried men more heavily. Others would pay a direct bounty
on reproduction, but it is probable that such rewards would merely
stimulate families of the lower types to increased fruitfulness. And so
one panacea after another may be weighed and found wanting.
=The Educated Public Must Be Made to Realize the Situation.--=It seems
probable that the most success will be met with through the slow and
unspectacular methods of education. The necessity of the situation must be
driven home so that it becomes part and parcel of the collective
intelligence of the educated public. Different ideals of life will have to
be established in the young. If knowledge of the facts of heredity is
thoroughly disseminated among the people and ideals regarding parenthood
are fostered, then much will have been accomplished by the psychic power
of suggestion alone toward the end desired.
=Utilization of Family Pride as a Basis for Constructive Eugenics.--=There
are few more powerful incentives to make the best of one's abilities, or
few greater deterrents from vice than family pride; and there is no
reason why this same sentiment may not be aroused in behalf of unborn
generations. The sentiment of caste or aristocracy in some form is well
nigh universal in mankind. The family of Mr. A came over in the Mayflower
and is therefore worlds above the family of Mr. B, who arrived fifty years
later. Mr. X's income is $5,000 a year, Mr. Y's only $1,500. The poor
family in the front suite of the tenement regards itself as far superior
to the one in the rear. Among criminals the professional house-breaker
feels himself to be of higher caste than the sneak-thief, and in turn is
surpassed by the bank-burglar. Even in the insane asylum the feeling is
rampant. With such a wide-spread tendency for a foundation the creation of
a sentiment of eugenic aristocracy is by no means a visionary undertaking.
=The Tendency for Like to Marry Like.--=Even now there is a decided though
unconscious tendency for like to marry like and thus create particular
strains. We have lines, for instance, which produce notably families of
scholars, others which yield mainly statesmen, and still other strains of
inventors, of financiers, of naval men, of soldiers, and of actors
respectively. And there is little doubt that people, with the facts of
inheritance of ability once before them, will be led to act more or less
in accordance with their knowledge. On the other hand, due apparently to
the same unconscious tendency for like to marry like, we find produced
criminalistic, feeble-minded, deaf-mute and tubercular stocks. The first
type of family is often termed _aristogenic_ and the second or defective
type, _cacogenic_.
=Public Opinion as an Incentive to Action.--=Much of our social conduct is
the result of the pressure of public opinion, yet so accustomed are we to
this that we ordinarily do not feel it as a hardship. There is little
doubt that similarly the more wholesome attitude toward parenthood
advocated by the eugenist would be taken as a matter of course, once the
idea became prevalent. It would come to be one of those socially
preconceived ideas which are as much actualities and which become
unconscious guides to action no less certainly than do the more obvious
personal habits of the individual. And just in the degree that we as a
race get the "feeling" that intellect, morals and skill are highly
desirable attributes in marriage selection, just in that degree will one's
affections in their earlier stages gravitate toward individuals who
possess such qualities in high degree. In the main, those stocks which
have shown by ancestral as well as personal achievement their superiority
will tend to insure most certainly a continuation of this superiority in
offspring.
=Choosing a Marriage Mate Means Choosing a Parent.--=Although marriages,
as all young folks know, are made in Heaven, it is interesting to see what
a vast number of these foreordained matches coincide with propinquity in
college, in church, or in the same social set. Moreover, children are born
here on earth. The one thing of all things that the eugenist desires is
for these young folk to get a clear-eyed vision of the fact that in
choosing a marriage mate they are also choosing the future father or
mother of their children with all that this implies.
=The Best Eugenic Marriage Also a Love Match.--=A few recent writers, who
show an utter misconception of what the aim of modern eugenics is, have
raised the cry of give us the old-fashioned love match instead of the
eugenic marriage, as if the eugenist's ideal of moral cleanliness, freedom
from transmissible physical taints or mental enfeeblement, and an attitude
of special approval toward marriages which bring together individuals of
more than average mental or spiritual endowment, had anything in it that
was inimical to love. No one better than he realizes the sordid depths to
which marital relations devoid of mutual affection and regard must reach.
Certainly there is nothing in the eugenic ideal when its full import is
understood that can shock the sensibilities of the most delicate-minded.
Indeed it is people of fine susceptibilities who will be the first to feel
repugnance toward a marriage which means mental or physical deterioration
of their own blood.
=Good Traits No Less Than Bad Ones Inherited.--=An inspection of such
charts as those shown in Figs. 37, 38 and 39, pp. 313, 314, 316--and an
abundance of such encouraging records may now be found--reassures us in
our convictions that good traits are no less inheritable than bad ones.
And what any healthy, mentally well-endowed person may be depriving the
world of if he or she declines to enter into a fruitful marriage can not
be better exemplified than in the following excerpt from Davenport:
"Many a man at the opening of his life work vows, as Judge John Lowell
of the middle of the eighteenth century did, as he was being graduated
from Harvard College, that he will never marry. But nature was too
strong for John Lowell and he married three times, and among his
descendants was the director of a great astronomical observatory, the
president of Harvard College, a principal founder and promoter of the
Massachusetts General Hospital and the Boston Atheneum; the founder of
the city of Lowell and its cotton mills; the founder of the Lowell
Institute at Boston; the beloved General Charles Russell Lowell and
his brother, James, both of whom fell in the Civil War, and James
Russell Lowell, poet, professor and ambassador; besides brilliant
lawyers and men entrusted with large interests as executors of
estates. Do you think John Lowell would have taken that vow could he
have foreseen the future?"
[Illustration: FIG. 37
Pedigree of family with artistic (dark upper section), literary (dark
right section) and musical (dark left section) ability (from Davenport).]
=The Elimination of the Grossly Unfit Urgent.--=But even if, under present
conditions of partial knowledge and lack of an adequate standard, the
constructive phase of eugenics must be left in the main to the awakening
conscience of the individual as humanity improves in general
enlightenment, the second phase, the elimination of the grossly unfit is
one of the greatest social obligations that confronts us to-day. For if
there is an alarming amount of mental impairment in civilized nations, and
if the problems of pauperism, inebriety, prostitution and criminality are
closely interwoven with the problems of mental unsoundness, as we have
every reason to believe from available data, then any means which will
operate toward securing normally functioning brains will at the same time
operate toward diminishing, defects and delinquencies. And inasmuch as a
considerable proportion of defects, both mental and physical, are
inheritable, it is obvious that if we can diminish the number of children
born into the world with defective brains or bodies we have made a long
stride in the right direction.
[Illustration: FIG. 38
Inheritance of ability (from Kellicott after Whetham).]
=Suggested Remedies.--=But how go about it? Various schemes have been
proposed, of which the chief are as follows:
1. Laws restricting marriage.
2. Systems of mating with the purpose of covering up and gradually
diluting out defective traits.
3. Segregation during the reproductive period.
4. Sterilization.
5. Education in the principles of eugenics.
=Inefficacy of Laws Which Forbid Marriage of Mental Defectives.--=The
utter inefficacy of the first proposition, namely the enactment of laws
restricting marriage, at least as regards the socially unfit whose
condition is based on impaired mentality, has been demonstrated time and
again. If they are forbidden marriage, they merely have children without
getting married. Most states have laws to prevent the marriage of such
individuals but these laws are almost wholly ineffective in preventing
procreation on their part. We might as well recognize once for all that in
such cases nothing short of close custodial care or sterilization will
accomplish the end desired.
As to the second proposition, systems of mating with the purpose of
covering up and gradually diluting out defective traits, this has been
shown to be possible with certain types of defectives. Whether it is
desirable or not is a different question.
[Illustration: FIG. 39
Inheritance of ability (chart condensed and incomplete) in three markedly
able families (from Kellicott after Whetham):
1, Charles Darwin; 2, his cousin, Francis Galton, founder of the modern
eugenic movement.]
=Systems of Mating Impracticable in the Main.--=By systems of mating, it
should be said, is not meant the arbitrary marrying of two individuals
willy-nilly, but rather it is the prevention from marriage of two
individuals having similar defects. In general the facts at our command
indicate that in the majority of cases the offspring from a marriage of an
insane, feeble-minded or epileptic person with a normal individual free
from all neuropathic taints are normal or at most show but slight effects
of the taint. But what normal individual would knowingly marry into such a
stock? With few exceptions such traits where inheritable are apparently
negative, that is, not represented by some positive abnormal factor but
due to the lack of some element or elements necessary to the proper
working of the normal brain. In the offspring of such a union the
necessary missing factors are supplied by the normal parent. Or in
Mendelian phraseology, the defective traits are recessive and are
dominated by the normality of the other parent. Such offspring, however,
while apparently normal of body are not normal of germ-plasm, inasmuch as
half of their germ-cells will carry the abnormality of the defective
parent as earlier explained (page 119) under Mendelism. We have already
seen (page 119) how by continually marrying into strong strains the
liability to recessive defect can be diluted out until the descendants are
no more likely to have defective children than are members of our ordinary
population. If, however, as is estimated in Bulletin No. 5 of the
_Eugenics Record Office_, about thirty per cent. of our general population
already carry recessive neuropathic taints, it certainly is a hazardous
proceeding to attempt thus to breed out nervous defects unless one is
absolutely sure of the normality of the strain into which it is proposed
to marry. The great difficulty is in determining whether or not there is a
defective ancestry in a given stock. We have at present no criteria for
identifying normal individuals who have defective germ-plasm. As a
practical test, however, if no defect has appeared in the stock for three
or four generations back, the marriage would be relatively as safe as are
the marriages of our average population to-day.
=Corrective Mating Presupposes Knowledge of Eugenics.--=But such a scheme
of corrective mating presupposes a relatively high degree of intelligence
and judgment on the part of the participants, and this is just what we do
not have and in the nature of things can not get, in the types of
feeble-minded, epileptic and degenerate strains we are striving to
eliminate. All our evidence shows that when unrestricted there is a marked
tendency for feeble-minded to mate with feeble-minded, degenerate with
degenerate. About sixteen per cent. of the feeble-minded, in fact, come
from consanguineous marriages. If we try to legislate them into specific
types of marriage then we encounter the same futility pointed out under
our discussion of restrictive legislation, they will produce offspring
without the formality of marriage.
In certain cases of insanity and in other than neuropathic defects one can
see how the system might be inaugurated with greater prospects of success,
but even then a knowledge of the principles of eugenics would be necessary
to the participants, or in other words we could only accomplish our end
through our fifth proposition, education.
=Segregation Has Many Advocates.--=As to the third proposition,
segregation during the reproductive period, this seems to have a larger
number of advocates than any other coercive measure. While on theoretical
grounds it is plausible enough, when we face the actual putting of the
method into practise we are confronted by the fact that tremendous sums of
money would be required to sequestrate and maintain colonies or industrial
refuges.
When one realizes that no state now provides for more than a small
minority of its defectives, and knowing also of the pressure that must be
brought to bear on legislatures to secure sufficient funds to provide for
these cases of extremest urgency, one can not be overly optimistic about
the practicability of extensive sequestration.
E. R. Johnstone, the superintendent of a large training school for
feeble-minded in New Jersey, points out that no state in the Union is
providing for many more than one-tenth of her feeble-minded and
epileptics. If his estimate is true, to place in institutions, treat and
train all its feeble-minded and epileptics would even now almost swamp any
state treasury. But what _will_ it be in the future if we permit this
unrestricted nine-tenths to go on and multiply their kind?
Leaving out of account the enormous sums spent in private charities even
now from one-fifth to one-seventh the total public expenditures of almost
any one of our states is going to maintain its defectives, dependents and
criminals. From the 1912 report of the secretary of state, in the state of
Wisconsin, for instance, I learn that of the total expenses for 1912,
sixteen per cent. was for charitable and penal institutions. The situation
is even worse in some other states. Think of it! Think what a large total
of expense it becomes! And the expense is far secondary from the
humanitarian standpoint to the misery involved.
In the _Survey_ of May 24, 1913, we find Mr. Hastings H. Hart, Director of
the Department of Child Helping of the Russell Sage Foundation, proposing
very specifically "a working program for the extinction of the defective
delinquent," which involves segregation during the reproductive period. He
gives the number of feeble-minded under public care as 20,000 in
institutions for the feeble-minded, 16,000 in almshouses, 5,000 in
hospitals for the insane, and 26,000 in prisons and reformatories, or a
total of 67,000 already under custodial care. And he asserts that as
nearly as can be judged, this is one-third of the feeble-minded persons in
the United States.
Between this estimate that one-third of our feeble-minded are in
institutions and Doctor Johnstone's that we are not providing for many
more than one-tenth of our feeble-minded and epileptic, there is a wide
discrepancy, but I know of no accurate data[20] whereby the matter can be
settled definitely. One point of difference may be that Doctor Johnstone
specifically includes epileptics and another may be one of definition of
feeble-minded. However, supposing that we could get them all into
institutions, institutional care at present by no means also implies
prevention of propagation. It is not an unusual history of feeble-minded
women in our county poor-houses that they alternate between periods of
housework in some family and periods of residence in the almshouse, the
return to the latter being only too often to bear an additional child.
Not a few students of the problem, however, advocate a rigid segregation
as the only reasonable preventive measure, no matter what the expense.
They point out that the cost is mounting up higher each year and that we
are only increasing it ultimately by procrastination. They urge, moreover,
that when counting the cost of the segregation of the feeble-minded we
should bear in mind also that we are reducing the expenses of our other
charity and penal institutions, since much of degeneracy, pauperism and
petty criminality centers in mental enfeeblement. Some believe that
colonies can be established which are in considerable measure
self-supporting. Doctor Johnstone, for instance, although his estimates of
the number of feeble-minded and epileptic is one of the highest, sketches
out in a recent paper (in _Pediatrics_, August, 1912) a plan which he
considers feasible.
But what assurance have we that we can prevent the production of
defectives by segregation? In reply may be cited a recent experiment on an
extensive scale. Cretinism is a condition due to disease of the thyroid
glands. It is characterized by goiter, marked deformities and imbecility.
It is hereditary and has been very prevalent in certain valleys of
southern Switzerland and northern Italy. Cretin mated with cretin and
consequently a large new supply was constantly produced. In recent years
in certain communities the sexes have been segregated (see _Eugenic
Review_, 1910, Jordan) with the result that in such places cretinism has
about disappeared.
Coming now to the fourth solution proposed, namely, sterilization,[21] let
us consider some of its alleged advantages and disadvantages.
=Sterilization.--=First of all, since there is some considerable popular
misunderstanding on the subject, it should be made plain that by
sterilization is not necessarily, nor in fact generally, meant
asexualization, or the removal of the reproductive glands. On the
contrary, in the male, sterilization is ordinarily accomplished by an
operation known as _vasectomy_, in which a small piece of each sperm duct
is removed. Such reports on it as I have found indicate that it is a
comparatively simple minor operation which involves no special
inconvenience or hardship on the subject beyond the deprivation of
offspring. In fact, according to Doctor Sharp's report, in the majority of
cases where it has been put into practise the patient has usually
submitted voluntarily after having the details of the situation explained
to him and has often advised fellow delinquents to do likewise.
Even should later developments show that a mistake had been made, in all
probability the matter could be remedied by a second operation in which
the cut ends of the ducts can be reunited. This has been accomplished
experimentally in dogs, and furthermore, in men rendered sterile by
occlusion of the duct through inflammatory diseases, the sterility has
been remedied by removing the blocked area and reuniting the ends of the
duct on either side.
In women the corresponding operation--a section of the oviduct--is termed
_salpingectomy_. Here, however, the operation is a more serious one as it
usually involves opening the abdominal cavity and the accompanying hazard
of infection, a danger sufficiently great that it is safe to say that the
operation will be resorted to more rarely than vasectomy in man.
=As a Eugenic Measure.--=Sterilization as a eugenic measure has many
advocates and perhaps more opponents; and among the latter, it must be
said, are many competent and thoughtful students of the subject who
recognize existing conditions and deplore their continuance as much as any
one. They maintain that while we may have to come to it as a last resort,
we are yet too ignorant of the actual effects of the operation, or are too
little informed on the inheritability of the specific traits we are trying
to eradicate, to launch forth on so radical a program. We must not forget
that when we put sterilization into effect we are going to have to deal
with individual cases, not general averages.
=To What Conditions Applicable.--=And just here, it seems to me, is the
crux of the situation. When confronted by the defective individual, in a
practical case, just what criteria are we going to use to determine
whether this particular individual should be sterilized or not? Nearly all
of the twelve states which have sterilization laws specify insanity,
feeble-mindedness, epilepsy and criminality.
=In Insanity.--=When it comes to insanity I strongly suspect that those
who have the selection of the examining board will have difficulty in
finding an alienist who is willing to take the responsibility of deciding
on just which insane individuals shall be operated on and which not. For
among the insane there are so many kinds and degrees of mental
unsoundness, and these are of such varying and as yet unknown eugenical
significance, that a positive decision is frequently out of the question.
Of the twenty-seven or more recognized forms of insanity who knows with
any considerable degree of certainty which are heritable, which not? Shall
we treat all manic-depressives alike? Shall we treat them as, for
instance, we would those suffering from dementia precox? Who will take the
responsibility of answering positively? Again, what shall we do in cases
of paresis, or general paralysis of the insane, an affliction which
probably invariably has syphilis as its antecedent? Yet it constitutes one
of the commonest forms of insanity found in asylums. Doctor George H.
Kirby, director of Clinical Psychiatry, Manhattan State Hospital, says
that with one exception there are more admissions of paretics to Manhattan
State Hospital than sufferers from any other form of mental disorder. He
continues, "We find that when either the father or the mother suffers from
paresis that many other members of the family may be infected with
syphilis, and furthermore, we find that a surprisingly large number of
children in these families are feeble-minded, nervous, or in other ways
abnormal." But here, it is clear, the patient has done the damage before
he reached the hospital, nor was it paresis as such that did the harm but
the syphilitic infection of which paresis itself was but the outcome.
Certainly the one fact which stands out conspicuously when we face most
concrete cases, is that at present we need more urgently than
sterilization laws for the insane, exhaustive studies of the
inheritability of specific mental infirmities that we may know with some
degree of certainty which warrant sterilization.
Yet on the other hand one of the most disquieting facts that confronts us
to-day is the large number of patients who are on parole from our
hospitals for the insane, subject to recall. What shall we do with them?
Shall we submit them to the tremendous hardship of still remaining under
custodial care although to all intents and purposes sane, or shall we make
their release contingent upon their submission to vasectomy or
salpingectomy?
In a few cases such as Huntington's chorea (Figs. 26, 27, pp. 114, 115) we
can proceed with a fair degree of assurance, for we know that this
dreadful malady is transmitted as a positive trait and that in all
probability half of the children of an afflicted individual will inherit
the defect. Such patients, if they ever rally sufficiently temporarily to
leave the hospital, or where encountered outside the hospital should
certainly be restrained from procreation. It is questionable if even their
children, though apparently normal, should be allowed to have offspring,
for usually the disorder does not manifest itself until middle life and
then it is too late to try to prevent its transmission since the affected
individual has already probably married and had children. But Huntington's
chorea is a comparatively rare form of insanity, and one of only a few
about which our knowledge as regards its transmissibility is fairly
satisfactory.
=In Feeble-Mindedness.--=When we come to institutions for the
feeble-minded, however, there seems to be much more unanimity of opinion
among physicians in charge of such institutions that sterilization would
be an effective and satisfactory disposition to make of many cases, if we
are to release the patients in question from custody. Unquestionably in
cases of imbecility it is easier than in insanities to pass conclusive
judgment on the inheritability of the condition in a large class of cases.
Practically all are agreed that either permanent custodial care through
the reproductive period or sterilization should be enforced. Some maintain
that such individuals should remain permanently in institutions anyway and
that therefore to sterilize them is needless, while others urge that if
sterilized many capable of making their own living could be freed and
allowed to do so.
According to Goddard the feeble-minded woman is about three times as
likely to find a mate as a feeble-minded man, hence it would seem to be of
much greater importance to sterilize the woman than the man.
Again it might be urged with much justification, that even though
sterilized, the feeble-minded individual because of lack of self-control
will transgress sexually and will thus certainly become a menace to
society in the spread of venereal diseases. If Mr. Hart's estimate is
anywhere near correct, that there are 60,000 feeble-minded women in the
United States of child-bearing age, and that 13,000 are already in
custody, then the task of getting all women of this class into custody is
not so insurmountable as would at first appear.
=In Cases of Epilepsy.--=As to epilepsy, I find a very decided difference
of opinion among physicians. Some consider it, on account of its
apparently strong inheritability, together with the shocking crimes
perpetrated by epileptic criminal types, one of the most serious menaces,
while others point out that we know nothing of the real cause of epilepsy,
that there are all degrees and shades, that it is probably referable to
different causes in different cases and that no one is able to say what
the offspring of any given epileptic will be.
As to criminal types, here again we face the difficulty of deciding any
particular case. Let us suppose that twenty-five per cent. of criminals
are mental defectives, how shall we sift them out from the seventy-five
per cent. who are supposed to be eugenically normal? Doubtless in many of
the twenty-five per cent. class, the indications of defective mentality
are sufficiently evident to prevent mistakes, but a considerable number of
uncertain status must also remain near the border-line.
=Sterilization Laws.--=Although twelve of our states already have
sterilization laws, only two, Indiana and California, seem to have made
any active attempt to enforce them. The situation is too new yet in
Wisconsin, Michigan and Pennsylvania for these states to have shown what
they intend to do. Although the Indiana law says, "it shall be compulsory
for each and every institution" to maintain the practise, it has fallen
into disuse since 1911, presumably because the governor believed the law
unconstitutional. It is of interest to see the motive underlying the law
in various states. In the majority it is purely eugenic. In Connecticut it
is mainly eugenic though partly therapeutic. In California it is
apparently in part therapeutic, since it is stated as being for the
physical, mental or moral benefit of inmates of various state
institutions, and in part punitive and eugenic, since individuals twice
committed for sexual offenses or three times for other crimes are subject
to the operation.
In Washington and Nevada the object is purely punitive, the persons
specified being habitual criminals and persons adjudged guilty of carnal
abuse of female persons under ten years of age, or of rape. In these
states also the court orders the operation instead of leaving it to the
decision of a board of medical experts.
=Social Dangers in Vasectomy.--=It has been urged against vasectomy that
it will work untold harm because it relieves of the responsibility of a
probable parentage. This argument does not appeal to one as very weighty
as far as the imbecile or other degenerate is concerned, because one of
the very traits characteristic of such individuals is lack of any sense of
responsibility. By this same token, however, we have a very good argument
for sequestration as against sterilization, for the degenerate, even
though sterilized, will not be restrained sexually and will be likely to
disseminate venereal diseases or commit rape. Furthermore, there will be
the temptation to sterilize and liberate certain types that would
otherwise have been kept permanently in custody.
=Our Present Knowledge Insufficient.--=When all is said and done, after we
take into account the meagerness of our present knowledge on the subject,
it is not to be wondered at that many thoughtful students of a
conservative turn of mind, feel that any considerable practise of
sterilization is premature. The problem has so many phases, and despite
occasional bits of positive knowledge, we are yet in such a sea of
ignorance regarding it, that in no field is the good Friar Laurence's
admonition of "wisely and slow; they stumble that run fast," needed more
at present than it is here.
There is little doubt that in theory the feeble-minded and similar
defectives should be sent to institutions and kept there, but the
important practical question is, can this be done? We can have no final
answer until it is tried. While the initial expense would undoubtedly be
great, if we could keep our defectives from propagation for a single
generation we could very materially lessen their numbers and in succeeding
generations the expenses of their care would rapidly diminish.
The one crying need that stands out most prominently in this whole field
is that of careful investigation of individual cases and specific types of
malady, together with an accurate census of conditions as a whole. Our
knowledge of individual malign heredities is too meager to carry us very
far at present. When we have found after adequate investigation in just
which specific types of defects heredity is an important factor--and we
shall undoubtedly find it to be one in many cases--then we can proceed
confidently with sterilization, if it will prove to be more practical and
desirable than sequestration.
=Sterilization Laws on Trial.--=It will be of great interest and
instruction to see how extensively, in the various states which have
recently passed sterilization laws, the experts selected will find it
expedient to carry on sterilization, and what criteria they will use in
deciding on individual cases. That sterilization can be put into effect is
indisputable, as may be seen from the fact that several hundred operations
have been performed in Indiana. If the board on whom the decision depends
happens to be one which feels that many people are likely to distress
themselves unduly over the border-line cases, and overlook the fact that
there is always a goodly residue with which to proceed without great risk
of mistake, then we may expect to see a vigorous campaign inaugurated, and
those of us who are still undecided in the matter will have an opportunity
of learning more certainly the merits or the failings of the scheme.
Certain married degenerate types would seem to be the ones most urgently
demanding attention. Having already begotten several defective children
and with nothing else in prospect but the production of the same kind, it
is difficult to see from any standpoint why a vasectomy on the male would
not be a merciful act. There are not a few such families where the father
is periodically in the hands of the law and yet not in permanent
restraint. Once in custody his release could be made contingent on
vasectomy.
=An Educated Public Sentiment the Most Valuable Eugenic Agent.--=Coming
now to the last proposition, education of the public in the principles of
eugenics, this is the method calculated to be of more far-reaching service
than any other, in the negative as well as in the positive phases of
eugenics. Education is necessary before we can have effective restrictive
measures for the mentally incompetent established and enforced, and it is
also a prerequisite to intelligent procedure on the part of normal
individuals in considering their own fitness for marriage.
Of greatest importance in preventing undesirable marriages, as far as
people of normal intelligence is concerned, will be the sentiment of
disapproval which will arise on the part of society itself when it becomes
really convinced that certain marriages are inimical to social welfare.
Public opinion is, in fact, one of the most potent influences in marital
affairs, simply because refusal to abide by the dictates of the community
means social ostracism.
That social disapproval of certain unions can become a very real factor in
preventing such marriage is evinced on all sides by the numerous barriers
to marriage already in existence based on race, religious sect or social
status. Even in our much vaunted democracies one is looked down on who
marries "beneath" his or her social set. This sentiment of taboo, so
readily and often so senselessly cultivated in our present human society,
will inevitably spring up in consequence of a wide-spread knowledge of the
facts of human heredity. It is to such a growth, to the establishment of a
disapproval which is the product of its own sentiments rather than to
legislative enactments, that society must look for the greatest
furtherance of the eugenic program.
Necessary as legal restraint is in certain cases, it must obviously be
restricted to only the most glaring defects. Moreover, legislation can not
run far in advance of public opinion.
=The Question of Personal Liberty.--=It must be admitted that there is a
reluctance on the part of many even thoughtful individuals to the
application of methods which savor in any way of restraint. An objection
not infrequently urged by such persons against the application of certain
eugenic principles is that they demand an unwarranted curtailment of
personal liberty.
To those who hoist the flag of personal liberty, it may fairly be asked,
how much personal liberty does the syphilitic accord his doomed and
suffering wife and children, or how much personal liberty is the portion
of the offspring of feeble-minded parents? Or, what quota of personal
liberty will accrue to the ill-fated descendants of the epileptic, the
habitual drunkard or criminal, the gross moral pervert, the congenially
deaf and dumb, or to even the progeny which may result from the union of
two well-established tubercular strains?
We do not hesitate to send the pick of our stalwart healthy manhood to war
to be slaughtered by the thousands and tens of thousands when an affront
is offered to an abstraction which we term our national honor, and,
sublimely unconscious of the irony of it all, we throw ourselves into a
well-nigh hysterical frenzy of protest when it is proposed to stop the
breeding of defectives by infringing to a certain extent on their personal
liberties.
Society has already found it necessary to suppress certain individuals
and yet we hear little complaint about loss of personal liberty in such
cases. But if it is necessary to restrain the man who would steal a purse
or a horse, is it not still more urgent to restrain one who would poison
the blood of a whole family or even of an entire stock for generations?
Surely there can be but one answer; society owes it to itself as a matter
of self-preservation to enforce the restraint of persons infected with
certain types of disease and of individuals possessing highly undesirable
inheritable traits, so that perpetuation of such defects is impossible.
=Education of Women in Eugenics Needed.--=One of the most crying needs of
the present is the awakening and educating of women to the significance of
the known facts. For they are perhaps the greatest sufferers, and once
informed, as a mere matter of safety if for no other reason, they will see
the necessity of demanding a clean bill of health on the part of their
prospective mates. Furthermore in the last analysis woman is the decisive
factor in race betterment, for it is she who says the final yea or nay
which decides marriage and thus determines in large measure the qualities
which will be possessed by her children. Above all, young women must come
to realize that the fast or dissipated young man, no matter how
interestingly or romantically he may be depicted by the writer of fiction,
is in reality unsound physically, and is an actual and serious danger to
his future wife and children.
=Much Yet to Be Done.--=But plain as is our duty regarding the application
of facts already known, when we consider that the student of heredity has
made only a beginning, it is equally evident that he must be urged on in
his quest for new facts, and the establishment of new principles. There is
imperative need to carry on proper experiments with plants and animals, to
collect necessary data regarding man, and for what is scarcely less
important, the publication of the facts already acquired so that the
public may be guided aright.
Just at present it is of the utmost importance to secure more trustworthy
statistics in order that we may intelligently go about instituting
suitable restrictive measures for undesirable human strains. We must know
the exact number and kinds of feeble-minded, epileptic and insane in our
population, and we must have more insight into the personal status and
pedigrees of our delinquents and criminals. For purposes of rational
procedure such information is indispensable. Much can be done by
hospitals, "homes" and penal institutions by determining and recording
more accurately all obtainable facts regarding the ancestry of their
charges. Moreover, in such states as Wisconsin, where the state hospitals
for the insane have each an "after-care-agent," the duties of such
officers might well include the collection of more adequate data regarding
the hereditary aspects of their patient's condition. And lastly, if in
every census, whether state or national, it were made an important part of
the work to secure accurate vital statistics, particularly as they pertain
to human heredity, the contribution toward enabling us ultimately to
purge the blood of our nation of certain forms of suffering, degeneracy
and crime would be inestimably great.
=A Working Program.--=And now after reviewing at some length various
aspects of man's hereditary and congenital endowment, the important
question arises as to whether it is possible, with the knowledge at
present available, to go ahead with a practical program which will insure
to the child of the future its right of rights, that of _being well-born_.
When one considers the matter it is evident that much can be done at once.
Most of the needs set forth in the preceding paragraph can clearly be met
in a fair degree by instituting the procedures indicated.
One of the obvious duties in a restrictive way that confronts us right at
the start is the care and control of the feeble-minded and of the
defective delinquent in such a way as to prevent procreation. Much help
can be given also through intelligent agitation for the establishment of
colonies for epileptics and the higher grades of feeble-minded which can
be made in considerable measure self-supporting. A given colony must, of
course, be for one sex alone. Much can be done, furthermore, by putting
into operation, both in and out of institutions, effective systems of
registering births and deaths together with accompanying facts which may
prove of eugenical significance.
Again, we should more surely identify and exclude undesirable immigrants
and also undertake thoroughgoing investigations to determine which races
we can not profitably assimilate into our own blood.
Physicians should pay more attention to the hereditary and congenital
aspects of their cases and make it more a matter of conscience than they
do at present to advise patients with regard to marriage. Prenuptial
medical inspection should become the custom, if not by law at least as a
voluntary procedure. Every parent must come to realize the grave risk to
which he is subjecting his daughter if a guarantee of physical fitness,
even more than assurance of financial standing or social position, is not
forthcoming from her prospective mate.
Wholly apart from the field of heredity though in a realm intimately
concerned with the birthright of the child, much practical good can be
accomplished by pondering the facts and the fictions of prenatal influence
and in the light of the knowledge thus gained, seeing that while foolish
and unnecessary worries are abolished, the conditions of health, nutrition
and occupation surrounding the expectant mother are the best obtainable.
It is the sacred duty of every individual, moreover, to see that the
maximal possibilities of his own germ-plasm are not lowered by vicious or
unwholesome living.
As individuals we can cultivate a greater sense of responsibility
regarding marriage and parenthood in those for whose training we are
responsible. We can study this whole subject conscientiously, keep pace
with new knowledge and see that other people are likewise informed. In
showing an enlightened interest in the ideals of eugenics and a
sympathetic approval of wholesome marriages, a sentiment toward parenthood
will gradually arise which will make it seem more desirable to many worthy
people than it does at present. If we are of good stock ourselves we
should recognize that it is highly desirable that we give to the race at
least four children. On the other hand, if we come from a strain which is
eugenically undesirable we should with equal conscientiousness refrain
from contributing to human misery. For where serious obstacles to a union
exist, renunciation is certainly a higher manifestation of love than is
consummation of a marriage which will result in untold misery to the
object of the affections. As a matter of fact, with adequate preliminary
knowledge as to what actually constitutes a serious drawback to marriage,
where such really exists and is recognized by the associated individuals,
love of the kind that leads to marriage is not likely to arise.
As has been suggested by various students of eugenics, it is even at
present perhaps not infeasible for earnest individuals to start in a quiet
way local centers for the keeping and filing of accurate records of their
family traits for the future use of their descendants. Such groups,
voluntary though they be, would soon acquire a degree of distinction that
would make other people of good endowments wish to join in and go on
record as eugenically desirable.
Lastly, it should not be forgotten that good traits are inherited as
certainly as bad ones. Moreover, in the realm of human conduct, even
though the fundamental features of behavior are based on an inherited
organization, man is not always driven by an inexorable linkage of
inherited neutral units into only one line of conduct, since more or less
capacity for alternative action is also inherited. It is the personal
duty of every member of society to aid in affording the opportunity and
providing the proper stimuli to insure that out of the many possibilities
of behavior which exist in the young at birth, those forms are realized
which are best worth while to the individual and to society. And while we
recognize that improved environment alone can not correct human
deficiencies we must nevertheless not relax our efforts to get cleaner
foods, cleaner surroundings, cleaner politics and cleaner hearts.
Why go on alleviating various kinds of misery that might equally well be
prevented? When one squarely faces the issue, surely the absurdity of our
present practises can not but be evident to even the most thoughtless.
=Which Shall It Be?--=As a matter of social evolution, human homes
originated in the necessity of an abiding place for the nurture and
training of the young past their first period of helplessness. Well in the
foreground of the mental picture which arises when we hear the very word
_home_, are children. What shall the home of the future be with regard to
its most important assets, the children? Shall we as a people continue to
be confronted at every turn by the dull countenance of the imbecile, the
inevitable product of a bad parental mating; or the feeble body and the
clouded intellect of the child sprung from a parentage of polluted blood;
or the furtive cunning of the born criminal, the will-less mind of the
bred degenerate, or the shiftless spawn of the pauper? Or shall it be a
type with laughing face, with bounding muscles, with unclouded brain,
overflowing with health and happiness--in short, _the well-born child_?
The answer is in our own hands. The fate of many future generations is
ours to determine and we are false to our trusteeship if we evade the
responsibility clearly laid before us. How conscientiously we heed known
facts, how actively we acquaint ourselves with new facts, and how
effectively we execute the obvious duties demanded by these facts, will
give us the answer.
THE END
GLOSSARY
ACQUIRED CHARACTERS, traits developed in the body through changes in
environment or function, in contra-distinction to those which have their
specific causes in the germ-cells.
ADAPTATION (L. _ad_, to; _aptus_, fit), fitness to environment.
ALBINISM (L. _albus_, white), a condition of deficiency in pigment.
ALLELOMORPH (Gr. _allelon_, of one another; _morphe_, form), one of a pair
of alternate Mendelian characters.
AMEBA (Gr. _amoibe_, change), a primitive single-celled animal.
AMPHIBIAN (Gr. _amphi_, both; _bios_, life), capable of living both on
land and in water.
ANTHROPOID (Gr. _anthropos_, man; _eidos_, form), man-like.
ARISTOGENIC (Gr. _aristos_, best; _genesis_, origin), pertaining to the
genetically most desirable human strains.
ASSOCIATION AREAS, those regions of the brain in which presumably the
higher mental processes are effected.
ATAVISM (L. _ad_, before; _avus_, grandfather), a return in one or more
characters to an ancestral type. See p. 8 for restricted modern usage.
ATROPHY (Gr. _a_, negative; _trophe_, nourishment), a wasting away of a
part of a living organism.
AXON (Gr. _axon_, axis), the process from a nerve cell which becomes a
nerve fiber.
BINET-SIMON SCALE, a series of tests graded to age and previous training
of the average normal child, much used in measuring mental deficiency.
BIOLOGY (Gr. _bios_, life; _logos_, discourse), the study of life and of
living things.
BIOMETRY (Gr. _bios_, life; _metron_, measure), the study of biological
problems by means of statistical methods.
BLASTOMERE (Gr. _blastos_, germ; _meros_, part), one of the early cells
formed by the division of the ovum.
BLASTOPHTHORIA (Gr. _blastos_, germ; _phtheiro_, destroy), deterioration
of the germ as the result of direct pathogenic or other disturbing agents.
BLENDING INHERITANCE, inheritance in which the characters of the parents
seem to blend in the offspring.
CACOGENIC (Gr. _kakos_, bad; _genesis_, origin), pertaining to genetically
undesirable human strains.
CELL, the fundamental unit of structure in plants and animals.
CENTROSOME (Gr. _kentron_, center; _soma_, body), a small body which
functions in indirect cell-division.
CHARACTER, any distinguishing feature, trait or property of an organism.
CHEMOTROPISM (chemical and tropism), defined, p. 198.
CHROMATIN (Gr. _chroma_, color), deeply staining substance of the
cell-nucleus.
CHROMOSOMES (Gr. _chroma_, color; _soma_, body), characteristic deeply
staining bodies, typically constant in number and appearance in each
species of animal or plant, which appear in the cell during indirect
division.
CHROMOTROPISM (Gr. _chroma_, color; _trope_, turning), defined, p. 198.
CLEAVAGE, the division of the egg-cell into many cells.
CONGENITAL (L. _con_, together; _gigno_, bear), present at birth.
CONJUGATION (L. _con_, together; _jugum_, yolk), the union of germ-cells
or unicellular individuals for reproduction.
CONSTRUCTIVE (or positive) EUGENICS, a system of securing a superior race
through propagation of the fittest individuals.
CORTEX (L. _cortex_, bark), the outer or investing layer of the brain.
CYTOPLASM (Gr. _kytos_, cell; _plasso_, form), the protoplasm of the cell
outside of the nucleus.
DALTONISM, the commonest form of color-blindness in which the affected
individual is unable to discriminate between red and green.
DENDRITES (Gr. _dendron_, tree), branching processes which spring from
nerve-cells.
DETERMINER (L. _determinare_, to determine), the distinctive cause or unit
in a germ-cell which determines the development of a particular character
in the individual derived from that cell. The terms _gene_ and _factor_
are sometimes used as synonyms of determiner.
DIHYBRIDS (L. _di_, two; _hybrida_, mongrel), the offspring of parents
differing in two characters.
DIPLOID (Gr. _diploos_, double; _eidos_, form), the dual or somatic number
of chromosomes.
DOMINANT CHARACTER (L. _dominare_, to be a master), a character from one
parent which manifests itself in offspring to the exclusion of a
contrasted character from the other parent.
DROSOPHILA, a genus of fruit-flies of which there are several species.
DUPLEX (L. _duo_, two; _plico_, fold), the condition in which a character
is represented by two determiners, one from each parent.
ELECTROTROPISM (Gr. _electron_, amber; _trope_, turning), defined, p. 198.
EMBRYO (Gr. _embryon_), the young organism in its earliest stages of
development.
EMBRYOGENY (Gr. _embryon_; _genesis_, generation), the development of the
embryo.
EUGENICS (Gr. _eugenes_, well-born), the science relating to improvement
of the human race through good breeding.
FACTOR, the determiner of a particular hereditary character.
FEEBLE-MINDEDNESS, deficiency in mental development. For grades, see p.
244.
FERTILIZATION, union of the sexual cells.
FETUS (L. _feuere_, to bring forth), the unborn young animal in its later
(after the second month in man) stages of development.
FLAGELLUM (L. _flagellum_, little whip), a vibratile, thread-like organ of
locomotion.
GAMETE (Gr. _gamos_, marriage), a mature germ-cell.
GENETICS (Gr. _genesis_, origin), the science which deals with heredity
and the origin of individuals in general.
GENOTYPE (Gr. _genea_, race; _typto_, strike), the germinal constitution
of an organism.
GEOTROPISM (Gr. _ge_, earth; _trope_, turning), defined, p. 198.
GERM-CELL, a reproductive cell.
GERMINAL VARIATIONS, variations which owe their origin to some
modification in the germ-cells.
GERM-PLASM, the material basis of inheritance.
GONAD (Gr. _gonos_, generation), a germ-gland.
HAPLOID (Gr. _haploos_, single; _eidos_, form), the single or reduced
number of chromosomes as found, for instance, in the mature germ-cells.
HELIOTROPISM (Gr. _helios_, sun; _trope_, turning), defined, p. 198.
HEREDITY (L. _heres_, heir), resemblance of individuals to their
progenitors based on community of origin.
HERITAGE (L. _heres_, heir), all that is inherited by an individual.
HETEROZYGOTE (Gr. _heteros_, other; _zygon_, yolk), an individual produced
through the union of germ-cells which are unlike in one or more
determiners. Adjective, _heterozygous_.
HOMOZYGOTE (Gr. _homos_, same; _zygon_, yolk), an individual produced
through the union of germ-cells which are alike in determiners. Adjective,
_homozygous_.
HYBRID (L. _hybrida_, mongrel), the offspring of parents which differ in
one or more characters.
IDENTICAL TWINS, twins which show identical inborn characters, both having
come presumably from the same ovum.
IDIOT (Gr. _idios_, peculiar, private), defined, p. 244.
IMBECILE (L. _imbecillis_, weak), defined, p. 244.
INHERITANCE (L. _in_, in; _heres_, heir), the sum of all characters which
are transmitted by the germ-cells from generation to generation.
INHIBITOR (L. _in_, in; _habeo_, hold, have), that which checks or
restrains.
INSTINCT (L. _in_, in; _stingno_, prick), defined, p. 203.
INTRA-UTERINE (L. _intra_, within; _uterus_, the womb), within the womb.
IRRITABILITY (L. _irrito_, excite), the property of responding to stimuli.
LININ (L. _linum_, flax), filaments of the cell-nucleus not readily
stained by dyes.
LUETIN TEST (L. _lues_, pest), a test for syphilis; see p. 188.
MAMMALS (L. _mamma_, breast), warm-blooded, hairy animals which suckle
their young.
MATURATION (L. _maturus_, ripe), the final stages in the development of
the sex-cells characterized by two divisions in one of which the number of
chromosomes is reduced by one-half.
MENDELIAN, MENDELISM, referring to Mendel, the founder of a theory of
heredity. See p. 67.
METAZOA (Gr. _meta_, over; _zoon_, animal), all animals higher than the
protozoa.
MITOSIS (Gr. _mitos_, thread), indirect nuclear division, characterized by
the appearance of a fibrous spindle and a definite number of chromosomes.
The latter split to form daughter chromosomes which diverge to the poles
of the spindle to form parts of the new nuclei.
MONGOLIAN, a type of feeble-minded individual, see p. 248.
MONOHYBRID (Gr. _monos_, single; L. _hybrida_, mongrel), the offspring of
parents, differing in one character.
MORON (Gr. _moros_, foolish), defined, p. 244.
MUTATIONS (L. _mutare_, to change), abrupt, inheritable germinal
variations. Frequently though not necessarily they are changes of
considerable extent.
NEURAL (Gr. _neuron_, nerve), pertaining to the nervous system.
NEURON (Gr. _neuron_, nerve), a nerve-unit consisting of a nerve-cell with
branching processes called dendrites and an axon or axis cylinder process
which gives rise to a nerve fiber.
NEUROPATHIC (Gr. _neuron_, nerve; _pathos_, suffering), relating to
disease of the nervous system.
NUCLEOLUS (L. dim. of nucleus), a well-defined body found within the
nucleus of a cell.
NUCLEUS (L. _nux_, a nut), the central organ of a cell.
NULLIPLEX (L. _nullus_, not any; _plico_, fold), the condition in which no
determiners of a given character exist in a particular individual.
OÖCYTE (Gr. _oon_, egg; _kytos_, cell), the ovarian egg in one stage of
development.
OÖGENESIS (Gr. _oon_, egg; _genesis_, origin), the development of ova from
primitive sex-cells.
OÖGONIUM (Gr. _oon_, egg; _gonos_, generation), a primordial egg-cell.
OVARY (L. _ovum_, egg), the organ in which the egg-cells multiply and are
nourished.
OVUM (L. _ovum_, an egg), the female sex cell.
PARTHENOGENESIS (Gr. _parthenos_, virgin; _genesis_, origin), development
of an egg which has not united with a male gamete.
PHENOTYPE (Gr. _phaino_, show; _typto_, strike), the existing type of
individual irrespective of hereditary possibilities which may reside in it
undeveloped.
PHOTOTROPISM (Gr. _phos_, light; _trope_, turning), defined, p. 198.
PLACENTA (L. _placenta_, a flat cake), the organ by which the fetus of the
higher mammals is attached to the uterine wall of the mother for purposes
of nourishment, respiration and excretion. In it the maternal and fetal
blood, although not intermingling, are brought into such close proximity
that an interchange of dissolved substances is possible.
POLAR BODIES, the minute cells which are separated from the egg in its
maturation divisions.
PRIMATE (L. _primus_, first), the highest order of animals, including
monkeys, apes and man.
PRONUCLEUS, the nucleus of the mature ovum or sperm-cell.
PROTOPLASM (Gr. _protos_, first; _plasma_, form), the essential living
substance.
PROTOZOA (Gr. _protos_, first; _zoon_, animal), single-celled animals or
animals composed of cells not separable into different tissues.
PSYCHICAL (Gr. _psyche_, the soul), pertaining to the mind.
RECESSIVE CHARACTER (L. _recessus_, a going back), a character from one
parent which remains undeveloped in offspring when associated with the
corresponding dominant character from the other parent.
REDUCTION DIVISION, a division of the maturing germ-cells in which the
dual or somatic (diploid) number of chromosomes is reduced to the single
(haploid) number.
REFLEX ACTION (L. _re_, back; _flectere_, bend), an automatic response of
the nervous and motor mechanism of the body.
RESTRICTIVE (or negative) EUGENICS, a system of improving the human race
by preventing reproduction of the unfit.
REVERSION (L. _re_, back; _verto_, turn), the reappearance of ancestral
traits which have for some generations been in abeyance.
RHEOTROPISM (Gr. _rheo_, to flow; _trope_, turning), defined, p. 198.
SALPINGECTOMY (Gr. _salpinx_, trumpet; _ectome_, cutting out), removal of
part or all of a Fallopian tube (oviduct).
SEGREGATION (L. _se_, aside; _grex_, flock), separation.
SEX CHROMOSOME, a special chromosome which is supposed to be concerned in
the determination of sex.
SEX-LINKED CHARACTERS, defined, p. 60.
SIMIAN (L. _simia_, ape), ape-like.
SIMPLEX (L. _sim_, same; _plico_, fold), the condition in which a
character is represented by a determiner from only one of the two parents.
SOMA (Gr. _soma_, body), the body considered apart from the germ-cells.
SPERMATID (Gr. _sperma_, seed), a cell resulting from the last division of
the germ-cell in spermatogenesis. It transforms into the spermatozoon.
SPERMATOCYTES (Gr. _sperma_, seed; _kytos_, cell), cells concerned in the
maturation divisions of the male germ-cells.
SPERMATOGENESIS (Gr. _sperma_, seed; _genesis_, origin), the development
of spermatozoa from primitive sex-cells.
SPERMATOGONIUM (Gr. _sperma_, seed; _gonos_, generation), a primordial
sperm-cell.
SPERMATOZOON (Gr. _sperma_, seed; _zoon_, animal), the functional male
sex-cell.
SPINDLE, a fibrous organ formed in indirect cell-division.
SPIREME (L. _spira_, coil), a characteristic stage preliminary to indirect
cell-division in which the chromatin material of the nucleus appears in
the form of a skein of filaments.
STEREOTROPISM (Gr. _stereos_, solid; _trope_, turning), defined, p. 198.
STERILIZATION (L. _sterilis_, barren), deprivation of reproductive power.
For methods, see p. 322.
SYNAPSE (Gr. _syn_, together; _hapto_, unite), the coming in contact of
the processes of one nerve cell with the processes or body of another.
SYNAPSIS (Gr. _syn_, together; _hapto_, unite), union of the chromosomes
in pairs preliminary to the reduction division.
TELEGONY (Gr. _telegonos_, born far away), the supposed influence of an
earlier sire on offspring born later of the same mother to a different
sire.
THERMOTROPISM (Gr. _thero_, heat; _trope_, turning), defined, p. 198.
THIGMOTROPISM (Gr. _thigmo_, touch; _trope_, turning), defined, p. 198.
TOXIN (Gr. _toxicon_, poison), poisonous compounds of animal, vegetable,
or bacterial origin.
TROPISM (Gr. _trope_, turning), the automatic directing of an organism
toward or away from a source of stimulus.
UNIT-CHARACTER, a character which behaves as an indivisible unit in
heredity.
VASECTOMY (L. _vas_, vessel; _ektome_, cutting out), removal of a portion
of the vas deferens (duct for conveying spermatozoa).
VESTIGEAL (L. _vestigium_, footstep), representing organs which existed
once in a more developed condition.
VOLVOX (L. _volvo_, roll), a small fresh-water organism occurring in
spherical colonies.
WASSERMAN REACTION, a test for syphilis, see p. 188.
X-ELEMENT, same as sex-chromosome.
ZYGOTE (Gr. _zygon_, yolk), the product of the union of two gametes.
REFERENCES FOR FURTHER READING AND STUDY
BATESON, W., 1909. _Mendel's Principles of Heredity._ Cambridge, The
University Press. The best technical account of Mendelism. It contains
also a translation of the original papers of Mendel.
CASTLE, WILLIAM E., 1911. _Heredity._ New York, D. Appleton and Company.
CASTLE, WILLIAM E.; COULTER, JOHN M.; DAVENPORT, CHARLES B.; EAST, EDWARD
M.; TOWER, WILLIAM L., 1912. _Heredity and Eugenics._ Chicago, The
University of Chicago Press.
CONKLIN, EDWIN GRANT, 1915. _Heredity and Environment in the Development
of Men._ Princeton, Princeton University Press.
DAVENPORT, CHARLES B., 1911. _Heredity in Relation to Eugenics._ New York,
Henry Holt and Company.
DONCASTER, L., 1911. _Heredity in the Light of Recent Research._
Cambridge, The University Press.
DONCASTER, L., 1915. _The Determination of Sex._ Cambridge, The University
Press.
ELLIS, HAVELOCK, 1912. _The Task of Social Hygiene._ New York, Houghton
Mifflin Company.
GALTON, FRANCIS, 1869. _Hereditary Genius: an Inquiry Into Its Laws and
Consequences._ London, Macmillan and Company.
GALTON, FRANCIS, 1889. _Natural Inheritance._ New York, The Macmillan
Company.
GALTON, FRANCIS, 1895. _English Men of Science; Their Nature and Nurture._
New York, D. Appleton and Company.
GALTON, FRANCIS, and SCHUSTER, EDGAR, 1906. _Noteworthy Families_ (Modern
Science). London, J. Murray.
GODDARD, HENRY HERBERT, 1912. _The Kallikak Family; a Study in the
Heredity of Feeble-mindedness._ New York, The Macmillan Company.
GODDARD, HENRY HERBERT, 1914. _Feeble-mindedness; Its Causes and
Consequences._ New York, The Macmillan Company.
HEALY, WILLIAM, 1915. _The Individual Delinquent._ Boston, Little, Brown
and Company.
KELLICOTT, WILLIAM E., 1911. _The Social Direction of Human Evolution; an
Outline of the Science of Eugenics._ New York, D. Appleton and Company.
MORGAN, THOMAS HUNT, 1913. _Heredity and Sex._ New York, Columbia
University Press.
PUNNETT, R. C., 1911. _Mendelism._ New York, The Macmillan Company. The
best popular account of Mendelism.
SALEEBY, CALEB WILLIAM, 1909. _Parenthood and Race Culture; an Outline of
Eugenics._ London, Cassell and Company.
SCHUSTER, EDGAR, 1912. _Eugenics._ London, Collins Clear-Type Press.
THOMSON, J. ARTHUR, 1908. _Heredity._ London, John Murray.
WALTER, HERBERT EUGENE, 1913. _Genetics._ New York, The Macmillan Company.
WHETHAM, W. C. D. and C. D., 1909. _The Family and the Nation._ London,
Longmans, Green and Company.
WOODS, FREDERICK ADAMS, 1906. _Mental and Moral Heredity in Royalty._ New
York, Henry Holt and Company.
VARIOUS AUTHORS, 1914. _Eugenics; Twelve University Lectures._ New York,
Dodd, Mead and Company.
JOURNALS:
_The Journal of Heredity._ The organ of the American Genetic
Association, Washington, D. C.
_The Eugenics Review._ Issued at the University of London.
_Memoirs and Bulletins_ published by the Eugenics Record Office, Cold
Spring Harbor, Long Island, N. Y.
Every one interested in eugenics should be acquainted with the work of
this office. In its own words its functions are:
1. To serve eugenical interests in the capacity of repository and
clearing house.
2. To build up an analytical index of the traits of American families.
3. To train field workers to gather data of eugenical import.
4. To maintain a field force actually engaged in gathering such data.
5. To cooperate with other institutions and with persons concerned
with eugenical study.
6. To investigate the manner of inheritance of specific human traits.
7. To advise concerning the eugenical fitness of proposed marriages.
8. To publish results of researches.
To such persons as will undertake to fill them out it furnishes free
in duplicate (one copy to be retained by the applicant) the following
blank schedules: 1. _Record of Family Traits._ 2. _Index to
Germ-plasm--A Parallel Family Record for Prospective Marriage Mates._
3. _Musical Talent._ 4. _Mathematical Talent._ 5. _Tuberculosis._ 6.
_Special Trait Chart._ 7. _Harelip and Cleft-palate._
_Publications of the Volta Bureau_ of Washington, D. C., an
institution given over entirely to data regarding deaf mutes.
_Studies in National Deterioration._ The University of London.
_Memoirs and Lectures_, from the Biometric Laboratory, University of
London.
_Treasury of Human Inheritance_, a series of studies being issued from
the Eugenics Laboratory, University College, London.
INDEX
Ability: 118;
calculating, literary, musical, 120.
Able child likely to be neglected, 257.
Achondroplasy, 113.
Acquired characters, inheritance of, 121.
Adami, 164.
Adaptations, establishment of, 140.
Adaptive responses, 201.
Agassiz, 297.
Albinism, in man, 116.
Alcohol: and crime, 279;
and degeneracy, 172, 179;
and germinal tissue, 172;
a poison, 168.
Alcoholism: 101, 117, 167;
factors in, 180;
in lower animals, 173-178;
views regarding inheritance of, 169, 170, 172, 178, 179, 180.
Alkaptonuria, 117.
Allelomorph, 77.
Alpine plants, non-inheritance of acquired characters, 131.
Alternative action in behavior, 207.
Altruism, possible origin of, 220.
Ambystoma, 132.
Ameba, 23, 24.
Ancestors, number of, 4.
Ancestry: a network, 3;
dual, 6;
in royalty, 5;
pride of, as a eugenic agent, 309.
Backward child, 256.
Backwardness, importance of early determination, 256, 257.
Bardeen, 126.
Barker, 229.
Barr, 246, 247, 248.
Barrington, 179.
Bateson, 77, 82.
Bees, inheritance in, 136, 137.
Behavior: lower animals, 197;
modifiability of, 200, 204-207, 217, 219, 224, 225, 337;
not wholly established by heredity, 217, 227;
rational, 205, 206;
various forms of, possible, 207, 219.
Bell, 152.
Bezzola, 170.
Billings, 249.
Binet-Simon test, 255.
Biometry, 16.
Birthmarks, 159, 160.
Birth-rate: significance of, 302;
too low in desirable stocks, 302, 304, 305, 307.
Blastomeres, 55.
Blastophthoria, 163.
Blended inheritance, 87, 92, 93.
Blends, mistakes for, 91.
Blindness, infantile, 183.
Blistering, 113.
Body: how built up from germ, 36;
duality of, 50.
Brachydactylism, 107.
Brain: in higher animals, 213;
mechanism, maladjustments of, 230.
Branthwaite, 180, 292.
Breeding, experiments, method of, 14, 15.
Brewer, 142.
Brieux, 101.
Bronner, 266.
Brown Sequard, 132, 133.
Cabot, 183.
Cacogenic strains, 310.
Cajal, 209.
Cancer, 117, 154.
Capsella, 131.
Castle, 134.
Cataract, presenile, 112.
Cattle: horn characters, 79;
roan, 81.
Cell: a unit of structure, 20;
diagram of, 21;
structure of, 20, 30.
Cell-division: 31;
indirect (mitosis), 32;
meaning of indirect, 34.
Cell-theory, 22.
Cellular basis of heredity, 22.
Ceni, 174.
Centrosome, 31.
Cerebral cortex, not functionally homogeneous, 211.
Character: defined, 12;
dominant, 74;
recessive, 74.
Characters: contrasted, 69;
determiners of, 13, 14;
independence of, 69;
inheritable and non-inheritable, 121, 122;
more than two pairs of, 87;
new combinations of, 82, 83, 84;
separable, 69;
symbols for, 78;
two pairs of, 82.
Chauvin, 132.
Chemotropism, 198.
Childbirths, intervals between, 165.
Children of the future: ours to determine quality of, 338, 339;
and home, 338.
Cholera, 152.
Chorea: 117;
Huntington's, 113-115, 243, 325.
Chromatin, 31.
Chromosome, 32.
Chromosomes: individuality of, 39, 48;
determiners in, 94;
in germ and body cells, 40;
Mendelian factors and, 93;
number and appearance, 34, 41;
pairs of, 40, 93, 94;
significance of, in heredity, 35, 49, 50, 51, 53, 54.
Chromotropism, 198.
Church, 242.
Cleavage, 36.
Cleft-palate, 178.
Cole, 166.
College graduates and birth-rate, 304.
Coloboma, 113.
Color-blindness, 60-62.
Conceptual thought, origin of, 206.
Conduct: importance to young of practise, 221, 223;
hereditary predisposition and, 218, 337;
responsibility for, 195.
Congenital traits, 123.
Conjugation, 25.
Consciousness, 206.
Conservation: of superior strains, 157;
human, 299, 300.
Constructive eugenics, 309.
Corneal opacity, 113.
Correns, 68.
Cortex of brain, 195, 213.
Cost, of caring for our disordered and delinquent, 257, 300.
Cretins, effects of segregating the sexes, 321.
Crime: and delinquency, 263, 287;
and feeble-mindedness, 264-270;
bearings of immigration on, 280;
classifications of, 276;
defined, 276;
heredity vs. environment in, 263;
increase in, 272;
mental disorders most frequently associated with, 279;
no specific hereditary factor for, 275.
Criminal: the born, 277;
the epileptic, 277.
Criminality, 117.
Criss-cross inheritance, 61.
Criteria for judging reproductive fitness, 304, 306.
Cytoplasm: 30;
in heredity, 51.
Daltonism, 60.
Dana, 257.
Darwin, pedigree of, 316.
Davenport, 92, 116, 231, 243, 257, 271, 273, 284, 291, 304, 312.
Davis, 185.
Deaf-mutism, 152, 153.
Death, natural, 28.
Decline of nations, 290, 300.
Defective delinquent, should prevent procreation of, 335.
Defectives: increase due to breeding, 290, 291;
natural elimination done away with among, 292;
unpardonable to let multiply, 288.
Defects: breeding out, 118, 119;
mental and nervous, 228.
Degenerate strains: 269;
not a product of surroundings, 273.
Degenerates, sterilization of married, 330.
Delinquency, causes of, 267, 274.
Delinquents not all defectives, 274.
Delinquent women and girls, many mentally defective, 265, 266.
Dendrite, 208.
De Sanctis, 256.
Determiners: 13, 77;
different producing the same character, 88, 90;
segregation of, 84.
Development: in higher organisms, 28;
suppressed, 9.
De Vries, 68.
Diabetes, 113.
Difficulty, educational value of, 222, 223.
Digital malformations, 107.
Dihybrids, 82.
Diploid number of chromosomes, 41, 43.
Disease: defined, 146;
inheritance of, 98, 148;
predisposition to, 148;
reappearance of not necessarily inheritance, 146.
Dominance: 74;
delayed, 81;
incomplete, 80, 100;
in human genealogies, 102;
in man, 99, 107.
Don Carlos, number of ancestors, 5.
Drosophila, 66.
Duplex character, 80, 99.
Dwarfing, by starvation, 130.
Dwarfs, true, 117.
East, 91.
Education: actual practise in carrying out projects important, 221;
affording opportunity for development of good traits, 226;
effects of not inherited, 142, 155;
establishing pathways through the nervous system, 210;
importance of difficulty in, 222, 223;
non-transference of skill acquired in one line to other lines, 213;
providing proper stimuli, 226;
training in motive necessary, 220;
value of interest in, 223.
Egg, a cell, 22.
Egg-cell and sperm-cell contrasted, 29.
Elderton, 179, 296.
Electrotropism, 198.
Ellis, 265, 301.
Embryo, relation to mother, 161.
Embryogeny, 36.
Emerick, 251.
Environment: direct action on germ cells, 124, 125;
effects of faulty, 158;
in crime and delinquency, 263, 266, 273, 274.
Epidermolysis, 113.
Epilepsy: 101, 117, 242, 249, 251, 252, 253;
in guinea-pigs, 132;
relation to feeble-mindedness, 249.
Epileptic, the criminal type, 277-279.
Epileptics, number of, 230, 246, 250.
Eugenic agent, educated public sentiment, 330.
Eugenics: and education, 309;
and personal liberty, 332;
a working program of, 335;
constructive, based on education, 301;
defined, 293;
desirable traits, 306;
education of women in, 333;
influence of public opinion on, 331;
much yet to be done, 333, 334;
positive and negative, 301.
Ewart, 10, 165.
Exceptional child likely to be neglected, 257.
Experimental breeding, method of, 15.
External conditions, influences of, 130.
Eye-color: 9, 103;
inheritance of, 104.
Eye-defects, 108, 110.
Family pride and eugenics, 309.
Farabee, 106.
Fay, 153.
Feeble-minded: prevention of procreation in, 258, 335;
results of non-restraint, 246.
Feeble-mindedness: 101, 117;
and crime, 264-269, 279;
grades of, 244;
inheritance of, 245;
not insanity, 238;
relation of alcohol to, 169-172.
Fernald, 256, 266.
Fertilization, 26, 29, 47, 48.
Fetus: poisoning of, 162;
relation to mother, 161.
Fiber-tracts in man, 214.
Fitness, criteria for judging, 304, 306.
Flexner, 186.
Forel, 169, 173, 303.
Fowl, Andalusian, 69, 70, 71.
Frederick the Great, number of ancestors, 5.
Friedreich's disease, 117.
Fruit-fly, 66.
Galton, 293, 295.
Gamete, 28, 40.
Gametes in dihybrids, 85.
Gametic matings in man, 100.
Geddes, 55.
Genealogies, imperfect, 98.
Genotype, 86.
Geotropism, 198.
Germ and body distinct, 37, 38.
Germ: control of possibilities in, 224;
singleness of, 50.
German emperor, number of ancestors, 5.
Germ-cells: affected by poisons, 126;
changes in, 126, 127;
early set apart, 37;
question of effects of body on, 128, 135;
effects of external influences on, 124;
in Miastor, 37, 38;
metabolic changes in, 138;
origin of, 36, 37;
possibilities of development, 127;
two classes of, 71, 73.
Germinal continuity, 39.
Germinal variation and the origin of new characters: 138;
cases analyzed, 141;
sexual reproduction in relation to, 138.
Germ-plasm and bad environment, 194.
Gifted persons, 212.
Glaucoma, 113.
Goddard, 118, 171, 174, 188, 235, 238, 245, 250, 256, 257, 264, 269, 326.
Gonads, transplantation of, 134.
Gonorrhoea: seriousness of, 182;
prevalence, 183.
Gorst, 234.
Gout, 153, 234.
Guinea-pigs: alcoholism in, 175;
Mendelism in, 75.
Guyer, 59.
Habit, 219.
Habits, modification of in lower animals, 204.
Hair-color, 105.
Hair shape, 105.
Hamburger, 150.
Handwriting, 120.
Haploid number of chromosomes, 41, 43.
Harelip, 178.
Hart, 266, 319, 326.
Healy, 256, 274, 278.
Hearing, hardness of, 118.
Heart disease, 154.
Hegner, 27, 38.
Heliotropism, 198.
Helm, 109, 111.
Hemophilia, 64.
Hereditary character defined, 12.
Hereditary mingling, mosaic rather than blend, 13.
Hereditary transmission, laws of, 68.
Heredity: and environment, 295;
dual ancestry in, 6;
defined, 1;
false, 163;
human, uncertainty of records, 98;
in protozoa, 22, 23;
in insanity, importance of, 261;
in sexually reproducing forms, 7;
in unicellular forms, 22, 23;
methods of study, 14, 15;
new discoveries in, 67;
not a blend, 13;
race betterment through, 289.
Heritage, blood, 1.
Heron, 307.
Heterozygote: 80;
detection of, 80.
Hill-folk, the, 271.
Hodge, 175.
Holmes, 203.
Home, for children, 338.
Homozygote, 80.
Huntington's chorea, 113-115, 243, 325.
Huxley, 195, 205.
Hybrids: 52;
whites and negroes, 297, 298.
Hypotrichosis, 113.
Hysteria, 117.
Ichthyosis, 65.
Ideals, importance of establishing in children, 223.
Idiots, 244.
Imbeciles, 244.
Immigrants, duty of excluding undesirable, 335.
Immigration: and mental unsoundness, 281, 282;
bearing on crime and delinquency, 280;
bearing on venereal diseases, 282;
importance of restricting, 283, 335.
Immortality: of protozoa, 23;
of the race, 3.
Immunity, artificial, not inherited, 155.
Inbreeding, in defectives, 271.
Individual, and race, 3.
Inebriate women, offspring of, 168.
Inebriety, constitutional, 180.
Infant mortality, 149.
Infection, prenatal, 147.
Inheritance: and disease, 146;
blended, 87, 93;
of tendencies, 107.
Inhibitions, 216.
Inhibitors, 79.
Insane, increase in numbers of, 233, 234.
Insanity: 117;
certain forms recessive, 243;
eugenical significance of, 234, 235, 240;
importance of early diagnosis, 259;
some forms not hereditary, 260;
types of, 239;
prevalence in the United States, 228, 229.
Insect colors, effect of temperature, 129.
Instincts: 203;
adjustable, 203;
not inherited acquirements, 144;
origin of intelligent behavior from, 203, 204.
Institutional figures misleading, 266.
Intelligence, 205, 206.
Intelligent behavior, opening up possibilities of, 204.
Ireland, 171.
Irritability, characteristics of living protoplasm, 197.
Jennings, 203, 204.
Johnson, 305.
Johnstone, 245, 319, 320, 321.
Jolly, 243.
Jordan, 4, 299.
Jukes, 270.
Kallikak family, 269, 270.
Kellicott, 314, 316.
Kellogg, 299.
Keratosis, 113.
Kidney diseases, 154.
Kirby, 187, 324.
Knox, 256.
Kraeplin, 242.
Laitinen, 174.
Language, as mental aid, 206, 207.
Lapsed intelligence, theory of, 145.
Larval stages, susceptibility of, 128.
Laws, sterilization, 323, 327, 329.
Lead-poisoning: 163;
experiments on rabbits, 163.
Lederbaur, 131.
Legal restraint of defectives limited, 331.
Lens: displaced, 113;
cataract, 112.
Leprosy, 152.
Leptinotarsa, production of variations in, 125.
Linden, Countess von, 129.
Linin, 31.
Little's disease, 215.
Locomotor ataxia, 187.
Loeb, 62, 203.
Longevity, 120.
Lord Morton's mare, 10.
Lorenz, 113, 114, 115.
Low birth-rate, 308.
Lowell, Judge John, 312.
Luetin test, 188.
Lunborg, 243.
MacDougal, 125.
Margaret, Mother of Criminals, 270.
Marriage: barriers to, 331;
inter-racial, 296;
medical inspection before, 191.
Mast, 203.
Maternal impressions, 159-160.
Maturation: 39, 41, 43, 44;
parallel between egg and sperm-cell, 44, 46.
Mechanical skill, 120.
Mechanism of heredity, 22, 25, 26, 28, 29, 30, 35, 37, 40-54, 94, 95.
Melancholia and crime, 279.
Memory: 120, 204;
not a complete test of normality, 268, 269.
Mendel: 68;
work on peas, 82.
Mendelian factors and chromosomes: 93;
inheritance and man, 97;
principles, rediscovery of, 68;
ratio, cause of, 71.
Mendelism, 67, 69.
Mental and nervous defects, 228.
Mental defective: defined, 255;
disproportionate increase in, 232;
numbers married, 231, 232;
inefficiency of marriage laws concerning, 315.
Mental deficiency: not always inherited, 248;
tests for, 254, 255.
Mental organization of lower vertebrates, 205.
Mental process as neural process, 195.
Mental unsoundness, 196.
Mentality, inheritance of, 19.
Mentally disordered, cost of caring for, 257, 258.
Mercier, 279.
Merriere's disease, 117.
Metazoa, 28.
Metz, 41.
Mice, 78.
Michigan, state report on mentally defective, 234.
Migraine, 101.
Mind, relation to brain, 195.
Mitosis: 32, 33;
meaning of, 34, 37.
Mjöen, 171.
Modifiability of behavior, 200, 204, 205, 207, 217, 219, 224, 225, 337.
Mongolians, 248.
Moral responsibility, 227.
Morgan, C. Lloyd, 146, 211.
Morgan, T. H., 59, 66.
Moron, 244, 268.
Morons and crime, 268.
Mosaic, heredity a, 13.
Motherhood, safeguarding, 165.
Motive, training in, 220.
Mott, 150.
Mulattoes, 92.
Multiple sclerosis, 64, 117.
Muscular atrophy: 113;
Gower's, 65.
Musical ability, 120.
Mutations: artificial production of, 125;
germinal, 125.
Mutilations, non-inheritance of, 134.
Myopia, 64.
Naegeli, 131.
Nam family, 271.
Natural selection partly done away with in human society, 292.
Near-sightedness, 64.
Nervous and mental diseases, 153.
Nervous organization, inheritable, 242.
Nervous response, in lower organisms, 196.
Nervous system: mainly inherited, 210, 216;
establishment of pathways in, 210;
maladjustments of, 231;
special developments in man, 213, 214, 215;
units of, 208.
Nervous systems of anthropoids, 214.
Neural pathways, not all established at birth, 217.
Neuritis optica, 65.
Neurons, 208.
Neuron theory, 208.
Neuropathic constitution, expression of, 241.
Neuropathic defects, carriers of, 253.
Neuter insects, heredity in, 136, 137.
New characters, origin of, 138.
Newman, 56.
Nicloux, 172.
Night-blindness, 65.
Nilsson-Ehle, 88, 89.
Noguchi, 186.
Nucleolus, 31.
Nucleus, structure of, 31.
Nulliplex character, 80, 100.
Obesity, 120, 154.
Offspring: from one parent only, 5;
different from either parent, 12.
Oöcyte, primary, secondary, 44.
Oögenesis, 44.
Oögonia, 44.
Optic nerve, atrophy of, 64.
Organs, formation of, 36.
Origin of sex cells, 12, 36.
Ovaries, transplantation of, 134.
Ovum, 26, 40.
Paralysis, general, 186.
Paranoia, 279.
Parent-body and germ distinct, 12.
Parenthood, cultivation of wholesome sentiment toward, 336.
Paresis: 186;
and crime, 279.
Parthenogenesis, 6.
Patterson, 56.
Paul, 163.
Pearson, 150, 151, 179, 296, 307.
Peas, 68, 82.
Performance tests, 256.
Peron, 133.
Personality determined by heredity, 2, 195.
Peterson, 242.
Phenotype, 86.
Phillips, 134, 135.
Phototropism, 198.
Pinard, 165.
Pineys, the, 271.
Plato, 290.
Poellman, 271.
Polar bodies, 44, 45.
Polydactyly, 108.
Potato-beetle, production of variations in, 125.
Potts, 292.
Predisposition to disease, 148.
Pregnancy, neglect of mothers during, 165.
Prenatal care: 336;
infection, 147;
influence, 11, 159, 162.
Prenuptial medical inspection desirable, 336.
Presence and absence theory: 78;
formulæ for man, 99.
Primrose, experiments on, 125.
Principles, Mendelian, 68.
Prisoners, many mentally subnormal, 266.
Pronucleus, 47.
Protective coloration, not of somatic origin, 135, 136.
Protoplasm, germinal, 39.
Psychical development, 196, 203, 205, 206, 213, 215.
Pyramidal tracts, 214.
Quagga hybrid, 10.
Race amalgamation: 297, 298;
deterioration, in a selected population, 303.
Racial degeneracy, not curable by improved environment alone, 294.
Ratio: the 1:2:1, 73;
the 3:1, 77;
the 9:3:3:1, 85;
the 27:9:9:9:3:3:3:1, 87;
the 15:1, 88;
the 63:1, 90.
Rational behavior, 205, 206.
Reason, 206.
Recessiveness: 74;
in man, 115.
Records of family traits desirable, 337.
Reduction division, 41, 42.
Reflexes, 203.
Regression, law of, 17.
Renault, 172.
Rentoul, 232.
Reproduction: asexual, 6, 26;
sexual, 26;
sexual and variation, 139.
Reproductive cells, 27, 28, 29.
Responsibility for conduct, 195.
Rest, importance of, in pregnancy, 165.
Reversion: 7, 8;
and atavism, 8;
in guinea-chicken hybrids, 8.
Rheotropism, 198.
Rheumatism, 154.
Ritter, 143.
Rogers, 246, 272.
Romanes, 133.
Rosanoff, 243.
Rossolimo, 256.
Rudin, 243.
Salpingectomy, 322.
Sanford, 205.
St. Vitus' dance, 117.
Schulze, 24.
Schuster, 296.
Sclerosis, multiple, 64, 117.
Segregation: in dihybrids, 84;
Mendelian, 69, 70, 75;
of defectives, 318.
Seguin, 256.
Self-control, importance of, 221, 267, 268, 284, 286, 287.
Sex: and chromosomes, 59;
and heredity, 53;
cells of Volvox, 25;
chromosome, 57, 58;
determination, 55;
differentiation and X-element, 60;
evolution of, 25-30;
hygiene, question of school instruction in, 285;
in certain insects, 56;
linked characters, 60, 65;
not a necessary factor in heredity, 6;
problem, knowledge alone not sufficient, 286.
Sexual vice, 284.
Sharp, 322.
Simplex character, 80, 99.
Skill, non-transference in brain, 212, 213.
Skin, color of, 92.
Smallpox, 152.
Social maladies, prevention of, 293.
Softening of the brain, 186.
Soma, 28.
Spermatid, 43.
Spermatocyte, primary, secondary, 43.
Spermatogenesis, 42.
Spermatogonium, 43.
Spermatazoon: 26, 40;
a cell, 22;
formation of, 43;
structure of, 43.
Spindle, in cell-division, 32.
Spottedness of hair-coat, 113.
Sprague, 281, 305.
Starfish, training a, 204.
Statistical methods, 15.
Statistics, trustworthy needed, 334.
Stature, inheritance of, 17.
Stereotropism, 198.
Sterility, 182.
Sterilization: 322;
in epilepsy, 326;
laws, 323;
laws, on trial, 329;
laws, states having, 327.
Stevens, 41.
Stockard, 174-178.
Strength, muscular, 120.
Stripes, reversionary, 8.
Stutzman, 305.
Sullivan, 168.
Superior strains, conservation of, 157.
Synapse, 210.
Synapsis, 41, 42.
Syndactyly, 65, 108, 111.
Syphilis: 184-190;
and prostitutes, 185;
cerebro-spinal form, 189-190;
prenuptial inspection for, 190-192;
prevalence, 186;
stages of, 185;
tests for, 188.
Syphilitics: children of, 187, 188;
married, 190.
Tabes dorsalis, 186.
Taints, 101.
Talent, inheritance of, 212.
Taylor, 297.
Telegony, alleged cases of, 10.
Temperament, inheritance of, 19.
Thermotropism, 198.
Thigmotropism, 198.
Third generation, segregation in, 69.
Thomsen's disease, 118.
Thomson, 55.
Thorndike, 296.
Tower, 125.
Training of children: and heredity, 218;
faults in, 221, 222.
Transmission, not necessarily inheritance, 163.
Tredgold, 170.
Treponema pallidum, 185.
Tribe of Ishmael, 271.
Tropic responses: often purposeful, 201;
uncertainties in, 202.
Tropisms: 197;
complications in, 200;
in plants and animals, 198;
relations to reflex actions and instincts, 203.
Tschermak, 68.
Tuberculosis, 118, 148-160, 162.
Twins: identical, 55;
sex of, 55.
Typhoid, 152.
Unemployed, frequently morons, 280.
Unfit, elimination of, urgent, 313.
Unit-character: 12;
inheritance of, 13.
Unicellular organisms: 21;
inheritance in, 22, 23.
Use and disuse, 122.
Van Ingen, 167.
Vasectomy, 322.
Venereal disease, 182.
Virchow, 147.
Voison, 133.
Volitions as tropisms, 199.
Volvox, 25, 26, 27.
War, eugenical effects of, 299.
Wasserman, provocative, 189.
Wasserman test, 188, 189.
Webbed digits, 65.
Weeks, 251, 252, 253, 291.
West, 167.
Wheat, 75, 81, 88.
Whetham, 314, 316.
Whitman, 145.
Wilmarth, 243, 245, 274, 291.
Wilson, 59, 62, 94, 95.
Woods, 296.
X-element, 57, 58.
Zebra hybrids, 10.
Zeros, the, 271.
Zygote: 26, 27;
chromosomes of, 40.
FOOTNOTES:
[1] The reader desiring more detailed information will find fuller
discussions in the following:
Wilson, E. B.: _Recent Researches on the Determination and Heredity of
Sex_. Science, January 8, 1909.
Wilson, E. B.: _The Chromosomes in Relation to the Determination of Sex_.
Science Progress, April, 1910.
Guyer, M. F.: _Recent Progress in Some Lines of Cytology_. Transactions of
the American Microscopical Society, April, 1911.
Morgan, T. H.: _Heredity and Sex_. Columbia University Press, 1913.
[2] A translation of Mendel's original papers will be found in _Mendel's
Principles of Heredity_, by W. Bateson.
[3] _Heredity of Skin Color in Negro and White Crosses_: Publication No.
188, of the _Carnegie Institution of Washington_.
[4] Whitman, C. O.: _Animal Behavior, Biological Lectures_, Marine
Biological Laboratory, 1898.
[5] _The Fight Against Tuberculosis and the Death Rate from Phthisis_,
London, Dulau & Co., 1911.
[6] Forel, August: _The Sexual Question_, p. 268.
[7] Loc. cit. p. 251.
[8] In this connection it is instructive to note from a Michigan state
report, just off the press, that, among 4,917 insane individuals
concerning whom satisfactory information was obtained, 65.4 per cent. "had
among their ancestors or family such hereditary influences as insanity,
apoplexy or paralysis, psychopathic abnormalities or alcoholism." See
_Report of the Commission to Investigate the Extent of Feeble-mindedness,
Epilepsy, Insanity and Other Conditions of Mental Defectiveness in
Michigan_. Wynkoop Hollenbeck Crawford Co., State Printers, Lansing,
Michigan, 1915.
[9] _Feeble-mindedness; Its Causes and Consequences_, by Henry H. Goddard,
The Macmillan Company, 1914.
[10] _The Binet-Simon Measuring Scale for Intelligence_, by Henry H.
Goddard, 1911. The Training School, Vineland, N. J. Price 15 cents.
[11] "Tests for Mental Defects," by Howard A. Knox, _Journal of Heredity_,
March, 1914. See also Knox: _Journal of the American Medical Association_,
1914.
[12] _The Individual Delinquent_, by William Healy, M. D. Little, Brown &
Co., Boston.
[13] _The Individual Delinquent_, by William Healy, M. D. Little, Brown &
Co., Boston.
[14] The Psycopathic Laboratory in connection with the Juvenile Court of
Chicago.
[15] See "The Foreign Born in the United States." _The National Geographic
Magazine_, September, 1914.
[16] See First Report of the Committee of the Eugenic Section of the
American Breeders' Association, "On Immigration", _American Breeders'
Magazine_, Vol. III, No. 4, 1912. Also Second Report of same, _The Journal
of Heredity_, July, 1914.
[17] "The Negro and His Health Problems," _Medical Record_, September 12,
1912.
[18] See D. S. Jordan, _The Human Harvest_, or V. L. Kellogg, _Eugenics
and Militarism_.
[19] For arguments indicating the superior eugenical fitness of college
graduates see "Wellesley's Birth-Rate," by Roswell H. Johnson and Bertha
Stutzman, _The Journal of Heredity_, June, 1915. See also, "Education and
Race Suicide," by Robert J. Sprague, _ibid._, April, 1915.
[20] Since the present manuscript went to press an excellent government
report (_Insane and Feeble-Minded in Institutions in 1910_, Department of
Commerce, Bureau of the Census, 1914, Washington, D. C.) has appeared. In
it one finds the estimate that not over one-tenth of our feeble-minded are
being cared for in special institutions.
[21] For summaries of existing sterilization laws and statements of the
issues involved see (1) _The Legal, Legislative, and Administrative
Aspects of Sterilisation_, Bulletin 10B, February 3, 1914, Eugenics Record
Office, Cold Spring Harbor, N. Y.; (2) _Sterilisation of Criminals_,
Report of Committee H of the American Institute of Criminal Law and
Criminology, Bulletin No. XV, September, 1914.
Transcriber's Notes:
Passages in italics are indicated by _italics_.
Passages in bold are indicated by =bold=.
Superscripted characters are indicated by ^{superscript}.
Subscripted characters are indicated by _{subscript}.
The original text contains a few letters with diacritical marks that are
not represented in this text version.
The original text contains male and female symbols. These are represented
as [male] and [female].
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