Project Gutenberg's Bacteria in Daily Life, by Mrs. Percy Frankland
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Title: Bacteria in Daily Life
Author: Mrs. Percy Frankland
Release Date: June 22, 2013 [EBook #43015]
Language: English
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BACTERIA IN DAILY LIFE
BY
MRS. PERCY FRANKLAND
FELLOW OF THE ROYAL MICROSCOPICAL SOCIETY; HONORARY MEMBER OF BEDFORD
COLLEGE, UNIVERSITY OF LONDON;
JOINT AUTHOR OF "MICRO-ORGANISMS IN WATER," "THE LIFE OF PASTEUR,"
ETC.
"Spirits, when they please,
Can either sex assume, or both; so soft
And uncompounded is their essence pure,
Not tied or manacled with joint or limb,
Nor founded on the brittle strength of bones,
Like cumbrous flesh; but, in what shape they choose,
Dilated or condensed, bright or obscure,
Can execute their aery purposes,
And works of love or enmity fulfil."
MILTON.
LONGMANS, GREEN, AND CO.
39 PATERNOSTER ROW, LONDON
NEW YORK AND BOMBAY
1903
_All rights reserved_
Transcriber's Note: Minor typographical errors have been corrected
without note. Irregularities and inconsistencies in the text have
been retained as printed. Words printed in italics are noted with
underscores; _italics_. The cover of this ebook was created by the
transcriber and is hereby placed in the public domain.
PREFACE
The title of this little volume sufficiently explains its contents; it
only remains to add that much of the text has already appeared from
time to time in the form of popular articles in various magazines. It
has, however, been carefully revised and considerably added to in
parts where later researches have thrown further light upon the
subjects dealt with.
G. C. FRANKLAND
NORTHFIELD, WORCESTERSHIRE,
_November, 1902_
CONTENTS
PAGE
BACTERIOLOGY IN THE VICTORIAN ERA 1
WHAT WE BREATHE 34
SUNSHINE AND LIFE 65
BACTERIOLOGY AND WATER 93
MILK DANGERS AND REMEDIES 118
BACTERIA AND ICE 149
SOME POISONS AND THEIR PREVENTION 168
BACTERIA IN DAILY LIFE
BACTERIOLOGY IN THE VICTORIAN ERA
A little more than sixty years ago the scientific world received with
almost incredulous astonishment the announcement that "beer yeast
consists of small spherules which have the property of multiplying,
and are therefore a living and not a dead chemical substance, that
they further _appear_ to belong to the vegetable kingdom, and to be in
some manner intimately connected with the process of fermentation."
When Cagniard Latour communicated the above observations on yeast to
the Paris Academy of Sciences on June 12, 1837, the whole scientific
world was taken by storm, so great was the novelty, boldness, and
originality of the conception that these insignificant particles,
hitherto reckoned as of little or no account, should be endowed with
functions of such responsibility and importance as suggested by
Latour.
At the time when Latour sowed the first seeds of this great gospel of
fermentation, started curiously almost simultaneously across the Rhine
by Schwann and Kützing, its greatest subsequent apostle and champion
was but a schoolboy, exhibiting nothing more than a schoolboy's truant
love of play and distaste for lessons. Louis Pasteur was only a lad of
fifteen, buried in a little town in the provinces of France, whose
peace of mind was certainly not disturbed, or likely to be, by rumours
of any scientific discussion, however momentous, carried on in the
great, far-distant metropolis. Yet, some thirty and odd years later,
there was not a country in the whole world where Pasteur's name was
not known and associated with those classical investigations on
fermentation, in the pursuit of which he spent so many years of his
life, and which have proved of such incalculable benefit to the world
of commerce as well as science.
Thanks to Pasteur, we are no longer in doubt as to the nature of yeast
cells; so familiar, in fact, have we become with them, that at the
dawn of the twentieth century we are able to select at will those
particular varieties for which we have a predilection, and employ
those which will produce for us the special flavour we desire in our
wines or in our beers.
Large and splendidly-equipped laboratories exist for the express
purpose of studying all kinds and descriptions of yeasts, for finding
out their characteristic functions, and cultivating them with all the
tenderness and care that a modern gardener bestows upon the rarest
orchids.
All this is now an old story, but some sixty years ago the great
battle had yet to be fought which was to establish once and for all
the dependence of fermentation upon life, and vanquish for ever those
subtle arguments which so long refused to life any participation in
the work of fermentation and other closely allied phenomena.
When, however, Pasteur finally cleared away the débris of
misconception which had so long concealed from view the vital
character of the changes associated with these processes, the
bacterial ball, if we may so call it, was set rolling with a will, and
information concerning these minute particles of living matter was
rapidly gathered up from all directions.
The recognition so long refused to bacteria was now ungrudgingly
given, for it was realised at last that, in the words of M. Duclaux,
"Whenever and wherever there is decomposition of organic matter,
whether it be the case of a weed or an oak, of a worm or a whale, the
work is exclusively performed by infinitely small organisms. They are
the important, almost the only, agents of universal hygiene; they
clear away more quickly than the dogs of Constantinople or the wild
beasts of the desert the remains of all that has had life; they
protect the living against the dead. They do more; if there are still
living beings, if, since the hundreds of centuries the world has been
inhabited, life continues, it is to them we owe it."
Fortunately, the provisions made by Nature for the preservation of the
bacterial race are of so lavish a description that no fear need be
entertained that this useful and indispensable world of life will be
wiped out. The fabulous capacity for multiplication possessed by them
(a new generation arising in considerably less than an hour), the
powers of endurance which some of them exhibit in presence of the most
trying vicissitudes of heat and cold (they have been known to survive
exposure lasting for seven days to a temperature of about -200° C.),
the inability of starvation or desiccation to undermine their
constitution, combine to render the question of the extinction of
bacteria as remote as it is undesirable.
Tempted by the prospects of exploring in this newly-revealed world of
life, investigators rushed into the field, and the bacterial fever has
been hardly less pronounced in these last years than that rush for a
material golden harvest which has characterised so many enterprises in
southern latitudes.
The scientific results of this microbe fever have happily, however,
been of a more solid and substantial character than can be said to
have followed the more tangible but sordid ventures in South African
mines. Vague hypotheses have given place to facts, and bacteria have
been brought more and more within the horizon of human knowledge,
thanks to the genius and untiring zeal of investigators all over the
world.
By mechanical improvements in microscopes, and subtle methods for
colouring bacteria, enabling us to study their form with precision, by
ingenious devices for supplying them with suitable food materials, or,
in other words, by the creation of bacterial nurseries, providing the
means for watching their growth and observing their distinctive habits
and character, this important branch of the vegetable kingdom has been
raised from obscurity to one of the principal places in our catalogue
of sciences, and Bacteriology has won for itself an individual footing
in the scientific curriculum of our great educational institutions,
and is represented in literature by such famous serials devoted to the
publication of bacterial and allied researches as the _Annales de
l'Institut Pasteur_, the _Centralblatt für Bakteriologie_, the
_Zeitschrift für Hygiene_, the _Annali d'Igiene Sperimentale_, and
other well-known journals which constitute an essential but
ever-increasing burden upon the library shelves as well as pocket of
the investigator.
Museums of bacteria have been established where not only specimens of
particular varieties of a permanent character for comparison and
reference can be obtained, but living cultivations of hundreds of
different micro-organisms are maintained; and only those who have had
the charge of bacteria can realise the enormous amount of skilled
labour involved in the catering for such a multitude, in which
individual likes and dislikes in regard to diet and treatment must, if
success is to be secured, be as carefully considered as is necessary
in the case of the most delicate and highly pampered patient.
Bacteria, by means of these depôts, can, in fact, be bought or
exchanged by collectors with as much facility as postage stamps, with
the all-important difference that this collecting of bacteria is not a
mere mania or speculation, but serves a most useful purpose.
To the busy investigator who cannot afford either the time or space in
which to maintain a large bacterial family, it is of immense
convenience to be able to obtain at a moment's notice a trustworthy
culture, say, of typhoid or tuberculosis, or specimens of obscurer
origin from air or water for purposes of investigation. These
bacterial cultures are all guaranteed pure, free from contamination or
admixture with other and alien micro-organisms, and are strictly what
they are represented to be. Although such a declaration is attached to
many commodities at the present day with ludicrous incongruity, in the
case of micro-organisms such a breach of faith is unknown, and the
antecedents of a microbe may be said to be regarded as of as much
moment and to be as jealously preserved as is the pedigree of the most
ambitious candidate for honours at a cattle or dog show!
Amongst some of the curiosities to be found on the shelves of
microbe-museums may be mentioned bacteria which give out light, and
thus, like glowworms, reveal themselves in the dark. These
light-bacteria were originally discovered in sea-water and on the
bodies of sea-fish, and cultures of them have been successfully
photographed, the only source of light being that provided by the
bacilli themselves. The amount of light emitted by a single bacillus
might indeed defy detection by the most sensitive plate procurable,
but when gathered together in multitudes, the magnitude of which even
eight figures fail to express, these phosphorescent bacteria enable
the dial of a watch to be easily read in the dark, whilst photographs
of the face of a watch taken in such bacterial light have been so
successful that the time at which the photograph was taken could be
distinctly seen.
Of bacteria it may indeed truly be said, as has Maeterlinck of the
labours of bees--"though it be here the infinitely little that without
apparent hope adds itself to the infinitely little, though our eye
with its limited vision look and see nothing, their work, halting
neither by day nor by night, will advance with incredible quickness!"
Mention may perhaps appropriately be made here of the highly
interesting fact discovered by Professor Percy Frankland, that
ordinary bacteria which do not phosphoresce are capable of affecting a
photographic film in absolute darkness, and can by this means produce
a picture of themselves. If, however, a transparent piece of glass is
placed between the bacteria and the film no photograph results,
showing that glass interferes with their activity in this respect. The
author points out that as this action upon the photographic film does
not take place through glass, it is in all probability due to the
evolution by the bacteria of certain volatile chemical substances
which either directly or indirectly enter into reaction with the
sensitive film. Similar phenomena have been discovered in regard to
many metals as well as organic substances, but this is the first
observation which has been recorded of the action of living structures
on sensitive films in the dark.
We have already referred to the important services which Pasteur has
rendered by distinguishing between different varieties of yeast, and
separating them out according to their functions and properties--pioneer
work which has been followed up by and borne such splendid fruit in
the hands of the renowned Danish investigator, Emil Christian Hansen
of Copenhagen. This work of isolating out individual varieties of
micro-organisms has been not only pursued with the energy familiar to
all in the case of bacteria associated with disease, but has been
pursued in various other, though perhaps less well known, directions.
A great deal of activity has lately been exhibited in so-called dairy
bacteriology, and a long list has already been compiled of milk,
cheese, and butter microbes; and agricultural authorities, even in
this country, are slowly awakening to the fact that, in order to
compete on modern lines with foreign dairy produce, dairy schools must
be established, where bacteriology is taught, and where instruction is
given in the principles of scientific butter and cheese making.
But bacteria of the brewery and of the dairy are not the only useful
germs which are to be found on the shelves of microbe museums. Wine
and tobacco manufacturers on application may respectively obtain the
bacterial means of transforming the crudest must into the costliest
claret, and the coarsest tobacco into the most fragrant Havana.
Already considerable progress has been made in the isolation of
particular varieties of wine-yeast, whilst highly encouraging results
have been obtained by Suchsland and others in the separation of
various valuable tobacco-fermenting organisms. Agricultural
authorities, again, owe a debt of gratitude to those distinguished
investigators whose labours have discovered the art of imprisoning the
micro-organisms which play such an important part in the fertilisation
of the soil. Bacterial fertilisers are amongst the latest achievements
which bacteriology has accomplished in this wonderful half-century,
and the purchase of special varieties of bacteria to suit the
requirements of particular kinds of leguminous plants is now fast
becoming a mere everyday commercial transaction. But efforts for the
amelioration of the conditions under which plant life is carried on
have not been confined to providing plants with suitable bacterial
friends; vigorous and successful efforts have been made to remove from
their _entourage_ those bacterial enemies and undesirable parasites
which have for so long played so important a part in the crop-returns
of many an agriculturist.
For the identification and separation of the plant-parasites of
various kinds we have largely to acknowledge our indebtedness to
American investigators, and the encouragement and support which Dr.
Erwin Smith, amongst others, has received from the Government of the
United States in the prosecution of these researches indicates how
great is the public importance attached to them. There are in America
alone fifty experiment stations where plant diseases are studied,
whilst at a number of the colleges and universities more or less
attention is given to the subject. Some idea of the loss occasioned to
agriculturists by these plant pests may be formed by a recent
announcement that the Department of Agriculture in Queensland was
prepared to offer a reward of £5,000 for the discovery of a means to
eradicate the prickly-pear disease. Plant pathology has not yet had a
distinct chair allotted to it in any of the great universities, but
the subject is of such vast industrial importance, that doubtless
before long some seat of learning will do itself the honour to
establish one, and so set the example.
A striking instance of the advantages of taking stock, so to speak, of
the attributes of bacteria will occur to everyone in the revelation
which has followed of their powers to solve one of the most knotty
problems of the day--the efficient manipulation of those vast
subterranean rivers of sewage which honeycomb every city of the world.
The purification which sewage underwent by passing it through the
pores of the soil, or, in other words, by filtration, was recognised
about the year 1870, soon after the Rivers Pollution Commissioners had
begun to make their classical investigations on the land treatment of
sewage; but although the rapid transformation of ammonia into nitrates
which followed the passage of the sewage through a few feet of soil
was noted, yet the mechanism of this nitrification process remained a
mystery until 1877, when two French chemists--MM. Schloesing and
Muentz--made the then astounding discovery that this change was
dependent upon the vital energies of micro-organisms.
The part played by bacteria in the purification of sewage thus became
an established fact, and the later experiments have been devoted to
studying the necessary conditions under which the maximum amount of
work is obtainable from these novel bacterial labourers.
Two different classes of bacteria are required to carry on the
purification of sewage: those which flourish in the _absence_ of air
and are known as anaërobic bacteria, and those to which the _presence_
of air is essential for the exercise of their functions, the latter
being therefore called aërobic bacteria.
The work of the anaërobic labourers consists in breaking down the
complex organic compounds present in sewage, whilst the completion of
the process of purification is left to the aërobic varieties. In the
ordinary course of nature both these processes are going on side by
side, but it has been found advisable to separate these two different
classes of bacteria as far as possible, and allot distinct premises to
the anaërobic and aërobic varieties respectively engaged in the
purification of sewage, for by so doing experience has shown that the
work is not only more expeditiously, but also more efficiently,
carried out.
Now the anaërobic bacteria are supplied along with the sewage, and the
retention of their services offers practically no difficulty as long
as an ample allowance of space and time is given them in which to
carry on their labours. The aërobic bacteria, however, besides
demanding space and time, insist upon their workshops being well
ventilated, and if the supply of fresh air is in any way curtailed
they stop work entirely. Hence the ventilation of the aërobic
workshops becomes a matter of primary importance if the valuable
services of these labourers are to be retained. To ensure a sufficient
supply of air being provided, it has been found advisable to have two
or more aërobic workshops or bacteria contact beds, and the sewage is
passed from one on to a second, and so on, until the purification is
complete. Under proper management the sewage should leave the works as
an inodorous, almost pellucid liquid, incapable of putrefaction, which
may be turned into rivers or other waterways without fear of rousing
the wrath of local riparian authorities.
But whilst the commercial side of bacteriology, so to speak, has made
such great strides, the purely scientific applications which have been
made of the facts it has furnished have by no means lagged behind.
Chemists, from Pasteur downwards, have made use repeatedly of special
bacteria to perform delicate operations in the laboratory which other
methods have either failed to accomplish or have performed in a clumsy
and less expeditious manner.
There can be no doubt that, as our knowledge grows from day to day, we
shall find more and more how much depends upon the work of individual
bacteria, and how much importance attaches to the selection of just
those varieties which are of value, and the banishment of those which
are detrimental; and thus the many applications which bacteria already
admit of render their easy access a matter of increasing consequence,
enhancing the value of bacterial institutions such as already exist on
the Continent.
But whilst the easy access of bacteria for experimental and scientific
purposes is of great importance to the investigator, their
indiscriminate distribution would equally be a source of uneasiness
and danger to the community at large. Already sensational fiction has
made considerable capital out of the pathogenic microbe, and with the
winged aid of penny publications it does not take long for suggestions
of such kinds to spread in society and assume practical shape, and
whilst the administration of bacterial poisons offers comparatively
but little difficulty, their identification would be a far greater
problem for experts than that presented by particular chemical
poisons. To cope with this danger to the public, specimens of
disease-germs from these bacterial depôts may not be supplied to
applicants unless the latter can prove to the satisfaction of the
director that they are connected with responsible public institutions.
In recent times, indeed, one of the most remarkable practical uses to
which bacteria have been put is that of poisoning-agents on a large
scale, or in other words vermin exterminators; if this new rôle for
bacteria becomes extended, as no doubt it will, the law for the sale
of noxious drugs and preparations will also doubtless be amended to
cover the distribution of bacterial-poisons.
It was in the year 1889 that Professor Loeffler, while experimenting
with mice in his laboratory at Greifswald, discovered a micro-organism
which was extremely fatal to all kinds of mice. The happy idea
occurred to the Professor that this lethal little microbe, which he
christened _Bacillus typhi murium_, might be turned to excellent
account in combating plagues of field mice in grain-fields, where the
devastation committed by these voracious rodents had become in parts
of Greece and Russia a serious source of loss to agriculturists.
Experiments were accordingly made on a small scale to test the
efficiency of this bacterial poisoner in destroying field mice, and so
successful were the results that Loeffler confidently announced the
possibility of keeping down these pests by distributing food material
infected with these bacteria over fields which were invaded by them.
The Greek Government took up the question, and Loeffler's method was
applied with brilliant results; the disease was disseminated with
extraordinary rapidity and severity, and the mice were readily
destroyed.
It is highly satisfactory to find that the character of this
mouse-bacillus has stood the test of time, for after a period of more
than ten years most encouraging reports concerning its efficiency
still continue to be received. In one of the latest of these, drawn up
by the Director of the Experimental Agricultural Institute in Vienna,
we read that in no less than seventy per cent. of the cases in which
it was employed it was completely successful in its work of
extermination, and it is interesting to note that in a considerable
number of these instances it was the domestic mouse against which its
energies were directed. The rat has, however, until recently escaped
the hand of the bacterial executioner, but his knell has also now been
sounded in the announcement that a rat-bacillus has been discovered.
Considering the undesirable notoriety which these rodents have of late
obtained in connection with their undoubted culpability in the
dissemination of plague, this discovery, if correct, should be warmly
welcomed. That there is plenty of work awaiting such a micro-organism
may be gathered from the fact that during the outbreak of plague in
Sydney the crusade against rats which followed led to the slaughter in
one year of over 100,000.
The discoverer of this useful member of the microbial community is
Tssatschenko, of the University of St. Petersburg, and in his memoir
he states that, whilst highly virulent as regards rats, it is quite
harmless to domestic animals of various kinds. Thus cats, dogs, fowls,
and pigeons when fed with food infected with the bacillus suffered no
ill effects whatever, whilst its administration in large quantities to
farm stock, such as horses, oxen, pigs, sheep, geese, and ducks, was
also without result; hence its distribution, according to its
discoverer, offers no danger to other animals.
This idea of employing bacteria as executioners was not original, for
Pasteur had already in 1888 suggested to the Intercolonial Rabbit
Commission in Australia that chicken-cholera microbes should be
employed for destroying the rabbits, which then, as now, are such a
source of difficulty and pecuniary loss to the country. No active
measures appear to have been taken, however, to carry out this
suggestion, one of the principal objections raised being the
undesirability of introducing a disease which was at that time
believed to be a stranger to the colony. Recently the idea has been
revived by Mr. Pound, the Government bacteriologist at Brisbane, in
consequence of his discovery that chicken-cholera, far from not
existing in Australia, has infested poultry yards more or less
extensively for several years past, although it has only lately been
accurately diagnosed as such. This chicken-cholera microbe is
particularly well suited for the work in question, inasmuch as, whilst
extremely fatal to rabbits, it produces, like Loeffler's bacillus, no
ill effect whatever on farm-stock of various kinds, and is perfectly
harmless to man, so that its handling by the uninitiated is not
attended with any personal danger.
This brings us to what may be designated the human side of
bacteriology, _i.e._ its relation to disease and its prevention. In
these important departments of life the services already rendered by
this infant prodigy of science can as yet be only approximately
appreciated. Anthrax, tuberculosis, cholera, typhoid, plague,
influenza, tetanus, erysipelas, are only a few of the diseases the
active agents of which bacteriology has revealed to us. Bacteriology
has, however, not been content to merely identify particular
micro-organisms with particular diseases, it has striven to devise
means by which such diseases may be mastered, and one of the most
glorious achievements of the past sixty years is the progress which
has been made in the domain of preventive medicine.
The classical investigations of Pasteur on the attenuation of
bacterial viruses such as those of chicken-cholera and anthrax, and
his elaboration of a method of vaccination with these weakened viruses
whereby the power of the disease over its victim is removed or
modified, are too well known to require repetition here. The success
which followed Pasteur's researches in this direction led him to
undertake that great and difficult task, the prevention of rabies in
the human subject--a task well-nigh superhuman in its demands, and one
which only he could accomplish in whose life the pregnant words of a
modern writer found expression--"il ne suffit pas de posséder une
vérité, il faut que la vérité nous possède." The victory over this
disease, which crowned a long life replete with brilliant
achievements, has been universally recognised, and numerous institutes
have arisen in all quarters of the globe for extending the benefits of
this discovery for the relief of suffering humanity. These Pasteur or
bacteriological institutes also furnish highly important centres where
original research work of various kinds is carried on, and the
stimulus which has thus been given to experimental science in the
remotest parts of the world cannot be overestimated.
Methods for the prevention of disease have, however, not been confined
to the elaboration and employment of modified or weakened bacterial
viruses; the subject has been still more recently approached from
another and quite different side. This new departure we also
originally owe to France, although its practical development has been
worked out in Germany.
It was in 1888 that two Frenchmen, Richet and Héricourt, communicated
a memoir to the _Comptes rendus_ of the Academy of Sciences,
describing the curious results they had obtained with rabbits
purposely infected with a disease microbe, the _Staphylococcus
pyosepticus_. Some of the rabbits died after being inoculated with
this micro-organism and some remained alive, and they proceed to point
out how it was that such different results were obtained. Before the
inoculations were made some of the animals received injections of
blood taken from a dog, which a few months previously had been
infected with this same microbe, but had recovered. The rabbits which
received the dog's blood all survived the inoculations, whilst those
which did not, succumbed in every case to the action of the
_Staphylococcus pyosepticus_. So struck were the authors by these
remarkable results that they repeated them, and their further
investigations fully confirmed those originally obtained, proving that
they were not "un fait exceptionnel."
Here we have the first steps in the direction of serum-therapy, that
new treatment of disease which during the last few years has been so
prominently before the public in the cure of diphtheria, tetanus, and
other maladies, and for the development of which we owe so much to the
labours of Behring, Roux, Kitasato, and other investigators.
The astounding fact that the blood of animals which have been trained
to artificially withstand a particular disease becomes endowed with
the power of protecting other animals from that disease is only in the
earliest stages of its application. The results, however, which have
already been accomplished are of so encouraging a character that the
hope is justified that serum-therapy is destined to revolutionise the
treatment of disease. One of the latest uses which has been made of
this method of combating disease is the employment of serum for the
cure of bubonic plague. During the recent outbreak of plague in India,
Yersin, formerly a student and assistant at the Paris Pasteur
Institute, was despatched to India to superintend the administration
of this new remedy, and the serum he employed was that derived from
horses which had been subjected to, and had recovered from,
inoculations with the plague bacillus. The treatment of snake bites by
means of curative serum will be dealt with in more detail later on; it
only remains to cite it here as another instance of the success which
is attending the new methods of protection against disease.
Another and highly ingenious application of serum has been brought
forward by Pfeiffer, Gruber, Widal, and others. This is the so-called
sero-diagnosis of disease, and has been employed already with success
in the identification of typhoid fever as such. The method sounds
simple in the extreme, and consists in taking a few drops of blood
from a patient supposed to be suffering from typhoid fever and mixing
them with a recent cultivation in broth of genuine typhoid bacilli. If
the blood is derived from a typhoid-infected person, then the bacilli
should exhibit a curious and characteristic appearance when examined
under the microscope. Instead of moving about as individuals in
various parts of the microscopic field, they should be seen gathering
or clumping together in numerous small heaps, their movements the
while becoming paralysed.
The State Board of Health of Massachusetts has recently taken up the
official sero-diagnosis of typhoid fever, and issues in response to
applications a simple outfit with instructions how to collect
specimens of blood and a form which they request shall be returned
filled in with all the details concerning the case under observation.
Only a few drops of blood are required for the examination, and these
before being despatched to the State Laboratory are collected on slips
of paper and allowed to dry. If the addition of this suspected blood
in the proportion of one to twenty to a young and vigorous culture of
typhoid bacilli succeeds in paralysing their movements, producing the
characteristic clumping together or agglutination of the bacilli, then
the reaction is considered positive and the case one of typhoid fever.
That, however, some risk attends the placing of too implicit a
reliance on this method of diagnosis alone is evident from the fact
that a _negative_ reaction, or in other words, absence of all
agglutinising phenomena, is sometimes associated with blood throughout
what is beyond all question a well-defined case of typhoid fever,
whilst in the first week of this disease the test is frequently
negative in character. Rouget, who has made a very careful inquiry
into the value to be attached to the sero-diagnosis of typhoid fever,
states that he has found in a large number of examinations of blood
derived from undoubted typhoid patients the agglutination phenomena
fail altogether; it is, therefore, not surprising that the
sero-diagnosis of this disease is still the subject of much discussion
and investigation.
An interesting example of how particular serums may be employed for
the detection of particular poisons has been furnished by Dr.
Calmette. In some districts of India the natives have an ugly custom
of wreaking their vengeance on their enemies by poisoning their
cattle, and to effect this both expeditiously and secretly they employ
subtle poisons which they know can only be detected with great
difficulty. Serpent venom is a favourite substance, whilst abrine, a
highly toxic vegetable poison, is another. The method adopted for the
application of this abrine is highly original, and consists in taking
small bits of wood shaped like miniature clubs, so diminutive in size
that they can be concealed in the hand. In the head of the club small
holes are bored, and tiny pointed rodlets of a hard greyish substance
are fitted into them. Armed with these crude instruments, the natives
scratch the cattle in several places, and, although but little
external sign of injury is to be seen, the rod-points penetrate the
skin and are broken off, and the poison is left to work its lethal way
through the animals' system. Mr. Hankin forwarded some of these
broken-off rod-points to Dr. Calmette for the identification of their
composition, and he diagnosed the material employed as abrine in the
following original manner. He first introduced some of this rod
material into animals, and found that their symptoms were suggestive
of abrine poisoning. To confirm his suspicions, however, he took some
more of this rod material, and, before inoculating it into animals, he
mixed it with serum derived from animals which had been artificially
rendered immune to abrine poison. Instead of the animals into which
this mixture of serum and "rod material" had been introduced dying
like the previous ones, they remained alive. Had the "rod material"
consisted of some poison other than abrine, the abrine serum would
not, according to Dr. Calmette, have negatived its action, and it has
thus been indicated how protective serums may be successfully employed
for the detection of poisons.
Foremost, however, among the beneficent reforms which have followed in
the wake of bacteriology must be placed the antiseptic treatment of
wounds, or Listerism, as it is now universally designated in
recognition of its renowned champion, the former President of the
Royal Society. "Lister comprend," in the words of Dr. Roux, "que les
complications des plaies sont dues aux germes microbiens venus du
dehors et il imagine les pansements antiseptiques. Avec l'antiseptie
commencent les temps nouveaux de la chirurgie." It only remains to add
that, with the modesty characteristic of a great man, its brilliant
author delights in repeating how any good which he may have been
permitted to do he owes entirely to the inspiration which he received
from the labours of Louis Pasteur.
But if the Victorian era has been productive of so many important
applications of bacteriology to commerce and medicine, this period has
been also fraught with results of the highest moment in the progress
of hygiene.
The terms of intimacy, so to speak, which we have been now able to
establish with bacteria has enabled us to discover details of their
life and habits which before were shrouded in mystery. Their
distribution in air has led to renewed endeavours on the part of
sanitary authorities to procure efficient ventilation in our hospitals
and public institutions; dust has acquired a fresh horror since it has
been shown how disease germs may be disseminated by its means; whilst
the important part which flies and lice may play in the spread of
epidemics has opened up a new field for research, and made us
conscious of a fresh source of danger in our daily life.
The general public, however, is hardly yet fully alive to the capacity
for mischief possessed and exercised by the common house-fly. True, it
is universally execrated and regarded as a tiresome attendant upon the
summer months, but it is not usually considered in any more serious
light. That however, the comparative indulgence with which this homely
insect pest has been treated is decidedly misplaced and fraught with
danger to health, the researches of numerous scientists have now
conclusively proved.
As long ago as the year 1888 Professor Celli showed that the germs of
consumption, anthrax, and typhoid fever could pass through the
digestive organs of flies and reappear in the excreta of the latter
not only alive but in full possession of their disease-producing
powers. Dr. Sawtschenko made similar experiments with cholera germs.
Healthy flies were placed under glass shades and fed with broth in
which these micro-organisms were growing, and the latter were not only
subsequently recovered from the digestive organs of the flies but also
from their excreta in a living and virulent condition.
This is, however, not the only means whereby these insects can
distribute deadly and other microbes, for it has been shown that in
crawling over substances containing bacteria these may become attached
to the feet of flies, and are in this manner transferred to other
materials upon which they may alight, just as Pasteur showed many
years earlier silkworms can communicate the fatal plague of pébrine by
crawling over each other's bodies, carrying in their disease-laden
feet the infection from one worm to another. During the recent
outbreak of bubonic plague in the East the part played by flies in
disseminating the virus has been repeatedly emphasised. Yersin was the
first who called attention to the presence in large numbers of
virulent plague bacilli within the bodies of flies which he collected
in the vicinity of plague-stricken persons, and it was found that
flies which had fed on plague-infected material and were then isolated
lived for several days afterwards, during which time virulent plague
bacilli were present in their bodies in immense numbers; thus were
these insects converted into winged messengers of evil of the most
repulsive type.
I am not aware whether any experiments on the vitality and
transmissibility of diphtheria and consumption germs by means of flies
have been made; but in view of the overwhelming evidence of the
culpability of these insects in spreading plague, it is not
unreasonable to presume a responsibility on their behalf in regard to
other diseases; indeed, in the report issued by the Army Medical
Commissioners of the Spanish-American War, it is emphatically stated
that flies played an important part in the dissemination of typhoid
fever.
There is no question as to the capability of certain micro-organisms
to reside for considerable periods of time within the bodies of flies,
and during this sojourn to abate no jot of their virulence. Indeed, it
has been shown that the bodies of these insects may constitute
incubators of a most successful type, for some varieties of bacteria
grow luxuriantly and multiply abundantly within them.
In the hot days of summer, when flies abound, it would be well to
banish these insects, as far as lies in our power, not only from our
sick-rooms in particular, but from our general surroundings. The
catholic taste of flies for garbage of all kinds is too well known to
require entering into, but the consequences which may follow from
their visits to dustbins and centres of disease, and then alighting
upon our food or persons, has received too little attention in the
past.
In regard to the subject of insects as disease disseminators, it may
be mentioned that Mr. Hankin, when studying plague conditions in
India, expressed his belief that ants in Bombay also assisted in
spreading the scourge, for he found that when he inoculated mice with
the excreta of ants, such insects having previously fed on
plague-stricken rats, the mice succumbed to plague in a few hours.
Fleas have also been conclusively proved to be carriers of plague
germs.
There is no doubt that the revelations of hygienic science have
aroused the vigilance and zeal of public authorities in various new
directions to try and cope with the spread of zymotic disease.
In no direction, perhaps, is the fruit of this energy so apparent as
in the increasing supervision which it has incited over two of the
greatest menaces to public health which hang over society--_i.e._ our
water and dairy supplies. Now that it has been proven beyond doubt
that the germs of consumption, typhoid fever, and cholera can be and
are distributed through the consumption of contaminated milk or water,
not to mention other diseases such as diphtheria and scarlet fever, an
ever-increasing demand is being made that these all-important articles
of diet shall be protected from pollution, and that public authorities
shall be made responsible for their distribution in a pure and
wholesome condition.
It is, however, undoubtedly in the matter of water that the greatest
service has been rendered by bacteriology to sanitary science, and for
the important advance in this department we are indebted to the
beautifully simple and ingenious methods devised by Robert Koch.
Not yet twenty years have passed since the new bacterial examination
of water was introduced and systematically employed, and the use which
has been made of the opportunities thus opened up of investigating
water problems on an entirely new basis is shown by the voluminous
dimensions which the literature on this one branch of bacteriology
alone has reached. Considerably upwards of two hundred different water
bacteria have been isolated, studied, and their distinctive characters
chronicled. The behaviour of typhoid, cholera, and other
disease-producing microbes in waters of various kinds has been made
the subject of exhaustive experiments; the purification power of
time-honoured processes in operation at waterworks and elsewhere has
been for the first time accurately estimated. Water engineers have
through these bacteriological researches been provided with a code of
conduct drawn up by the light of erudite scientific inquiries, which
has now rendered possible the removal of the process of water
purification from the rule of empiricism guided by tradition, and to
raise it to the level of an intelligent and scientific undertaking.
The above short sketch may serve to convey some idea of the rise and
phenomenal development of bacteriology during the past sixty years. To
record, even in outline, the individual triumphs of the various
branches of this science would require volumes, whilst the astounding
mass of work already accumulated by its devotees is but the earnest,
the guarantee of yet greater achievements in the future.
The progress which has been made in this brief period of time must not
necessarily be expected to continue at this rapid rate; it may be that
generations to come have yet the hardest and the longest tasks to
accomplish; for in science, as in other walks of life, it is, as a
rule, the easiest problems, which are first disposed of, and the
farther we advance the more complicated, the more intricate become the
questions to be attacked, the difficulties to be overcome.
The late Queen's reign has bestowed a splendid legacy of
bacteriological discoveries upon those who, in the future as in the
present, must inevitably follow in the footsteps of those great and
brilliant leaders of bacteriological science belonging to this
auspicious era, Louis Pasteur and Robert Koch.
WHAT WE BREATHE
Few people realise that, with the advent of autumn, the great majority
of the swarms of bacteria which have been circulating in the air
during the hot summer months take their leave of us and disappear.
Practically, however, we are all conscious of this fact, for we know
what greater difficulties attend the keeping of food sweet and
wholesome in the summer than are met with in the winter; bacteria, not
unlike some other armies of occupation, securing a footing rather by
their numbers at this season of the year, than by virtue of the
superior strategy or, in other words, special attributes of their
units. Bacterial operations are, however, distinctly favoured by the
accident of temperature, the warmth of the summer encouraging their
vitality and multiplication.
When Pasteur first announced his conviction that the familiar
phenomena of putrefaction and decay were due to minute living
particles present in our surroundings, his sceptical critics sought to
ridicule his conclusions by declaring that, were this the case, the
air must of necessity be so heavily laden with living forms that we
should be surrounded by a thick fog--"dense comme du fer." We do not
now, forty years later, require to recite the exquisitely simple
experiments which, whilst sufficiently establishing his theories,
served to effectually suppress those of his opponents.
Since Pasteur's pioneering work was carried out, a vast number of
investigations have been made in all parts of the world by scientists
of almost every nationality on the subject of the distribution of
bacteria in air, and not only on their distribution, but on their
functions or the place they occupy in the economy of nature. With our
increased knowledge concerning their distribution has come our ability
to differentiate between individuals, and to adequately assess the
value and importance of their work from various points of view.
In the bacterial treatment of sewage we have not only one of the
latest, but perhaps also one of the most successful examples of that
system of division of labour, or specialisation of energy, which forms
such a characteristic feature of work of all kinds at the present
time. Other familiar instances of the applications of individual and
special bacterial labourers to the solution of industrial problems are
to be found in the conduct of commercial undertakings of such national
magnitude and importance as brewing and agriculture. But it is not
with these beneficent or great industrial classes of bacteria that we
are now more immediately concerned, but rather with the malevolent
varieties, or the so-called "submerged tenth," for which no labour
colony has at present been created to direct their energies into
useful and profitable channels.
We know that as regards mere numbers the bacteria in air may vary from
0 to millions in a couple of gallons, these extremes being dependent
upon the surrounding conditions or relative purity of the atmosphere.
Out at sea, beyond the reach of land breezes, it is no uncommon thing
to find none whatever; on mountains and even hills of humble elevation
the paucity of bacteria is very marked if there are no abnormal or
untoward circumstances contributing to their distribution. In
illustration of this the recent investigations of the air on the
summit of Mont Blanc by M. Jean Binot are of especial interest,
inasmuch as the altitude at which they were carried out is the highest
at which the search after bacteria has so far been pursued. This
intrepid investigator spent no less than five days in the observatory,
which is situated on the top of the mountain. As was to be
anticipated, frequently no bacteria at all were found, and it was only
when such comparatively large volumes of air as one thousand litres
(about 200 gallons) were explored that microbes in numbers varying
from four to eleven were discovered. The air of the country is far
freer from microbial life than that of cities; whilst open spaces,
such as those afforded by the London parks, are paradises of purity
compared with the streets with their attendant bacterial slums.
That it is no exaggeration to describe streets from the bacterial
point of view as slums is to be gathered from the fact that much less
than a thimbleful of that dust which is associated with the blustering
days of March and the scorching pavements of summer may contain from
nine hundred to one hundred and sixty millions of bacteria. But
investigators have not been content to merely quantitatively examine
street dust; in addition to estimating the numerical strength of these
bacterial dust-battalions, the individual characteristics of their
units have been exhaustively studied, and the capacity for work,
beneficent or otherwise, possessed by them has been carefully
recorded. The qualitative discrimination of the bacteria present in
dust has resulted in the discovery of, amongst other disease germs,
the consumption bacillus, the lock-jaw or tetanus bacillus, bacteria
associated with diphtheria, typhoid fever, pulmonary affections, and
various septic processes. Such is the appetising menu which dust
furnishes for our delectation.
There can be no doubt, therefore, that dust forms a very important
distributing agent for micro-organisms, dust particles, aided by the
wind, being to bacteria what the modern motor-car, with its benzine or
electric current, is to the ambitious itinerant of the present day.
Attached to dust, bacteria get transmitted with the greatest facility
from place to place, and hence the significance of their presence in
dust.
Mention has been made of the fact that the germs of typhoid fever have
been discovered in dust, and the belief in the possibility of this
disease being spread by dust is gaining ground.
An interesting case in point is afforded by an outbreak of typhoid
fever which occurred in Athens a few years ago, and in which the
starting-point or nucleus was discovered to be a group of labourers
who were engaged upon excavating the soil in a street through which a
sewer had once been taken. The epidemic subsequently spread to those
districts of the city swept by the prevailing wind, which passed over
the place where the soil had been turned up and exposed. M. Bambas,
who brought his observations before the International Congress of
Hygiene at Buda-Pesth, was convinced from the inquiries he made that
this outbreak of typhoid was due to the disturbance of the soil and
the dissemination by means of the wind of typhoid-dust-particles to
certain parts of the city.
That this hypothesis is by no means without experimental justification
is shown by the properties possessed by the typhoid bacillus in regard
to its vitality in soil which have been discovered. Thus numerous
investigators have studied the important question of the behaviour of
this micro-organism in soil, and have found that it can exist over
periods extending from three to twelve or more months in the ground.
This property of the typhoid bacillus may possibly explain the
appearance over and over again of typhoid fever in particular
localities, suggesting that the bacteria had become indigenous in the
soil.
Dr. Mewius, of Heligoland, describes an epidemic of typhoid fever in
the island, concerning which he made a most searching and elaborate
inquiry. It appears that a case of typhoid occurred and was concealed
from the medical authorities, so that no steps for disinfection could
be taken in the first instance; and, following the primitive custom
which prevails on the island, the dejecta was thrown over and upon the
cliffs, this being the usual method of disposing of sewage. Ample
opportunity was thus given for its desiccation and subsequent
distribution as dust. That this typhoidal matter did subsequently
become pulverised and spread the infection Dr. Mewius has no doubt,
the germs having been conveyed to the open rain-water cisterns which
constitute the water-supply of the majority of the inhabitants. His
theory is again supported by the coincidence between the prevailing
direction of the wind and the quarter where the outbreak occurred.
That diphtheria germs can remain for a long time in a living and, what
is more, virulent condition in dust has been clearly demonstrated by
Germano, amongst other investigators, this organism being specially
endowed with the capacity for resisting the, to other microbes, lethal
effect of getting dried up.
Bacteria, however, survive this desiccation process much better when
they are herded together in large numbers than when they have to face
such untoward conditions as isolated individuals. This has been well
illustrated in the case of diphtheria bacilli, and the difference in
their powers of endurance under these respective conditions is very
striking. Thus when a few only were exposed to a very dry atmosphere
on silken threads they disappeared after eight days; but when somewhat
larger numbers were taken they contrived to exist for eighteen days,
whilst when great multitudes of them were herded together even one
hundred and forty days' starvation in these desert-like surroundings
could not entirely stamp out their vitality.
This dangerous property possessed by the germs of diphtheria should,
if possible, increase the vigilance with which the outbreaks of this
disease are watched and dealt with. Abel cites an instance in which a
wooden toy in the sickroom of a child suffering from diphtheria was
found six months later to have _virulent_ diphtheria bacilli upon it.
This reminds me of a case in which tetanus or lock-jaw ensued from the
use of some old cobwebs in stopping the bleeding of a cut. The wound
was a perfectly clean one, and nothing need have resulted from this
obedience to a superstitious prejudice had not the cobwebs
unfortunately arrested some tetanus germs, and these getting access to
the wound set up the typical symptoms of lock-jaw. That this
implication of the cobweb was no idle accusation was subsequently
proved by portions of the same web, on being inoculated into animals,
inducing in the latter well-defined symptoms of tetanus.
That cobwebs readily catch dust is familiar to everyone who has the
mortification of seeing them adorn ceilings and corners; that they
also arrest bacteria follows as a natural consequence of the presence
of dust, and hence these delicate filaments may become veritable
bacterial storehouses, more especially as it is usually in the dark
and remote corners that they best succeed in eluding the vigilance of
the domestic eye, and are thus also out of reach of the lethal action
of sunbeams; and hence their unwelcome lodgers may manage to maintain
a very comfortable existence over long periods of time.
That the bacillus of consumption should have been very frequently
found in dust by different investigators is hardly surprising when it
is realised that the sputum of phthisical persons may contain the
tubercle germ in large numbers, and that until recently no efforts
have been made in this country to suppress that highly objectionable
and most reprehensible practice of indiscriminate expectoration.
Considering that the certified deaths from phthisis in 1901, in
England and Wales only, reached the enormous total of 42,408, and
bearing in mind the hardy character of the _bacillus tuberculosis_
when present in sputum, it having been found alive in the latter even
when kept in a dry condition after ten months, it is not too much to
demand that vigorous measures should be taken by the legislature to
cope with what is now regarded as one of the most fruitful means of
spreading consumption. We know that in some of the states of America
public opinion has permitted the enactment of laws penalising this
practice. Local rules to the same effect exist in our Australian
colonies. On the Continent the trend of public opinion is evident by
the prohibition found in the railway carriages and the notices to that
effect conspicuously posted in public places. In this country public
opinion moves so slowly that we are not yet ripe for any such strong
step, and so far one of the few attempts at official activity in this
respect is to be found in a circular issued by the Local Government
Board of Ireland to the various local authorities stating that
"tuberculous sputum is the main agent for the conveyance of the virus
of tuberculosis from man to man, and that indiscriminate spitting
should therefore be suppressed." The public exhibition of notices
calling attention to the danger accruing from expectoration in public
resorts is, as already pointed out, one means of educating the people,
and it has been stated that such a notice is posted in every beerhouse
in Manchester. The question has also been raised of the inspection of
beerhouses and the suggestion made that licences should be withdrawn
in the case of those holders who did not wash the floors of their
public rooms and keep them in a sanitary state. At the present time,
in this country, it is perhaps more to the private conscience of the
individual and the pressure of public opinion than to penal enactments
that we must look for effective reform in this direction, for the
objection of the English to official sanitary control is deeply
rooted. It is to be hoped, however, that with the spread and
popularisation of the knowledge acquired through the arduous labours
of so many scientific authorities, it may come to be regarded as a
matter for both public and private morality that every step should be
taken which lies in the power of each member of society to minimise
the opportunities for the spread of a disease which by its very
familiarity we have until the last few years accepted as incurable and
the ravages of which as inevitable.[1]
[1] Since the above was written, the first international
conference of the Central Committee for the Prevention of
Consumption has been held in Berlin. The official report of
the English National Association for the Prevention of
Tuberculosis was presented to the Congress, and the
encouraging announcement was made that the Corporations of
Glasgow, Manchester, and Liverpool had made expectoration in
tramcars a punishable offence; and that the Glamorganshire
County Council had passed a bye-law providing as penalty for
expectoration in public buildings a fine of £5, which
enactment had been sanctioned by the Secretary for the Home
Department.
Now that we are considering the status of street dust in bacterial
circles, it will not perhaps be out of place to inquire into the
character of another waste product of streets, _i.e._ the discarded
ends of cigars and cigarettes. That what is carelessly tossed away on
the one hand may be as carefully collected on the other is well known,
as is also the fact that such material may subsequently be raised
once more to the dignity of a marketable commodity. Under these
circumstances, it is of hygienic interest and importance to ascertain
whether disease germs, should they have obtained access to this
tobacco refuse, are in a virulent or quiescent condition.
Some experiments to decide this question in connection with the
tubercle bacillus have been recently carried out in Padua by Dr.
Peserico, who, whilst extending our knowledge on the subject of
bacteria and tobacco, has also confirmed the earlier results obtained
by Kerez.
Portions of cigar-stumps smoked by phthisical persons in whose saliva
the tubercle bacillus was known to be abundantly present were
inoculated into guinea-pigs, with the result that fifty per cent. of
the animals thus treated succumbed to tuberculosis. Thus neither the
fumes nor juice of the tobacco had destroyed the consumption bacillus.
In these experiments the cigar ends were used directly they were
discarded, in another series of investigations they were collected and
kept in a dry place for from fifteen to twenty days before being
tested; but even storage for this length of time did not prevent the
animals inoculated with them from contracting tuberculosis. In another
series of experiments Dr. Peserico kept the infected cigar-ends in
damp surroundings, and it was satisfactory to find that under these
conditions the tubercle bacillus at the end of ten days was entirely
deprived of its virulence. Encouraged by these results, inoculations
were made with cigar-ends which had been left in the open and exposed
to normal atmospheric conditions, which included falls of rain and
snow, and in this case also no symptoms of tuberculosis followed their
introduction into the guinea-pigs. These experiments show that the
tubercle bacillus is prejudicially affected by contact with tobacco
when the latter is kept in a moist condition, but that in a dry
condition the properties in tobacco inimical to its vitality are not
liberated and the bacillus can retain its virulent properties for a
period of over twenty days.
In view of the importance of this discovery on the destruction of the
toxic character of the tubercle bacillus by contact with moist
tobacco, further experiments were made in which emulsions of tobacco
were infected with tuberculous sputum. It was found that the bacilli
steadily declined in virulence as the length of time they were kept in
the emulsion was prolonged. Thus whereas after a few hours they were
still armed with all their virulent properties, after three days, out
of the four animals inoculated with the emulsion three succumbed to
tuberculosis, after five days two out of four succumbed, whilst after
eight days only one animal out of the four was infected, and after a
period of ten days' immersion in the tobacco emulsion the tubercle
bacillus failed to kill a single animal.
Cigar- and cigarette-ends were collected from the streets and cafés of
Padua by Peserico, but in spite of consumption being stated to be very
prevalent in this city, in no single case could the presence of the
tubercle bacillus be discovered, although, as in the other
investigations, the surest method for its detection, _i.e._ animal
inoculations, was employed.
Brief reference may be made also to the experiments conducted to
ascertain if cigars and cigarettes, as sold, contain the tubercle
bacillus. The more interest attaches to this investigation because it
is well known that the operators employed in tobacco factories are, as
a rule, an unhealthy class, diseases of the respiratory organs, and
especially tuberculosis, being very prevalent amongst them. A German
official report on this subject states that the average duration of
life of such factory hands only reaches thirty-eight years. Doubtless
the lightness of the occupation encourages many to seek employment in
these factories whose state of health would debar them from obtaining
work under more trying circumstances. Some of the conditions under
which cigars and cigarettes are made, such as the workers using their
saliva to facilitate the rolling of them and fixing of the leaves, and
the testing of the "drawing" properties of a cigar by placing it in
the mouth, with the facilities offered for the dissemination of dried
tuberculous sputum as dust, contribute to make it highly probable that
tobacco as it leaves the factory may contain the germs of consumption.
Before leaving the subject of tobacco and disease germs it may be of
interest to inquire what justification in fact there is for the
practice adopted by anxious mothers, when travelling in times of
epidemics of zymotic disease, of thrusting themselves and their
children into the sanctum of the other sex--the smoking compartment of
a railway carriage. I have frequently seen this done, despite the
voluble protests of its legitimate occupants. Tassinari has made some
very interesting experiments on the effect of tobacco smoke on the
vitality of various descriptions of disease germs. He constructed an
apparatus in which he suspended pieces of linen soaked in broth
infected with the particular micro-organism to be tested. Tobacco
smoke was then admitted, and the microbes were retained in this
stifling atmosphere for half an hour. In these surroundings cholera
and typhoid germs were destroyed, and other bacteria, such as the
anthrax bacillus and the pneumonia bacillus, were so prejudicially
affected, that when subsequently transferred to their normal
surroundings it was only with extreme difficulty that they could be
revived. When, however, the tobacco smoke was made to pass through
water before reaching the bacteria, its pernicious influence was
entirely removed, and the latter suffered no detriment. Hence the
practice, so often seen in the East, of passing tobacco smoke through
rose or other perfumed water before inhaling it, whilst doubtless
rendering it less noxious to the smoker, deprives the exhaled tobacco
fumes of all their bactericidal or disinfecting properties.
To return, however, after this somewhat lengthy digression, to the
question of dust and its bacterial properties, we have learnt enough
to enable us to realise that the movement for the migration of the
working-classes from crowded streets to rural districts, in which Mr.
George Cadbury has played so practical and important a part in the
creation of his model village, with its gardens and open spaces, some
five miles from the city of Birmingham, is, if only bacterially
considered, a very real barrier against the dissemination of disease,
for the denser the population, the greater will be the crowd of
bacteria, and the greater the chance of pathogenic varieties being
present amongst them. Again, we know that sunshine is one of the most
potent germicides with which nature has provided us;[2] and it
requires no effort of the imagination to realise how, in the gloomy
back courts and crowded tenements of our great smoke-laden cities,
bacteria succeed in obtaining a firm hold on their surroundings, and,
in the shape of spores, attaining an undesirable and hoary old age, in
which they are in some cases almost indestructible. Fräulein Dr. E.
Concornotti has shown that this is no figment of fancy only, for she
has recently made a special and very elaborate study of the
distribution of pathogenic or disease bacteria in air, searching for
them in the most varied surroundings, such as prisons, schools, casual
wards, etc., with the result that, out of forty-six experiments in
which the character of the bacteria found was tested by inoculation
into animals, thirty-two yielded organisms which were pathogenic. Dr.
Concornotti concludes her valuable memoir by stating that her
investigations proved conclusively that the dirtier or more slumlike
the surroundings, the greater was the frequency with which she found
bacteria associated with disease in the air.
[2] See "Sunshine and Life."
Messrs. Valenti and Terrari-Lelli have quite recently been able fully
to endorse these statements in the results they have obtained in their
systematic study of the bacterial contents of the air in the city of
Modena. In their report they state that the narrower and more crowded
the streets, the greater was the number of bacteria present in the
air, and the more frequently did they meet with varieties associated
with septic disease.
Numerous detailed investigations have also been made of the bacterial
contents of the dust in hospitals. That cases of infection arising
within hospital precincts are of no uncommon occurrence may be
gathered from the observations made by Lutand and Hogg, who report no
fewer than 2,294 such cases having arisen in the space of six years in
certain Paris hospitals, whilst Solowjew records 1,880 cases as
occurring in the space of four and a half months in the St. Petersburg
city hospital. Solowjew made a special study of the bacterial contents
of dust collected in hospitals, and states that 41·8 per cent. of the
samples examined contained disease germs. The degree of infection
possessed by dust in such surroundings must, of course, depend upon
the degree of cleanliness which characterises the management of any
particular institution; and such investigations as the above can only
help to emphasise the immense importance of common cleanliness and the
reasonableness of taking every precaution possible in the disinfection
of utensils, etc.
Some years ago Messrs. Carnelley, Haldane, and Anderson carried out an
elaborate series of investigations on the air of dwelling-houses in
some of the poorest parts of Dundee. The samples were taken during the
night, between 12.30 a.m. and 4.30 a.m., and in their report the
authors state that the one-roomed tenements were mostly those of the
very poor; "sometimes as many as six or even eight persons occupied
the one bed," whilst in other cases there was no bed at all. As
regards the number of bacteria present in the air in these one-roomed
houses, an average of several examinations amounted to sixty per
quart; in two-roomed houses it was reduced to forty-six, and in houses
of four rooms and upwards only nine micro-organisms in the same volume
of air were discovered.
On comparing the mortality statistics with the composition of the air
of dwelling-houses of different dimensions, the authors arrive at the
following conclusions: "That, as we pass from four-roomed to three-,
two-, and one-roomed houses, not only does the air become more and
more impure, as indicated by the increase in the carbonic acid and
organic matter, and more especially of the micro-organisms, but there
is a corresponding and similar increase in the death-rate, together
with a marked lowering of the mean age at death."[3]
[3] It is, of course, obvious that other circumstances
besides overcrowding have to be reckoned with in considering
these statistics. In the one-roomed houses the wages earned
by the occupants must have been small, and the amount
available for even the bare necessaries of life very
limited, that, in fact, they were to be reckoned amongst
the class defined by Mr. Rowntree as living in "primary
poverty," whose earnings are insufficient to keep the body
in a properly nourished condition. Mr. Rowntree has shown by
statistics that the height, weight, and general condition of
the poor are very much below those of the well-to-do
labouring classes.
Mention may also here be made of the investigations made by these
gentlemen on the air of Board schools, which showed that in those
buildings where mechanical ventilation was used the carbonic acid
gas was three-fifths, the organic matter one-seventh, and the
micro-organisms less than one-ninth of what was found in schools
ventilated by the ordinary methods. In commenting upon this series of
investigations, the authors write: "When we come to consider that the
children who attend average Board schools for six hours a day are
during that time subjected to an atmosphere containing on an average
nearly nineteen volumes of carbonic acid per 10,000, and a very large
proportion of organic matter, and no less than 155 micro-organisms at
least per quart, we need not be surprised at the unhealthy appearance
of very many of the children. It must also be borne in mind that many
of them are exposed for nine hours more to an atmosphere which is
about five times as impure as that of an ordinary bedroom in a
middle-class house. They are thus breathing for at least fifteen hours
out of the twenty-four a highly impure atmosphere. The effects of this
are often intensified, as is well known, by insufficient food and
clothing, both of which must render them less capable of resisting the
impure air. The fact that these schools become, after a time,
habitually infected by bacteria renders it probable that they also
become permanent foci of infection for various diseases, and
particularly, perhaps, for tubercular disease in its various forms."
Further practical evidence of the manner in which the general
death-rate for certain diseases is influenced by the conditions under
which the poor are housed is afforded by statistics which have been
collected at Glasgow. In the case of zymotic diseases, whereas the
death-rate in tenements consisting of one or two rooms was 4·78 per
1,000, it fell to 2·46 in those of three or four rooms, and to 1·14
per 1,000 in those of five rooms and upwards. Again, in the case of
acute diseases of the lungs, the death-rate was as high as 9·85 in the
smallest tenements, and but 3·28 in the largest.
Of great interest are the certified mortality statistics of phthisis
in the British Army in the period 1830-46 and 1859-66 respectively; in
the former it was 7·86 per 1,000, whilst in the latter period it had
fallen to 3·1, this important difference being coincident with an
increased cubic space per head in the barracks.
Such facts as these, if only fully realised, should surely serve to
stimulate municipal and other local authorities to provide decent and
wholesome accommodation for the poor. It has been recently estimated
that in London the total number of persons living in tenements of one
to four rooms is 2,333,152, and of these nearly half a million live
the life of the one-room tenement of three to a room and upwards. In
the stirring words of Mr. John Burns, M.P.: "At least a million of
people who live thus on wages that barely sustain decent life, are but
prisoners of poverty, whose lot in life is but a funeral procession
from the cradle to the grave ... for these, as soon as practicable,
better homes should be provided at once in the interest of physique,
of morals, of industrial efficiency, and municipal health."
Yet, despite all these facts and the overwhelming evidence which has
been collected on the dire results which follow in the wake of
overcrowding and insanitary dwellings, we find a prominent magistrate
in one of our great industrial cities publicly expressing himself as
follows at a municipal banquet: "The Town Council sometimes attempted
too much. For instance, they had been far too anxious to get quit of
the slums. Now slums, in his opinion, were one of the necessities of
all large towns, and it was impossible in the present state of
civilisation to dispense with slums unless they could take the people
living in them, who were not fit to live anywhere else, and drown them
wholesale, as would have been done in the time of the French
Revolution."
We have seen how bacteria may be distributed by dust, how they may
linger in crowded tenements and badly ventilated buildings, that
insanitary surroundings provide, in fact, for the scientist a
well-stocked bacterial covert, where he may with ease bag his
thousands of germs of various descriptions. The fact already referred
to, that the bacteria of consumption may be released in the sputum of
phthisical persons, has perhaps already suggested the possibility of
other bacteria being likewise discharged into the surrounding air, but
it is no doubt difficult to realise that the utterance of even a few
words may liberate a variety of bacteria, the mischievous or harmless
character of which depends upon the condition of the speaker's health.
But even the health of a speaker if satisfactory is not necessarily a
safeguard against his dissemination of disease germs, for it is well
known that the mouth secretions of healthy people may frequently
contain the _staphylococcus pyogenes aureus_, and also, though less
frequently, the _diplococcus lanceolatus_, both virulent microbes;
whilst that diphtheria bacilli may be present in the mouths of people
who are not suffering from the disease has been demonstrated
repeatedly. What a capacity, then, for spreading evil does the public
orator possess! It makes one tremble to think of the aërial condition
of the House of Commons when a big debate is on, for it has been found
that the sharper the enunciation of the consonants, and the louder the
voice, the larger is the number of organisms discharged and the
farther they reach!
If this danger attends the speaking of healthy people, what must be
the risk accompanying the listening to speeches from persons suffering
from consumption, influenza, or any other disease which specially
affects the air passages! What applies to speaking applies to a still
greater degree to the act of coughing or sneezing.
To Schäffer we owe the discovery that leprosy bacilli may be
disseminated in immense numbers by the coughing of leprosy patients,
whilst it has been estimated that a tuberculous invalid may discharge
a billion tubercle bacilli in the space of twenty-four hours, whilst
the dried sputum of consumptive persons has actually engendered
tuberculous symptoms in the lungs of animals which were made to inhale
it. Plague bacilli have been found in masses in the mouths of plague
patients, and were found, moreover, before any symptoms of the disease
had declared themselves; and the sputum of infected persons is
regarded by some authorities as one of the most important vehicles by
which plague is spread. The culpability of air in the dissemination of
tuberculosis amongst animals has been made the subject of some very
exhaustive and valuable investigations by Kasselmann. In as many as 71
per cent of bovine tuberculosis cases the respiratory organs,
Kasselmann found, were the seat of the disease. The undoubted
contamination of the air which takes place in the surroundings of
tuberculous animals is not, however, due to the bacilli being exhaled
by such cattle in the mere process of respiration, for it has been
repeatedly found by various investigators that the air expired by
infected animals is free from the dreaded tubercle bacteria. As in
man, so in animals--it is by the act of coughing that tuberculous
secretions are discharged through the mouth and nasal passages, some
of which in the form of spray may enable the bacilli to remain
suspended in the air for periods of five hours or more, whilst other
portions of such secretions fall on the ground or in the feeding
troughs, and later on, as dust, may again relentlessly claim their
toll of victims.
In other cases of tuberculosis the excrementitious matter becomes, of
course, a fertile source of infection to the surroundings. The dire
results which may follow the introduction of a single tuberculous
animal into a healthy stall of cows may be realised from the fact that
in one instance a whole herd of twenty-eight animals became in the
course of one year infected in consequence of the admission of one
diseased cow, the cow-house having previously had a perfectly clean
bill of health in this respect.
On the Continent the risk of wholesale infection by such means is
greater than in this country; for abroad the animals are to a much
greater extent stall-fed, and kept shut up both winter and summer. A
case is mentioned by the well-known veterinary authority, M. Nocard,
of a whole stall of animals becoming infected through the cow-man who
tended them being consumptive. He slept in a loft over the cows, and
his tuberculous sputum in the form of dust was conveyed to the stalls
beneath and so spread the infection.
It has been stated on high authority that domestic pets such as
parrots may contract consumption from their masters, and that no less
than thirty-six per cent. of these birds brought to the veterinary
college in Berlin are found to be suffering from tuberculosis.
In that much-dreaded South African cattle disease, rinderpest, the
infection, contrary to what is found in the case of tuberculous
animals, is principally spread by the _materies morbi_ being liberated
in the air expired by afflicted cattle, the contagious area
surrounding an infected animal extending to as much as a hundred yards
and more. Again, as regards pleuro-pneumonia in cattle, the contagion
is given off in the air expired, and owing to the length of time which
elapses before the lung becomes completely healed and healthy, even
after a period of from six to nine months, the expired air may still
prove a source of infection.
In an official report on the open-air treatment of consumption in
Germany a case is mentioned in which the patient, a farmer by
occupation, had contracted the disease from some tuberculous cattle
which he had on his farm. The writer goes on to say, "This case is
worthy of special attention, inasmuch as it indicates that in addition
to the danger of contracting the disease from the use of milk or meat
derived from tuberculous animals, the tending of such animals may
serve to convey the infection to man possibly much more frequently
than has hitherto been supposed."
In addition to the above instances of the responsible part played by
air in the dissemination of consumption many others might be cited,
but perhaps the most striking is that in which a scientific assistant
of Tappeiner contracted the disease, and succumbed to it, in the
course of some experiments which were being made to ascertain whether
consumption could be communicated to animals by spraying them with an
emulsion of the sputum of consumptive patients.
It is of historical interest to note that these experiments were being
conducted by Tappeiner three years before Robert Koch made the now
classical announcement to the scientific world that he had succeeded
in identifying, isolating, and in cultivating outside the human body
the specific cause of consumption in the shape of the now familiar
_bacillus tuberculosis_. The opinion expressed by Koch at the Congress
on Tuberculosis recently held in London, that human and bovine
tuberculosis are distinct diseases, is still the subject of contention
and experimental investigation. Even if the opinion of this great
authority is correct, and in this connection it is interesting to note
that already in 1896 this opinion was brought forward by Smith in the
_Medical Record_ at a time when Koch was maintaining the _identity_ of
human and bovine tuberculosis--granted that Koch is correct, it should
not, as so many fear, cause any relaxation in the efforts which have
been at last made to safeguard our dairy produce by reasonable
hygienic precautions; for even if tuberculosis is not transmissible
from the cow to man, we know that in the hygienic supervision of our
dairy industry we place a great barrier between us and the _bacillus
tuberculosis_ and those numerous other disease germs which can and do
gain access to milk from the _personnel_ of a dairy and so spread
infection. With the alarming prevalence of consumption is it not
justifiable to regard as certain that a definite proportion of the
people engaged in milking, for example, are consumptive? And knowing,
as we now do, how such persons can give off the germs of the disease
in the simple act of speaking, the contamination of our milk with
human tubercle bacilli must be regarded almost as a certainty. Would
it not be reasonable that a code of simple precautions to be taken,
coupled with a few of the more cogent facts concerning consumption and
its distribution, should be drawn up and circulated amongst all
engaged in the dairy industry? The National Health Society has done
much for the prevention of disease by disseminating, through leaflets
and lectures, simple facts concerning health and its preservation;
might it not make itself the vehicle for the transmission of some such
code which, whilst instructing, should impress upon its readers the
responsibility which rests upon each and every individual member of
society, by his or her own personal efforts, to assist in the great
task of combating disease?
A fact which urgently needs the widest recognition is the possible
dissemination of disease germs by individuals not themselves suffering
from the disease in question, but who have resided in the immediate
surroundings of infected persons.
Dr. Koch was the first to call attention to this danger when he
discovered, during the Hamburg cholera epidemic, that _perfectly
healthy_ persons were infected with cholera vibrios, and were the
unconscious means of spreading the disease. Still more recently it has
been found that true typhoid germs may similarly be present in persons
not suffering from typhoid fever but sharing the same living-rooms.
Huxley has said "science is nothing but trained and organised common
sense," and it is in this spirit that we must endeavour to make use of
the discoveries which have been made in the prevention of disease, in
which the science of bacteriology has played so great and important a
part.
SUNSHINE AND LIFE
It was nearly a century ago that a German physician incidentally
wrote, "Our houses, hospitals, and infirmaries will, without doubt,
some day be like hot-houses, so arranged that the light, even that of
the moon and stars, is permitted to penetrate without let or
hindrance." This was spoken long before the world of micro-organisms
had been discovered, but curiously has found an echo in the writings
of a distinguished bacteriological chemist in recent years. "Laissons
donc entrer largement partout l'air et le soleil," writes M. Duclaux;
"c'est là une maxime bien ancienne, mais si les mots sont vieux l'idée
qu'ils revêtent est nouvelle." The interpretation of this ancient
maxim is indeed very modern, and we must turn to the investigations
made within the past few years to learn with what justification M.
Duclaux thus expresses himself, for it is only comparatively recently
that we have learnt the novel fact that sunshine, whilst essential to
green plant life, is by no means indispensable to the most primitive
forms of vegetable existence with which we are acquainted, _i.e._
bacteria. In fact, we have found out that if we wish to keep our
microbial nursery in a healthy, flourishing condition, we must
carefully banish all sources of light from our cultivations, and that
a dark cupboard is one of the essential requisites of a
bacteriological laboratory.
That light had a deleterious effect upon micro-organisms was first
discovered in this country by Messrs. Downes and Blunt, and their
investigations led Professor Tyndall to carry out some experiments on
the Alps, in which he showed that flasks containing nutritive
solutions and infected with bacteria when exposed in the sunshine for
twenty-four hours remained unaltered, whilst similar vessels kept in
the shade became turbid, showing that in these the growth of bacteria
had not been arrested. In these experiments mixtures of
micro-organisms were employed, and the interest of the French
investigations which followed lies in the use of particular
microbes--notably the anthrax bacillus and its spores,[4] Roux
demonstrating very conclusively that the bacillar form was far more
sensitive to light than the spore form, while Momont, in a classical
series of experiments, not only fully confirmed these observations,
but showed also that the intensity of the action of light depends to a
very large extent on the environment of the organism. Thus, if broth
containing anthrax bacilli is placed in the sunshine, the latter are
destroyed in from two to two and a half hours, whilst if blood
containing these organisms is similarly exposed, their destruction is
only effected after from twelve to fourteen hours of sunshine. This
difference in resistance to insolation was also observed in the case
of _dried_ blood and broth respectively--eight hours' exposure killing
the bacilli in the former, whilst five hours sufficed in the latter.
[4] In the interior of some bacilli there appears a round or
oval body, having a very bright and shining lustre, which is
known as a _spore_, and plays a most important part in
the propagation of many kinds of bacilli. These spores are
capable of resisting many hardships, which would be
immediately fatal to the parent bacilli from which they have
sprung.
This is an instance of the apparent idiosyncrasies possessed by
micro-organisms, which render their study at once so fascinating and
so difficult, and it is through being thus constantly confronted with
what, in our ignorance, we mentally designate as "whims," that we can
hardly resist the impression of these tiny forms of life being endowed
with individual powers of discernment and discrimination. Indeed,
these powers of selection and judgment are in certain cases so
delicately adjusted that in some of the modern chemical laboratories
micro-organisms have become indispensable adjuncts, and by their means
new substances have been prepared and fresh contributions made to the
science of chemistry.
Momont is not able to give any satisfactory explanation of this
different behaviour of the anthrax bacilli in these two media, but
goes on to show that yet another factor plays an important part during
insolation.
In the above experiments air was allowed to gain access to the vessels
containing the broth, but if the precaution be taken of first removing
the air and then exposing them to the sunshine, a very different
result was obtained, for instead of the anthrax bacilli dying in from
two to two and a half hours, they were found to be still alive after
fifty hours' insolation. There appears, therefore, to be no doubt that
sunshine in some way or other endows atmospheric oxygen with
destructive power over the living protoplasm of the bacterial cells;
indeed, there is considerable reason to believe that the bactericidal
effect is due to the generation of peroxide of hydrogen, which is well
known to possess powerfully antiseptic properties.
Numerous investigations have been also made to determine whether all
the rays of the spectrum are equally responsible for the bactericidal
action of light.
Geisler's work in St. Petersburg is especially instructive in this
respect, for by decomposing with a prism the sun's light, as well as
that emitted by a 1,000-candle-power electric lamp into their
constituent rays, he was able to compare the different effects
produced by the separate individual rays of both these sources of
light.
The organism selected was the typhoid bacillus, and it was found that
its growth was retarded in all parts of the two spectra excepting in
the red, and that the intensity of the retardation was increased in
passing from the red towards the ultraviolet end of the spectrum,
where it was most pronounced of all.
But whereas from two to three hours of sunshine were sufficient to
produce a most markedly deleterious effect upon the typhoid bacillus,
a similar result was only obtained by six hours' exposure to the
electric light.
Dr. Kirstein, of the University of Giessen, in the course of some
experiments he made to ascertain how long different varieties of
bacteria can exist when they obtain access to the air in the form of
fine spray, and subsequently, as happens under ordinary circumstances,
get dried up, noted also the effect upon their vitality of exposure in
daylight and darkness respectively. For this purpose the apparatus in
which the experiments were carried out was in some cases kept in a
dark cellar, whilst in others it was left standing in the laboratory
in ordinary daylight.
Delicate bacteria, such as the fowl-cholera bacillus, it was found,
could not survive exposure to daylight in this dried-up condition for
more than ten hours, but when they were put in the dark their lease of
life was prolonged for more than twice that length of time; whilst as
regards varieties of tougher constitution, such as diphtheria and
tubercle bacilli, whose initial vitality was very considerably greater
under these adverse circumstances, confinement in the cellar enabled
them to exist more than four times as long as they were able to in the
healthy atmosphere of the well-lighted laboratory.
Dr. Onorato, of the University of Genoa, has recently shown, also,
that influenza bacilli are entirely destroyed after the sun has been
shining on them continuously for three and a half hours.
Such facts indicate how essential to health is plenty of light in our
dwelling-rooms, and how important it is that in the designing of
houses the trapping of the maximum amount of sunshine should be very
carefully considered. Architects might indeed with advantage be
compelled to include in their qualifications a knowledge of the
fundamental facts of sanitary science. The fashion of shutting the
sunshine out by barriers of blinds and curtains drawn across the
windows, a practice which seems to be almost entirely independent of
the habitual gloom of the surroundings or general scarcity of
sunshine, might possibly be modified were it but known that by thus
excluding light we are conferring an inestimable benefit upon the
members of the microbial community, which may at any moment comprise
some of the subtlest and most dangerous antagonists with which we have
to reckon in the struggle for existence.
From a hygienic point of view, also, the question of the potency of
sunshine in regard to the bacteria present in water is both important
and interesting, for it is to water at the present time that we look
for the dissemination of some of the most dreaded zymotic diseases.
Comparatively little has been done in this direction, but those
results which have been obtained are exceedingly suggestive. Professor
Buchner has published some preliminary experiments which he made with
particular micro-organisms. In these investigations boiled tap-water
was used to ensure the absence of all bacteria except those which were
subsequently introduced, and, whilst some of the vessels were exposed
to the sunshine, others were simultaneously preserved in the dark. It
was found that typhoid, cholera, and various other bacilli were most
deleteriously affected by insolation. Perhaps an example will best
serve to illustrate the nature of the results obtained. Some boiled
water contained in a flask was inoculated with an immense number of a
bacillus, closely resembling the typhoid organism, normally present in
the body and frequently found in water, the _bacillus coli communis_.
So many were introduced that nearly one hundred thousand individuals
were present in every twenty drops of the water. This flask then,
containing water so densely sown with microbes, was placed in the
sunshine for one hour, whilst another and similar flask was kept
during the same time in the dark. On being subsequently examined it
was ascertained that whereas a slight increase in the number of
bacilli had taken place in the "dark" flask, in the insolated flask
_absolutely no living organisms whatever_ were present.
Professor Percy Frankland has also investigated the action of sunshine
on micro-organisms in water, and in one of his reports to the Water
Research Committee of the Royal Society an account is given of the
effect of insolation on the vitality of the spores of anthrax in
Thames water. These experiments show again what an important influence
the surroundings of the organism have on the bactericidal potency of
the sun's rays, for the remarkable fact was established that when
immersed in water anthrax spores are far less prejudicially affected
by sunlight than when exposed in ordinary culture materials such as
broth or gelatine. Thus it was only after one hundred and fifty-one
hours' insolation in Thames water that these spores were entirely
destroyed, whilst a few hours' exposure in the usual culture media is
generally sufficient for their annihilation. In water not subjected to
insolation anthrax spores were found to retain their vitality for
several months.
In case the reader should be tempted to compare these results with
those obtained by Buchner, it must be borne in mind that whereas those
experiments were made with _bacilli_, these were directed to determine
the behaviour of _spores_ in water, which are some of the hardiest
forms of living matter with which we are acquainted. This alone would
sufficiently explain the results obtained, whilst each variety of
microbe may be, and doubtless is, differently affected during
insolation.
We know now that a remarkable improvement takes place in the bacterial
condition of water during its prolonged storage in reservoirs, and
although, no doubt, the processes of sedimentation which have been
shown to take place during this period of repose are to a large extent
responsible for the diminution in the number of bacteria present, yet
it is also highly probable that insolation assists considerably in
this improvement, at any rate, in the upper layers of the water. As
the depth of the water increases the action of light is necessarily
diminished. Indeed, exact experiments conducted in the Lake of Geneva
to ascertain by means of photographic plates the depth to which the
sun's rays penetrate showed that they did not reach beyond five
hundred and fifty-three feet, at which depth the intensity of the
light is equal to that which is ordinarily observed on a clear but
moonless night, so that long before that their bactericidal potency
would cease.
It is the more important that this limit to the powers of sunshine in
water should be duly recognised, inasmuch as solar enthusiasts, when
first the fact became known, rashly jumped at the convenient
hypothesis, based on very slender experimental evidence, that the
sun's rays were possessed of such omniscient power to slay microbes,
that they might safely be relied upon to banish all noxious organisms
from our streams, and that local authorities might therefore
comfortably and without any qualms of conscience turn sewage into our
rivers and so dispense with the cost and labour of its treatment and
purification.
This was actually suggested in a proposal made for dealing with the
sewage of the city of Cologne. Fortunately further investigations have
removed these most erroneous and dangerous ideas; and whilst all due
credit may be given to sunshine for what it really does accomplish in
the destruction of bacteria in water, there is now no doubt as to its
potency being confined to the superficial layers of water.
Perhaps Dr. Procacci's experiments will most clearly convey some idea
of this limitation, for he made a special study of this particular
phenomenon. Some drain water, containing, of course, an abundance of
microbial life, was placed in cylindrical glass vessels, and only the
perpendicular rays of the sun were allowed to play upon it. The column
of water was about two feet high, and whilst a bacteriological
examination at the commencement of the research showed that about two
thousand microbes were present in every twenty drops of water taken
from the surface, centre, and bottom of the vessel respectively, after
three hours' sunshine only nine and ten were found in the surface and
centre portions of the water, whilst at the bottom the numbers
remained practically unchanged. Professor Buchner, of Munich,
demonstrated the same impotence of the sun's rays to destroy bacteria
much beneath the surface of water, in some ingenious experiments he
made in the Starnberger See, near Munich. He lowered glass dishes
containing jelly thickly sown with typhoid bacilli to different depths
in the water during bright sunshine; those kept at a depth of about
five feet subsequently showed no sign of life, whilst those immersed
about ten feet developed abundant growths; in both cases the exposure
was prolonged over four and a half hours.
In our own rivers Thames and Lea frequently about twenty times more
microbes have been found in the winter than in the summer months, but
it would be extremely rash to therefore infer that the comparative
poverty of bacterial life was due to the greater potency of the sun's
rays in the summer than in the winter. Doubtless it may contribute to
this beneficial result; but we know as a matter of fact that, in the
summer, these rivers receive a large proportion of spring water, which
is comparatively poor in microbes, and that this factor also must not
be ignored in discussing the improved bacterial quality of these
waters at this season of the year.
Another point which must be taken into consideration in regard to the
effective insolation of water is its chemical composition, for it has
been shown[5] that the action of sunshine in destroying germs in water
is very considerably increased when common salt is added to the water,
and this opens up a wide field for experimental inquiry before we can
accept sunshine as a reliable agent in the purification of water.
[5] PERCY FRANKLAND, _Our Secret Friends and Foes_, 4th
edition, p. 188.
Again, we must remember that a great deal depends upon the condition
of the microbe itself. If it is present in the spore or hardy form,
then considerably longer will be required for its annihilation. This
fact has been abundantly shown in the case of anthrax, which in the
condition of spores will retain its vitality in water flooded with
sunshine for considerably upwards of a hundred hours, the bacilli
being far more easily destroyed. We must also bear in mind that the
individual vitality of the microbe is an important factor in
determining its chance of survival; if it is in a healthy, vigorous
condition, it will resist the lethal action of sunshine for
considerably longer than when its vitality has been already reduced by
adverse surroundings.
It is, therefore, sufficiently obvious that the power of insolation to
bacterially purify water is by no means easy of estimation, and that
numerous and very varied factors have to be taken into account when we
attempt to endow it with any measure of practical hygienic importance.
In connection with the vitality of anthrax germs in water, which has
afforded material for so many laboratory investigations, it is of
interest to consider what chance exists of anthrax being communicated
by water. Until a few years ago, as far as I am aware, no instance had
been recorded of anthrax having been actually communicated by water,
until an outbreak of anthrax on a farm in the south of Russia was
distinctly traced by a skilled bacteriologist to the use of water from
a particular well, in the sediment of which the bacillus of anthrax
was discovered.
Anthrax bacilli have also been detected in the water of the River
Illinois in the vicinity of Chicago, one of the chief sources of
pollution of which is the slaughtering of cattle and the discharge of
their offal into the river.
The likelihood of such contamination taking place through the drainage
of soil makes it of importance to ascertain what may become of the
bacilli of anthrax derived from the bodies of animals which have died
of this disease, and whose carcasses have been buried and not burnt.
The anthrax bacillus cannot produce the hardy spore form within the
bodies of animals, but it does outside. Now it has been shown that the
bacilli of anthrax taken from the blood of an animal dead of anthrax
are destroyed rapidly in ordinary River Thames water, for example, but
that if the temperature of the water to which they gain access is
somewhat higher than usual, such bacilli are able to sporulate or
produce spores in the water, and in that hardy form can retain their
vitality and virulence for several months.
That anthrax bacilli can produce spores in water under certain
conditions has not hitherto been dwelt upon in discussing the question
of their vitality in water, and it is of obvious importance in
connection with the action of sunshine on anthrax germs in water,
knowing as we now do the very different manner in which the spores and
bacilli respectively behave when under the influence of the sun's
rays.
It was not, perhaps, unnatural that rash assumptions as to the
efficacy of sunshine should have been readily accepted when such
remarkable feats performed on microbes by sunshine were being
continually put forward.
Thus it has been found that insolation, even when it does not destroy,
may effect profound changes in the physiological character of certain
micro-organisms.
Dr. Lohmann, of Rostock, discovered that some hours' exposure to
bright sunshine entirely destroys yeast cells, whilst even feeble and
intermittent sunshine is capable of paralysing them, and that they
only recover their vitality when removed from this obnoxious
influence. This recuperative power is not, however, shared equally by
all varieties of yeast, some possessing it in a far greater degree
than others. Dr. Lohmann also found that yeast cells, after being
exposed to sunshine, assumed a shrunken and distorted appearance,
showing that insolation had produced a striking physiological effect
upon the structure of these cells.
Professor Hansen published some years ago a most interesting memoir on
some of the characteristic features of the moulds which are to be
found on manure heaps, in which he records how light exerts a very
important influence on the manner in which the spore or fruit of these
lowly vegetables is set free or distributed. All the various phases in
the fructification process of some of these moulds were carefully
watched by Dr. Hansen. He kept his caged specimens near a window with
an eastern aspect, and he states that in the first instance the stalks
inclined towards the light, but that afterwards they assumed an
upright position. Darkness was nearly always chosen for the liberation
of the spores, but in a few instances a small number were released
during the daytime, and it was noticed that when this did occur they
were invariably discharged on the side away from the source of light.
In various other ways he confirmed this interesting observation, and
found that the fruit of the mould was invariably discharged in the
opposite direction to that in which the stalk had previously inclined
under the influence of light. The force with which the spores were
discharged varied very considerably, sometimes being cast to a
distance of four inches or more from the stalk, and sometimes being
found close to and even on the stalk.
The manner in which sunshine may also modify the pigment-producing
powers of micro-organisms is remarkable.
Many microbes are able to elaborate when grown on various culture
media, such as gelatine or slices of potato, most brilliant and
beautiful pigments ranging from intense blood-red to the most delicate
shades of pink, and embracing every gradation of yellow, as well as
browns, greens, and violets. Now it has been found that some of these
pigment-producing bacteria, when exposed to sunshine on these
nutritive materials, fail to exhibit their characteristic colour,
although the duration of insolation may not have sufficed to destroy
their actual vitality. One of these organisms originally obtained from
water has been specially studied in this respect by M. Laurent. If
slices of potato are streaked with a small number of this particular
bacillus (_bacille rouge de Kiel_) a magnificent patch of blood-red
colour makes its appearance in the course of a day or two, but if, on
the other hand, similar slices of potato are exposed to three hours'
sunshine, a colourless growth subsequently develops, except where here
and there a few isolated spots of pale pink are visible. When the
insolation is prolonged for five hours nothing whatever appears on the
potato, the bacilli having been entirely destroyed. But this is not
all. M. Laurent found that if he took some of the colourless growth
and inoculated it on to potatoes he obtained again, but without
insolation, a colourless vegetation--in fact, three hours' insolation
had so modified the physiological character of the bacillus that _a
new race had been generated, a race deprived of its power of producing
this red pigment_. In what numerous directions the character of
microbes may be and are being modified, even by simple exposure to
sunshine, opens up a wide field for speculation and research, whilst
the tractability of these minute and most primitive forms of life, if
we only approach their education with sufficient insight and patience,
may enable us to make them serve where they now are masters.
The remarkable discoveries on the modification of the
disease-producing properties of certain bacteria by sunshine may
perhaps encourage the idea that we are making some progress towards
the attainment of this desirable millennium. That diminution of the
virulence or disease-producing power of such deadly microbes as those
of cholera, anthrax, and tuberculosis can be brought about through
simple exposure to the sun's rays seems almost inconceivable, yet it
has been discovered that by placing the cholera bacillus, for example,
in the sunshine its virulent character undergoes such a profound
modification that it is actually reduced to the condition of a
vaccine, and may be employed to protect animals from infection with
its still virulent brethren. Yet this is what has been undoubtedly
shown by Dr. Palermo in very carefully conducted investigations. He
was, moreover, able to indicate, within a very narrow margin, the
precise amount of insolation necessary to bring about this result: for
if the cholera cultures were only exposed for three hours, their toxic
properties were not reduced to the condition of vaccine; but if the
insolation was continued for three and a half hours up to four and a
half hours, they became endowed with the requisite immunising
properties, and animals treated first with the so-called
sunshine-cholera-vaccine were able subsequently to withstand otherwise
fatal doses of virulent cholera cultures. Dr. Palermo also found that,
besides producing this subtle modification in the character of cholera
bacilli, sunshine exerted a remarkable physiological change in these
organisms, for when examined under the microscope they no longer
exhibited their typical activity, having been deprived of all powers
of movement, whilst those kept during the same length of time in the
dark had not abated one jot of their customary mobility.
But sunshine not only controls in this wonderful manner the action of
the living bacillus, but it also operates upon the products elaborated
by disease organisms. Thus the microbe producing lock-jaw or tetanus
may be grown in broth, and the latter may be subsequently passed
through a porcelain or a Berkefeld filter, so that the resulting
liquid is entirely deprived of all germ life. This tetanus-filtrate,
as it is called, is endowed with very powerful toxic properties, and
it will retain its lethal action even when kept for upwards of three
hundred days, providing it is screened from all light; but place such
filtrates in diffused light, and they lose their poisonous properties,
requiring, however, upwards of ten weeks to become entirely harmless;
if, on the other hand, they be exposed to sunshine, they are
completely deprived of their toxic character in from fifteen to
eighteen hours. Again, as little as five hours' sunshine is sufficient
to greatly modify the toxic action of diphtheria cultures. It is of
interest also to note that even the venom of the rattlesnake, that
most potent of all poisons, cannot emerge unscathed from an exposure
to sunshine maintained during a fortnight.
Interesting as all these isolated observations are, they indicate what
an immense amount yet remains to be done before we can hope to have
any connected conception of the mechanism, so to speak, of insolation.
At present there is too large an allowance, which we are compelled to
make, for the unknown to permit of our adequately manipulating this
marvellous agency in relation to bacteriological problems. But who
shall say what part has been, and is being still, played by sunshine
in determining the individual character of microbes, operating as it
has done from time immemorial upon countless generations of these
minute germs of life?
The problem of insolation has been attacked from an entirely novel
point of view by Dr. Masella, who has endeavoured to find out whether
sunshine plays any part in the predisposition of animal life to
infection.
Now sunshine has long been credited with possessing therapeutic
powers, and, indeed, traditions of cures effected by the ancients by
means of insolation have been treasured up and handed down to the
present day. Even as late as the beginning of the present century we
may read of a French physician seriously recording his claim to have
cured a dropsical patient within two weeks by placing him daily for
several hours in the sunshine, and many medical journals of recent
years contain communications on the beneficial results derived from
the use of sunshine in the treatment of various diseases. It seems
curious, therefore, that whilst so much has been done to test the
action of light on disease microbes in _artificial_ surroundings, such
as are to be found in laboratory experiments, hardly any
investigations have been made to try and define more precisely how
sunshine may affect their pathogenic action within the animal system.
Dr. Masella's researches, undertaken with the express object of, if
possible, elucidating this question, are therefore of special interest
and importance.
The first series of experiments was carried out to ascertain whether
exposure to sunshine increases or reduces an animal's susceptibility
to particular diseases, those selected for investigation being typhoid
fever and cholera. For this purpose guinea-pigs were exposed to the
full rays of the sun during a period of from nine to fifteen hours for
two days, whilst other guinea-pigs, for the sake of comparison, were
not permitted to have more light than that obtainable in a stable
where only diffused light was admitted. Both these sets of animals
were subsequently infected with virulent cultures of cholera and
typhoid germs respectively, and were in neither case exposed to
sunshine. The results which Dr. Masella obtained were remarkable, for
he found that those animals which previous to infection had been
placed in the sunshine died more rapidly than those which had been
kept in the stable, and that the exposure to the sun's rays had so
increased their susceptibility to these diseases that they succumbed
to smaller doses, and doses, moreover, which did not prove fatal to
the other guinea-pigs. Still more striking was the part played by
insolation in the course of these diseases in animals exposed to
sunshine _after_ inoculation, for instead of dying in from fifteen to
twenty-four hours, they succumbed in from three to five hours.
Here, then, we find sunshine, in some mysterious manner not yet
understood, far from benefiting the animal and assisting it in
combating these diseases, actually contributing to the lethal action
of these bacteria. It has been asserted on the authority of some
medical men that in cases of small-pox recovery is rendered more easy
and rapid when light is excluded from the patient's room; whether Dr.
Masella's experiments will permit of any such interpretation being
placed upon them remains to be seen; they are, at any rate, extremely
suggestive.
That it is possible for temperature to have some determining influence
upon the course of certain diseases has been shown by O. Voges, who,
experimenting with a minute bacillus which he isolated from tumours
characteristic of a cattle disease very prevalent in South America,
found that although this bacillus was the undoubted _fons et origo_ of
the disease, he could not produce fatal results in animals if he kept
them in cold surroundings; only when the temperature was raised to
from 35-45 degrees Centigrade did the infected animals succumb. The
dependence of the activity and virulence of this micro-organism upon
temperature is also borne out in actual experience, the disease being
the more prevalent and the more fatal the hotter the climate of the
country.
It may be mentioned in passing that this bacillus has the distinction
of being the smallest yet discovered; the influenza bacillus hitherto
held the palm in this respect, but it must yield its position to its
more successful rival, for Voges states that when magnified about
fifteen hundred times it is only just discernible in the microscopic
field.
Even the smoke-laden atmosphere of our great cities, our leaden skies
and dreary fogs and mists, may after all, then, if we can only learn
to look at them from Dr. Masella's point of view, become a source of
benefit and a subject for congratulation; yet our inherent love of
light and sunshine would cause us willingly to hand over our murky
climate had we but the chance of obtaining in exchange that of any of
the sunny cities of the south. Moreover, in the case of tubercular
disease experience is daily impressing upon us the wisdom, and indeed
necessity, of absorbing as much sunshine as possible, and hence the
pilgrimage which is now recommended to Davos and other resorts where
invalids can get the maximum amount of bright sunshine. And not only
is this the outcome of practical experience, but De Renzi has shown by
actual experiment that sunshine acts beneficially in cases of
tuberculosis in animals. Thus, guinea-pigs were infected with
tuberculous material and exposed in glass boxes to the sun for five or
six hours daily, others being similarly infected but protected from
sunshine. The animals which had received the sunshine died in 24, 39,
52, and 89 days respectively, whilst those which had not been sunned
succumbed in from 29, 25, 26, and 41 days; or, in other words, De
Renzi found that insolation had very materially increased the infected
animals' power of coping with tuberculosis.
The part which sunshine plays, or may be made to play, in disease is
very obscure, but it would appear at least justifiable to assume that
it is an agent which further investigation may show we cannot afford
to disregard, contributing as it may to the production of a healthy
tone in the system, and thereby materially assisting the body to defy
the insidious attacks made upon it from without.
The so-called open-air treatment of consumption which has made such
giant strides in the last few years is an example of how, by
contributing to the general health of an individual, the powers for
resisting a localised disease may be so increased that the latter can,
in many cases, be thrown off altogether. In no country has more
progress been made in the establishment of institutions for the cure
of consumption on these lines than in Germany. At the end of the year
1899 there were forty-nine such institutions in Germany, with four
thousand beds; in a little more than twelve months later there were no
less than sixty such, with accommodation for altogether five thousand
patients. It is of interest to note that amongst the earliest of these
institutions to be founded was that erected and endowed by the famous
Badischen Anilin and Soda Fabrik Company, for the exclusive benefit of
those of their workpeople who were suffering from tuberculous disease.
We have learnt that sunshine is endowed with distinctly lethal action
as regards particular bacteria, that it can modify the subtle
properties of toxic solutions, and we are asked to believe that it may
exercise an important influence on the animal system in determining
the power of the latter to deal with the agents of disease; but, as we
have seen, the mechanism of it all is shrouded in mystery, and we are
at a loss to divine how it works. Might not some fresh light be thrown
upon this problem if we could ascertain the effect of sunshine on some
of these natural fluids of the body, which recent brilliant research
has shown to be endowed with such wonderful protective or immunising
properties? So far as I am aware, the action of sunshine on these
anti-toxins or protective fluids has not yet been investigated. Can
sunshine interfere with the therapeutic effect of diphtheria-serum,
for example? If simple insolation can so profoundly modify the
character of toxic fluids, it is not unreasonable to anticipate some
action on these anti-toxins, and their study in this connection would
appear to offer an important step in the direction of unravelling the
mystery attending the action of light on life.
BACTERIOLOGY AND WATER
Whilst the Hamburg cholera disaster of 1892 will certainly rank in the
annals of epidemiology as one of the great catastrophes of recent
times, it will also be memorable as one of the most instructive which
has ever taken place.
It is perhaps not unnatural that this should be the case, for since
the last European epidemic of importance our study of the principles
of sanitation has received a new impetus, and this impetus must be in
great part ascribed to the science of bacteriology, which has sprung
into existence within the past two decades. We have now no longer to
confront mysterious and unknown morbific material, but have been
brought face to face with some of the most dreaded foes of the human
race. We are no longer groping, as it were, in the dark, but have a
definite object, in the shape of well-recognised micro-organisms
associated with specific zymotic diseases, for our common crusade.
But it is the light which has been thrown for the first time upon
numerous intricate problems connected with the sanitary aspects of
public water-supplies which constitutes not the least important of the
many services rendered by bacteriology to the public. Perhaps one of
the most striking of these may be considered the insight which it has
afforded into the value of various processes of water-purification,
furnishing us with the most subtle and searching tests, surpassing in
delicacy those of the most refined chemical methods.
Thus for years the processes of sand-filtration, as practised at
waterworks in dealing with river and other surface waters, were
regarded by chemical experts as of but little or no value, because, on
chemical analysis, but little or no difference was found to exist
between the filtered and unfiltered samples respectively. Water
engineers started this method of water treatment in London as far back
as the year 1839, with no other object than the distribution of a
water bright and clear on delivery, but, unknown to themselves, they
were carrying out a system of water-purification the nature and extent
of which has been left to the infant science of bacteriology to
unravel and reveal.
It was in the year 1885 that Dr. Koch's new bacteriological
water-tests were introduced, and systematically applied for the first
time to the London water-supply by Professor Percy Frankland, and the
entirely unexpected result obtained, that whereas the River Thames
water at Hampton contained as many as 1,644 micro-organisms in about
twenty drops, this water, after passing through the sand-filters,
possessed as few as thirteen in the same number of drops. The
remarkable purification effected in the treatment of the water was
thus very clearly shown, and an entirely new aspect was given to the
processes of sand-filtration.
The importance of these results was quickly appreciated by the
official water-examiner, the late Sir Francis Bolton, and at the
request of the Local Government Board regular monthly bacteriological
examinations of the London water-supply were conducted.
It is amusing to recall that, at the time when these results were
first published, the public, instead of being reassured by these
facts, were greatly alarmed, and it is a matter of history that the
mere demonstration of the presence of micro-organisms in
drinking-water caused a fall in the price of several of the water
companies' stocks!
These investigations, which have since been confirmed by others both
in this country and on the Continent, have clearly shown, then, that
sand-filtration, when carefully carried out, offers a most remarkable
and obstinate barrier to the passage of microbes, and there was every
justification in presuming that if disease organisms should at any
time be present in the raw untreated water, they would also undergo a
similar fate, as there was no reasonable ground for supposing that
they would behave any differently from the ordinary harmless water
bacteria.
But this was a hypothesis only, and, however satisfactory experiments
in this direction made in the laboratory might prove, there was always
the uncertainty attaching to a fact which had not passed through the
ordeal of practical experience.
The answer to this searching and all-important question has been
furnished in the most conclusive manner by the history of the cholera
epidemic in Hamburg and Altona respectively in the year 1892.
These two cities are both dependent upon the River Elbe for their
water-supply, but whereas in the case of Hamburg the intake is
situated _above_ the city, the supply for Altona is abstracted below
Hamburg _after it has received the sewage of a population of close
upon 800,000 persons_. The Hamburg water was, therefore, to start
with, relatively pure when compared with that destined for the use of
Altona. But what was the fate of these two towns as regards cholera?
Situated side by side, absolutely contiguous, in fact, with nothing in
their surroundings or in the nature of their population to especially
distinguish them, in the one cholera swept away thousands, whilst in
the other the scourge was scarcely felt; in Hamburg the deaths from
cholera amounted to 1,250 per 100,000, and in Altona to but 221 per
100,000 of the population. So clearly defined, moreover, was the path
pursued by the cholera, that although it pushed from the Hamburg side
right up to the boundary line between the two cities, it there
stopped, this being so striking that in one street, which for some
distance marks the division between these cities, _the Hamburg side
was stricken down with cholera, whilst that belonging to Altona
remained free_. The remarkable fact was brought to light that in those
houses supplied with the Hamburg water cholera was rampant, whilst in
those on the Altona side and furnished with the Altona water not one
case occurred.
We have seen that the Hamburg water, to start with, was comparatively
pure when compared with the foul liquid abstracted from the Elbe by
Altona, but whereas in the one case the water was submitted to
exhaustive and careful filtration through sand before delivery, in
Hamburg the Elbe water was distributed in its raw condition as drawn
from the river.
But further testimony was afforded later to the truth of these
results, for during the winter, whilst the cases of cholera had almost
completely died out in Hamburg, suddenly a most unexpected and
unaccountable recrudescence of the epidemic occurred, and this time in
Altona. This outbreak could not be traced to any direct infection from
Hamburg, but must have arisen in Altona itself. In all about
forty-seven cases were recorded between December 23rd, 1892, and
February 12th, 1893. A searching inquiry was instituted, and it was
ascertained that the number of bacteria found in the filtered water,
usually about fifty, had during these months risen to as many as 1,000
and more in about twenty drops of water, clearly indicating that the
filtration of the water was not being efficiently carried out. That
this was actually the case was proved by the fact that one of the
sand-filters which had been cleaned during the frost had become frozen
over, and was not able to retain the bacteria. That the outbreak did
not become more serious Koch ascribes to the fact that this, to all
intents and purposes raw untreated water, was largely diluted with
efficiently filtered water before delivery. Dr. Koch, who personally
superintended this inquiry in Altona, traced another local outbreak of
cholera in the city to the use of a well-water obviously open to
pollution, which was used by about 270 persons. In one of the houses
employing this water, and in the immediate vicinity of the well, a boy
died of cholera on January 23rd, and during the week following a
number of cases occurred amongst persons using this source. On
discovering the cholera bacilli in this polluted water, its
contamination was placed beyond doubt, and five days after the well
was closed all cases ceased in the locality.
There cannot be any longer a doubt as to the value of sand-filtration
as a means of water-purification, but the responsibility which we have
seen attaches to this treatment of water cannot be exaggerated, for
whilst when efficiently pursued it forms a most important barrier to
the dissemination of disease germs, the slightest imperfection in its
manipulation is a constant menace during any epidemic.
It is, as a rule, during the winter months that the largest number of
bacteria are present in the filtered water, and it is therefore of
especial importance that during this season, when the raw river water
is generally richest in bacterial life, and when, therefore, the
filters are most taxed and the consequences of frost are most to be
apprehended, that those entrusted with this responsible task should be
unremitting in their endeavours to obtain a good filtrate.
That waters submitted to exhaustive natural filtration, such as those
derived from deep wells sunk into the chalk, and usually almost
entirely devoid of bacterial life, may at times become the carriers of
disease has been proved by the disastrous outbreak of typhoid fever
which occurred some years ago at Worthing.
This town has long been supplied with water of the very finest quality
for dietetic purposes, and nothing could have been more unexpected
than this most fatal epidemic. It must, however, be borne in mind that
such deep-well waters are not necessarily immaculate, for in the event
of any fault in the water-bearing strata occurring, the filtration
becomes inefficient, and the water may then, as in the case of
Worthing, be the bearer and disseminator of zymotic disease.
The bacteriological methods for the examination of water, although
when first introduced but a few years ago were lightly looked upon,
and by many opposed, have now become of paramount importance in all
questions of water-purification. The immense mass of evidence of a
purely bacteriological character which was taken, and indeed required
by the Royal Commissioners of 1893 on the London water-supply,
indicates clearly enough the change which has taken place in the
public estimation of the value of these methods; and it is highly
significant that in their report the Commissioners lay stress upon the
importance of extensive storage and efficient filtration, two factors
the meaning and worth of which rest almost entirely on the results of
bacteriological research.
Cholera is not, however, the only water-carried disease which has
borne eloquent testimony to the services rendered by the efficient
purification of public water-supplies. The experience of the State of
Massachusetts in America, in regard to typhoid fever and
drinking-water, is also exceedingly instructive.
Massachusetts has, by creating a Board of Health, and affording the
same every facility for the prosecution of hygienic investigations of
the greatest importance, laid the whole scientific world under a deep
obligation. The reports issued have a very wide circulation, and
embrace a variety of subjects, but second to none in interest and
importance is the account of the experimental work carried out by the
officials of the Board on the purification of water and sewage. These
experiments have become classical, and have been conducted with a zeal
and thoroughness which deserve the highest praise. It is in looking at
the results achieved by the city of Lawrence in regard to its
water-supply that some conception can be obtained of the immense
importance to the community of the scientific experiments conducted in
the State Laboratory. No expense has been spared, and for years past
elaborate and costly experiments on a large scale have been carried
out to determine the most efficient manner in which water may be
rendered fit and safe for drinking.
Now the death-rate in a community from typhoid fever may be taken as
an index of the general sanitary conditions prevailing in such a
community, the character of the public water-supply, not without
justification, being regarded as a prime factor in its determination.
One of the most significant points in the sanitary history of the
State of Massachusetts is the almost uniform decline in the mortality
from typhoid fever in proportion as measures have been taken to
introduce better water-supplies and to improve those which already
exist. Thus in the twenty years, from 1856 to 1876, the death-rate
from this disease was 8·6 per 10,000 of population, whilst in the
period from 1876 to 1895 it had fallen to 4·1 per 10,000, the
improvement in respect of typhoid-mortality being coincident with the
improvement made during the last twenty years in providing public
water-supplies. In the words of one of the State reports, "The
death-rate from typhoid fever has generally fallen as the per cent. of
the population supplied with public water has risen, for the reason
that the majority of the deaths from this disease have occurred among
communities and portions of communities _not supplied with public
water_."
That this improvement is being maintained is seen from the fact that
in the four-year period 1896-99 the deaths from typhoid fever in
Massachusetts were further reduced to 2·6 per 10,000.
It is, however, in the city of Lawrence that the most striking insight
is obtained as to the manner in which typhoid fever may be controlled
by conditions surrounding the water-supply to the community. Thus,
whereas the death-rate from typhoid fever reached a mean of 11·2 per
10,000 in 1886-90, it fell to 7·7 in 1891-95 and to 2·5 in 1896-99. It
was in the autumn of the year 1893 that the raw river-water supplied
to the city from the Merrimac River was first begun to be filtered,
and since that time the sand-filters have been subjected to systematic
and most elaborate bacterial supervision, and improvements have been
constantly introduced so as to secure the most efficient purification
possible of the water before distribution, and the results are
reflected in the marked diminution in typhoid fever which has followed
these strenuous efforts to obtain the best water-supply available.
The splendid example set by the State of Massachusetts, in promoting
the welfare of the people by the encouragement of original researches
in practical hygiene, has stimulated other American States to create
Boards of Health and enact laws for the protection of their rivers and
streams. In view of all that has been done to promote sanitary science
in the United States, it is surprising to learn that Lake Michigan,
which receives the untreated sewage of municipalities and small towns
aggregating over two million people, still furnishes Chicago with its
drinking water, and undergoes no preliminary purification before
distribution. The city of Chicago, by constructing the Chicago
Drainage and Ship Canal, opened in January, 1900, has diverted its own
sewage from Lake Michigan, but this great sewer has only been made
possible because of its advantages as a commercial waterway; and it
has been stated, on high authority, that every project for the
drainage of Chicago into the Illinois which has not recognised the
waterway features has been predestined to failure. Dr. Egan, of the
Illinois State Board of Health, however, points out that "with the
present increase in population the Great Lakes, if they continue to be
used as common sewers, will soon become totally unfit for use as
drinking water, ... and one of two alternatives must be
followed--either every source of water-supply must be filtered, or the
sewage of the towns must be efficiently purified before it is allowed
to flow into the lakes."
Doubtless this seeming inertia of the citizens of Chicago in the
matter of filtering their water is attributable to the fact that
already the authorities have expended eighty-five million dollars in
their waterworks and sewerage systems, which represents an investment
of something over fifty dollars per head of population, and that plans
in connection with the great canal which has been described as "the
greatest feat of sanitary engineering in the world," and to which
reference has already been made, will, when carried out, involve an
expenditure of thirty or forty million dollars more. In the face of
such burdens even so prosperous a community as Chicago does not care
to contemplate further capital charges, at any rate until the
unsatisfactory conditions shadowed by Dr. Egan become more pressing in
regard to the source of their water-supply.
The systematic investigations carried out in the great Institutes of
Health on the Continent and elsewhere should surely make the sporadic
work, as by comparison it must be designated, produced in this country
an eloquent argument for the creation of a British Imperial Board of
Health adequately endowed by the State, manned by the ablest
investigators, and forming a centre for the prosecution of researches
which in other countries, as in our own, have contributed so greatly
to the health and welfare of mankind.
Why should England for ever have to knock at the door of foreign
institutes for information and guidance in matters in which once she
was the leader and enlightened example to every civilised country?
The question of how far polluted water-supplies, besides possessing
the potentiality for spreading cholera and typhoid, may disseminate
consumption, has been approached in a very instructive manner by Dr.
Musehold, of the German Imperial Board of Health.
Some ten years ago the discovery of the tubercle bacillus in water for
the first time was announced by a Spanish investigator, Fernandez. The
water containing the bacillus tuberculosis was derived from an open
ditch, and hence had been doubtless exposed to contamination of divers
kinds.
In the course of the elaborate experiments on London sewage and its
treatment, carried out by Professor Frank Clowes, Chief Chemist to the
London County Council, an instance was recently met with in which a
guinea-pig, inoculated with a portion of coke-deposit derived from a
bacterial sewage bed, died from typical tuberculosis, and sections of
its organs showed the presence of numerous tubercle bacilli. Dr.
Musehold has now submitted the whole question of the vitality of
virulent tubercle bacilli present in the expectorations of consumptive
persons in sewage, in river water, and on cultivated land
respectively, to an exhaustive examination, and the novelty as well as
importance of these researches merit their being carefully considered.
In the first instance tuberculous sputum was introduced into river
water in its natural condition, and as this water was abstracted from
the River Spree, in Berlin, it was exposed at any rate to a certain
degree of surface contamination. In this water, kept in ordinary
daylight, the tubercle bacilli remained alive and in a virulent
condition for over five months; in ordinary sewage for six and a half
months. Some of the sewage-infected samples were left in the open air
and exposed to ordinary meteorological conditions, but even the ordeal
of getting frozen up in their surroundings did not in the slightest
shorten the lease of virulence possessed by the tubercle bacilli. Some
of this tubercle-infected sewage was poured over garden soil in which
radishes were growing, and after the bacilli had spent eighty-eight
days in these surroundings, during which time they had experienced
frost, snow, rain, and sunshine, they still retained their virulence.
Of special interest are the investigations Dr. Musehold made to
ascertain if tubercle bacilli could be detected on the fields attached
to a hospital for consumption and irrigated with the sewage from the
same. Not only were tubercle bacilli found, but they were also, as was
to be expected from the laboratory experiments cited above, discovered
in a highly virulent condition.
That disease germs may be distributed with the vegetables grown on
municipal sewage farms is not a mere whim or fancy of the faddist, but
is a very real danger, and must be regarded as a menace to the health
of all who consume such articles as lettuces, radishes, celery, and
other vegetables which are not first cooked before being placed on the
table.
This forcibly suggests the desirability of all expectorations from
consumptive patients being thoroughly disinfected, or, in other words,
deprived of their virulence before being admitted to sewage.
The importance of such precautions being taken is borne out by the
examinations of the clear effluent derived from the treatment of the
sewage of a consumptive hospital which revealed the presence of
virulent tubercle bacilli, whilst they were also discovered in the
bottom of a ditch conducting the effluent away.
Such facts as these deserve the earnest attention of all public
authorities, and it is to be hoped that the overwhelming evidence
which is now available regarding the distribution and Spartan
character of the tubercle bacillus will lead to serious efforts being
made to bestow upon it that measure of consideration which in the case
of recognised zymotic diseases leads to the enactment of rules and
regulations for the restriction at least of the fateful activities of
these malignant foes of mankind.
Before leaving the subject of bacteria in relation to water, it will
be interesting to glance at what is known regarding the attitude taken
up by these minute forms of life towards that large and
ever-increasing class of waters vaguely grouped together under the
synonym of mineral waters. The fortunes made in manufacturing
artificially aërated waters and the mine of wealth contained in a new
mineral spring are sufficient evidence of the popularity enjoyed by
this description of beverage. The beer and spirit statistics of the
country and their contributions to the national revenue do not,
however, permit us to indulge in the belief that this large
consumption of harmless drinks is due to their displacing the use of
intoxicants--the increasing sale of non-alcoholic beverages cannot in
fact be taken as an index of the growing sobriety of a nation; far
more must the greater demand be attributed to the improvements in
manufacture which have cheapened production and placed what was
formerly an article of luxury almost prohibitive in price, and hence
reserved for the few, within comparatively easy reach of the many.
Perhaps also an increased sale may be assisted by a prevailing
impression that by substituting carbonated for ordinary potable water,
the risk of contracting zymotic disease is, if not altogether removed,
at any rate very materially diminished.
It will be therefore instructive to see how far this assumption is
justified by actual facts.
The first fact to be recognised is that the number of bacteria present
may and does fluctuate between such wide limits as is represented by
as few as three, and as many as 100,000 being found in about twenty
drops of artificially aërated waters. Seltzer water, manufactured from
well water, was found by Sohnke to contain numbers varying from 200 to
6,000, whilst when only distilled water was used, _i.e._ water
previously deprived of all bacterial life, only from ten to thirty
microbes were present. But an important and far too little recognised
factor in the manufacture of aërated waters is the contamination which
so frequently takes place subsequent to the initial purification of
the water by sterilisation. In some instances this contamination is
due to the storing of water before use in reservoirs, where an
excellent opportunity is offered for microbial multiplication.
Merkel found water which originally only boasted of from four to five
bacteria per cubic centimetre, subsequently, when ready for
distribution as seltzer water, contained considerably over 3,000. In
this case storage had been resorted to. Again, insufficient importance
is attached to the efficient cleansing of the syphons on their return
to the factory. The experiments made by Slater in this country and
Abba in Italy have conclusively shown that the gaseous aëration of
water exerts an inhibitory action on the growth of at least some
varieties of water bacteria, for both these investigators found that
in proportion as the amount of gas present was diminished by being
allowed to escape, so was the multiplication of the bacteria present
promoted and their numbers increased. Unsavoury as may be the idea of
swallowing down myriads of even harmless microbes, yet the real
significance of the whole question from a hygienic point of view lies
in the evidence as to the fate of disease germs in aërated waters.
On this important matter there fortunately exists some precise and
conclusive information in regard to the bacteria associated with two
essentially water-borne diseases, _i.e._ typhoid fever and cholera.
The investigations made to test the vitality of the anthrax bacillus
are of significance as again emphasising the superior degree of
vitality possessed by the spore over the bacillar form of this
micro-organism, but the chances of this disease being disseminated by
water are usually regarded as too remote to excite much interest in
the fate of the _b. anthracis_ in seltzer water. It may, however, be
mentioned that whereas the bacilli succumbed after being in the
seltzer water from fifteen minutes to an hour, the spores were still
living after one hundred and fifty-four days. Investigations on the
vitality of cholera bacilli in aërated waters have been made by
Hochstetter in Germany, by Slater in England, and by Abba in Italy,
and these various authorities all agree that the lease of life of
these micro-organisms is a very short one in ordinary unsterilised
carbonated waters, and that they are in fact destroyed in from half an
hour to three hours. As regards typhoid bacilli the case is different,
for the same investigators found that in ordinary unsterilised aërated
water these bacteria can live as long as eleven days. In seltzer water
their vitality is not so marked, but even then it greatly exceeds that
of the accommodating cholera microbes, extending to five days.
Thus supposing typhoid bacilli to be present in the water employed for
the manufacture of aërated waters--and we cannot afford to disregard
such a possibility--we have no guarantee that such waters will be safe
for drinking purposes unless a considerable period has been allowed to
elapse between their production and consumption.
It was considerations of this kind which led M. Duclaux, the
accomplished director of the Paris Pasteur Institute, to write now
some years ago: "Contentons-nous de conclure que l'usage de l'eau de
seltz, recommandé en temps d'épidémie peut en effet être
recommandable, surtout si on laisse vieillir l'eau quelques jours. On
a chance d'y voir diminuer ou même périr les germes nuisibles."
On the whole, therefore, the scientific report on bacteria and
artificially aërated waters may be regarded as a reassuring one. It is
to be regretted, however, that in England we do not follow the example
set by Italy, where the aërated water manufacturers are closely looked
after by the State, and no factory may be opened unless a satisfactory
guarantee can be given of the chemical and bacteriological purity of
the water which is intended to be used, whilst the authorities must
also be assured that the methods employed are satisfactory from a
hygienic point of view. The sale of all aërated waters prepared from
insanitary water-supplies is strictly prohibited by the State.
It will now be of interest to ascertain what is the result of the
endeavours which have been made to explore the bacterial flora of
those highly prized and largely circulated natural mineral waters,
which abound in so many parts of the world and are practically the
making of so many health resorts.
Perhaps the most exhaustive examinations of mineral water which have
been so far made are those published by Dr. Eugenio Fazio, who studied
the bacterial condition of some of the celebrated springs situated
near Naples at Castellamare, Telese, Acetosella, and Muraglione, care
being taken to select examples of different types of water, samples
being collected from chalybeate, carbonated sulphur, and alkaline
springs respectively.
All these various mineral waters were characterised by a remarkable
paucity of bacteria; in the chalybeate and alkaline springs sometimes
as few as two microbes only in a cubic centimetre were found, and the
largest number recorded only amounted to forty-five. The satisfactory
significance of such figures will be appreciated when we realise that
they rival very closely the numbers which characterise the purest
spring and the deepest well water, and which are usually regarded as
the aristocracy among drinking-waters. Of special interest is Dr.
Fazio's discovery that the variety of bacteria present in these waters
is extremely restricted, as a rule only three, or at most four,
different kinds of bacteria being detected.
This is also characteristic of the pure water derived from deep wells
sunk into the chalk, usually but very few different kinds of bacteria
being found amongst the limited number of their Lilliputian
inhabitants, whilst in samples collected from rivers or other surface
sources, especially those which have been polluted with sewage or
similar refuse matters, the bacterial population is frequently as
diverse as it is unwieldy.
From the exacting point of view of the uncompromising bacteriologist
the most satisfactory waters in existence for drinking purposes should
be those derived from sulphur springs. Dr. Fazio and other
investigators have frequently found absolutely no bacteria whatever in
these waters, and often only four in a cubic centimetre. When we
remember the high temperature of so-called thermal sulphur waters,
which in many cases reaches more than fifty degrees Centigrade, it is
perhaps surprising that even four individuals can be found in a cubic
centimetre capable of withstanding the nauseous atmosphere of
sulphuretted hydrogen in addition to such hot environment. Perhaps in
the bacterial community these hot sulphur springs provide that place
of punishment which figured so largely in the imagination of the early
Christian fathers; certain it is that in this bacterial hell, in the
picturing of which so many of the old masters seem to have revelled,
but very few individuals are to be found, and those which are there
are almost entirely derived from one family.
In giving weight to the highly satisfactory results of these bacterial
examinations in forming an estimate of the microbial quality of
natural mineral waters, it must be borne in mind that these
investigations were all made of the said waters in a state of nature
straight from the source, and before they had undergone the barbarous
ordeal of commercial manipulation such as the process of bottling.
We are all of us sufficiently acquainted with the first principles of
germ life to realise how deftly and how directly any inattention to
hygienic details is reflected in the larder or the store-room; and it
requires but little stretch of the imagination to picture the
bacterial armaments which would at once invade these peaceful waters
on the first suggestion of relaxed vigilance, or removal of that rigid
surveillance so essential for their protection and preservation.
MILK DANGERS AND REMEDIES
It may with justice be said that in no department of applied
bacteriology is more activity apparent than in that which has for its
object the building up of a scientific basis for dairy practice.
Although this is undoubtedly true, yet, unfortunately, unlike its
continental neighbours, the British public, with whom practically
rests the control of our dairy industries, has hitherto held itself
strangely aloof, evincing little or no sympathy in researches which,
even if they fail to interest, should surely impress with a sense of
the great hygienic importance attaching to them. But this apathy is
not only to be deprecated in the interests of health, but also on
economic grounds.
We have only to turn to the reports issued by the Board of Agriculture
to realise what this characteristic British apathy has brought about
in the dairy industry of this country. Thus in the year 1898 we are
officially informed that we imported 359,425,136 pounds of butter, the
little country of Denmark alone sending over to us 163,883,360 pounds!
Our cheese imports reached the enormous total of 262,018,624 pounds,
whilst 817,274 cwts. of condensed milk and 10,691 of milk and cream
were supplied to us from without.
If we glance at the energy and enthusiasm displayed by other
countries, and notably Denmark, in the prosecution and scientific
development of the dairy industry, we shall not wonder at the high
standard of excellence achieved, or at the readiness displayed by
Great Britain to absorb their produce. Thus, whilst in England it may
be questioned whether in a single dairy the artificial souring of
cream by pure cultures of bacteria is carried out, in Denmark the use
of so-called special bacterial butter-starters is rapidly gaining
ground. Thus, whereas in 1888 at the Odense Exhibition not a single
sample of butter was exhibited in which pure bacterial cultures had
been employed, in 1894, 46·7 per cent. of the samples shown were thus
produced, in 1896, 89·2 per cent., in 1897, 94·4 per cent., 1898, 95·9
per cent, and in 1899, _every sample_, and since this year nearly
every dairy of importance in the country employs special bacterial
butter-starters.
The Danes are enlightened and shrewd enough to realise that in order
to retain their existing markets and acquire fresh ones, it is
necessary to take advantage of every improvement in methods of
manufacture which scientific research has placed at their disposal,
and their reward is justly reaped in the prosperity of their dairy
industry and the high reputation enjoyed by their produce. If we
contrast the adaptability and elasticity of the continental mind in
regard to new discoveries with the crude conservatism of the British
manufacturer, then, indeed, is the success of our rivals and
corresponding decline of our own prosperity most perfectly
intelligible.
Again, we are informed that the recent visit to London of a deputation
representing Russian agricultural interests is already bearing fruit,
and contracts have been signed for the regular importation of large
quantities of Russian dairy produce. The English market is already
well supplied with Russian eggs, but an opening has now been found
here for the disposal of Russian butter and cheese.
Finland, again, the total population of which is less than half that
of London, exports to this country no less than 12 million marks'
worth of butter annually.
As a writer recently put it: "Foreigners and colonists have captured
our butter markets; if the consumption of milk sterilised in bottles
becomes the fashion, they will likewise capture our milk markets." And
this is no fanciful suggestion, for whilst the production of
Pasteurised milk does not involve any considerable outlay in
apparatus, its transport may be effected with the greatest ease.
Indeed, frozen milk has been introduced into England from Norway and
Sweden. It is first Pasteurised, then frozen in large wooden boxes,
and shipped in the congealed condition, in which state it remains
unchanged for a long period of time.
But it is undoubtedly with the public that the responsibility really
rests, for as long as it does not care to create the demand for
Pasteurised dairy products all the efforts of enlightened agricultural
authorities in this country must inevitably end in failure.
On the Continent and in America dairy-bacteriology, as already pointed
out, has made enormous strides, and has practically revolutionised the
conduct of dairy work; and if we could but rouse ourselves from our
lethargy we likewise should be able not only to boast of progress, but
also to better hold our own ground in this important branch of
agriculture; and one result would be that dairy troubles, which for so
long have been accepted as more or less necessary evils, would yield
here, as they have done elsewhere, to a more rigid attention to
details, the significance of which scientific research has so
successfully shown.
Some of the most easily preventable, but at the same time most
aggressively assertive, dairy troubles are undoubtedly directly
dependent upon the conduct of milking operations.
In the first place, the cow itself is only too frequently in an
uncleanly condition, and as its coat offers exceptional facilities for
the harbouring of dust and dirt, the danger of foreign particles
falling into the milk is always present unless precautions are taken
to negative, or at least minimise, all such chances of contamination.
Professor H. L. Russell, of the Wisconsin Agricultural Experiment
Station, cites in his little volume on _Dairy Bacteriology_ an
instructive experiment which brings home very forcibly the importance
of such precautions. A cow pastured in a meadow was selected for the
experiment, and the milking was done out of doors, so as to eliminate
as far as possible any intrusion of disturbing foreign factors into
the experiment, such as the access of microbes from the air in the
milking-shed. The cow was first partially milked without any
precautions whatever being taken, and during the process a small glass
dish containing a layer of sterile nutrient gelatine was exposed for
one minute beneath the animal's body, in close proximity to the
milk-pail. The milking was then interrupted, and before being resumed
the udder, flank, and legs of the animal were thoroughly cleansed with
water; a second gelatine surface was then exposed in the same place
and for the same length of time. The results of these two experiments
are very instructive. When the cow was milked without any special
precautions being taken, 3,250 bacteria were deposited per minute on
an area equal to the surface of a ten-inch milk-pail; after, however,
the animal had been cleansed, only 115 bacteria were deposited per
minute on the same area.
Thus a large number of organisms can, by very simple precautions and
very little extra trouble, be effectually prevented from obtaining
access to milk. Even in the event of the milk being subsequently
Pasteurised, clean milking is of very great importance; but still more
imperative is it when it is destined for consumption in its raw,
uncooked condition. If we consider how cows become covered with dirt
and slime, that obstinately adhere to them when they wade through
stagnant ponds and mud, and realise the chance thus afforded for
malevolent microbes to exchange their unsavoury surroundings for so
satisfactory and nourishing a material as milk, then indeed
precautions of cleanliness, however troublesome, will not appear
superfluous.
That a very real relationship does exist between the bacterial and
dirt contents of milk has been clearly shown by actual investigation.
A German scientist has made a special study of the subject, and has
determined in a large number of milk samples the amount of foreign
impurities present per litre, and the accompanying bacterial
population per cubic centimetre.
The following results may be taken as typical of those obtained: in
milk containing 36·8 milligrammes of dirt per quart as many as
12,897,600 bacteria were present per cubic centimetre; in cleaner
samples, with 20·7 milligrammes of dirt per quart, the number of
bacteria fell to 7,079,820; whilst in a still more satisfactory
sample, containing 5·2 milligrammes of dirt per quart, there were
3,338,775 bacteria per cubic centimetre.
Such results indicate how important a factor is scrupulous cleanliness
in milking operations in determining the initial purity of milk, for
there is no doubt that bacterial impurities in milk are in the first
instance, to a very great extent, controlled by the solid impurities
present.
I do not know of any determinations which have been made of the actual
amount of such solid impurities present in our public milk-supplies,
but such estimations have been made in many of those belonging to
large cities in Germany. Thus, Professor Renk found in a litre of milk
supplied to Halle about 75 milligrammes, whilst in another sample as
much as 0·362 grammes per litre were detected. In Berlin 10
milligrammes, and in Munich 9 milligrammes per litre, were found. Dr.
Backhaus has estimated that the city of Berlin alone consumes daily
with its milk no less than 300 cwt. of cow-dung. If we associate these
amounts of solid impurities with their consequent bacterial
impurities, then we shall obtain some idea of what the microbial
population of these milk-supplies may amount to.
These impurities are almost wholly preventable, but, unfortunately,
but little importance is apparently attached to their presence in milk
as a rule by dairymen.
In a letter published in the _Sussex Daily News_ a correspondent and
well-known authority on dairy matters sounds a timely note of warning
to our dairy managers:--
"I happen to know," he writes, "for a fact that Americans who
visited one of our Dairy Shows at Islington were so disgusted at
the method--or rather lack of cleanly method--exhibited there as
our ordinary way of milking cows, that these visitors stated that
nothing would induce them to drink milk while in England. I
mention this circumstance so as to bring home to the minds of
English dairy-farmers who may read this letter how very backward
we are in this country as compared with more studious and careful
foreign competitors. It is insisted upon by our foreign teachers
that our cow-stalls are too short and not roomy enough, and our
cow-houses badly constructed; that we do not (1) groom our cows or
(2) clean the teats, nor (3) sponge their udders, bellies, and
sides before milking with clean, tepid water; (4) that the milkers
do not tie up the cow's tail nor clean their own hands and
persons, nor (5) cover their clothes with a clean, well-aired
blouse during milking; that (6) they generally milk in a foul
atmosphere (bacterially), tainted with the odour of dung, brewer's
grains, or farmyard refuse. I am sorry to state that there is too
much solid fact about the contentions which, based upon
bacteriology, are given as causes of injury to quality....
Cleanliness is now a matter requiring the primary attention of
English dairy-farmers. The study of bacteria proves that such
inattention is greatly the cause of foreign butters beating ours."
It follows as a natural sequence that all the cans and vessels used
for dairy purposes should be absolutely beyond suspicion of
contamination. Professor Russell has shown by actual experiment that,
even where the vessels are in good condition and fairly well cleaned,
the milk has a very different bacterial population when collected in
them and in vessels _sterilised by steam_.
Two covered cans were taken, one of which had been cleaned in the
ordinary way, and the other sterilised by steam for half an hour.
Previous to milking the animal was carefully cleaned, and special
precautions were taken to avoid raising dust, whilst the first milk,
always rife with bacteria, was rejected. Directly after milking
bacterial gelatine-plates were respectively prepared from the milk in
these two pails, with the following results: In one cubic centimetre
of milk taken from the sterilised pail there were 165 bacteria; in
that taken from the ordinary pail as many as 4,265 were found.
Another experiment illustrates perhaps even more strikingly the effect
of cleanly operations in milking upon the initial bacterial contents
of milk. The preliminary precautionary measures were carried out by an
ordinary workman, and are in no sense so refined as to be beyond the
reach of ordinary daily practice. "The milk was received in steamed
pails, the udder of the animal, before milking, was thoroughly carded,
and then moistened with water, so as to prevent dislodgment of dirt.
Care was taken that the barn air was free from dust, and in milking
the first few streams of milk were rejected. The milk from a cow
treated in this way contained 330 bacteria per cubic centimetre, while
that of the mixed herd, taken under the usual conditions, contained
15,500 in the same volume. The experiment was repeated under winter
conditions, at which time the mixed milk showed 7,600 bacteria per
cubic centimetre, while the carefully secured milk only had 210 in the
same volume. In each of these instances the milk secured with greater
care remained sweet over twenty-four hours longer than the ordinary
milk."
An organism which has exceptional opportunities for finding its way
into cows' milk is the _Bacillus coli communis_, normally present in
the fæces of all animals. This microbe is a very undesirable adjunct
to milk, and may greatly interfere with the souring process, by
multiplying extensively, and so producing a change in the milk which
renders it impossible for the particular souring bacteria to carry on
their work, resulting in their collapse and ultimate extinction. But
this is not the only injurious effect which these Coli bacilli can
produce in milk, for there is a growing conviction that their presence
is responsible for many intestinal disturbances with which young
children are specially troubled. Quite recently determinations of the
bacterial contents of cow-dung have been made, and it has been
ascertained that _a single gramme_,[6] freshly collected, of this
material may contain as many as 375,000,000 bacteria, of which the
majority were found to be the above undesirable organism, the _B. coli
communis_.
[6] One gramme = 15 grains.
Milk may also contain bacteria characterised by their remarkable
resistance to heat, which is due to their possessing what is known as
the hardy spore in addition to the ordinary rod form. The numbers in
which they are present in milk varies with different samples; but they
may be taken as a sort of index as to the care observed in milking,
for they are always present in great quantity in uncleanly-collected
milk. Careful studies have been made of this class of milk bacteria by
Professor Flügge and others, and it has been found that when added to
milk upon which puppies were subsequently fed the latter succumbed
under symptoms of violent diarrhoea.
The danger of even a few bacteria gaining access to milk is serious,
on account of the fabulous rapidity with which they multiply when they
find themselves in such congenial surroundings. Professor Freudenreich
has made very exhaustive investigations to show how milk microbes may
multiply in the time which elapses between milking and the receipt of
the milk by the consumer. The following example will convey some
notion of what bacterial propagation under these circumstances is
capable of.
The sample of milk in question was found to possess on reaching the
laboratory, two and a half hours after milking, a little over 9,000
bacteria in a cubic centimetre. The sample was divided into three
portions, which were kept at different temperatures, and after
definite intervals of time they were examined. The following table
shows at a glance the results obtained:--
NUMBER OF BACTERIA IN ABOUT TWENTY DROPS OF MILK.
+-----------------+---------------------------------------+
| | Temperature. |
| When Examined. +------------+-------------+------------+
| | 15° C. | 25° C. | 35° C. |
+-----------------+------------+-------------+------------+
| After 3 hours | 10,000 | 18,000 | 30,000 |
| After 6 hours | 25,000 | 172,000 | 12,000,000 |
| After 9 hours | 46,000 | 1,000,000 | 35,280,000 |
| After 24 hours | 5,700,000 | 577,500,000 | 50,000,000 |
+-----------------+------------+-------------+------------+
Thus, after being kept in the laboratory for three hours the original
9,000 bacteria had in one case doubled, and in another more than
trebled themselves. It will be seen that the temperature most
favourable to the multiplication of these bacteria was 25 degrees
Centigrade.
If a sample of milk containing originally such a comparatively small
number of bacteria--for a figure under 10,000 per cubic centimetre
sinks into utter insignificance when we read of samples containing
2,500,000--if such relatively bacterially pure samples may support
such prodigious numbers of these Lilliputians, what the microbial
population of less satisfactory samples may amount to well-nigh
baffles our powers of calculation. Professor Russell writes: "If we
compare the bacterial flora of milk with that of sewage, a fluid that
is popularly, and rightly, supposed to be teeming with germ life, it
will almost always be observed that milk when it is consumed is richer
in bacteria by far than the sewage of our large cities. Sedgwick, in
his Report to the Massachusetts Board of Health for 1890, found that
the sewage of the city of Lawrence contained at the lowest 100,000
germs, whilst the maximum number was less than 4,000,000 per cubic
centimetre.[7] This range in numbers is much less than is usually
found in the milk-supply of our large cities."
[7] American sewage, it must be noted, is usually weaker and
poorer in bacterial life than that of our country, by reason
of the greater amount of water with which it is diluted.
Numerous researches have been carried out during the last half-dozen
years to try and localise the origin of some of the principal dairy
troubles, with a view to their possible extinction, or at least
control. In the course of these investigations quite a number of the
bacteria found in milk have been successfully hunted down, and their
offences brought home to them.
Thus, from so-called "bitter" milk a bacillus has been isolated by
Professor Weigmann, and found responsible for this particular change.
Another microbe was discovered in bitter cream whose office apparently
consisted in rendering milk strongly acid and extremely bitter. Again,
that objectionable condition of milk known as slimy, ropy, or stringy,
is brought about by certain bacteria which render it viscous; whilst
another crop of microbes are occupied in conferring upon it the power
of sticking to everything that touches it, making it capable of being
drawn out into threads from several inches to several feet in length.
Although we object in this country to slimy milk, in Holland it is in
special request for the production of a certain cheese known under the
name of Edam. In Norway this kind of milk forms a popular drink called
Taettemjolk, and to produce it artificially they put the leaves of the
common butter-wort (_Pinguicula vulgaris_) into milk. Professor
Weigmann has discovered a micro-organism which frequents the leaves of
this plant endowed with particular powers of producing slimy milk, and
doubtless the credit of furnishing Taettemjolk is really due to this
microbe, and not to the innocent butter-wort. "Soapy" milk, again, has
been traced to a specific germ discovered in large numbers in straw
used for bedding, whilst it was also detected in the hay that served
for fodder. During milking these sources had supplied the infection,
and the peculiar fermentation was distinctly shown to be microbial in
origin. So-called red and blue milk, and those various hues ranging
from bright lemon to orange and amber, are also now known to be
directly attributable to bacterial activity.
But of even greater significance than all these bacterial dairy
troubles is the risk of spreading disease which is furnished by milk
contaminated with pathogenic micro-organisms.
"There can be no shadow of doubt," said the _Lancet_ now many years
ago, "that the contagia of typhoid and scarlet fever are disseminated
by milk, and that boiled milk enjoys a much greater immunity from the
chance of conveying disease."
This was written at a time when the study of bacteria was yet in its
infancy, and before any direct experimental evidence had been obtained
on the behaviour of microbes in milk or concerning the part played by
them in the dissemination of disease. The writer evidently did not
venture to cast further aspersions on the character of milk, or he
might have included diphtheria amongst the diseases which can be
spread by its means; but there is another omission which still more
conclusively indicates the remote age in the history of bacterial
science at which this correspondent to the _Lancet_ wrote, and that is
the absence of all reference to the tubercle bacillus in relation to
milk. At the present day hardly a bacteriological journal is published
which does not contain some reference to the question of tuberculosis
and milk, and the transmissibility of this disease when present in
cattle to man.
As regards the dissemination of various zymotic diseases by milk, the
evidence which has been collected points very conclusively to the
responsible part which may be played by milk in this connection. Many
instances have been cited, also, of the culpability of milk in
distributing typhoid germs. A striking case which occurs to me, and
which may be mentioned in passing, is one which occurred in a city in
America a few years ago, in which an outbreak of this disease was
traced to a dairy in which the vessels had been washed out with
typhoidal-polluted water. No less than 386 cases of typhoid declared
themselves in six weeks, and of this number over 97 per cent. occurred
amongst families obtaining their milk from the same dairy. A careful
inspection revealed the fact that the milk-cans had been rinsed out
with water from a shallow well contaminated with typhoid dejecta.
Diphtheria is also justly associated with infected milk, and if we
take into consideration the now established fact that diphtheria
bacilli thrive and multiply with particular facility in milk, even
more so than in ordinary broth cultures; that they have been found in
air in a vital and virulent condition, and may be scattered far and
wide attached to dust particles; and if we remember the numerous
opportunities offered for the infection of milk by persons handling
it, who either themselves are suffering from this disease or are in
diphtheria surroundings--then indeed we can readily understand how
milk becomes a diphtheria-carrier of the first order.
Tuberculosis in cattle, and how this disease may affect the character
of dairy produce, is, as already pointed out, a subject which is
attracting the attention of a large number of investigators.
The general public is perhaps hardly aware of how widespread this
disease is amongst cattle, and it is only of late years that very
careful inquiries have elicited the fact that it is not only very
extensively distributed, but may be present in animals to all outward
appearance in perfect health.
In Germany it was asserted a few years ago that every fifth cow was
tuberculous, and even this was regarded as a moderate estimate. The
distinguished Danish pathologist, Professor Bang, is responsible for
the announcement that during the years 1891-3 17·7 per cent. of the
animals slaughtered in Copenhagen were infected with tuberculosis. In
Paris we have been told that, of every thirteen samples of milk sold,
one was infected with tubercle bacilli, whilst in Washington one in
every nineteen samples of milk was stated to be similarly tainted.
The existence of tubercular disease in cows, and its transmission to
other animals fed with their milk, has been brought out in a striking
manner in investigations published by the Massachusetts Society for
the Promotion of Agriculture. In one case as many as over 33 per cent.
of the calves fed with milk from tuberculous cows succumbed to the
same disease. According to Hirschberger, 10 per cent. of the cows
living in the neighbourhood of towns where the conditions of their
environment are not generally the most satisfactory or conducive to
health suffer from tuberculosis, and 50 per cent. of these animals
yield milk containing tubercle bacilli.
The demand which is being made by municipal authorities to be invested
with the power of inspecting the country farms from whence their
cities are supplied with milk and other agricultural produce could not
have received stronger support than was recently supplied by a case
tried in Edinburgh, and as this is only a sample of what is doubtless
a daily, although undetected occurrence in many municipalities, it
will not be out of place to quote the following from the published
report of the proceedings:--
"A cow was brought into the city for sale as food, and the
evidence showed it to be in the last stages of tubercular disease.
'Its head was hanging down; it breathed with difficulty, and it
had frequent fits of coughing; while its udder was swollen with
the disease.' All the organs were diseased, and the milk teemed
with bacilli. Yet, it seemed, the milk from this animal had been
regularly sent into Edinburgh for sale. In face of facts like
these, it is difficult to see on what grounds the claim of towns
to inspect country dairies doing a town business can be resisted.
At least the towns should have the power to refuse admission to
milk from sources not open to inspection. It is not enough for the
county authorities to say that they inspect the dairies in their
own areas. In this case the condition of the animal was only found
out when it was brought into the town to be sold for food."
Further comment is unnecessary!
Some German investigators have discovered the interesting fact that
the centrifugal method of separating milk not only has a remarkable
effect upon its bacterial contents, but also upon tubercle bacilli
when present. On examining the so-called "separator slime," it is
found to contain not only large quantities of solid matters, but also
masses of bacteria which have been thrown out during the operation.
This method of treating milk has, curiously, a particular effect upon
tubercle bacilli present, for Professor Scheurlen has found that they
are nearly all left in the slime. Naturally his observation was not
slow in being tested by other investigators; but Professor Bang has
quite independently confirmed Scheurlen's discovery, and, still more
recently, Moore purposely infected milk with these bacilli, and found
that they were deposited in the slime to a most remarkable extent.
Coupled, however, with this peculiar behaviour of tubercle bacilli in
separated milk is the fact called attention to by Ostertag, that
tuberculosis is much more prevalent among swine in Denmark and North
Germany, where the centrifugal process in creaming is extensively
used, and where, until recently, this slime was given to the animals
in its raw, uncooked condition.
Before leaving this subject of separated milk, reference may be made
to a danger, which has recently been publicly called attention to,
surrounding the use which is made of skim milk. By an arrangement with
the farmers who supply the milk, those clients who principally use it
for producing butter return the skim milk to them after it has been
through the separator, when it is employed for stock-feeding purposes.
The milk in large dairies derived from different farmers is mixed, and
hence the skim milk which is returned is also mixed. Thus, in the
event of the milk from one farm being infected, not only is the whole
milk-supply of a particular dairy infected, but, in returning the
mixed skim milk likewise infected in its proper proportion to the
different farmers, the virus is distributed over several farms. So
real is this danger, and such unfortunate results have followed this
practice of returning mixed infected skim milk, that since 1894 the
Prussian Government has issued special orders for its disinfection by
means of heat, in the hope of coping with this difficulty.
The longevity of the tubercle bacillus and its remarkable vitality
under all kinds of untoward circumstances have not unnaturally added
fresh significance to this frequent discovery of its presence in milk;
moreover, laboratory experiments have shown that these germs can live
for upwards of one hundred and twenty days in butter, and from sixty
to seventy days in cheese. It is not surprising, therefore, to find a
Royal Commission appointed in 1890 with the express object of
inquiring and reporting upon "What is the effect, if any, of food
derived from tuberculous animals on human health?"
In the summary appended to the report we read: "Tuberculous matter in
milk is exceptionally active in its operation upon animals fed either
with milk or with dairy produce derived from it. No doubt the largest
part of the tuberculosis which man obtains through his food is by
means of milk containing tuberculous matter."
That the Commissioners were alive to the great importance of this
means of spreading disease is further shown by the following
significant paragraph: "In regard to milk, we are aware of the
preference by English people for drinking cow's milk raw, a practice
attended by danger on account of possible contamination by pathogenic
organisms."
The Commissioners spared no pains in endeavouring to throw light upon
the important question they were appointed to report upon, and five
years elapsed before they published the results of their inquiries. A
decade ago the opinions expressed by them represented the current
opinions of the leading bacteriological authorities in scientific
circles at home and abroad, and these opinions were gradually
filtering down to the general public, which is so conservative in
clinging to traditions and popular delusions, when, like a flash out
of the blue, the bacteriological Jove, Professor Robert Koch, hurled
his thunderbolt into the arena, and at the British Congress on
Consumption, held in London in the summer of 1901, declared his belief
that bovine and human tuberculosis were distinct diseases. The
significance of such a challenge to current scientific opinion, and
its far-reaching influence if proved to be correct, was quickly
appreciated by the distinguished audience who had gathered to hear
what so great an authority as Dr. Robert Koch had to say on
consumption and its distribution. The vital question raised by the
original discoverer of the tubercle bacillus is still the subject of
discussion, experimental inquiry, and much controversy, and we cannot
here attempt to discuss the _pros_ and _cons_ for the acceptance or
rejection of this new theory concerning the character of tuberculosis.
It would, however, be regrettable in the extreme if the publication of
this opinion were to encourage dairy authorities to relax in the
slightest the efforts now so tardily being made by them to protect
their dairy produce and ensure its safety for food-supply.
Before leaving this branch of the subject reference must be made to
some very important researches recently published by Professor
Ostertag, of Berlin, on the presence of tubercle bacilli in the milk
derived from cows which, whilst reacting to the tuberculin test,
exhibit no _clinical_ symptoms of tuberculosis. The importance of
this investigation to farmers and all breeders of stock is evident,
for it has not infrequently been urged that all the milk from such
tuberculin-reacting cows should be discarded for dietetic purposes.
Professor Ostertag, at the request of the German Government, has
carried out a most elaborate and very extensive series of
investigations to determine the question as to whether such milk is
dangerous to health. I cannot do better than quote the conclusions
appended to the original memoir, in which Professor Ostertag expresses
himself as follows: "The milk of cows which only react to tuberculin
does not contain tubercle bacilli; calves and pigs can be fed during
weeks and months with milk derived from such cows without contracting
tuberculosis."
A very important rider, however, is added, in which it is pointed out
that inasmuch as no doubt exists as to the highly infectious character
of the milk derived from cows the _udders of which are tuberculous,
and from animals in which the disease is clinically recognisable_, the
weeding out of all such animals must be regarded as the most important
measure for the prevention of the dissemination of tuberculosis
through milk.
We must now pass on to a consideration of some of the methods which
are available for obtaining germ-free milk, some of which are,
however, attended with too great labour and inconvenience to admit of
practical application. Thus, wishing to prepare some sterile milk
without altering its chemical composition to feed certain microbes
with, I had to patiently heat it for from one to two hours on five
successive days, watching the while that the temperature remained
between 58° and 65° centigrade. The milk was sterile, and I kept it
for months, but such a process, of course, is impossible for domestic
purposes.
The addition of chemicals to milk is both undesirable and ineffectual;
amongst such substances boracic acid, borax, and salicylic acid are
employed, but whilst the two former have been found to produce but
little effect upon disease germs present in milk, salicylic acid
hinders curdling more than other substances, and even if added in the
small proportion of twelve grains per quart is said to impart a taste
to the milk, and is, moreover, incapable of destroying typhoid bacilli
if present.
Authorities are, moreover, not agreed as to the harmlessness of this
ingredient, and in France the employment of salicylic acid in the
preservation of food is strenuously opposed by doctors, who consider
its habitual use injurious to health.
A Departmental Committee of the Local Government Board was appointed
in this country to inquire into the use of preservatives in foods.
In their report they state that from 42 up to 126 grains of boracic
acid were detected in milk offered for sale, and that on one occasion
no less than 80 grains of this material were present in a pint of
milk sold to their inspector. It is pointed out that as long as
preservatives are permitted there is no guarantee against the addition
of excessive amounts to milk, and that evidence has been obtained
pointing to an injurious effect of boracised milk upon the health
of young children. The Committee report that in Denmark the use of
preservatives is strictly prohibited, and the prohibition is strongly
enforced; neither are preservatives permitted in Belgium.
The application of heat to milk is, in fact, the only advisable and
reliable method for rendering it free from germs, but a great deal
depends upon the manner in which the heat is applied and the cleanly
condition or otherwise of the milk employed.
The difficulties which have to be overcome in producing efficiently
sterilised milk are due, in the first place, to the remarkable power
of resisting heat which characterises not only some disease germs, but
also some of the microbes which are particularly partial to milk;
secondly, to the sensitiveness of milk to heat, as exhibited by its
alteration in taste and other respects through exposure to high
temperatures.
To overcome these difficulties many ingenious pieces of apparatus have
been devised, based upon a process originally introduced by Pasteur
for preventing certain defects in wine and beer, and which consists in
the application of a temperature of about 60° Centigrade. This process
is known as Pasteurisation, after its renowned initiator.
So-called "Pasteurised" milk has become during the last year or so
increasingly popular in this country, whilst on the Continent it has
been largely dealt in for several years past, and has commercially
proved a great success. Indeed, so strong is the prejudice amongst our
neighbours across the Channel against using unboiled milk that in
Leipzig and other cities in Germany endeavours have been made by
charitable and other societies to encourage the use of sterile milk
amongst the poorer classes, whilst it has been stated that the
introduction of Pasteurised milk among the poor of New York City,
through the philanthropic efforts of Mr. Nathan Straus, has done much
to reduce the high rate of mortality amongst infants during the hot
summer months. In France, _i.e._ in Paris and Grenoble, in order to
reduce if possible the lamentable mortality amongst infants from
diarrhoea in the summer months, which was largely attributed to the
use of unboiled milk, sterilised milk was distributed to the poor at
the cost of the community in general. In Grenoble, according to
statistics collected by Berlioz during the years 1894-6, the
death-rate of infants under a year old in the months of July, August,
and September fed on raw milk reached 69·3 per 1,000, whilst amongst
those supplied with sterilised milk it was reduced to 27·9 per 1,000.
Just, however, as all is not gold that glitters, so all sterilised
milk so-called is not necessarily free from bacteria. Indeed,
according to a recent German authority, "the complete and certain
sterilisation of milk is not yet to hand."
Dr. Weber examined the sterilised milk as supplied by various
companies in the city of Berlin. As many as 150 bottles were tested
from eight different sources, with the result that not one of these
eight companies was found to be supplying milk free from bacteria, or,
in other words, what it professed to be--sterile. True, the percentage
of sterile bottles varied from 5 per cent. in some of the supplies to
86 per cent. in others.
Thus it may be realised how, as has been already pointed out,
difficult a matter it is to devise an efficient apparatus for the
reliable sterilisation of milk. So far it appears that the best
results have been obtained with an apparatus devised by Flaack, a
director of the Brunswick Sterilising Milk Company, and known as the
Flaack apparatus. Exhaustive examinations made during the course of a
whole year in the Hygienic Institute at Würzburg never once showed a
failure, all the samples tested being germ-free.
Some supervision is, therefore, necessary in the case of these
milk-sterilising companies to ensure that the public is obtaining what
it is paying for, as it has been shown by Professor Flügge, a
world-renowned authority on the subject of milk and its sterilisation,
that the bacteria left over in these so-called sterilised milk samples
are by no means invariably a harmless residue, but, on the contrary,
may consist of individuals which he has gathered together in a class
under the heading of poisonous peptonising bacteria, and which owe
this unfortunate designation to the rapidity and energy with which
they can engender the putrefaction of albumen. As indicating how
essential it is that every detail in the sterilisation of milk should
be adequately assessed, I may mention a paper recently published by H.
L. Russell and E. G. Hastings, of the Wisconsin Agricultural
Experiment Station in the United States, on the importance of
Pasteurising milk in closed rather than in open vessels, bacteria
having been found more resistant in milk when heated in contact with
the air than in closed vessels, this variation being attributed to the
formation of a surface pellicle, which readily forms on milk when
heated in open vessels to a temperature of about 60° Centigrade or
above. Experiments showed that organisms present in this pellicle or
skin were capable of retaining their vitality when exposed to a
temperature _six degrees higher_ than that of the milk beneath the
membrane in which they were destroyed.
Objections to the use of boiled milk have been frequently made on the
grounds of its being more difficult of digestion, and hence less
wholesome than the raw article. I may only point out that in this, as
in most other matters where opinions may be made or unmade, and in
consequence of the facts available being scanty must be more or less
arbitrary in character, Dr. Duclaux, the successor to Pasteur as
Director of the Pasteur Institute in Paris, has expressed himself as
follows in an article on "La digestibilité du lait stérilisé." After
reviewing the various special researches which have been made on the
subject, he says:--
"Ceci nous amène à une conclusion qu'il faut bien avoir le courage
de tirer, c'est que ces études chimiques sur la digestibilité du
lait ne sont pas adéquates à la question à résoudre.... En
attendant, tenons-nous-en à cette conclusion générale, que le lait
pasteurisé, chauffé ou stérilisé, est encore du lait, devant la
science comme devant la pratique, et que si son emploi présente
parfois des inconvénients, ceux-ci sont légers et amplement
compensés par les avantages."
BACTERIA AND ICE
The fate of bacteria when frozen excited the curiosity of
investigators already in the early years of bacteriology, for in 1871
we find Burdon Sanderson recording the fact that water which he had
obtained from the purest ice contained microzymes, or, as we now
prefer to call them, micro-organisms.
It is quite possible that at the time this announcement was made it
may have been received with some scepticism, for it was undoubtedly
difficult to believe that such minute and primitive forms of vegetable
life, seemingly so scantily equipped for the struggle for existence,
should be able to withstand conditions to which vegetable life in more
exalted circles so frequently and lamentably succumbs.
The tormented agriculturist realises only too well what havoc is
followed by a return in May to that season
"When icicles hang by the wall,
And Dick the shepherd blows his nail
And Tom bears logs into the hall,
And milk comes frozen home in pail."
Again, with what solicitude those of us who have gardens wait to see
what will have survived the iron grip of winter in our favourite
flower borders, and how frequently we have to face blanks in the ranks
of some of its most cherished occupants! Numerous bacteriologists,
however, have now confirmed this fact, the fields of ice and snow have
been repeatedly explored for micro-organisms, and it has been shown
how even the ice on the summit of Mont Blanc has its complement of
bacterial flora, that hailstones as they descend upon the earth
contain bacteria, that snow, the emblem of purity, is but a whited
sepulchre, and will on demand deliver up its bacterial hosts. Quite
apart from its general scientific interest, the bacterial occupation
of ice is of importance from a hygienic point of view, and a large
number of examinations of ice as supplied for consumption have been
made. Thus, Professor Fraenkl and also Dr. Heyroth have submitted the
ice-supply of the city of Berlin to an exhaustive bacteriological
examination. These investigations showed that the bacterial population
of ice as supplied to Berlin is a very variable one, and fluctuates
between great extremes, rising to as many as 25,000 bacteria in a
cubic centimetre (about twenty drops) of ice-water, and falling to as
few as two in the same measure.
There are numerous circumstances which come into play in determining
the density of the bacterial population in ice. First, of course, the
initial quality of the water from which the ice is derived is a factor
of great importance, for the purer the water the fewer will be the
bacteria found in the resulting ice.
Again, if the ice field is wind-swept by air bearing an unduly rich
complement of bacteria, as may be expected in the vicinity of populous
cities, for example, then the ice will reflect in its bacterial
contents the undesirable neighbourhood in which it was produced. Water
in repose, again, yields purer ice than water in movement during
freezing, for during rest opportunity is given for the bacteria
present in suspension to subside, the process of sedimentation or
deposition of bacteria which takes place under these conditions
playing an important part in water-purification; when, however, the
water is disturbed by swift currents, or agitated by storms, this
process is interrupted, and the bacteria become entangled in the ice
and frozen _in situ_.
The importance attaching to the physical conditions under which ice is
produced in enabling an estimate to be formed of the safety or
otherwise of the same for consumption may be gathered from the
following extract from an American report on the subject:--
"On the whole it is evident that the conditions surrounding water
when it freezes are very important factors in determining the
purity of the ice formed. If there is a considerable depth of
water in portions of a somewhat polluted pond or river, and the
ice is formed in these portions in comparatively quiet water with
but little matter in suspension, this ice will probably be
entirely satisfactory for domestic use. On the other hand, ice
formed in shallow portions of such ponds or rivers, even during
still weather, or in any portion if there is a considerable
movement of the water by currents or wind while it is forming, may
be rendered by these conditions entirely unfit for domestic use."
We have learnt that ice contains bacteria, that its bacterial contents
are to a certain extent dependent upon the bacterial quality of the
water before crystallisation, and that an important factor in
determining its purity is afforded by the physical conditions
prevailing at the time of freezing.
It will be of interest to ascertain in more detail what effect the
process of freezing has upon the number of bacteria present in the
water--what is the degree of bacterial purification effected during
the conversion of water into ice.
Now Professor Uffreduzzi, in his investigations on the ice-supply of
Turin, part of which is derived from a much-polluted portion of the
River Dora, found that about 90 per cent. less bacteria were present
in the ice than were present in the water from which it was produced.
In the making of ice, therefore, a remarkable removal of bacteria may
be effected which approaches very nearly the degree of bacterial
purification which is achieved during the best-conducted
sand-filtration of water.
Uffreduzzi's results have been repeatedly confirmed by other
researches. Thus, in regard to ice obtained from the River Merrimac,
water which contained originally about 38,600 bacteria per cubic
centimetre, on its conversion into ice had only from three to six.
Sewage, again, containing about a million and a half bacteria per
cubic centimetre after being frozen only contained under 74,000. It
should be mentioned that this last figure represented the number of
bacteria obtained by thawing the _outside_ of the sewage ice-cake;
_inside_ the cake there were more found--about 121,000. The difference
in these figures is due to the fact that, whereas the outer layers of
ice looked quite clear, towards the centre the ice contained sewage
sludge and hence more bacteria had become arrested; but in spite of
this the bacterial purification effected is very striking, although
not sufficient to render the use of ice from such a polluted source
either palatable or desirable.
It is, of course, a well-known fact that water possesses the power of
purifying itself during its transformation into ice, and that the
process of crystallisation not only prevents a considerable proportion
of the matters in suspension from becoming embodied in the ice, but
also eliminates a large percentage of the matters in solution, the
latter being driven from the water which is being frozen into the
water beneath. If, therefore, ice in the act of forming can get rid of
matters in solution, it is not difficult to understand how it can
eject bacteria, which though so minute are yet bodies of appreciable
dimension and in suspension. But that there are limits to this power
of excluding bacteria, and that, as in the case of other mechanical
processes, an overtaxing of the available resources is at once
reflected in the inferiority of the product, is shown by the frozen
sewage experiment, in which the ice, having had too large a supply of
bacteria in the first instance to deal with, was unable to get rid of
more than a certain proportion, and was obliged to retain a very
considerable number. Hence great as is the degree of purification
achieved by ice in forming, yet it must be recognised that its powers
in this direction are limited, and that the fact of water being frozen
does not necessarily convert a bad water into immaculate ice.
It is worthy of note that the city of Lawrence, in Massachusetts,
obtains the greater portion of its ice from a river which in its raw,
unpurified condition was rejected for purposes of water-supply in
consequence of the numerous and severe epidemics of typhoid fever
which accompanied its use. Since the application of sand-filtration to
this water, however, the death-rate from typhoid in this city, instead
of being abnormally high, has fallen abnormally low, and this
improvement is attributed to the excellent quality of the water
supplied to the city, and has taken place despite the use which still
continues of ice from the polluted river. The authorities consider the
city's immunity from typhoid amply justifies their sanctioning the
distribution of this river-ice, the freezing of the water having
rendered it sufficiently pure to remove all danger to health from its
consumption.
So far we have been considering the effect on bacteria of freezing
carried on under more or less natural conditions; but much interesting
work of a more detailed character has been carried out with reference
to the behaviour of particular varieties of micro-organisms when
frozen under more or less artificial conditions.
Thus Dr. Prudden froze various bacteria in water at temperatures
ranging from -1° C. to -10° C., and he found that different varieties
were very differently affected by this treatment; that, for example, a
bacillus originally obtained from water, and introduced in such
numbers as represented by 800,000 individuals being present in every
twenty drops, after four days' freezing had entirely disappeared, not
one having survived. On the other hand, similar experiments in which
the typhoid bacillus was used resulted in the latter not only enduring
a freezing of four days' duration, but emerging triumphant after it
had been carried on for more than 103 days!
In these experiments it should be borne in mind that, as the ice was
frozen to a solid block or lump, there was no opportunity for the
mechanical committal of the bacteria during freezing to the water
beneath; all the bacteria present were imprisoned in the ice, and the
fact that the typhoid bacteria were not destroyed by being frozen
shows that they can withstand exposure to such low temperatures,
although, as we have seen, the other variety of bacillus employed was
destroyed.
Dr. Prudden, however, discovered an ingenious method by which even
typhoid bacilli were compelled to succumb when frozen. In the course
of his investigations he found that bacteria which had offered the
stoutest resistance under freezing were extremely sensitive to this
treatment if the process was carried on intermittently, or, in order
words, if the temperature surrounding them was alternately lowered and
raised.
In this manner the bacteria may be said to be subjected to a
succession of cold shocks, instead of being permitted to remain in a
continuously benumbed condition. The vitality of typhoid bacilli was
put to the test under these circumstances, the freezing process being
carried on over twenty-four hours, during which time, however, it was
three times interrupted by the ice being thawed. The effect on the
typhoid bacteria was striking in the extreme; from there being about
40,000 present in every twenty drops, representing the number
originally put into the water, there were only ninety at the end of
the twenty-four hours; and after a further period of three days,
during which this treatment was repeated, not a single bacillus could
be found. This signal surrender to scientific tactics forms a marked
contrast to the stout resistance maintained for over 103 days under
the ordinary methods of attack.
But, although the typhoid bacillus appears to submit and meekly
succumb to this plan of campaign, yet the conclusion must not be
rashly drawn that all descriptions of bacteria will be equally feeble
and helpless in these circumstances.
Doctors Percy Frankland and Templeman have shown that the spore form
of the anthrax bacillus is able to successfully challenge all such
attempts upon its vitality. Thus when put into water and frozen at a
temperature of -20° C., the process being extended over a period of
three months and interrupted no fewer than twenty-nine times by
thawings, when examined even after this severe series of shocks, it
showed no signs of submission and clung to life as tenaciously as
ever.
The more sensitive form of anthrax, however, the bacillus, was readily
destroyed; for after one freezing its numbers were already so much
reduced that it was only with difficulty that even one or two could be
found, and after the second freezing every one out of the large number
originally present had died.
Renewed interest has been of late revived in the question of the
behaviour of bacteria at low temperatures, in consequence of the
possibility of obtaining, by means of liquid air and liquid hydrogen,
degrees of cold which were undreamt of by the scientific philosophers
of fifty years ago. Public interest has also been quickened in such
inquiries on account of the important part which low temperatures play
in many great commercial developments, their application rendering
possible the transport from and to all parts of the world of valuable
but perishable foodstuffs, thus encouraging local industries by
opening up markets, and bringing prosperity to countries and
communities which before were seeking in vain an outlet for their
surplus produce.
The application of cold storage for preservation purposes is, however,
no novelty; for nature ages ago set us the example, and of this we
have been lately reminded afresh by the discovery announced by Dr.
Herz of a mammoth in Siberia, which, despite the thousands of years
which have elapsed since it was originally overwhelmed and frozen, is
described as being in a marvellous state of preservation.
Thus we are told that "most of the hair on the body had been scraped
away by ice, but its mane and near foreleg were in perfect
preservation and covered with long hair. The hair of the mane was from
four to five inches long, and of a yellowish brown colour, while its
left leg was covered with black hair. In its stomach was found a
quantity of undigested food, and on its tongue was the herbage which
it had been eating when it died. This was quite green."
Considering that certainly more than eight thousand years had elapsed
since this creature was peacefully consuming what proved to be its
last meal, nature's method of cold storage must indeed be regarded as
unsurpassable in the excellence of its results.
I believe it was in the year 1884 that the first attempts were made to
follow more closely and in greater detail the precise effect upon
different bacteria of submitting them to temperatures of such a low
degree as -130° C., obtained by means of solid carbonic acid. These
experiments were carried out by Pictet and Young, and are recorded in
the _Comptes Rendus_ of the Paris Academy of Sciences.
They differ from those which we have so far been considering, inasmuch
as the bacteria were not frozen in water, but in culture-material, or,
in other words, like the mammoth, whilst enjoying a midday meal!
One of the micro-organisms experimented with was a bacillus known at
that time as the rinderpest bacillus, capable of producing disease in
animals when inoculated into them and existing both in the spore and
bacillar form. Pictet and Young specially state that the spore form
was present in the specimens employed by them, and hence the fact that
this micro-organism was alive after being frozen and exposed to this
low temperature of -130° C. for the space of twenty hours is not,
perhaps, so surprising when we bear in mind the remarkable feats of
endurance exhibited by spores which have with justification obtained
for them a prominent place amongst the so-called curiosities of
bacteriology. But of more interest than their mere survival in these
circumstances is the fact that, on being restored to animation--or, in
other words, released from their ice-prison--these bacteria were
discovered to have retained all their pathogenic properties, this
period of enforced rigidity having in no way affected their
disease-producing powers.
Such results naturally only served to whet the scientific appetite for
more, and the liquefaction of air and of hydrogen placing much lower
temperatures at the disposal of investigators, those bacteriologists
who were fortunate enough to command a supply were not long in
availing themselves of the opportunity thus given them of further
testing the vitality of micro-organisms.
Botanists had already shown that exposure to liquid air, which means a
temperature of about -190° C., and to liquid hydrogen, which means a
temperature of about -250° C., did not impair the germination powers
of various descriptions of seeds, such as those of musk, wheat,
barley, peas, vegetable marrow, and mustard, and that their actual
immersion in liquid hydrogen for the space of six hours did not
prevent them coming up when sown just as well as ordinary seeds which
had not undergone this unique experience; hence the opportunity of
submitting other members of the vegetable kingdom to these low
temperatures was eagerly sought for by bacteriologists. Dr. Macfadyen
found this opportunity in the laboratories of the Royal Institution,
and, Professor Dewar having placed a generous supply of liquid air and
liquid hydrogen at his disposal, he submitted specimens growing in
various culture-materials, such as gelatin, broth, potatoes, etc., of
typhoid, diphtheria, cholera, anthrax with spores, and other bacteria,
for twenty hours and seven days respectively, to a temperature of
about -190° C. In no instance, however, whether exposed when growing
in fluid or solid media, could any impairment of their vitality or the
slightest alteration in their structure be observed. Similar results
were obtained when liquid hydrogen, or a temperature of about -250°
C., was applied. The question of the retention or otherwise of the
disease-producing powers of these bacteria was not investigated, and
in this connection much interest attaches to Mr. Swithinbank's
investigations on the vitality and virulent properties of that
notorious malefactor amongst micro-organisms, the _bacillus
tuberculosis_, when exposed to the temperature of liquid air. The
specimens of the consumption bacillus employed were originally
obtained from the human subject, and they were exposed for periods
varying from six hours to six weeks to -190° C. In each case the
malignant properties of the tubercle bacillus after exposure were
tested by their direct inoculation into animals, and the results
compared with those which followed similar inoculations made with
bacilli which had not been frozen in this manner, but had been grown
in ordinary circumstances. In no single case, Mr. Swithinbank tells
us, were these frozen tubercle bacilli deprived of their virulence,
and the length of exposure, at any rate as far as could be judged
after six weeks, appeared to make no difference in this respect. It is
true that the pathogenic action of the frozen bacilli appeared to be
somewhat retarded--that is, they took rather longer to kill animals
than the ordinary unfrozen bacilli--but in every case their
inoculation produced the typical tuberculous lesions associated with
them.
Of particular interest, however, in view of what has been already
discovered about the lethal effect upon bacteria of violent
alternations of temperature, are Mr. Swithinbank's observations on the
vitality of the tubercle bacillus when exposed to such extreme
variations of temperature as are represented by a passage from -190°
C. to that of 15° C.
The _bacillus tuberculosis_ is admittedly a tough antagonist to deal
with, and enjoys an unenviable notoriety for its robust constitution
amongst the pathogenic members of the microbial world; hence a
knowledge of its behaviour in these trying circumstances, as we now
know them to be to bacterial life, becomes of special interest. Great
must have been the investigator's satisfaction, then, when he
discovered that the vitality of the consumption bacillus had been so
seriously impaired by this treatment that its pathogenic properties
collapsed, and the animals which were inoculated with these specimens,
instead of with the continuously frozen bacilli, suffered no
inconvenience, and remained in good health.
But although no appreciable change either in the structure, vitality,
or malignant properties of the particular bacteria investigated have
been noted as resulting from their exposure to extremely low
temperatures, yet there is no doubt that a certain proportion of the
individual micro-organisms present--those probably whose constitution
is less robust than their more fortunate associates--do succumb under
these trying conditions.
This fact has been well brought out by Dr. Belli, of the University of
Padua, in the experiments which he made with the fowl-cholera bacillus
and the anthrax bacillus in the presence of very low temperatures.
Thus he exposed a large number of fowl-cholera bacilli in broth to the
temperature of liquid air, as many as 396,000 bacilli being present in
every twenty drops of the liquid. After exposing them continuously for
nine hours to -190° C., he had the curiosity, after thawing them, to
count how many were left alive, and he found that an enormous
mortality had taken place amongst them; for, instead of nearly 400,000
bacilli being present in one cubic centimetre, there were only about
9,000. On the other hand, in the broth tubes kept during that time in
ordinary surroundings, the bacilli had flourished remarkably, and had
greatly increased in numbers. Thus not only had no multiplication
amongst these bacilli taken place, which circumstance is always
regarded as indicative of their vital condition--not only, then, had
their vitality been arrested--but a very large number of them had been
actually destroyed in consequence of this severe treatment; but that
the residue were not only alive, but unimpaired in their energies on
being restored to animation, was proved by their being able to destroy
animals, not having parted with any of their malicious propensities.
Dr. Belli carried out similar experiments with the bacilli of anthrax
and obtained very similar results. With regard to both these varieties
of pathogenic bacteria, he mentions that their action upon animals was
not quite so rapid as is characteristic of normal specimens of these
micro-organisms, thus confirming the experiments in this direction
made with frozen tubercle bacilli.
Not content with the exhibition of their powers of endurance, Dr.
Belli determined to make yet another demand upon the vitality of these
bacilli. For this purpose he immersed them in the liquid air itself,
thus bringing them into direct contact with it, effecting this by
lowering into the liquid strips of filter-paper soaked in broth
containing these bacilli. But, in spite of remaining for the space of
eight hours in these surroundings, they emerged triumphant, exhibiting
no modification whatever either in their structure or pathogenic
properties.
There are doubtless many other trials yet awaiting bacteria, to which
they will most certainly be submitted before the limits of their
powers of endurance have been adequately tested, but it is difficult
to conceive of a severer strain upon their vital resources than the
imposition of the conditions of which the above is but a brief sketch.
The triumphs achieved in this direction by micro-organisms are,
however, closely approximated by the remarkable record established,
according to the recent researches of Dr. Krause, by typhoid, anthrax,
tubercle, and some other bacteria of preserving unimpaired not only
their vitality but their virulence after having undergone for a period
of twenty hours a pressure of no less than that of 500 atmospheres.
When we reflect that a pressure of 500 atmospheres is equal to a
pressure of about 7,500 pounds to the square inch, and that the normal
pressure under which life is maintained upon this planet is
approximately that of fifteen pounds to the square inch, this
bacterial victory over physical conditions will be more readily
appreciated.
The more intimate becomes our knowledge of bacteria, the more must we
marvel at the equipment with which they have been provided for
enabling them to maintain themselves in the struggle for existence--a
struggle which is as severe and as remorseless in this lowly region as
it is in those domains the inhabitants of which have risen to far
loftier heights on the great ladder of life.
SOME POISONS AND THEIR PREVENTION
Little did the learned Dutchman Leeuwenhoek dream when, more than two
hundred years ago, he recorded, in his _Arcana Naturæ_, that he had
found "viva animalcula" in his saliva, that this, the first beginning
of bacteriology, would lead, a couple of centuries later, to the
inauguration of a new era in the treatment of disease, in which these
so-called animalcula, from being considered as curiosities, would come
to be regarded as powers for good and evil of the first importance.
Protective inoculation or serum therapy, of which the public have
lately heard so much in connection with diphtheria, is the direct
outcome of bacterial investigations which during the last two decades
have been pursued with such zeal in every part of the globe.
The vast domain of immunity, which until recently was an undiscovered
country, is now being bit by bit annexed, and in all directions
workers are engaged upon opening up new tracts, in overcoming
difficulties, in changing chaos into order.
The problems which surround immunity are of so complex and subtle a
character that their mastery is by no means either easy or rapid, and
many recondite researches appear at frequent intervals on this subject
in foreign and other scientific journals, rendering it a difficult
matter to keep pace with the new discoveries and the latest theories.
The interest in this country in toxins and anti-toxins not unnaturally
centres round that branch of the subject which deals with diphtheria,
this disease having of late years figured so prominently in our
mortality tables, whilst the production of diphtheria and other
anti-toxic serums has been so finely elaborated abroad that it already
constitutes an article of commerce, and doubtless helps to swell the
exports of our great continental commercial rival.
In this connection the following statistics, published by Dr. Jalzer,
of the Mülhaus Hospital, are of interest regarding the mortality from
diphtheria before and after the introduction and application of
diphtheria anti-toxin. The death-rate from this disease, writes Dr.
Jalzer, which in 1892 and 1893 was fully 50 per cent., fell in 1895 to
38·5 per cent., in 1896 to 28·8 per cent., in 1897 to 16 per cent., to
20 per cent. in 1898, 15·15 per cent. in 1899, and 18·75 per cent. in
1900.
So far the efforts which have been made to mitigate _human_ suffering
have attracted most attention; but it will be remembered that Pasteur,
before he commenced the study of hydrophobia, had already won his
laurels in combating disease in the victory he gained over anthrax,
the ravages of which so frequently decimated the herds of the French
farmer and robbed him of his well-earned return on his capital and
labour.
In summoning the brilliant Director of the German Imperial Board of
Health to South Africa to investigate the nature of rinderpest, and,
if possible, discover a means of protecting cattle from its onslaught,
the Cape Government afforded another opportunity for the scientific
study of a disease associated with animals, upon the successful
mastery and limitation of which the agricultural prosperity of South
Africa is so largely dependent, being as it is one of the most fatal
and contagious maladies to which cattle are subject. Apart from the
great commercial importance attending Dr. Koch's discovery of a device
whereby cattle can be immunised or protected from contracting
rinderpest when exposed to its contagion, this discovery is of great
scientific interest, inasmuch as it has inaugurated a new departure in
methods of immunisation.
The previous methods in vogue for inducing immunity in animals from a
particular disease consisted in converting the virus itself into a
vaccine, as was done by Pasteur in his classical investigations on
anthrax and its prevention; and secondly, the employment of anti-toxic
serums, in which the virus is not directly inoculated into the animal
to be protected, but in which an intermediary is employed between the
virus and its victim. This intermediary, or living machine for the
generation of the anti-toxin, is usually a horse, which is
artificially trained by being given gradually increasing doses of the
virus or toxin, until it ultimately withstands doses which in the
first instance would infallibly have killed it. When the animal has
arrived at this satisfactory stage or condition of complete immunity,
some of its blood is from time to time drawn off, and the serum thus
obtained constitutes the anti-toxin which now figures so prominently
in modern therapeutics. Besides diphtheria-anti-toxic serum there are
also those of tetanus, or lock-jaw, plague, the famous anti-venene
serum, about the discovery and preparation of which greater detail is
given later on, and many others which are still the subject of
experimental inquiry.
Now Koch's method for the compassing of rinderpest differed from both
the systems above mentioned, inasmuch as he neither employed
artificially weakened cultures of the virus, or an anti-toxic
rinderpest-serum; instead he took one of the natural secretions of an
animal infected with rinderpest, and by injecting this into a healthy
animal it was discovered that the latter, as is the case with a
vaccine, suffered only local and temporary discomfort, and acquired
pronounced immunity from the active virus. The secretion selected by
Dr. Koch and his assistant, Dr. Kolle, for this purpose was the gall,
and it might be supposed, from the fact that its inoculation into
healthy animals did not communicate the disease, that the rinderpest
bacteria were absent from the gall. But this is not so, for Dr. Kolle
has succeeded in isolating the latter from the gall of infected
animals, and, moreover, has proved them on isolation to possess their
full complement of virulence. Further investigations made by Koch and
Kolle have shown that the explanation of this seeming anomaly is to be
found in the fact that the gall of an animal suffering from rinderpest
contains a substance which prevents the migration of the rinderpest
bacteria, with which it is associated, from the point of inoculation.
Hampered in their movements by the controlling influence of this
special substance which has been generated in the gall, the bacteria
remain rooted to the spot where they are first situate, and only a
passing and exceedingly slight local affection results, which on its
departure leaves the animal with an immunity from rinderpest lasting
some four months. A number of interesting investigations have not
unnaturally been stimulated by this remarkable discovery, and
researches on the properties inherent in the gall of healthy animals
of various kinds have been recently carried out by Dr. Neufeld, of the
Institute for Infectious Diseases in Berlin, which are, however, of a
too technical nature to deal with here.
As an illustration of the practical use to which Koch's gall
immunisation method may be put in dealing with outbreaks of
rinderpest, reference to a recent report furnished by the Health
Officer of Shanghai may be of interest. Dr. Arthur Stanley describes
the outbreak as follows:--
"A large herd of cattle infected with cattle-plague was brought to
Shanghai from the Tanyang district, around the Grand Canal, for
export to the allied troops in the north of China. The disease
spread to an adjacent dairy, most of the cattle dying. On this
dairy becoming infected a police cordon was established round it
to prevent ingress and egress of cattle and ingress of persons
unconnected with the dairy, while the outside infected herd was
removed to an isolated part of the settlement. Having been
previously convinced of the futility of police cordons in the
prevention of cattle-plague, I was not surprised to find, within a
short time, that the disease had spread, by the meeting together
of cattle-coolies at a common tea-house, to three other dairies at
a distance of a quarter, a half, and two miles from the original
source of infection.
"As the animals are not, as a rule, taken away from the immediate
vicinity of the dairy, there being no grazing fields, and as
neither fodder nor dung is taken from one dairy to another, it is
practically certain the infection was carried by the
dairy-coolies.
"Immediately on this second series of dairies becoming infected it
was resolved to apply the gall immunisation method of Koch as
being the means at hand. About 1,500 cubic centimetres were
collected from the gall-bladder of a rinderpest animal, and 10
cubic centimetres were injected into the dewlap of each of the
twenty remaining cattle in the dairy.
"The injection caused slight local swelling and tenderness, but no
constitutional symptoms and no alteration in the milk-supply, an
important matter in a dairy. In all sixty-eight cattle were
injected with cattle-plague gall. Of these, seventeen were among
isolated uninfected herds; the remaining fifty-one belonged to
infected herds, and among the latter eleven died of cattle-plague
subsequent to the injection."
Dr. Stanley points out that ten of these animals, judging by the time
which elapsed _after_ the injection, when they showed the first
symptoms of the disease, _must have been already infected when the
injections were made_; the eleventh animal, however, undoubtedly
contracted the disease after and in spite of the injection.
"Considering," continues Dr. Stanley, "the usual excessive
mortality during an outbreak of this disease, the result may
almost be compared to the success of vaccination against
small-pox. Three young bullocks, each having received 20 cubic
centimetres of cattle-plague gall, were purposely exposed to
severe infection. They remained well, while unprotected animals
around them died of the disease."
In the domain of immunity there is, however, no more fascinating or
interesting story than that which deals with the discovery and
elaboration of a cure for snake-bites, a discovery which, while
attracting but comparatively little attention in this country, should
prove of paramount importance to our fellow-subjects in the great
Indian Empire. The significance to India of Professor Calmette's
discovery of a specific cure for snake-poison may be gathered, indeed,
from the statistics which have been compiled of the number of deaths
attributed by Indian officials to this cause alone, amounting, it is
said, to some 22,000 annually.
The Pasteur Institute in Paris has despatched many pioneers of science
to various quarters of the globe, but perhaps no scientific missionary
has produced more fruitful results than has Dr. Calmette. It was while
acting in the double official capacity of Médecin de 1st Classe du
Corps de Santé des Colonies and Director of the Bacteriological
Institute of Saïgon, in Cochin China, in the autumn of 1891, that
Calmette first commenced his experiments on the neutralisation of
serpent venom in the animal system.
He had, indeed, exceptional opportunities in the matter of serpent
venom wherewith to carry out his investigations, for during the rainy
season a village in the neighbourhood of Bac-Lieu (Cochin China) had
been attacked by a band of most venomous serpents.
These creatures, driven by the floods into the very huts of the
natives for shelter, created a terrible panic, and no fewer than forty
individuals were bitten by them. The panic was certainly not without
justification, for these serpents belonged to the species known as
_naja tripudians_, or _cobra de capello_, renowned for the deadly
nature of their venom, and widely distributed over India, Burmah,
Sumatra, Java, Malacca, and Cochin China; but until Calmette set to
work to systematically study the nature of this reptile's venom but
little precise or reliable information had been obtained as to its
character.
The governor of the district gave orders that as many as possible of
the reptiles were to be captured alive and forwarded to the Director
of the Bacteriological Institute, and a plucky Annanite actually
succeeded in securing ninety specimens, which were forwarded in a
barrel to Dr. Calmette.
This formidable gift was received with enthusiasm by the director, who
realised the importance and scope of the inquiry, which he at once set
himself to systematically work out.
Forty of these reptiles arrived alive, and several were at once
sacrificed to secure their venom glands. Each gland, resembling both
in size and shape a shelled almond, contains about thirty drops of
venom, and in this transparent limpid liquid is embodied a toxin of
extraordinary strength. It was, of course, necessary in the first
instance to ascertain, within as narrow a limit as possible, the exact
degree of toxic power inherent in the venom, and to determine, if
possible, the precise lethal dose in respect of each variety of animal
experimented upon.
A correct calculation of the quantity of venom required in every case
was, however, found to be quite impossible, for so virulent is the
poison that a single drop of an emulsion produced by pounding up eight
glands in 300 grammes of distilled water is sufficient, when
introduced into the vein of a rabbit's ear, to kill it in five
minutes. All the mammals to which Calmette administered this cobra
venom, such as monkeys, dogs, rabbits, guinea-pigs, rats, succumbed
more or less quickly, according to the size of the dose.
Small birds and pigeons die very rapidly, but the domestic fowl is
more fortunate, being somewhat less susceptible. Frogs also fall a
prey to the venom, but they are far more refractory than rabbits, for
it takes thirty hours to kill a frog with a dose of venom which would
infallibly destroy a rabbit in ten minutes. Toads, curiously, do not
enjoy to the same extent this power of resisting its toxic action, for
they die more quickly than frogs, whilst it makes short work of
lizards and chameleons. Fish form no exception to the rule, and even
invertebrates, such as leeches, are killed by minute traces of venom.
Whilst Calmette has found that the venom of different kinds of
reptiles exhibits marked differences in its toxic character, he has
also discovered that the venom secreted by one and the same serpent
varies considerably, according to the length of time the animal has
fasted. He describes how he kept a _naja haje_ (Cleopatra's asp) in
his laboratory, which during the whole eight months that it lived
never took any food whatever, although it was offered the most diverse
dainties. On its arrival it was made to bite on a watch-glass, this
being one method adopted for collecting the venom; the liquid was at
once dried, and 0·7 milligramme was found to kill a rabbit weighing
nearly four pounds in four hours. Two months later on, when the venom
was again collected, 0·25 milligramme proved a fatal dose. On the
death of the animal, at the end of eight months, the venom extracted
from the glands was so toxic that it only required 0·1 milligramme to
kill a rabbit of about the same weight as the previous one. The same
curious fact was noted in the case of a cobra's venom. Another
circumstance which appears to control the degree of toxicity inherent
in serpent venom is the interval of time which elapses between two
successive bites. The longer the interval the more virulent is the
venom; and Calmette points out that these observations are in
accordance with what has for a long time been known in France with
respect to indigenous vipers--that their bites are far more dangerous
and far more fatal in the spring, after the winter period of torpor is
over, than in the autumn.
Until quite recently it was thought that the only creatures which
could resist the fatal action of this poison were serpents, both
poisonous and non-poisonous. Calmette was led to this conclusion
because, although he inoculated large doses, as much as ten drops,
into cobras, they suffered absolutely no inconvenience, and the same
results were obtained with harmless snakes. On repeating these
experiments, however, and using much larger quantities of venom,
Calmette has found that they do ultimately succumb. That their
susceptibility in comparison with other animals is very slight, may be
gathered from the fact that a lethal dose of venom for reptiles is
roughly estimated to amount to as much as three times the quantity of
venom normally present in their respective poison glands. These
animals, therefore, although very refractory, are not absolutely
immune from the action of venom-toxin.
There are, however, other animals which enjoy a relative although not
absolute immunity to snake poison, and amongst these may be mentioned
swine, hedgehogs, and the mongoose. Swine, it is well known, will
greedily devour reptiles, and in some countries they are specially
trained up and employed for this purpose. Of particular interest,
however, are some experiments which were carried out to test the
traditional immunity towards this toxin ascribed to the mongoose.
These animals are very useful in sugar plantations, and are largely
employed to keep down the serpents and rats with which they abound,
for the carnivorous little mongoose is extremely partial to such prey.
Attempts have been made by sugar planters to introduce them into
Martinique, where they are not found in the wild state, as in the
island of Guadeloupe.
Six specimens of the mongoose were forwarded to Calmette from
Martinique, and these particular animals, it was stated, had never
been set at liberty since they were imported, so that they had had no
previous experience of snakes or venom. On arriving at the laboratory,
one of these little creatures was placed in a glass cage along with a
large cobra. The cobra, at once rising up and dilating its neck,
darted with fury upon the mongoose; but the latter, thanks to its
extraordinary agility, escaped being caught, and took refuge,
stupefied and terrified for the moment, in a corner of the cage. This
stunned condition, however, did not last long, for just as the
incensed cobra was preparing to make a fresh attack upon its
insignificant little victim, the latter, with wide-open mouth, rushed
and jumped upon the head of its enemy, viciously bit through its upper
jaw, and broke its skull in a few seconds. Thus, although in size but
a little larger than a squirrel, this tiny creature was more than a
match for a cobra two yards long.
Artificial inoculations of cobra venom into the mongoose fully
substantiated all the observed facts as to its remarkable immunity
from this poison. A dose sufficient to kill a large rabbit in three
hours was absolutely without effect; only when the venom was
introduced in quantities amounting to as much as eight milligrammes
was it followed by fatal results. Thanks, therefore, to their
extraordinary agility and remarkable power of resisting the effects of
this lethal toxin, these little animals are able to battle
successfully with the most dangerous reptiles.
The rapidity with which serpent venom becomes absorbed by the system
is almost incredible, and is well illustrated by the following
experiment. A rat was inoculated with venom near the tip of its tail.
_One minute later_ the latter was cut off a short distance above the
point of inoculation; but this operation was quite unable to save
the animal's life, for even in that brief interval the poison had
accomplished its fatal work, and a few hours later claimed its victim.
This rapid diffusion of the venom helps to explain the difficulty
which is experienced in arresting the course of the poison by local
treatment, for its passage is too rapid to permit of its being
overtaken by superficial measures of even the most stringent
character. But Calmette points out that local precautions are not to
be neglected, for although they cannot nullify the action of the
venom, they undoubtedly do delay its progress, and thus create a
longer interval or respite, during which an opportunity is afforded
for administering the anti-toxin. Before, however, passing on to the
investigations which have culminated in the production of a specific
antidote for this terrible toxin, there are a few more details which
Calmette has furnished as to its character which are of interest.
Serpent venom is characterised not only by its intensely virulent
properties, but also by the tenacity with which it retains them under
diverse circumstances. Thus it may be stored up for a whole year, and
yet at the end of that time be as active as ever; and even after
several years, although its toxic powers are somewhat reduced, it
still retains them to a very appreciable extent.
Unlike the bacterial toxins, this venom toxin can stand exposure to
considerable temperatures without injury to its activity, and that of
the cobra only suffers after it has been submitted to 98° Centigrade
for twenty minutes. Sensitiveness to temperature varies, however,
with the snake from which the venom is derived. Thus the venom of
the so-called "tiger-snake" of Australia will stand being exposed
for ten minutes to from 100° to 102° degrees Centigrade, and its
virulence only disappears when this temperature has been applied
for twenty minutes. The venom of the "black snake," another
Australian variety, loses its toxicity at a temperature of between
99° and 100° Centigrade; whilst an exposure to only 80° Centigrade
for ten minutes is sufficient in the case of viper venom, according
to Messrs. Phisalix and Bertrand, to profoundly modify its lethal
action. A continuous exposure for a fortnight to a temperature of
38° Centigrade does not affect cobra venom in the least; but if during
that same time it has been placed in the sunshine, it entirely loses
all its lethal properties. Thus, a pigeon was inoculated with about
thirty drops of venom which had been exposed to the sun's rays for
fourteen days, and it survived; whilst another pigeon was inoculated
with a little over six drops of similar venom which had been kept
during this time in the dark, and it died in a quarter of an hour.
All these elaborate researches as to the character of serpent venom
were essential to enable the next step to be taken in the elaboration
of the antidote. Before this great achievement could be accomplished
it was necessary to first succeed in artificially immunising animals
against the effects of this powerful toxin, so that the serum of such
animals could be applied for the protection and cure of other animals
from the effects of snakebites.
It may be readily conceived that the task of artificially rendering
animals immune from snake poison was not an easy one, for the process
depends upon training the animal to gradually withstand larger and
larger doses of the venom; and considering the intensely toxic
character of the substance which had to be handled, the danger was
ever present of the animal succumbing to venom poison before its serum
had acquired the requisite pitch of protective power to render it of
service as an anti-toxin. Dr. Calmette tells us that he carried out a
very large number of experiments before he met with success. But it is
not necessary here to discuss his various efforts; suffice it to say
that at length his labours were rewarded, and the following extract
from one of his memoirs describes the methods which he adopted for
this purpose:--
"The best method of procedure for the purpose of vaccinating large
animals destined to produce anti-venomous serum consists in
injecting them from the outset with gradually increasing
quantities of the venom of the cobra mixed with diminishing
quantities of a one-in-sixty solution of hypochlorite of lime.[8]
The condition and the variations in the weights of the animals
are carefully followed, in order that the injections may be made
less frequently if the animals do not thrive well. Quantities
of stronger and stronger venom are in turn injected, first
considerably diluted, and then more concentrated; and when the
animals have already acquired a sufficiently perfect immunity, the
venoms derived from as large a number of different species of
snakes as possible are injected. The duration of the treatment is
of considerable length--at least fifteen months--before the serum
is sufficiently active to be used for the purposes of treatment."
[8] More recently the snake venom employed by Dr. Calmette
for the immunisation of his horses consists of a mixture of
colubrine and viperine poisons, the former making up about
80 per cent. of the mixture. A solution of this mixture is
heated at about 73° C. for half an hour and then filtered,
and injected into horses.
An immense number of animals have been vaccinated by this method at
the Pasteur Institute at Lille, where Dr. Calmette is now director;
and in one of his memoirs we are told that they have horses there
which have yielded during a period of eighteen months serum extremely
active against venom. These horses receive in a single inoculation,
without suffering the least inconvenience, doses of venom sufficient
to kill fifty horses fresh to the treatment.
Large quantities of this serum have been forwarded from the Lille
Institute to various parts of the world where venomous serpents are
most frequently met with, and already important evidence has been
collected as to its efficacy in cases of human beings bitten by
dangerous reptiles. So impressed with its importance are Indian
medical authorities, that its preparation has been included in the
work which the new great bacteriological institute at Agra is carrying
on.
The importance of the production _in situ_ of this anti-venomous serum
has been recently demonstrated by the experiments which have been
conducted in the Plague Research Laboratory, Bombay, by Mr. Lamb and
his colleagues, on the keeping properties of such serums in India.
From the careful investigations which have been made on this subject,
these gentlemen state that anti-venomous serum undergoes a progressive
and fairly rapid deterioration when stored in hot climates, and that
this deterioration is greater and more rapid the higher the mean
temperature to which it is subjected.
The protective potency of this horse-serum may be gathered from the
fact that it suffices to inject a rabbit, for example, with a quantity
amounting to about one two-hundred-thousandth of its weight to ensure
the latter acquiring complete immunity from a dose of venom capable of
otherwise killing it in twelve hours.
The rapidity with which it acts is also extremely remarkable. Thus, if
a rabbit receive two cubic centimetres (about fifty drops) of
anti-venomous serum in the marginal vein of one of its ears, it will
suffer with absolute impunity an injection of venom into the marginal
vein of the other ear capable of killing it under ordinary
circumstances in a quarter of an hour. Its curative powers are not
less remarkable, for it is possible to inject venom sufficient to kill
an animal in two hours, and to let one hour and three-quarters elapse
before administering the antidote, and yet at this late stage to save
the victim's life, although it is necessary where such a long interval
has occurred between the respective venom and serum injections to
employ the latter in larger quantities than is usually required. Dr.
Calmette believes that the anti-toxin may be applied at an even more
advanced stage of the disease if it is employed in yet larger doses.
Another novel and important feature about this anti-venomous serum is
the fact that it not only protects animals from one species of very
active venom, such as that of the cobra and other poisonous snakes,
but it also affords protection from the dreaded venom of scorpions.
This is a very remarkable and significant discovery, for hitherto the
opinion has been stubbornly held that each toxin requires its specific
anti-toxin for its correction. Dr. Calmette has, however, frequently
indicated by his researches that this view cannot be considered so
completely proven as is claimed by its supporters, and his latest
investigations support the theory that particular toxins may be
counteracted by several anti-toxins of different origin. Thus it has
been shown by Calmette and Roux that rabbits hyper-vaccinated against
rabies acquire the power of resisting venom-poison, and that the serum
of horses vaccinated against tetanus or lock-jaw also nullifies the
action of serpent venom.
The practical bearing of this discovery is obvious, and the hope is
justified that the at present cumbrous appliances required for the
elaboration of anti-toxins of such varied origin will ultimately give
way to simpler and less costly methods, which will admit of these new
antidotes being more widely circulated and applied.
We have seen that although most animals fall an easy prey to serpent
venom, yet there are a few notable exceptions, amongst which may be
mentioned hedgehogs, swine, and the mongoose. Now the very natural
question arises why, if these animals are already in such a high
degree immune from this poison, should not they be employed to furnish
forth protective serum, instead of laboriously training up susceptible
animals to become artificially immune and supply this venom
anti-toxin?
This brings us face to face with one of the many problems connected
with the subject of immunity which so far have successfully eluded all
attempts made to solve them. Experience has shown repeatedly that
although _artificially_ acquired immunity from a particular poison can
be handed on by means of an animal's serum, yet the _natural_ immunity
from a given poison enjoyed by one species of animal cannot be
similarly transferred to less-favoured varieties.
This fact has long been recognised in the case of poisons of bacterial
origin. Thus, white rats are absolutely immune from diphtheria, but
Wassermann showed some years ago that the serum of these animals has
no power whatever to counteract the action of diphtheria-toxin in
other animals. Guinea-pigs were inoculated with fatal doses of
diphtheria toxin along with white-rat serum; but although other
guinea-pigs treated with the same toxin mixed with the ordinary
artificially elaborated anti-diphtheritic serum survived, those which
received the rat serum died in every case.
Now very similar results have been obtained by Calmette in respect to
the serum of animals naturally immune from serpent venom. The serum of
the refractory little mongoose, as well as that of the hedgehog, is
wholly unable to save other animals from the lethal effect of venom
poison, and similar results have been noted in respect to swine serum.
But a very curious fact has also been discovered by Calmette--_i.e._
that these so-called naturally immune animals very frequently are
quite incapable of being artificially trained to elaborate a serum
possessing protective powers which can be transferred to another
animal.
How splendid a domain for beneficent research lies before the
scientific investigator is apparent to all, and the important work
already accomplished is but an augury of yet greater discoveries
awaiting the labours of such leaders as Calmette. It is not
surprising, therefore, that the scientific interest in toxins and
anti-toxins shows no signs of abatement. On the contrary, the
competition for obtaining and working the new "claims" which pioneer
research enthusiasts are constantly engaged in "pegging out" remains
as keen as ever.
Despite, however, the extraordinary interest which this subject has
aroused in scientific circles all over the world, nearly ten years
elapsed before any notice was taken of the curious discovery made by
two brothers that the blood of eels contained a highly poisonous
principle, and the memoir containing this remarkable announcement
remained until comparatively recently buried in the Italian journals
where it was first published.
Calmette was, we believe, the first to call attention to this
discovery of the brothers Mosso and give it the prominence it
deserves, and both he and other investigators have not only fully
confirmed it, but have greatly added to our knowledge concerning the
character of the poison contained in eel serum.
Now the venerable Izaak Walton, in one of his quaint and most
fascinating discourses, which although written more than two centuries
ago have a freshness as if penned but yesterday, waxes enthusiastic
over the eel, and supplies an elaborate recipe for its preparation for
the table, telling us "it is agreed by most men that the eel is a most
dainty fish; the Romans have esteemed her the Helena of their feasts,
and some the queen of palate-pleasure." The announcement that the
blood of eels is poisonous will hardly, despite its scientific
interest, form a comfortable subject for reflection to the modern
votaries of this novel Helena. Indeed, in the present timid temper of
the public, this article of diet would not improbably share the
ill-odour which befell the unfortunate oyster and be practically
banished from our tables; but although the oyster is perhaps
justifiably at present ostracised from our _menus_, taking the
majority of its breeding-grounds into consideration, it would be the
height of injustice to measure out similar drastic treatment to the
eel.
That the oyster bred in sewage-contaminated beds may revenge itself
upon its consumer by infecting him with the germs of typhoid has been
repeatedly contended, but that the eel, although its unsavoury
surroundings are proverbial, can be held responsible for poisoning
those who eat it has never, we believe, been seriously maintained,
although there is an old Italian saying which bids us "give eels and
no wine to our enemies."
Public confidence, however, in the eel as an article of food need not
be shaken, for it is satisfactory to learn that researches which, on
the one hand, condemn eels as living generators of a highly poisonous
substance, on the other hand allay any alarm which they may have
reasonably raised by showing that this toxic principle is entirely
destroyed in the processes of digestion, and that, therefore, taken
through the mouth it is rendered harmless, and only when introduced
into the system by inoculation beneath the skin or injected into the
peritoneum can it assert its dangerous properties. That the blood of
eels is, however, justifiably to be in future classed amongst the
toxins, the number of which has of late been so increased, is at once
apparent when we learn that about a dozen drops inoculated into a dog
weighing about fourteen pounds will destroy the latter in less than
ten minutes, whilst pigeons, rabbits, and guinea-pigs similarly
treated, only with smaller quantities, also invariably succumb to its
lethal action.
Quite recently an endeavour has been made to determine precisely the
degree of toxicity possessed by eel's blood, or, in other words, to
standardise the poisonous principle contained in it, so as to afford a
guide to those experimenting on the subject; and it has been asserted
that one cubic centimetre, or about twenty drops, injected into the
veins of a rabbit weighing four pounds, may be regarded as a fatal
dose for such an animal. But many difficulties surround such an
attempt to exactly define the degree of toxic action possessed by such
a substance, for, in the first place, the blood varies in respect to
this property in different eels, whilst it also differs widely in
character at different stages of the life of the fish. This seasonable
variation in toxic character has been noticed in the case of viper
venom, which it will be remembered was shown to be far more lethal in
action when collected from snakes in the spring of the year than in
the winter months.
The toxic substance contained in eel serum was originally called by
its discoverers, the Mosso brothers, _ittio-tossina_; and they record
the fact that the blood of rabbits and frogs, which animals had
succumbed to its action, did not coagulate after death, whilst,
curiously, in the case of dogs this abnormal phenomenon was not
observed.
There are various means which may be resorted to for destroying the
poisonous principle contained in eel blood, and from a dietetic point
of view it is satisfactory to know that heat-exposure for a quarter of
an hour to a temperature of from 57·7° to 77·7° Cent. entirely removes
it, whilst its virulence is greatly modified by submitting it for a
longer period, twenty-four hours, to a much lower temperature, _i.e._
37° Cent. It also gradually loses its toxic properties eight days
after it has been collected, even when carefully shielded from light,
a feature which contrasts favourably with viper venom, which can be
kept for more than a year and remains as active as when first derived
from the snake. We have seen also that its toxic properties invariably
succumb to the processes of digestion, so that even if fashion or fad
or advertising speculators, backed by scientific names, were to decree
that a wealth of nourishment and support was contained in raw eel
"juice," and the edict went out that it was a desirable and highly
important article of invalid diet, the general public may, according
to its wont, innocently accept the edict and in this case suffer no
evil consequences.
But another and very remarkable method of mitigating the virulence of
eel blood, and one which so far has received no explanation, is
mentioned by Dr. Wehrmann, of Moscow, who has been lately studying the
character of this fish's blood in Dr. Calmette's laboratory at the
Pasteur Institute at Lille. Dr. Wehrmann found that if blood serum be
taken from animals previously rendered artificially immune to the
action of serpent venom, and if some of this so-called anti-venomous
serum be injected under the skin of eels some hours before they are
killed, the lethal properties of their blood after death are
considerably reduced. Thus, an eel weighing about six ounces received
subcutaneous injections of five cubic centimetres of anti-venomous
serum; after the lapse of four-and-twenty hours it was killed and
bled, and its serum inoculated into animals in the usual way. But
whereas two cubic centimetres of normal eel blood sufficed to kill a
guinea-pig, this eel's blood had to be administered in _twice_ that
quantity to produce a fatal result, so that its toxic character had
been reduced to a very appreciable extent. The readiness with which
eel serum parts with its lethal properties, and the restricted
conditions under which they can operate, sufficiently assure us that
in the present state of our knowledge there is no danger to be
apprehended from this fish, and in the absence of any experiments to
show what is the effect on human beings of subcutaneous inoculations
of such blood, there is no call for this substance to be scheduled
under the Poisons Act. We have, however, by no means exhausted the
extremely curious properties which characterise this material, and
these properties are brought to light in a remarkable manner in
connection with the investigations which have been carried out to
artificially protect animals from its lethal influence, and also in
some interesting experiments which have been made to compare the
toxicity of eel blood with that of vipers.
It is far from an easy matter to secure for experimental purposes an
adequate supply of eel serum, for even a big fish weighing nearly five
pounds is not capable of yielding more than about twenty-five cubic
centimetres of blood, and from this only from ten to twelve cubic
centimetres of serum are obtainable. Calmette has shown that not only
the venom glands of reptiles contain toxic substances, but that the
blood of such snakes also possesses lethal properties, only in a far
less degree. Curiously, the serum of eels is no less than three times
as toxic as the serum of the most vicious viper, and, moreover,
produces far more discomfort and pain to the animals into which it is
introduced than accompanies the injection of viper blood. In the case
of viper blood its introduction is followed by no symptoms of
discomfort, the animal remains quite quiet, growing more and more
somnolent, a condition which is followed by an abnormal fall of
temperature, ultimately ending in complete collapse, symptoms which in
a much more modified degree characterise the injection of _heated_ eel
serum into animals. This heated eel serum, which we have seen is
deprived of the objectionable characteristics of ordinary eel serum,
produces but very transitory symptoms in animals, occasioning some
degree of somnolence, and now and again a reduction in temperature, a
condition from which, however, the animals rapidly recover in from two
to three hours. Animals, however, treated with this heated eel serum
acquire a power of resisting the lethal action of unheated or ordinary
eel serum, and this artificially induced condition of immunity
continues for about three days after the completion of the treatment.
The protective properties of this heated serum are not restricted to
animals subsequently inoculated with eel serum, but are extended also
to animals which afterwards receive injections of viper serum; but of
much greater interest and importance is the remarkable fact that
heated eel serum, as well as weak doses of the latter not heated but
diluted with water, are capable of protecting animals from the fatal
consequences of the far more potent viper venom.
It is interesting to note that, although diluted eel serum can protect
an animal from so deadly a poison as viper venom, the serum of vipers
is quite unable to afford any such service in the case of animals
inoculated with ordinary eel serum. The full complement of protective
power obtainable from this treated eel serum is only able to slowly
assert itself, for it is necessary for a period of as long as
twenty-four hours to elapse after its introduction to ensure the
animal's system being thoroughly impregnated with it and enable it to
withstand a lethal dose of viper venom.
In this respect, what may be designated treated or protective eel
serum differs very markedly from anti-venomous serum, which we have
seen is serum derived from animals trained up to withstand fatal does
of serpent venom, for anti-venomous serum acts immediately, and at
once confers immunity on an animal from the lethal effects of such
venom.
The rapidity with which it acts is indeed one of the most astonishing
properties of this particular anti-toxin. Thus if two cubic
centimetres of anti-venomous serum be inoculated into the marginal
vein of a rabbit's ear, it at once confers upon the latter complete
immunity from snake poison. Immediately after the injection of the
serum, venom sufficient to destroy an ordinary rabbit in a quarter of
an hour may be injected with impunity into the vein of the other ear.
But not only are the _protective_ powers of this serum so remarkable
in their degree, but its _curative_ powers, a much more difficult
property to establish in a substance, are extraordinarily intense, as
may be gathered from the following example. Four rabbits were
inoculated with a quantity of venom calculated to destroy them in the
space of two hours; one of these four animals was abandoned to its
fate, but the other three received, practically at the eleventh hour,
viz. just fifteen minutes before the expiration of the calculated two
hours' respite, an intravenous injection of a small quantity of
anti-venomous serum, only amounting to one four-hundredth part of the
weight of each animal respectively. The rabbit which received only the
venom died at the end of two hours, whilst the other three remained in
perfect health.
But although eel serum can be persuaded to part with its poisonous
character and even exercise protective powers over otherwise doomed
victims, it is not able to stretch forth a healing hand to the
afflicted, for, when once the poison has been introduced, whether it
be eel or viper blood, or the venom of snakes, it is absolutely
powerless to mitigate or stop in any way the deadly progress of the
toxin. Thus whilst eel blood may acquire _protective_ properties it
cannot acquire _curative_ properties, and, therefore, treated eel
serum cannot be legitimately enrolled with the anti-toxins which have
been elaborated, as, for example, anti-venomous serum, for, to be
worthy of such rank, a substance must be capable of wielding both
protective and curative powers.
But, although eel serum may under certain conditions protect from the
lethal action of serpent venom, eels are not themselves under ordinary
circumstances endowed with any power to withstand the influence of
this poison, for a good-sized eel will succumb to a dose of venom
which is sufficient to kill a guinea-pig.
Considerable interest is attached to the fact that anti-venomous serum
not only acts as an anti-toxin towards serpent venom, but also towards
a poison of quite a different character, such as that present in the
normal blood of eels, for this fact tends to confirm the view upheld
by some authorities, that specific toxins do not necessarily only
yield to specific anti-toxins, and that a particular anti-toxin may
act as such towards divers toxins of varied origin and character.
Calmette has brought this point out very clearly in his later
investigations on the vegetable poison abrine, a very powerful toxin,
furnished by the active principle of the seeds or beans of a
leguminous plant common in India and South America, and frequently
used, as already mentioned, by the natives in India to revenge
themselves on their enemies in poisoning their cattle. Immunising
serums of various kinds were selected for testing their protective
action on animals poisoned with abrine, and it was found that
anti-tetanic, anti-diphtheritic, anti-anthrax, and anti-cholera serums
all individually exerted a decided immunising action with regard to
this powerful vegetable poison. The hope is, therefore, perhaps not
beyond the realm of possibility, that at some future time the
complexity of drugs which now figure in the chemists' pharmacopoeia
may be replaced by a few substances the application of which will come
within the means and understanding of all. So far we have not dealt
with the artificial immunisation of an animal from the action of eel
poison, but this apparently offers very little difficulty, and is
accomplished by introducing very small and gradually increasing doses
of eel serum into the system, care being taken to proportion the
quantity given according to the weight and general condition of the
animal to be immunised. A rabbit, for example, treated in the above
manner, subsequently yielded a serum which was proved to possess both
preventive and curative powers in respect to both eel poison, and
viper venom and blood, entitling this so called anti-eel serum to take
its place amongst the anti-toxins, and furnishing yet another instance
of a substance exercising its immunising influence over various
toxins.
This process of gradually acclimatising, as it were, animals to a
particular poison by repeated doses of the same poison, recalls the
old proverb, "Seek your salve where you got your sore," and brings us
to a consideration of some of the primitive antecedents of a practice
which, at the present time, promises to bring about so profound a
revolution in the art of medicine. The modern system of inoculation
has, however, arisen quite without reference to such antecedents,
which latter were not based upon any scientific laws or
considerations, but owed their evolution to local customs and
experience handed down from age to age by tradition, and in many cases
preserved through a simple faith in the superstitions which surrounded
them.
To such a category must be added the curious superstitions indulged in
by the native population of Tunis regarding methods of preventing
hydrophobia in persons bitten by rabid animals. Dr. Loir refers to
these primitive ideas on the art of healing in a report of the work
carried out at the Anti-rabic Institute at Tunis, one of the many
centres for the prevention of rabies by Pasteur's method which have
been established in every quarter of the globe except Great Britain,
the inhabitants of this "great conservative island-Empire," as a
renowned foreign scientist describes it, still preferring a trip to
Paris to countenancing the establishment of an anti-rabic institute in
their own country. The Arab physicians in Tunis have from time
immemorial sought to specially identify themselves with cures for this
disease, which is so prevalent as to be a veritable scourge to the
country. A much-vaunted remedy advocated by the profession consists in
pounding up the charred head of a rabid dog with vinegar, and
administering an emulsion of the same to the patient. The dung of
camels is also highly prized as a remedy, as also the water of certain
wells which the simple faith of the natives has endowed with
supernatural curative properties. But the strangest prescription of
all consists in broth made from lambs a year old, to which is added a
peculiar kind of beetle, but in such a small quantity that the latter
ingredient only equals the weight of a grain of corn. This concoction
is given to the unfortunate patient twenty-three days after he has
been bitten. In the urine, according to the Arabian doctors, seven
small worms should be found which represent the embryos of dogs
engendered by the virus in the human body, and which when once got rid
of the patient recovers!
In the face of such crude traditions upheld with so much tenacity by
the native population, it is surprising that the Tunisian Anti-rabic
Institute has met with such a large measure of support in the shape of
applicants for admission, which, on an average, number over one
hundred annually. The mortality amongst those treated closely
approaches the satisfactory results obtained at the Paris Institute,
where the death-rate amounts to about 0·38 per cent. of the persons
treated.
There is perhaps no more interesting chapter in the history and
literature of medicine than might be compiled by searching out the
early uses of drugs and the primitive application of methods in the
art of healing, and tracing their connection, if possible, with the
practices which are in vogue at the present day. In the matter of
toxins and anti-toxins, or in respect to the modern theories of
preventive medicine, there would appear to be a curious link between
the methods based upon elaborate scientific inquiries and those which
arose through simple experience and expediency.
The idea of a poison, as the old proverb above tells us, being a
corrective for itself is no new idea, for we read how in ancient
times, for example, the Ophiogenes of the Hellespont were renowned for
their immunity to snake poison, and one account of them states
particularly that they fed upon serpents, and that to this diet they
probably owed their reputed magical art in withstanding the action of
serpent venom. Again, a traveller in Egypt, Hasselquist, tells us how
the serpent-charmers there eat serpents, making them into a kind of
broth, and that invariably before starting off to catch these reptiles
they partake of some of it.
In a paper by Mr. T. R. Rao on the Yánádés tribe of the Nellore
district, Madras Presidency, the author mentions that these strange
people have, amongst other characteristics, absolutely no fear in
catching cobras, which they draw out of their holes without any alarm
as to their fangs, and that they appear to protect themselves against
the effects of snake-bites by swallowing the poison-sacs of snakes.
Bruce describes how he saw a serpent-charmer in Cairo who allowed
himself to be bitten by a viper between the forefinger and the thumb,
and made no endeavour whatever to apply remedies, neither did he
exhibit the slightest anxiety as to the consequences. That this was no
trick, and that the viper was really possessed of all its deadly
faculties at the time it bit the man, was proved by the fact that a
pelican subsequently bitten by the same animal died in thirteen
minutes. Bruce also tells of a man who "with his naked hand took a
viper from a number of others lying at the bottom of a tub. He put it
on his head, then in his breast, and tied it about his neck like a
necklace. Next it was made to bite a hen, which died in a few minutes;
and, to complete the experiment, the man took it by the neck, and,
beginning at the tail, ate it as one does a carrot or a stick of
celery, without any seeming repugnance."
A most interesting account of snake-charmers is given by Drummond Hay,
in his book on _Western Barbary_, in which he relates his experiences
with some of these wonderful individuals belonging to the sect called
Eisowy. Members of this sect, he mentions, frequently handled
scorpions and poisonous reptiles without fear or hesitation, and they
were never attacked by them. He was present at one of their
exhibitions of feats with snakes in which they both allowed themselves
to be bitten and provoked the snake to bite them. The charmer thus
bitten then in his turn ate or chewed the reptile, which, he remarks,
writhing with pain, bit him in the neck and hands till it was actually
destroyed by the Eisowy's teeth.
In South Africa snake poison is actually taken as a protection against
snake-bites, and if we turn to the _Lancet_ of the year 1886, we shall
find a letter from Mr. Alfred Bolton stating that his curiosity had
been aroused by the fact that while in South Africa cattle and horses
frequently died from the effect of snake-bites, the natives themselves
seldom or never appeared to suffer any inconvenience from such
injuries other than would follow any accident which would set up local
inflammation. On inquiry he found that they were in the habit of
extracting the poison gland from the snake immediately it is killed,
squeezing it into their mouths and drinking the secretion, thereby
apparently acquiring absolute immunity from snake-bites. So impressed
was Mr. Bolton by what he observed that he adds: "I can no longer
refuse to believe in the efficacy of the snake virus itself as a
remedy against snake poison."
Savage tribes have learnt from bitter experience how to protect
themselves from snake-bites, and it is well known that they have a
method of inoculation which they employ with success. The Creoles of
Surinam use an ointment as a protection against snake-bites, which is
regarded as highly efficacious. It is reputed to consist principally
of the pounded head of a rattlesnake, which concoction would therefore
include the contents of the venom glands. This is then mixed with the
juices of a certain plant, which addition probably mitigates the
intensity of the venom by acting as a diluent. This substance is
generally applied by making an incision in the wrist or forearm and
rubbing it in, after which individuals thus treated appear to enjoy
security from the venom of snake-bites.
What applies to serpent venom would also appear to hold good in regard
to other poisons, such as that contained in the sting of a bee. This
poison is extraordinarily tenacious of its irritant properties, and,
unlike eel poison, retains its virulence even when exposed to high
temperatures.
An interesting memoir on the immunity of the bee-keeper from the
effects of bee poison was published a short time ago by Dr. Langer in
a German scientific journal. He issued a number of circulars with
questions to be answered, and sent these to more than a hundred
bee-keepers in different parts of the country, with the result that a
hundred and forty-four stated that they were now immune to bee poison,
nine having been fortunately endowed with a natural immunity to this
irritant, whilst only twenty-six out of the whole number applied to
stated that they were still susceptible.
This condition of immunity to bee poison is obtained after a varying
number of stings have been inflicted; in some cases thirty, at the
rate of from three to four a day, are sufficient to ensure freedom
from further discomfort, but the inoculations may have to be prolonged
up to one hundred stings to secure complete immunity.
In experiments carried out on animals this immunity to bee poison has
been also induced by repeated application of the irritant. It was
formerly generally supposed that the irritant nature of a bee's sting
was due to the presence of formic acid; but inasmuch as bee poison can
retain its poisonous character in spite of being submitted to heat,
which would effectually volatilise the formic acid present, this
assumption must be abandoned, and opinion is more inclined now to
regard this irritant substance as partaking of the nature of an
alkaloid.
Before closing this brief review of some of the most recent
discoveries which have been made in the domain of immunity, we must
mention some extremely suggestive and important researches on the
poison of tetanus, or lock-jaw, which have emanated from Dr. Roux's
laboratory at the Institut Pasteur in Paris.
It will perhaps be remembered that Pasteur, when working at
hydrophobia, experienced the greatest difficulty in exciting rabies in
animals with certainty, and that it was only when the fact of its
being a disease which essentially affects the nervous system of the
animal was taken into account that it occurred to him to cultivate the
virus in the medium for which it had seemingly the greatest affinity,
viz. the nervous tissue of an animal; it was only on taking this step
that he succeeded in invariably provoking rabies in the animals under
experiment.
In the case of tetanus we have another disease affecting the
nerve-centres of the body, and although many authentic cases have been
cited in which the treatment with anti-tetanic serum has been entirely
successful, a great many instances have occurred in which it has been
of no avail at all, more especially when the disease has obtained a
firm hold on its victim. Now Dr. Roux has not only been carrying out
experiments to ascertain what is the result of directly attacking, as
Pasteur did in the case of rabies, the nerve-centres of an animal with
the tetanus toxin, but he has also taken another and very important
step further, and has investigated, not only the action of the toxin,
but also that of the anti-toxin on the nerve-centres of an animal
suffering from tetanus.
In describing the cerebral inoculations which he has conducted on
animals, Dr. Roux points out that the operation, in itself, is
attended with no pain or even inconvenience to the animal in question,
that subsequently it eats with its usual appetite, and shows no signs
of discomfort.
First, as regards the infection of an animal with the tetanus virus
introduced directly into the brain, it has been found that very much
smaller quantities produce a fatal result than when subcutaneously
inoculated. Thus, a rabbit which received two cubic centimetres of the
poison under the skin took four days to succumb to tetanus, whilst
one-twentieth of the quantity inoculated into the brain sufficed to
kill another rabbit of the same size in less than twenty hours.
Another very instructive example of this susceptibility of the
nerve-centres for certain poisons is afforded in the case of rats
and the toxin of diphtheria. Rats possess a natural immunity from
this substance, and can successfully withstand a dose of diphtheria
poison introduced under the skin which would infallibly kill several
rabbits. This state of immunity, however, entirely disappears when
the toxin is brought directly in contact with nervous tissue, for
a very small quantity of diphtheria poison--insufficient to cause
under ordinary circumstances even a passing swelling at the seat of
inoculation--will, when introduced into the brain of a rat, kill the
animal.
Again, rabbits are generally credited with possessing high powers of
resisting the action of morphia, a large dose of this substance
introduced subcutaneously producing no result whatever. A cerebral
inoculation, however, of a minute quantity of morphia causes an
immediate reaction, and the animal, after remaining in a more or less
dazed condition for several hours, finally succumbs to this drug. Dr.
Roux is inclined to regard this difference in the susceptibility
exhibited by animals to one and the same poison as being due to a good
deal of the toxin, when subcutaneously introduced, failing to reach
the nerve-centres, it having been destroyed or arrested in the system
before it could attack them.
What is the nature of the subtle forces which may so beneficially
intervene between the toxin and its victim has long been a problem
which has excited the interest and ingenuity of some of the most
brilliant scientific authorities of the day, and it is one which, even
in the hands of men like Metchnikoff, is still awaiting a satisfactory
solution!
The important point was next approached by Dr. Roux as to whether an
animal, successfully trained to withstand large doses of the poison,
as ordinarily introduced, could also resist it when directly
inoculated into the brain. Is, in fact, the undoubted immunity to
tetanus poison which may be possessed by an animal due to the
nerve-centres having become insensible to this substance? The answer
to this question would appear to be in the negative, for animals
artificially protected from tetanus poison introduced under the skin
succumbed to a small dose inoculated direct into the brain, which
would otherwise have not produced even a slight passing tetanic
affection of the limb where the inoculation was made. Immense numbers
of experiments were made under varying conditions, but the result was
fully confirmed, showing that the nerve-centres had not acquired any
immunity to the poison, although the blood serum of the victims to
such cerebral inoculations was proven over and over again to be
endowed with strong protective properties against tetanus poison.
The endeavour was then made to, in Dr. Roux's words, "place the
anti-toxin where the toxin is working," and preserve the vital force
of the nervous tissue. To arrest tetanus by substituting cerebral for
subcutaneous inoculations of the anti-tetanic serum was the next feat
attempted. Several guinea-pigs and rabbits were inoculated
subcutaneously with virulent doses of tetanus poison sufficient to
kill them in about seventy hours; some were subsequently treated with
anti-toxic serum introduced in the ordinary way under the skin, whilst
others were inoculated with from six to seven drops of this protective
serum direct into the brain. The results were extraordinarily
successful. Although but a few drops of the anti-toxin were used for
the _cerebral_ inoculations, the animals survived the otherwise fatal
doses they had received of the toxin; whilst out of seventeen
guinea-pigs which received _subcutaneous_ inoculations of the
anti-toxin only two recovered, and the quantity of the anti-toxin
employed reached as much as from ten to twenty cubic centimetres in
some of the experiments, contrasting in a remarkable manner with the
few drops which sufficed in the case of the cerebral inoculations.
Dr. Roux sums up this splendid result in the following modest words:
"Il ne suffit pas de donner de l'anti-toxine, il faut la mettre au bon
endroit."
The significance and far-reaching application of this most important
discovery cannot easily be overestimated. Hitherto the preparation of
an anti-toxin has been the chief point considered, but Dr. Roux and
his able coadjutor, M. A. Borrel, have shown how great may be the
results which attend its method of administration, and have opened up
an entirely new direction for investigation.
Although the subject of immunity is not, as we have seen, by any means
wholly a latter-day creation, yet its approach and consideration from
a modern point of view, assisted by the resources and equipment
provided by modern scientific methods, justifiably entitles the
nineteenth century to claim it as its own discovery.
However brilliant and successful the labours may be of those who will
follow in the future, subsequent generations will know how to venerate
those great leaders of scientific thought, amongst whom we must rank
Pasteur, to whose genius the world owes so great a debt of gratitude,
and the vast extent of whose labours cannot be adequately measured at
the present day by reason of the restricted scientific horizon which
encircles public opinion in this country.
THE END
PLYMOUTH
WILLIAM BRENDON AND SON
PRINTERS
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