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.