ruining large tracts of the South of France, the latter not unnaturally
hesitated. ‘Considérez, je vous prie, que je n’ai jamais touché un ver
à soie. Si j’avais une partie de vos connaissances sur le sujet, je
n’hésiterais pas,’ he wrote to his friend; but in spite of his
hesitation, he left for Alais, and at once commenced a campaign which
lasted during the summers of the next five years. Almost immediately on
his arrival he detected in the sick silkworms the corpuscles of Cornalia
and Filippi, which we now call the _Micrococcus ovatus_. These
micrococci are comparatively large and very bright; they occur in the
tissues and blood of the silkworm, and are found even in the eggs of the
moth. They cause the disease known as Pébrine. The occurrence of the
micrococci in the eggs was one of the most important new facts observed
by Pasteur. It was the first recorded instance of a parasitic organism
being conveyed from one generation to another by the egg; and, although
recently the germ of the Texas fever (allied to the malarial organism)
has been shown to pass from one brood to another through the egg of the
tick which conveys it, it is satisfactory to record that the cases in
which this occurs are restricted in number and comparatively rare. The
ease with which _Micrococcus ovatus_ could be detected suggested a
remedy. A child, when trained, can readily identify the organism.
Healthy moths produce sound eggs and healthy larvæ; diseased moths
produce diseased progeny. At the present day, throughout the silkworm
districts of the South of France, as soon as the moth has deposited her
eggs on the piece of linen provided for that purpose, she is pinned up
with the cloth; and during the ensuing autumn and winter the women and
children are occupied in microscopically examining the body of the moth,
crushed in a little water, for traces of the micrococcus. Should any be
found, the eggs on the corresponding piece of linen are at once
destroyed. Pasteur also showed that the infected stock spread the
disease by distributing the micrococci on the mulberry-leaves, whence
they enter the silkworm by the mouth; and that the sick inoculate the
healthy by crawling over them and piercing the skin with their pointed
claws. He therefore emphasized the importance of segregating the sound
caterpillars.
The above account conveys no impression of the difficulties under which
Pasteur worked. His researches were not only new to himself but to the
world. Processes which at the present day are carried out by every
medical student had to be devised for the first time. He had to combat
the criticism of scientific men, and to overcome the almost invincible
ignorance of the agriculturist, an ignorance which at one time advocated
the desperate remedy of asperging with absinthe the leaves of the
mulberry on which the silkworms fed.
Perhaps Pasteur’s greatest difficulty was the fact that the silkworms
did not suffer from Pébrine alone; and it was some time before he
recognized that he had to deal, not with one disease, but with two. The
second disease, known as the ‘Flacherie,’ is a disease of the digestive
system caused by overcrowding and insanitary conditions in the silkworm
nurseries. Like Pébrine, it is caused by a micrococcus, _Micrococcus
bombycis_. It was whilst investigating this creature that Pasteur
discovered that, although the germ itself cannot survive a lengthy
period of desiccation, it does in certain circumstances form spores
which can survive conditions fatal to the mature organism. This is the
first case recorded of a pathogenic organism producing spores, the
existence of which has explained so many problems in the spread of
disease.
During the period from 1865 to 1870 Pasteur was by no means occupied
solely by the silkworm epidemic. In many respects it was a sad epoch in
his life. Only nine days after his first arrival at Alais he was
summoned to Arbois to see his dying father, but arrived too late. In
the autumn of the same year he lost his little daughter Camille, the
second who had died. In 1868 he himself was prostrated by a stroke of
paralysis, and, although he slowly recovered, it left traces for the
remainder of his life.
Few distinguished men of science are left to pursue their investigations
undisturbed; and Pasteur was no exception. He had much to do with
promoting the publication of the works of Lavoisier, for whose
researches he had the profoundest respect. He actively intervened in the
elections of the Academy of Science, which appears to consume an
infinity of time. He made some preliminary investigations into cholera,
an outbreak of which towards the end of the year 1865 carried off 200
victims a day in Paris. He spent a week at Compiègne as the guest of
Louis Napoleon, and in a series of _séances_ explained the methods and
results of his labours. He wrote on the work of Claude Bernard; he drew
up schemes for certain reforms in the University; he gave advice on the
higher education of the country, and tried to stem the troubles of the
École Normale. In fact, he drew lavishly upon his reserve of health and
energy until the breakdown of 1868 was inevitable.
After a tedious recovery he recommenced his work. The success of his
methods had been acknowledged by the Austrian Government, who conferred
on him in 1868 the prize of 5,000 florins offered to anyone who should
succeed in discovering the best means of dealing with Pébrine. The same
year the University of Bonn conferred on him the honorary degree of
Doctor of Medicine; and in 1869 he was elected a foreign member of the
Royal Society. As was to be expected, detractors were not wanting: but
these were silenced by the campaign undertaken in 1869 by Pasteur on
foreign soil. The Master of the Imperial Household, Marshal Vaillant,
who devoted his declining years to scientific experiments, had repeated
in his apartments in the Tuileries the observations of Pasteur on the
silkworm disease, and had verified the accuracy of his conclusions. He
suggested to the Emperor that the Villa Vicentina, a property belonging
to the Prince Imperial, should be placed at Pasteur’s disposal for
further research. This villa, situated a few miles from Trieste,
belonged at one time to the Princess Élise, one of the sisters of
Napoleon I., who had lived quietly there after the fall of the First
Empire. On her death it passed to her daughter, the Princess Baciocchi,
and she in turn bequeathed it to the Prince Imperial. It had been a
great centre of the silkworm industry; but for some years no cocoons had
been produced, owing to the ravages of the disease.
By short stages, owing to his precarious health, Pasteur made his way to
Illyria, taking with him some sound silk-moth eggs, and during the
winter not only confirmed his previous researches, but re-established
the industry on such a scale that in the following spring the sale of
cocoons from this estate alone reached the figure of 26,940 francs.
During this winter he dictated to his wife the classic book in which he
recorded the results of his last five years’ work. Pasteur returned to
Paris through Munich, where he had the pleasure of meeting Liebig, one
of the most determined of his adversaries. Although he was unable to
induce the German savant to discuss scientific affairs, he always dwelt
with pleasure on the courtesy and cordiality with which he was received.
On his return the Emperor nominated him a Senator for life; but, before
the gazette appeared in which the nomination would have been recorded,
war was declared. From his birth Pasteur had been an ardent patriot, and
during the progress of the war he suffered acutely. So much did he feel
the reverses of his country, and what he regarded as the undue
harshness of the victors, that he felt constrained to return the
diploma of Doctor of Medicine which two years before he had accepted
from the University of Bonn. He did so in a letter which contained some
expressions of feeling with regard to the head of the invading army.
These had better have been omitted, but were perhaps pardonable under
the circumstances; they in no way excuse the terms of reply which Dr.
Naumann, Dean of the Faculty of Medicine at Bonn, permitted himself to
use--terms which would be discreditable in an ill-bred street _gamin_.
From 1871 to 1876, the year in which he published his ‘Études sur la
Bière,’ Pasteur was again largely occupied with the study of
fermentation. Part of his object was undoubtedly to place the French
brewers on an equality with the German; and in this he certainly had a
large measure of success. To one who knew Paris under the Second Empire
and who revisits it under the Third Republic, one of the first changes
observable in the life of the _café_ is the enormous consumption of
‘bocks.’ Pasteur’s work, however, went far beyond the establishment of a
national industry. He started investigations which have changed brewing
from an art into a science; and his most fitting memorial in this
respect is the bust which decorates the hall of the Carlsberg
Institution at Copenhagen, an institution devoted to the study of all
problems of fermentation. In his ‘Études’ Pasteur laid great stress on
the fact that every fermentation is brought about by micro-organisms,
and he dwells at length on the marked influence which certain bacteria
exercise on the nature of the fermentations, and on the character of the
beer produced. He did not, however, see, what Hansen demonstrated in
1883, that many of the commonest diseases of beer are caused by certain
species of yeast-cell differing specifically from those which cause its
normal fermentation. Indeed, he paid but small attention to species,
regarding it as waste of time, as it undoubtedly often is, to trouble
about names and synonyms.
As Professor Jörgenson and Dr. J. R. Green have shown in two
recently-published works, we have learnt much about brewing during the
last five-and-twenty years. The nucleus of the yeast-cell has been made
visible by appropriate staining; some thirty different species of
yeast-cell have been described, and their properties as ferments have
been investigated; Buchner, by grinding up the yeast-cells, has produced
an extract, called zymase, capable of converting sugar into alcohol; the
fact has been established that it is not so much bacteria as other
fungi, allied and often congeneric with the yeast-cell, which produce
disease in beer; still, allowing a full measure of credit to later
workers, we may look back to Pasteur’s researches in the early seventies
as establishing for the first time a scientific basis for brewing.
The same remarks are applicable to Pasteur’s work on the diseases due to
specific organisms in the region of preventive medicine. We have built
and are building a lordly edifice, but he drew the plan and even laid
the foundations. More than two centuries ago Robert Boyle--‘the Father
of Chemistry and Brother of the Earl of Cork’--had said that he who
could solve the nature of fermentations would be without doubt more
capable than others of explaining certain phenomena of disease. Towards
the end of his ‘Études sur la Bière,’ Pasteur wrote: ‘The ætiology of
contagious diseases is on the eve of having unexpected light shed upon
it.’ He was already thinking of his investigations into the cause and
prevention of contagious disease.
There is a certain malady known, when it attacks cattle and sheep, as
‘charbon’ or ‘sang de rate,’ and when it attacks man, as ‘woolsorter’s
disease.’ The term ‘anthrax’ covers the disease in both beast and man;
and anthrax is produced by a bacterium known as _Bacillus anthracis_,
which had been recognized and was accused of causing the disease before
Pasteur began to interest himself in such matters. It annually carried
off 20 per cent. of the sheep in the agricultural district of La Beauce,
and in Auvergne some 10 to 15 per cent. In certain localities the loss
was greater, amounting at times to an annual death-rate of 50 per cent.
The disease was by no means confined to France; it was spread over
Europe. In the government of Novgorod it was responsible for over 56,000
deaths in three years. In Egypt it was regarded as the direct descendant
of the plagues of Pharaoh. It ravaged the large sheep farms of the
Argentine Republic.
The bacillus which causes this disease, and which at times by inhalation
effects a lodgment in the bodies of those engaged in handling wool and
hides, was already known when Pasteur took up the study of pathogenic
germs. About the same time it was also attracting the attention of the
young German physician Dr. Koch, who subsequently became a severe critic
of some of Pasteur’s work; but in this article we are dealing with
Pasteur, and limitations of space compel us to leave unnoticed the
brilliant work of many investigators who have made the latter end of the
nineteenth century one of the greatest epochs in medical history.
Pasteur and his assistants made many fascinating studies on the
behaviour and life-history of the _Bacillus anthracis_. He found it very
susceptible to slight variations of temperature. The few degrees by
which the temperature of a bird’s blood exceeds that of a mammal were
sufficient to prove fatal to the bacillus; but by an ingenious
experiment he showed that if the temperature of a bird be artificially
lowered it becomes susceptible to the disease, though it readily
recovers if the artificial surroundings be removed. Pasteur further
noted that the bacillus was not equally fatal in all animals, and that
it changed its character when passed through the body of certain classes
of animals. It was, however, not in studying the _Bacillus anthracis_
that he made the far-reaching discovery of the attenuated virus. This he
first noted when at work on chicken cholera, a disease very fatal in
poultry-yards; and he made the important discovery by one of those happy
accidents which only occur to those who possess the genius for
observation. During his numerous experiments he one day chanced to
inoculate some fowls with a forgotten culture some weeks old. To his
surprise the chickens, though made ill, did not succumb; in fact, they
rapidly recovered. He immediately tried what the effect would be if
these same fowls were inoculated with fresh cultures of a kind so
powerful as to be undoubtedly fatal to a healthy bird which had never
suffered from the disease. To his delight, the inoculated fowls resisted
the poison, and proved, in fact, immune. This simple experiment is the
basis of the world-wide prophylactic measures which are now being
carried on against all forms of bacterial disease; and, although
Pasteur’s explanation of the weakening of the virus--which he attributed
to oxygenation--has been shown to be erroneous, he must still be
regarded as the originator of methods for the production of immunity by
means of artificially attenuated organisms.
If the virus of chicken-cholera can be attenuated, and when attenuated
produces immunity from later attacks, the same is probably true of other
germs which can be cultivated outside the body. Arguing in this fashion,
Pasteur returned to his study of anthrax. Here he also succeeded, and in
the spring of 1881 he demonstrated the value of his treatment. Out of a
flock of fifty sheep one-half were inoculated, the other half were not;
the whole flock was then infected with the disease. In less than a
month the uninoculated were dead of ‘charbon,’ the inoculated were
perfectly healthy. The telegram announcing the result to Pasteur,
anxiously waiting in his laboratory at Paris, ended with the words
‘Succès épatant!’
So striking a demonstration naturally had a profound effect. It inspired
confidence in the treatment. Since the date of this experiment some
millions of sheep have been inoculated against anthrax, and several
hundred thousand oxen; and it has been calculated that, within the
succeeding twelve years, seven million francs were saved by this means
alone to French agriculture. Perhaps the convincing nature of Pasteur’s
work in this connexion is best shown by the fact that the insurance
companies of France insist on inoculation before they will insure sheep
and cattle.
We have left ourselves but little space to dwell on the work which
occupied the greater part of the last twelve years of Pasteur’s life.
Already, in the midst of his work on anthrax, he was thinking of rabies;
and in 1881 he proved that it was conveyed through the saliva of the mad
dog, and that it could be communicated to rabbits. Saliva, however, was
not in every case to be depended on. In some cases it failed to convey
the disease. Experiment showed that the poison was concentrated in the
brain. To this day no one has succeeded in finding the organism--if it
be an organism--which causes rabies. Hence it cannot be cultivated on
gelatine in test-tubes, and no modified culture of bacteria can be
produced, as is now done in the case of diphtheria and other diseases.
Other means had to be devised. After countless experiments it became
evident that, if the spinal cord of a hydrophobic rabbit be kept dry at
a temperature of 25° C. for a couple of weeks, the strength of the
virus has so far vanished that, if an emulsion of the cord be injected,
it produces no rabies, but has only a slight vaccinating effect. If two
days later an emulsion of a twelve-days-old spinal cord be injected, the
vaccinating effect is stronger; but the body, already inured to slight
doses of the poison, remains unaffected. Thus, by gradually increasing
the strength of the dose, a virus may at length be injected which would
infallibly produce rabies but for the previous inoculations. When an
animal is bitten by a mad dog, the poison transmitted takes some time to
develop--some weeks at least, and often many months. If now the
artificially introduced virus ‘gets the start,’ so to speak, of the
naturally introduced poison, by the time the latter is at its height the
animal has become gradually immunified to the specific poison and
suffers little harm. The arsenic-eaters of the Tyrol afford an analogous
case. They consume amounts of arsenic which would infallibly produce
peripheral neuritis in men unaccustomed to such a diet.
It needed no small courage on Pasteur’s part to inoculate his
fellow-creatures against hydrophobia. In 1885 a boy some nine years old,
from Meissengott in Alsace, was brought by his mother to the laboratory
suffering from fourteen wounds inflicted by a mad dog. After long
consultations with his assistants and the most anxious deliberations, he
consented to the inoculation of the boy. The next fortnight was a time
of intense anxiety, but all went well. His second patient is
commemorated by the bronze statue which ornaments the front of the
Pasteur Institute in Paris. It represents the struggle between a peasant
boy, armed only with his sabot, and a mad dog; the boy was terribly
bitten, but the treatment saved his life. It is not easy to arrive at an
accurate estimate of the death-rate caused by rabies; but the most
careful and moderate estimates show that, before this treatment was in
use, some fifteen to twenty out of every hundred persons bitten by mad
dogs died a most painful and horrible death. During the fourteen years,
from 1885 to 1899, over 23,000 persons known to have been bitten by
rabid dogs have been inoculated at the Pasteur Institute; and their
average mortality has been 0·4 per cent. In 1899, the latest year for
which statistics are available, 1,614 cases were treated, with a
mortality of 0·25 per cent. Of these, 1,506 were French and 108 were
foreigners. Of the 108 foreigners, 12 came from Great Britain and 62
from British India. It is little short of a national disgrace that we
should still be dependent on French aid to succour those amongst us who
are so unfortunate as to be bitten by a mad dog; but the nation which
gave the use of anæsthetics to the world, and which first showed the
value of antiseptics, is largely dependent to-day on foreign aid in
dealing with great outbreaks of all sorts of diseases within its
borders. The German Koch and the Russian Haffkine are called in to cope
with the cholera in India; we fall back upon the Swiss Yersin and the
Japanese Kitasato to elucidate the true nature of plague, and to devise
methods for combating its ravages. When rinderpest broke out in South
Africa it was again to Koch that we turned. The unsatisfactory position
of Great Britain in these matters is to some extent due to a small but
active section of society whose affection for their lapdogs has
overpowered their sense of duty to their neighbours. It is, however, we
fear, still more due to the unintelligent treatment of men of science by
the Government of the country, and to the want of appreciation of the
value of science shown by society at large. If, to balance the list
given a few lines above, we recall the work of our countryman Major Ross
on the malarial parasite, it serves only to remind us of the
difficulties placed in the way of his research by the officials of the
service to which he belonged and the slightness of the recognition which
for many years he received from the Government.
In 1874 the French National Assembly voted Pasteur, as some recognition
of his work on seri-culture, a pension of 12,000 francs a year; nine
years later this was increased to 25,000 francs, and it was further
agreed that the pension should be continued to his wife and children. In
1881 he was nominated to represent France at the International Medical
Congress, which met that year in London. The reception accorded him
when, with his host, Sir James Paget, he mounted the platform in St.
James’s Hall, overwhelmed him. ‘C’est sans doute le prince de Galles qui
arrive,’ he remarked to his host, never dreaming that such acclamations
could be meant for him. The following year he succeeded to Littré’s
_fauteuil_ at the Academy. In 1888 the President of the Republic opened
the Pasteur Institute, which had been erected and endowed by a public
subscription from all countries and from all classes; and there in 1892
he received a distinguished collection of scientific men, who had come
from all parts of the world to congratulate him on his seventieth
birthday.
Three years later his health began rapidly to fail. Two strokes of
paralysis followed one another at a short interval, and on September 28,
1895, he died. He lies buried in the Institute he loved so well. A
nobler monument, or one more worthy of him who lies therein, has never
been erected by man. The benefits which his simple, strenuous,
hard-working, noble life conferred on humanity cannot be estimated. They
help us, however, to realize the truth of the old Arabian proverb, ‘The
ink of science is more precious than the blood of the martyrs.’
M. Vallery-Radot has given what will probably prove to be the definitive
Life of Pasteur. He has written at length, and he has written well.
That he is not a man of strict scientific training in no way detracts
from the merit of the work; rather, in many respects, this makes the
book more readable. The pupils of Pasteur, who are now carrying on his
work, have, out of the abundance of their knowledge, helped in the more
technical portions of the book; whilst M. Vallery-Radot, from his
intimacy and relationship with the subject of his biography, has been
able to supply those personal details which form so essential and so
interesting a part of every good biography.
For one who knew Pasteur only during the last decade of his life to
attempt any account of his character may savour of impertinence. Still,
it is impossible to close this article without some tribute to his
simple dignity of manner, and, above all, to his infinite kindness. No
man has done more to lessen suffering in this world, both in man and in
the lower animals, and probably but few have felt so much sympathy with
suffering in others. As a boy--and French country boys are not more
thoughtful about the suffering of animals than those of other races--he
refused to go shooting. ‘La vue d’une alouette blessée lui faisait mal.’
As an old man it was a touching sight to see him amongst the sufferers
under treatment at the Institut Pasteur, patting the little children on
the head, heartening up the timid and giving sous to the brave,
infinitely tender to the frightened mothers. ‘Men of science, my Sandra,
are always the humanest,’ as Laura said in ‘Vittoria.’ Another
dominating trait in his character was his unflinching desire for truth;
to ‘prove all things,’ and to ‘hold fast that which is good,’ was the
motto of his working life. His success was in no small measure due to
the rigorous tests he applied at all stages of his investigations; it
was also due to the untiring assiduity with which he worked, never
sparing himself, never in any way thinking of himself. But, above all,
it was due to the intense thought he bestowed upon his researches.
Concentrating his intellect upon the problem in question, he thought out
all possible solutions, and was prepared for all possible eventualities.
It was this power of thought, coupled with a matchless gift of
observation and experiment, that enabled him to leave a name which
cannot be forgotten whilst civilization endures.
MALARIA
_There in a wailful choir the small gnats mourn_
_Among the river sallows, borne aloft_
_Or sinking as the light wind lives or dies._
JOHN KEATS: ‘To Autumn.’