PASTEUR'S LIFE AND WORK 
IN RELATION TO THE 
ADVANCEMENT OF MEDICAL SCIENCE 
BY 
L. A. STIMSON, M.D. 
VlCE-PREESIDENTN. Y. ACADEMY OF MEDICINE; PROFESSOR OF SURGERY, UNIVERSITY 
OF THE CITY OF NEW YORK 
NEW YORK 
Press of STETTINER, LAMBERT & CO. 
22, 24 & 26 Reads Street 
1893 PASTEUR S LIFE AND WORK 
IN RELATION TO THE 
ADVANCEMENT OF MEDICAL SCIENCE 
BY 
L. A. STIMSON, •'M.D. 
V1CE-PREESIDENT N. Y. ACADEMY OF MEDICINE; PROFESSOR OF SURGERY, UNIVERSITY 
OF THE CITY OF NEW YORK 
NEW YORK 
Press of STETTINER, LAMBERT & CO. 
22, 24 & 26 Reade Street 
*893 Pasteur's Life and Work 
IN RELATION TO THE ADVANCEMENT OF 
MEDICAL SCIENCE.1 
Mr. President and Fellows of the New York Academy of 
Medicine : 
Among the many wise provisions of those who have 
brought this Academy to its present standard of intellec- 
tual and material prosperity must be counted that which 
provides for this annual reunion of its members, in order 
that, laying aside for the moment the special interests that 
absorb them in the various Sections during the year, they 
may turn their attention to some matter of general inte- 
rest and wider import. The same wise foresight throws 
open the doors to our non-professional friends ; and in 
order that they may be not only welcome, but also inte- 
rested in our proceedings, it suggests that the topic of 
the evening and its treatment should be such that the de- 
ficiencies of their training and of their opportunities may 
not wholly deprive them of the possibility of finding 
pleasure therein. 
In casting about for a subject that would meet the re- 
quirements of the occasion, that would interest both the 
professional and the non-professional hearer, and that 
possessed sufficient intrinsic merit to compensate for de- 
fects in its presentation, I was reminded that nothing is 
more interesting than to review the course of one of the 
masters of science, to receive his exposition of the princi- 
ples of his method, to study their illustration in examples 
drawn from his own experience, to trace the operation of 
1 Anniversary Discourse before the New York Academy of Medicine, No- 
vember 17th, 1892. Reprinted from Transactions. 4 
Stimson : Pasteur's Life and Work. 
his mind, to learn how even mistakes may be profitable 
and instructive, and to appreciate at what price notable 
discoveries and solid progress are made. 
The story of the life of such an one should be of interest 
to all, and if it dealt with the broader problems of our 
own science the requirements of this occasion would be 
fully met by it. 
Furthermore, there is in the review of the progress of 
any science or of the development of any great idea or 
broad principle something far more worthy of respect 
and attention than the simple personal element or the mo- 
mentary interest of the recital. In the world of ideas the 
novelty of to-day becomes the commonplace of to-morrow. 
The ideas which came like revelations or inspirations to 
our fathers are fed to us in our school books, and appear 
to us to have existed, like the alphabet or the solar sys- 
tem, from the beginning of the world. As we read the 
history of a past removed from us, perhaps, by but a few 
generations, we are amazed that men's actions should 
have been determined by such faulty notions of political, 
economical, or religious principles, and that they could 
have been so blind to what is now so clear. And when we 
read books that within a few years have revolutionized 
thought, that have been received and acclaimed almost as 
if they had been divinely inspired, we ask ourselves in 
vain in what the novelty and the originality could have 
consisted, so commonplace, so trite even, have those 
novel and original ideas become. It therefore becomes 
a pious duty to those who have so raised the general level 
of our knowledge or of our principles, that while we en- 
joy the fruits of their labors we should still be mindful of 
their part in it and should bear their names in constant 
and grateful remembrance. 
The science of medicine is so closely interwoven with 
other sciences, so many of its most important advances 
have been made by the aid of those whose names are not 
upon its roll of members, that we shall never be at a loss 
to find a worthy and appropriate subject for our study, Stimson : Pasteur's Life and Work. 
5 
our honor, and our gratitude; and there is a peculiar 
propriety in the public and professional recognition of 
our obligations to those who are not strictly of us. I of- 
fer no excuse, therefore, for asking your attention this 
evening to a brief review of the life and accomplishments 
of a man who is by profession a chemist and whose only 
medical title is that of honorary membership in an acade- 
my of medicine. And yet, although so widely removed 
from us by training and occupation, it has fallen to his lot, 
in a larger measure, perhaps, than to that of any other 
man, to open important pathways of research in medicine 
and to establish a doctrine of causation of disease upon 
which a mighty and efficient structure of prevention and 
cure has already been erected. Upon principles discov- 
ered and established by him rests the modern treatment 
of surgical wounds, with the saving already effected of 
hundreds of thousands of lives, and to him a few years 
ago (1876) Prof. Tyndall wrote in these words : " For the 
first time in the history of science we have the right to 
cherish the sure and certain hope that, in respect to epi- 
demic diseases, medicine will soon be delivered from em- 
piricism and placed on a really scientific basis. When 
that great day shall come, humanity, in my opinion, will 
recognize that it is to you that the greatest part of its grati- 
tude is due." And at the meeting, last summer, of the Brit- 
ish Medical Association, the author of the address on bac- 
teriology expressed the gratitude of the world to him as 
the one whose genius had raised that branch of study to 
the rank of a science. Let us, then, add to-night our trib- 
ute of homage and gratitude to 
LOUIS PASTEUR. 
Born in December, 1822, in a village near the central 
eastern frontier of France, of humble parents who labored 
and sacrificed to advance his education as though they 
foresaw his future, we find him at the age of eighteen 
already a tutor in the college of Besangon, which had just 
given him his baccalaureate degree, with a reputation es- 6 
Stimson : Pasteur's Life and Work. 
tablished for exceptional ability and industry, and with a 
maturity of character far beyond his years. His position 
was a modest one : it lodged and fed him and gave him 
five dollars a month ; but it also gave him an opportunity 
to continue his studies, and it placed his foot upon the 
first round of that wonderful ladder of educational and 
scientific organization which offers to every young lad 
in France who chooses to attempt to climb it a sure and 
certain promise of rewards and honors, in accordance 
with the measure of his ability and industry. 
Three years later he won a place in the Ecole Normale 
at Paris, where almost all his work has since been done, 
and of which he has become the supreme glory. In this 
great school, where the students are invited rather to 
independent investigation than to attendance upon meth- 
odical instruction, Pasteur found both stimulus and oppor- 
tunity for the gratification of his passion for chemistry; 
and it is interesting and suggestive to see the lad em- 
ploying in his self-instruction those methods of close 
observation, rigid self-criticism, and control experimenta- 
tion which have been the foundation of his later successes, 
and displaying the same skill and beauty of manipulation, 
the same strength and clearness of thought, the same 
absolute honesty, and the same breadth of view. A single 
incident may be quoted in illustration, and also because 
it was the first step in his long line of research and dis- 
covery, each subsequent one of which was the natural, 
logical successor of those which had preceded. 
Molecular physics and chemistry, and the structure 
and polarity of crystals, were at that time receiving much 
attention, and it was held by some of Pasteur's teachers 
that in the arrangement of molecules was to be found the 
explanation of all chemical and allied phenomena. Into 
the study of this subject Pasteur had entered with his 
usual ardor, when a note was sent to the Academie des 
Sciences by the mineralogist Mitscherlich which threat- 
ened to destroy the theory. Mitscherlich pointed out 
that, although the double tartrate and paratartrate of Stimson : Pasteur s Life and Work. 
7 
soda and ammonia were identical in chemical composi- 
tion, specific weight, crystalline form, and double refrac- 
tion, yet, while the tartrate in solution deviated the beam 
of polarized light, a solution of the paratartrate did not 
affect it. Apparently the admitted identity in the num- 
ber, arrangement, and distances of the atoms in the two 
substances did not make them identical in all respects. 
The crystals of the two acids and of their compounds 
had already been studied and described in great detail. 
Pasteur set himself to repeat the investigation, and he 
discovered, what had been overlooked by all others, that 
the crystals of tartaric acid, and those of its compounds, 
were asymmetrical in this sense, that if one was split in 
two the two halves, while identical in form, were not 
superposable; they were, so to speak, right- and left- 
handed respectively; each was identical with the mirror 
image of the other, as a right hand is identical with the 
reflection of a left hand in a mirror. A solution of these 
asymmetrical tartaric crystals deviated the beam of po- 
larized light to the right. We may, for convenience, call 
them right-handed crystals. The crystals of paratartaric 
acid he found to be symmetrical, and, as has been al- 
ready said, they were without action upon polarized light. 
But on examining the crystals of the salt formed by com- 
bining this acid with soda and ammonia, he found, to his 
great surprise and delight, that they were asymmetrical, 
and asymmetrical in two forms; there were both right- 
and left-handed crystals; and a solution of one kind devi- 
ated light to the right, and a solution of the other deviated 
it to the left; when they were mingled the effect of one 
neutralized the effect of the other. And thus the objection 
raised in the famous note of Mitscherlich was answered. 
Pursuing the investigation, he found a new form of tar- 
taric acid, one whose crystals were left-handed, and which 
deviated light to the left. He made known his discovery 
to the Acad6mie des Sciences, and it was referred at once 
for report to the veteran Biot, the discoverer of the 
polarization of chemical substances. He summoned Pas- 8 
Stimson : Pasteur s Life and Work. 
teur to his laboratory, supplied him with the acids and 
bases, and told him to prepare the crystals. When this 
had been done he bade him separate the alleged right- 
handed from the left-handed, and then, pointing to each 
little pile in turn, he said: " Do you declare that these 
will deviate the light to the right, and these to the left?" 
On receiving an affirmative answer he at once prepared 
a solution of each and applied the test, and as the pre- 
dicted result appeared the illustrious old man caught the 
youth in his arms, saying: "My dear young friend, I 
have so loved Science all my life that this makes my heart 
throb." 
We can perhaps gain some conception of the sharpness 
of the scrutiny that enabled Pasteur to recognize these 
differences from a remark made to him by Mitscherlich. 
" I studied," said the latter, " those two salts, in their 
minutest details, with so much care and assiduity that if 
you discovered anything that I had failed to find, it could 
only have been by the guidance of a preconceived idea." 
The path thus opened was followed by Pasteur with 
results that were most suggestive of unsuspected under- 
lying principles. He found molecular asymmetry to be 
the characteristic, the stamp, of life; the invariable, though 
sometimes hidden, feature of all substances that have the 
most influence in the manifestations of vegetable and 
animal life ; it is the line of demarkation between living 
and dead chemistry. 
One of the observations made at this time led to the 
next and most important step in his career. He caused 
a solution of the paratartrate of ammonia to ferment, 
and he noticed that, as the process advanced, the solu- 
tion, which at first was without action upon polarized 
light, gradually deviated the plane to the left. Of the two 
forms of the acid-the right and left-of which the salt 
was composed, only the former was broken up in the 
process ; the latter-the left-remained unchanged, and 
constituted, therefore, the bulk of the solution. 
The explanation was to be sought in the nature of the Stimson : Pasteur's Life and Work. 
9 
process of fermentation. He had proved molecular asym- 
metry to be peculiar to life, to living chemistry ; he found 
it present and active in fermentation; he sought the life 
from which it came, and he made the great discovery of 
the agency of living ferments. At one stroke he swept 
away all the old theories, including that of Berzelius-the 
" theory of contact "-and that still older one to which 
Liebig had given his name and support, and which was 
held almost universally at the time-that which invoked 
an atomic movement communicated to the fermentable 
solution by dead and decomposing albuminoid matter. 
And in the place of these explanations which did not ex- 
plain, these theories each of which was limited to some 
restricted group of fermentations, these solutions which 
depended upon unproved and unprovable assumptions 
and each of which raised a new problem to be solved, he 
gave us a simple theory which rested at every point upon 
demonstrated facts, and which not only was applicable to 
all recognized fermentations, but also vastly enlarged the 
boundaries of that class, bringing within it other processes 
whose kinship had not been appreciated, and adding a 
multitude of others whose existence even had not been 
suspected-the theory, namely, that the process is one 
that is correlative with life, not, as formerly supposed, 
with death, and that all these varied manifestations have 
a common cause, the active growth and multiplication of 
minute organisms. 
The origin of these minute organized ferments was so 
entirely unknown, their appearance in the fermenting 
liquids was so mysterious, that Pasteur felt it to be neces- 
sary to investigate the theory of spontaneous generation, 
which was invoked by so many to account for their ap- 
pearance. He was strongly dissuaded from the under- 
taking by his best and closest scientific friends, on the 
ground that the problem was practically insoluble; but he 
persisted. Never had he worked with more thorough- 
ness, greater watchfulness, keener intelligence, and 
sharper insight than in the remarkable experiments 10 
Stimson : Pasteur's Life and Work. 
which completely overthrew the theory and laid bare the 
errors and defects in the experiments of those who main- 
tained it. The story, which is far too long to be told 
here, is one of the most interesting and instructive in the 
history of scientific research; it has been told and retold 
many times, and by no one more clearly and attractively 
than by Prof. Tyndall, who has himself done so much to 
extend and illustrate it. 
Returning from this scientific excursion to continue his 
work on fermentation, Pasteur took what may be called 
his first step in the investigation of disease, although the 
disease was merely one of certain vegetable products, not 
of man or even of beast. He studied what was called the 
disease of wines-that sudden change which occurs some- 
times after the wine has been kept for years, and which, 
within a few weeks, wholly destroys its value. It is suf- 
ficient here to say that he found the change to be a fer- 
mentation, with living, organized ferments, and that he 
devised efficient preventive measures which are now in 
general use, the savings effected by which are already 
estimated by millions. 
In like manner, a few years later, he relieved the manu- 
facture of vinegar and that of beer from empiricism and 
faulty methods, and gave them the security of a scientific 
basis ; and at the end of that work he uttered, with the 
caution so characteristic of all his statements made before 
the complete demonstration, this suggestive sentence : 
" The etiology of contagious diseases is perhaps on the 
eve of receiving an unexpected light." 
His success in detecting and removing the cause of the 
deterioration of wine was promptly followed by another 
equally important economical discovery, one which affects 
even more forcibly the imagination of the multitude and 
the emotions and the resources of those who are directly 
interested. The cultivation of the silkworm is an im- 
portant industry in France and Italy. In 1853 France 
produced twenty-six million kilogrammes of cocoons, 
worth one hundred and thirty million francs. During Stimson : Pasteur's Life and Work. 
11 
the following decade the production was so reduced by a 
disease of the worms that in 1865 it amounted to only 
one-sixth of what it had been in 1853-a money loss of 
more than one hundred million francs annually. The in- 
dustry was threatened with total destruction. Innumer- 
able researches into the cause of the disease had been 
made, remedies of the most varied kinds had been tried, 
and the French Government had even agreed to pay to 
the inventor of an alleged cure five hundred thousand 
francs if it should prove efficient. But nothing availed, 
and each year the crop was smaller. The senate appointed 
a committee to consider the matter, and that committee at 
once turned to Pasteur and asked him to investigate the 
disease. To his objection that he knew nothing about it, 
that he had never even seen a silkworm, they replied : 
" So much the better; you will approach the subject 
without prejudice." The sacrifice that was asked of him 
was great, for it required the prolonged abandonment of 
those researches in fermentation which were so plainly 
leading him to a great future; but he saw his duty and 
he followed it. He went at once to one of the desolated 
districts, and was so impressed by the sight of the dis- 
tress occasioned by the epidemic that he resolved not to 
return to Paris before he had exhausted every line of in- 
vestigation. The industry is one that is carried on by a 
multitude of small proprietors, not by a few large cor- 
porations. Every family in the village hatches out as 
many worms as it can care for, filling every corner in the 
house with them, from the kitchen to the garret, and they 
watch them through their four moultings and into their 
cocoons with the greatest solicitude. Day and night 
they are afoot, to give them food and protect them against 
changes in the weather. It is said that during the season 
the salutation of the villagers when they meet is not 
" How are you?" but "How are they?" In the close 
struggle for life in those older communities the gain or 
the loss of the little revenue from a few silkworms meant 12 
Stimson : Pasteur's Life and Work. 
in many a family comparative ease or dangerous want; 
the general loss of a crop was a public calamity. 
Into the details of the investigation we cannot now 
enter. It was pursued for five years with unflagging de- 
votion and in the face of much criticism and even active 
hostility. His critics said he was a chemist and should 
confine himself to his profession. They were surprised 
at his ignorance, and they showed that his efforts were 
doomed to certain failure. But these prophecies were 
not realized, and, on the other hand, his were. A year 
after the beginning of his work he inspected fourteen par- 
cels of eggs and the moths that had produced them, and 
gave a written prediction of the health of the worms that 
would be hatched from them the ensuing year. In twelve 
out of the fourteen the prediction was exactly fulfilled, 
and in the remaining two the result was a partial con- 
firmation. He found the cause of the disease to be the 
infection of the worms by minute corpuscles, and that 
even an apparently healthy moth might bear the infection 
within itself, and that, if it were thus infected, the eggs 
it laid would produce only diseased, useless worms. He 
showed that safety was to be had only by killing the 
moths after the eggs had been laid, examining their 
bodies for the corpuscles, and hatching only those eggs 
that came from uninfected moths. 
At last his success was universally admitted, and to 
this day, wherever in Europe the silkworm is cultivated, 
there will be seen, at the proper season, work rooms 
filled with women and young girls busily engaged with 
their microscopes in searching for and throwing out the 
tainted eggs which he taught them to recognize. 
Pasteur emerged from this trial again a conqueror, but 
also, alas! a cripple. In the midst of it, October, 1868, he 
was stricken with hemiplegia ; he slowly regained the use 
of his limbs, but he bears to this day its traces on his face 
and in his gait. 
Such was his life up to the age of fifty years. It had 
been one long, unbroken record of successful effort, of Stimson : Pasteur s Life and Work. 
13 
brilliant discoveries in science, of vast additions to the 
economic resources of the world, and of hearty recogni- 
tion and appreciation. Had it ended then, he would still 
have ranked among the notables of science. It appeared, 
indeed, to be near its end. Crippled in body by paraly- 
sis, utterly depressed in mind by the terrible calamities 
that overwhelmed his country, he no longer had the heart 
or the strength to work. And yet the future was to show 
that the past, brilliant as it had been, was only a prepa- 
ration and training for a still more brilliant series of 
triumphs in a field of the highest interest, and one, too, 
from which he would naturally have supposed himself to 
be wholly excluded, so far as personal effort was con- 
cerned, although he had recognized its possible connec- 
tion with the work he had already done. 
There was yet to be accomplished by him an advance 
in medical science similar to that which had been made by 
his countrymen three-quarters of a century earlier, an ad- 
vance of which Virchow has said : " The year 1800 forms 
a great turning point in medicine. At that time, under 
the influence of the French Revolution, the great Parisian 
school was formed ; and we must give honor to the genius 
of our neighbors that they were able at one stroke to dis- 
cover the principles of an entirely hew science. If we 
now see medicine developing itself in the greater breadth 
of objective knowledge, we must never forget that the 
French were the pioneers, as the Germans were in the 
middle ages." 
The same province of France-Franche-Comtd, or, to 
speak more broadly, Burgundy-which had sent Bichat 
to Paris to begin the work of which Virchow has thus 
spoken, had now sent Pasteur to give to that work its lat- 
est and most striking development. To the objective 
knowledge of the changes effected by disease was now to 
be added, by the same method of observation and experi- 
ment, a knowledge of thej cause of disease, with all the 
vast possibilities of prevention and cure which flow from 
such knowledge. 14 
STIMSON : Pasteur's Life and Work. 
The germ theory of disease is by no means a new one ; 
its origin, indeed, is lost, as Virchow says, in the darkness 
of the middle ages, and it distinctly appeared, under the 
name contagium animatuni, in the sixteenth century. But 
at the time of which we are now speaking it was still only 
a theory. Nineteen years ago, in the Anniversary Dis- 
course which the late Prof. Dalton delivered before this 
Academy, he ventured, as he said, "to cast the profes- 
sional horoscope for the present and to anticipate, as 
nearly as may be, what we are to expect from it in the 
immediate future." He found that " if there be any one 
direction in which progress is now so marked as to con- 
stitute a dominant feature of the present state of medi- 
cine, and to embrace a practically new medical idea, I 
should say it was that of the origin and propagation of 
disease by independent organic germs. Perhaps it would 
be wrong to say that this doctrine is even yet distinctly 
formulated. It is certainly far from being definitely 
established as a general truth. ... So far it exists in the 
form rather of a scientific instinct than of a positive be- 
lief, and its gray light hangs about the edge of the medi- 
cal horizon like the coming dawn of a new period." 
In his enumeration of the facts which seemed to him to 
justify this anticipation, Dalton laid especial stress upon 
what he termed Pasteur's brilliant researches in fermen- 
tation and spontaneous generation. It must be remem- 
bered that these researches had gone far beyond the sim- 
ple demonstration of the presence and agency of germs. 
Pasteur had not merely found the germs ; he had isolated 
them, had devised methods to obtain pure cultures, and 
had studied their natural history in detail. In short, he 
had laid the foundation of the modern system of bacterio- 
logy. The work was already bearing fruit in the field of 
medicine. The study of the dust of the air and the proof 
of its agency in exciting putrefaction had led Lister to 
the antiseptic treatment of wounds, the importance of 
which was just beginning to win recognition. The inte- 
rest in the subject was especially quickened in 1872 by Stimson : Pasteur's Life and Work. 
15 
some striking experiments made in Paris which showed 
that septicaemia could be produced in animals by the in- 
jection of infinitesimal quantities of the blood of other 
animals that had died of the disease, and every labora- 
tory was occupied with the subject. In the address just 
quoted Prof. Dalton said that between the years 1870 and 
1873 more than two hundred papers were published upon 
septicaemia. Pasteur naturally followed this movement 
with the keenest interest. More than ten years previ- 
ously he had foreseen the possibility and had expressed 
the wish that he might be able to carry his researches 
sufficiently far to prepare the way for a radical investiga- 
tion into the origin of disease. But he had no thought of 
taking a personal part in it, for, although the University 
of Bonn had conferred upon him the degree of doctor of 
medicine, and the Paris Academy of Medicine had made 
him an honorary member, he was, as he said, not a physi- 
cian. He limited himself to making suggestions to those 
who sought his counsel. I recall one of them, made at 
that time, that the dressings to be applied to wounds 
should be sterilized by heat. It now seems almost too 
commonplace to deserve mention ; it was then an absolute 
novelty. 
After a year or two, however, the interest became too 
deep or the pressure too great, and he entered the new 
field. Faithful to his method of experimentation, as con- 
trasted with that of observation, he turned first to certain 
infectious diseases of animals, for in them observation 
and inference could be controlled and verified by experi- 
ment as it could not be in man. 
It had been known since 1850 that the blood of cattle 
affected with splenic fever, or " charbon," contained vast 
numbers of a rod-shaped micro-organism to which the 
name bacteridium had been given. The disease had long 
been prevalent in Europe, and in France alone it annually 
destroyed horses, cattle, and sheep valued at from fifteen 
to twenty millions of francs. It is communicable to man, 
the so-called " malignant pustule " or " anthrax." Davaine 16 
Stimson : Pasteur s Life and Work. 
and Ray er had noted in 1850 the presence of the bacilli 
in the blood, but had drawn no inference from it. Thir- 
teen years later Davaine was reminded of them by read- 
ing Pasteur's description of the microbe of butyric fer- 
mentation, and suggested, in a communication to the 
Academic des Sciences, that they were the cause of the 
disease. The matter had been rather tepidly discussed 
from time to time for several years, experiments had 
yielded conflicting results, and the claim of a causa] rela- 
tion between the bacillus and the disease was far from hav- 
ing been established. The question derives a peculiarinte- 
rest from the fact that in 1876 it became the subject of 
some of the earliest studies in bacteriology of one whose 
fame in connection with that branch of science has since 
become world-wide-Prof. Koch. In the same year Pas- 
teur began his investigation, and in the following year he 
was able not only to demonstrate the agency of the bacil- 
lus in producing the disease, but also to explain the con- 
tradictory results obtained by previous experimenters. 
He showed that the bacillus, to employ his own term, was 
aerobic-it needed free oxygen to live-and that conse- 
quently the death of the animal, by cutting off the supply 
of free oxygen, led to the death of most of the bacilli 
within it in a few hours. According, therefore, to the 
length of time that had elapsed between the death of the 
animal and the taking of its blood for inoculation would 
the experiment succeed or fail. He showed that the 
deaths that followed the late inoculations were due to an 
anaerobic microbe-one that did not need free oxygen- 
and thus was explained the absence of the anthrax bacillus 
from the bodies of those victims ; the deaths were due to 
septicaemia, not to charbon. The investigation gave to 
science not only the full story of the bacillus of charbon 
but also that of a microbe of septicaemia, and the life his- 
tory of each was traced with a completeness that made it 
possible to explain all apparent contradictions and ob- 
scurities. He made pure cultures, he traced the bacillus 
through all its stages, recognized those in which it is Stimson : Pasteur's Life and Work. 
17 
vulnerable and those in which it can successfully resist 
the action of powerful antiseptics, and, in a word, discov- 
ered much that has since been again and again rediscov- 
ered and is often credited to others. He even followed 
the bacillus of charbon into the grave of its victim, and 
thence through the bodies of earthworms back to the sur- 
face of the soil, and even upon the blades of grass that 
grew over it. 
Coincidently with the study of charbon he carried on 
that of chicken cholera, and he allowed himself to step 
aside for a moment from these two diseases, which can be 
studied so thoroughly upon animals, to discover the mi- 
crobe of furuncles, of suppuration, and of osteomyelitis in 
man. With the latter he did nothing beyond the identi- 
fication and the cultivation-his methods of further study 
were unavailable ; but the study of charbon and chicken 
cholera was pursued until he had discovered and estab- 
lished a great principle whose possibilities for good elude 
even the grasp of the imagination. This great principle 
is the attenuation of virus, the reduction of the virulence 
of the microbe to a point at which inoculation with it will 
not kill, and yet will confer immunity against a subse- 
quent attack. This discovery, the crowning work of his 
life, was made, like all his others, not by chance, but by 
prolonged search with this definite object in view. He 
had long meditated on the immunity against small-pox 
conferred by vaccination, and on the immunity against 
recurrence conferred by a number of infectious diseases, 
and had sought to discover how far the latter was true of 
the diseases he was studying. The first results were ob- 
tained with the microbe of chicken cholera. If this mi- 
crobe is cultivated in sterilized broth and successive cul- 
tures are made at short intervals, the virulence remains 
unchanged ; a drop of the twentieth culture will kill as 
surely as a drop of the first. But if the interval is length- 
ened, if the second culture is made after the first has 
stood for a few weeks or months, its virulence is less ; 
and if this second culture is kept for a similar length of 18 
Stimson : Pasteur's Life and Work. 
time, the third, made from it, will be less virulent. Inocu- 
lation with the first kills all the fowls that are inoculated; 
inoculation with the second kills only a part of them ; 
inoculation with the third kills still fewer; and finally a 
culture is obtained, from inoculation with which all the 
fowls recover after having been ill for a day or two. 
These survivors are then able to bear inoculation with 
the strongest culture: they have acquired immunity. 
Moreover, the microbes of diminished virulence thus ob- 
tained, the " domesticated " microbes, as they have been 
called, can be indefinitely cultivated and continued ; it is 
not necessary to begin again with those of full virulence 
and repeat the attenuation. In short, a new disease, or a 
new form of disease, had been created, one that bore to 
chicken cholera the same prophylactic relation that cow- 
pox does to small-pox, and there was no danger that this 
protective disease would ever disappear and be lost; so 
long as chicken cholera existed its " vaccine " could be re- 
created, if necessary, by appropriate cultivation. 
Jenner's vaccination against small-pox was the shrewd 
application of a chance observation of a certain relation 
between two existing diseases; Pasteur's discovery of the 
means of attenuating a virus and conferring immunity 
thereby was effected by long-continued, intelligent ex- 
perimentation guided by wide observation and profound 
thought. The former was the brilliant utilization of a 
fact that had already been observed by others ; the latter 
was the original discovery of a principle. If cow-pox 
were to die out vaccination would be at an end, but in 
the attenuation of a virus the disease is made to protect 
against itself: the bane bears its own antidote. 
Pasteur at once sought to extend his study to other mi- 
crobic diseases that conferred immunity when the attack 
was survived. He found by experiment that charbon 
was such an one, but unfortunately the mode of develop- 
ment of its microbe is different from that of the microbe 
of chicken cholera ; the latter multiplies wholly by scis- 
sion, the former develops partly by " spores " which Stimson : Pastezir's Life and Work. 
19 
withstand exposure to the air and retain virulence not- 
withstanding prolonged delay in cultivation. He was 
forced first to find a mode of development in which the 
spores would not be formed. The personal side of the 
story of the search has been touchingly told by one of his 
children. Days and weeks were passed in experimenta- 
tion. Pasteur became more and more absorbed and pre- 
occupied ; he went about with what his daughter called 
" his expression of impending discovery." To the timid 
questions of those who were waiting and watching with 
so keen interest, his only reply was that he could not an- 
swer, that he dared not formulate his hopes. At last he 
returned one day from his laboratory in triumph, and 
tears of joy rose to his eyes as he told the story of suc- 
cess. 
The difficulty had been overcome by cultivating the 
germs in broth at a temperature of about io8° F.; this 
gave a steadily diminishing virulence, any grade of which 
could be subsequently maintained by suitable cultivation, 
and among these grades were some that were too weak to 
kill but yet were strong enough to protect. 
The announcement of the discovery, on February 28th, 
1881, was promptly followed by a challenge to a public 
test that should prove its truth or expose its falsity. 
Fifty sheep and ten cows were provided ; half of them 
were inoculated with the attenuated virus, and three 
weeks later all, the vaccinated and the unvaccinated, re- 
ceived each an injection of full strength. It was done in 
the presence of a great crowd of farmers, veterinaries, 
physicians, journalists, and legislators, and two days later 
they reassembled to see the result. That result was a 
complete confirmation of the prediction. Of the twenty- 
five sheep that had not been protected by inoculation, 
twenty-two were dead and three were dying ; the unpro- 
tected cows were living, but evidently very ill; all the 
protected animals, sheep and cows, were in perfect 
health. 
A veterinary surgeon, who had been loud in expression 20 
Stimson : Pasteur's Life and Work. 
of his disbelief, was so overwhelmed by the success of the 
demonstration that he immediately offered himself for 
inoculation, and was saved from it only by the forcible 
interference of his family. 
A few months later Pasteur sent one of his assistants to 
Berlin to repeat this demonstration before a committee 
appointed for the purpose, at his request, by the Minister 
of Agriculture; the committee, of which Virchow was a 
member, confirmed his statements at all points. 
A third veterinary disease, the measles of swine, was 
next studied, its microbe discovered and cultivated, its 
virulence attenuated, and protection obtained. 
It will be readily believed that, while he was thus so 
earnestly and successfully studying diseases of the lower 
animals, Pasteur was not unmindful of those affecting 
man. As I have already mentioned, he had isolated and 
cultivated the microbes of suppuration, of furuncles, and 
of osteomyelitis, and in addition he had studied those 
found in the blood of patients affected with typhoid or 
puerperal fever. In the latter he had recognized several 
distinct varieties-one of them the micrococcus of suppu- 
ration-and in a communication to the Acad6mie des 
Sciences he had advised the employment of antiseptics in 
midwifery. He had already made the suggestion at the 
Maternity, where it was followed by the happiest results. 
But he felt himself disqualified from pursuing these lines 
of research by his lack of training in medicine, and by 
the impossibility of employing in them the instrument 
which he had learned to handle with such marvellous 
skill-experimentation. The only diseases of man that he 
could thoroughly investigate were those that also affected 
the lower animals. One of these had attracted his atten- 
tion while he was engaged upon those that have been 
already mentioned, and when that work was finished he 
gave himself up wholly to it; and during the last few 
years it has become the one subject with which his name 
is chiefly associated in the minds of all save those who are 
professionally familiar with his other work. There is Stimson : Pasteur's Life and Work. 
21 
much in this fact, too, that is saddening, for in connection 
with it he has suffered much, like other benefactors of the 
world, from those who, honestly perhaps, but none the 
less cruelly, ignorantly, and blindly, have grossly mis- 
stated his results and misrepresented both him and his 
methods. 
This disease is hydrophobia. His study of it was seri- 
ously hampered at first by the difficulty of obtaining a 
pure culture of the microbe from the saliva and by the 
great length of the period of incubation under the then 
known methods of inoculation. He finally obtained the 
microbes from the nerve centres of animals dead of the 
disease, and made his cultures, not in flasks of sterile 
broth as he had done with the microbes of other diseases, 
but in the bodies of other living animals. He found that 
in a rabbit, inoculated from a rabid dog, the period of in- 
cubation was fourteen days; successive inoculations from 
rabbit to rabbit gradually reduced this period to a week, 
and when some eighty or ninety successive inoculations 
had been made (covering a period of more than two years) 
he had obtained a disease of uniform virulence. That is, 
if a small portion of the spinal cord of a rabbit that had 
just died of this disease was mixed with a little water and 
injected into a vein of another animal, the latter would 
certainly develop and die of the disease. He then sought 
to attenuate this virus so as to make it protective, and 
he found that this could be accomplished by drying the 
spinal cord ; that if an animal received successive injec- 
tions, under the skin, of portions of cords that had been 
dried in sterilized air for shorter and shorter periods, be- 
ginning with fourteen days, it could ultimately receive 
with impunity an injection of full strength. He found, 
next, that the protective action of these inoculations was 
more rapid than the deadly action of the poison intro- 
duced by the bite of a rabid dog; that, in other words, 
an animal that had been recently bitten by a rabid dog 
could be saved from rabies by these inoculations. 
But to extend this protection from animals to man was 22 
Stimson : Pasteur s Life and Work. 
a step which he long hesitated to take. It was at last, 
in a measure, forced upon him. On the morning of July 
4th, 1885, a little boy on his way to his school in a village 
of Alsace was attacked and severely bitten by a rabid 
dog. A physician cauterized the wounds with carbolic 
acid and advised the parents to take the child to Paris, 
where, as he said, was the only man who could do any- 
thing for him ; he lived in the Rue d'Ulm, and his name 
was Pasteur. The advice was followed, and on the morn- 
ing of July 6th the mother and child presented themselves 
at the laboratory. Pasteur, deeply moved by the distress 
of the parent and strong in the confidence his experiments 
had created, asked the advice of two professors in the 
School of Medicine who were familiar with his investiga- 
tions. Both approved of the attempt, and the lad received 
his first injection that same day. On each succeeding 
day another and more virulent inoculation was made; 
and as the danger, if danger there was, was thus daily 
increasing, so increased likewise the anxiety of Pasteur. 
His days were agitated, his nights sleepless; and even 
long after the treatment had ended and the child had re- 
turned to his home Pasteur wrote to him every week, and 
then every fortnight, for news of his well-being. 
Thus began the application of the remedy to man. The 
announcement of its success to the Acad6mie des Sciences 
created a profound sensation ; and when a second pa- 
tient came to Paris for treatment-a brave young shep- 
herd who had been bitten while defending some children 
from a rabid dog-the public press was filled with ac- 
counts of it, and for the time it was the topic of chief in- 
terest in the city. This interest promptly brought an 
important practical result. The number of patients ap- 
plying for treatment became far too great for the limited 
accommodations of the Ecole Normale, and a public sub- 
scription was opened, under the auspices of the Academie 
des Sciences, for the erection of a special building for the 
treatment of the bitten and for bacteriological study of 
infectious diseases. Subscriptions to this fund poured in Stimson : Pasteur s Life and Work. 
23 
from all quarters; one of the largest gifts came from the 
Czar, in recognition of the saving of the lives of sixteen 
Russians who had been bitten by a rabid wolf; another 
came from the Emperor of Brazil, in recognition of the 
high scientific value of the work ; another from Alsace- 
Lorraine, from which had come Pasteur's first patient; 
and a multitude of others from corporations and in- 
dividuals throughout France. As has been said by a 
biographer, this time the prophet was not without honor 
in his own country. Far from it! In May, 1886, a festival 
was given at the Trocadero in aid of the Institut Pasteur, 
at which the greatest celebrities of the literary, musical, 
and theatrical world of Paris assisted ; and when Coque- 
lin recited a poem in honor of the Master, the audience 
rose and joined in the greatest ovation that had ever been 
offered to a man of science. 
But this subject, interesting as it is, must not now be 
followed further. The Institut Pasteur was established, 
and during the years 1886-1891 there were treated within 
it 11,029 individuals who had been bitten by rabid ani- 
mals. Of these 98 have died. I quote from a report of 
the Board of Health of the city of Paris.1 Comparing 
this mortality of less than one per cent (0.88 per cent) 
with the mortality among those not treated, as ascer- 
tained by the authorities of the city of Paris for the years 
1887 (15.90 per cent) and 1888 (13.33 Per cent), or with 
that given by medical writers (15 per cent), it appears 
that the work of this charity has already resulted in the 
saving of about 1,500 men, women, and children from 
death in one of its most terrible forms. In reply to a 
question addressed him a few weeks ago, M. Pasteur 
writes me that during the year 1891 201 persons living in 
Paris were treated at the Institut, with no deaths, and 
that during the same period, in the same city, four persons 
had died of hydrophobia from among the very limited 
1 Rapport sur les cas de rage humaine constates dans le Departement de la 
Seine de 1880 a 1891. Conseil d'hygiene publique et de sahibrite, 1892. 24 
Stimson : Pasteur's Life and Work. 
number of those who had been bitten and had not been 
treated by inoculation. In addition to these 201 Parisians 
more than 1,300 other patients, coming from greater or 
less distances, were treated at the Institut Pasteur during 
the year, and similar institutions have been at work in 
seventeen other cities. 
It would be interesting and profitable to study in detail 
the means and the methods by which these vast results 
have been obtained, but time forbids more than a brief 
reference to them. 
Of his method, the experimental method, which he 
used with such transcendent skill; the method handed 
down to us by the great experimenters of the past-Gali- 
leo, Pascal, Newton-he has given us a description and 
an appreciation. " Admirable and sovereign method," he 
calls it, " which is always guided and controlled by ob- 
servation and experience freed from every metaphysical 
conclusion ; a method so fruitful that great minds, dazzled 
by its conquests, have believed that it could solve all 
problems. 
" One can do nothing without preconceived ideas, but 
we must have the wisdom to believe in their deductions 
only so far as experience confirms them. Preconceived 
ideas, under the rigid control of experimentation, are the 
vivifying flame of the sciences of observation ; their dan- 
ger is in fixed ideas. Do you remember Bossuet's fine 
saying : ' The greatest disordering of the mind is to be- 
lieve that things are because one wishes them to be ' ? To 
enter upon a path, and to stop every moment to make 
sure you are not going astray-that is the true method." 
In these impatient times such a method seems all too 
slow ; but see how far and how safely it has taken him. 
Doubtless his mistakes, his false routes, might be counted 
by thousands; but he himself detected and corrected 
them, and no step definitively taken has ever had to be 
retraced, no statement that he has ever made has proved 
to be incorrect. His caution in approaching a conclusion 
is equalled only by his assurance after it has been reached ; Stimson : Pastezir's Life and Work. 
25 
each is absolute. His comments upon puerperal fever 
were made almost with an apology. " I tell you these 
things," he said, " as they appear to me. But I do not for- 
get that I am ignorant of medical science, and I earnestly 
ask for your judgment and your criticism." How different 
his tone when he felt himself master of the subject! 
" What I " he cried with magnificent scorn one day in the 
Academic de Medicine-" what! Do you say that 1 may 
have worked twenty years on a subject and yet should 
hold no opinion on it; that the right to verify, to control, 
to discuss, to interrogate, shall belong only to him who 
does nothing to throw light upon it, to him who, with his 
feet on the fender in his library, has only read, with more 
or less attention, the results of my labor? You say that 
in the present state of science it is the part of wisdom to 
hold no opinion [on spontaneous generation]. Well, as 
for me, I hold one, for I have earned the right to hold it 
by twenty years of assiduous labor ; and it would be well 
for every impartial mind to share it." 
To those who were not aware of the thought and labor 
upon which it rested, such absolute confidence might 
seem foolhardy and arrogant; but those who tested it 
soon learned to respect it, and those who had once met 
him in debate shrank from again falling into his redoubt- 
able hands. " Come with me," said a man once-"come 
with me to the Academy and see me strangle Pasteur." 
"Take care," was the reply-" take care, my friend. 
Pasteur is a man who makes no mistakes." 
Absolutely open and sincere, solicitous only that the 
truth should be known, he never hesitated to make public 
his reasons and his processes, to submit them to any open 
test, and to stand or fall by the result. When the dis- 
cussion on fermentation was at its height, Pasteur went 
in person to Munich to show his experiments to Liebig. 
When spontaneous generation was in question, Pouchet 
was invited to make experiments in concert with him. 
Challenged to a test upon a large scale of his proposed 
treatment of the silkworm disease, he had himself carried 26 
STIMSON : Pasteur s Life and Work. 
upon a mattress across France and Italy to Austria, and 
from an estate which had not previously been able to 
raise enough silk to pay for the eggs they had to import, 
he there made in one season a net profit of twenty-six 
thousand francs. 
We have seen his public tests at Paris and Berlin with 
the attenuated virus of charbon. When Koch at that 
time said that the theory of attenuation was too good to 
be true, Pasteur sought him at a scientific meeting at 
Geneva and publicly challenged him to a discussion. 
Koch declined, saying he would reply in print. A few 
months later he published a pamphlet accepting the dis- 
covery as one of the highest scientific value. 
Few men have had so many scientific controversies, and 
no one, perhaps, has come out of them so uniformly suc- 
cessful and with his success so uniformly conceded. The 
latter fact is due in part to the resolution with which 
Pasteur has held himself and his opponents down to 
statements capable of proof or disproof. Sooner or later 
the debate would reach a point at which he could force 
an issue on some one decisive fact, and then he always 
demanded the appointment of a committee to determine 
that fact. 
Heated as these discussions often were, ardent as was 
his support of his own views, and pitiless as was his expo- 
sure of error, it is a pleasure to note that on his side the 
personal element, in the unworthy sense, is always ab- 
sent. His interest is in the truth, not in himself; and if 
he is intolerant of frivolous or prejudiced contradiction, 
if he grows impatient at times over the mental sluggish- 
ness of those who can only grope and crawl where he has 
run, it is only because of his burning zeal for the estab- 
lishment and the advancement of the truth. 
The work that we have thus followed has been done in 
almost exactly a half-century of life, the period between 
the ages of twenty and seventy years. And how magnifi- 
cent it is when it is summed up ! 
In science he has laid at rest the theory of spontaneous Stimson : Pasteur's Life and Work. 
27 
generation which for centuries had blinded and misled, 
and in its place he has given us a new world, that ol " the 
infinitely small he has made clear the nature of fermen- 
tation, and by that explanation he has brought into one 
group of exquisite simplicity what had previously been a 
chaotic mass of unrelated processes and changes. 
In medicine he has given us the science of Bacteri- 
ology ; he laid the foundations of antiseptic surgery, by 
which hundreds of thousands of lives and countless limbs 
have been saved ; he demonstrated the microbic nature of 
certain diseases, and he gave us the principle of protec- 
tion by an attenuated virus with its vast possibilities for 
good, and he has himself applied that principle in one dis- 
ease to save from a terrible death hundreds of our fellow- 
creatures. 
I hesitate to close such a record with a reference to 
material gains, and yet, in the words of Prof. Huxley, 
Pasteur's discoveries would be sufficient in themselves 
to make good the war indemnity of five thousand million 
francs paid by France to Germany. 
In the address which he made ten years ago on his re- 
ception into the French Academy, after an eloquent de- 
claration of his faith in God, his belief in immortality, and 
his conviction of the reality of those lofty preoccupations 
which are put aside as non-existent by the positivists, 
Pasteur said : 
" The Greeks understood the mysterious power of these 
hidden things. They gave us one of the most beauti- 
ful words in our language, enthusiasm-e'v 0s6?, a god 
within. 
" The grandeur of human actions is measured by the 
inspiration which gives rise to them. Happy is he who 
bears within himself a god, an ideal of beauty, and who 
obeys it-ideal of art, ideal of science, ideal of patriotism, 
ideal of the virtues of the Gospel. Those are the living 
springs of great thoughts and great deeds." 28 
Stimson : Pasteur s Life and Work. 
Pasteur's whole life has shown that he possesses such 
an ideal and that it directs every act. 
May the happiness that he predicated of such a posses- 
sion, the happiness that he has so abundantly earned by 
his devotion to the truth and by the benefits he has con- 
ferred, be his reward !