.._.

5~*
H 13

LOUIS PASTEUR

BY

S. J. HOLMES, Ph.D.

PROFESSOR OF ZOOLOGY IN THE UNIVERSITY OF CALIFORNIA

WITH ILLUSTRATIONS

NEW YORK

HARCOURT, BRACE AND COMPANY

N

COPYRIGHT, I924, BY
HARCOURT, BRACE AND COMPANY, INC.

PRINTED IN THE U. S. A. BY

THE QUINN C: BODEN COMPANY

RAHWAY. N. J.

X

PREFACE

This small volume has been written for students
and general readers who may desire to know
something of the life and work of Pasteur, but who
hesitate to undertake the perusal of more compre-
hensive biographies. In the preparation of this
sketch I have been greatly indebted to the incom-
parable Life of Pasteur by Vallery-Radot, and I
hope that what I have written may induce many
of my readers to make the acquaintance of this
larger work. I owe much also to the valuable
History of a Mind by Emile Duclaux who was for
several years one of Pasteur's ablest co-workers
and hence exceptionally qualified for the task which
he has so well accomplished. Among other useful
sources of information especial mention may be
made of Roux's UCEuvre medicate de Pasteur,
which, like the preceding works, was written on
the basis of intimate personal knowledge.

The present book is the product of a long-felt
admiration for Pasteur and his achievements. I
do not pretend to have made any new contributions

iii

iv PREFACE

to Pasteur's biography. It has been my aim to set
forth, briefly and simply, the chief discoveries of
this great investigator, to describe his methods of
critical experimental enquiry, and to show how he
was led on, step by step, from one field of research
to another, making discoveries of the highest impor-
tance in every field he traversed. I have endeav-
ored also to give an idea of Pasteur's personality
and its relation to his scientific work. So remark-
able and inspiring a career as that of Pasteur can-
not be too widely known, and I make no apology,
therefore, for adding to the number of books upon
this great man.

I am indebted to Dr. T. D. Beckwith of the
Department of Bacteriology of the University of
California for reading the whole manuscript, and
to Dr. J. H. Hildebrand, Professor of Chemistry
in the same institution, for reading the chapters
which deal with Pasteur's chemical researches.

S.J.H.

UNIVERSITY OF CALIFORNIA,
BERKELEY, CALIFORNIA.

CONTENTS

PAGE

Preface iii

CHAPTER

I. Home Life, Early Training and Ambitions . 3

II. Experiments in Chemistry and Crystalliza-
tion 21

III. The World of Microscopic Life .... 41

IV. Studies in Fermentation 61

V. Controversies over Spontaneous Generation . 83

VI. The Diseases of Wine and Vinegar . . .111

VII. The Diseases of Silk Worms 125

VIII. The Dark Days of the War: Studies on Beer 143

IX. Antiseptic Surgery, Fowl Cholera and An-
thrax 151

X. The Dawn of a New Era in Medicine . . . 179

XI. The Conquest of Hydrophobia .... 201

XII. Last Days 229

Index 243

<2V7?J

ILLUSTRATIONS

FIGURE PAGE

i. Pasteur at the Age of Twenty-one . . facing 18

2. Right-handed and Left-handed Crystals of

Tartaric Acid , . 27

3. Forms of Protozoa 47

4. Cells of Yeast 50

5. Forms of Bacteria 51

6. A Test Tube Plugged with Cotton and Showing

a Bacterial Colony Growing in the Culture
Medium 57

7. Flask with Curved Neck Used for Keeping Boiled

Infusions Supplied with Air Free from Germs 91

8. Flask with Sealed Neck Partly Filled with

Boiled Infusions 93

9. Apparatus Designed to Free Air from Germs by

Drawing It Through Sulphuric Acid . . .103

10. Apparatus Designed by Tyndall for Freeing Air

from Floating Matter 105

11. Organisms Found in Diseased Wine .... 122

12. Pasteur in His Laboratory .... facing 165

13. Pasteur and Madame Pasteur . . . facing 230

14. Tomb of Pasteur facing 241

LOUIS PASTEUR

CHAPTER I

HOME LIFE, EARLY TRAINING AND

AMBITIONS

In the London Times for December 13, 1922, oc-
curs this item: "M. Victor Berard, The President
of the Senatorial Commission of France on Edu-
cation, announces that the bells of Dole will be
rung for two minutes preceding five o'clock on the
evening of December 27, and that all the bells of
the Franche-Compte from the plain of the Saone
to the crests of the Jura will reply to them. He
suggests that during these two minutes all the bells
should ring in unison to recall the great work
which France has accomplished during the last
hundred years." On this occasion the French peo-
ple, who love to honor their great men, paused to
celebrate by a beautiful and fitting ceremony, the
hundredth anniversary of the birth of Louis Pas-
teur, who was born in the little village of Dole,
December 27, 1822.

Most biographies have something to say about
parents and other ancestors if only to chronicle a

few dry details of names and dates. The parents

3

4 LOUIS PASTEUR

of Louis Pasteur, however, were persons of very
superior quality, although occupying an obscure sta-
tion as did their families before them. The great-
grandfather had actually been a serf of the soil
who was given his freedom in 1763 for four pieces
of gold. Thenceforth he followed the occupation
of a tanner which continued to be a family trade
during the two following generations. I have an
especial admiration for the sturdy character of the
father, Jean Joseph Pasteur, a serious, hard-work-
ing man, with only the merest rudiments of educa-
tion, but with a great appreciation of learning, and
willing to make many sacrifices so that his son
might profit by the educational advantages which
it had never been his own privilege to enjoy. Jean
Joseph Pasteur had served in the armies of the
great Napoleon during the war in Spain. The
Third Regiment to which he belonged was espe-
cially noted for bravery, and along with many other
survivors of this valiant group he was given the cross
of the Legion of Honor at the hands of the Em-
peror. Through his substantial merit he had slowly
risen through the ranks to the position of sergeant
major. Throughout life Sergeant Pasteur cherished
the intense devotion to Napoleon that was felt by
so many of the common soldiers of the armies of

HOME LIFE AND EARLY TRAINING 5

France. The downfall of Napoleon after the daz-
zling and brilliant victories that placed Europe
under the feet of France affected him deeply.
After his discharge from the Army in 1814 he re-
turned to his humble family trade of tanner, re-
signing himself, with shattered hopes and wounded
pride, to the new regime.

The life of the solitary and disappointed soldier
was soon brightened by the acquaintance of a
young girl, Jeanne Etiennette Roqui, whom he
used to watch while she was working in a garden
on the opposite bank of a small river that ran past
the tannery. Feelings other than melancholy
broodings began to arise in the breast of the "old
soldier" as the villagers called him (he was only
twenty-five), and he was married, after what pre-
liminaries we do not know, to the young girl of
the garden. The marriage proved to be happy.
Madame Pasteur is described as kind hearted, viva-
cious, imaginative and enthusiastic, — qualities con-
trasting quite strongly with the reserve, caution
and introspective bent of her husband. The first
child died when only a few months old. Then
came a daughter, and four years afterward their
only son, Louis Pasteur. Two younger daughters
completed the Pasteur family.

6 LOUIS PASTEUR

Soon after the birth of Louis Pasteur the family
moved to the little village of Arbois which was des-
tined to be their permanent home. Here the father
established a tannery which yielded a very modest
income. The parents were hard-working and
frugal, but they gave their children such educa-
tional advantages as the village afforded. Louis
went to the primary school and then to the little
college of Arbois where he worked diligently
enough, but without attaining any special distinc-
tion. The father wishing to improve upon his own
limited education, worked along with his son, help-
ing him as best he could with his lessons in the
evening. A quiet, industrious, studious home, this
maison Pasteur, devoted to the inculcation of ster-
ling virtues of character, — a home in which the
father and the mother, different as they were in
temperament, were strongly attached to each other,
and solicitous above all else for the welfare of their
children. Jean Joseph Pasteur was ambitious that
his son become a scholar. If only Louis could at-
tain the station of professor in some small French
college, what more in the way of worldly advance-
ment could be desired? Doubtless the sturdy sol-
dier used to meditate on his son's prospects during
his Sunday walks which he was in the habit of

HOME LIFE AND EARLY TRAINING 7

taking, always on the same road from Arbois to
Besangon, after he had attired himself in his best
clothes decorated with the white ribbon of the cross
of the Legion of Honor.

In the college of Arbois Louis Pasteur awakened
the interest of the head master, M. Romanet, who
devoted especial attention to training the mind of
his pupil. Pasteur's mind worked slowly, but very
carefully, and he was exceedingly scrupulous in
regard to the accuracy of his information. In this
he resembled his father. Romanet perceived be-
neath the quiet demeanor of this industrious lad
promises of future achievement which had not
impressed other and less discerning instructors, and
he encouraged Pasteur in the development of those
habits of careful and accurate thinking which are
commonly given little credit by teachers as com-
pared with facility of learning and glibness of
expression.

When Pasteur had finished his course in the little
college of Arbois the question What next? began
to agitate the family. Romanet had tried to per-
suade his pupil to look forward to going to the
Ecole Normale at Paris, but this meant much ad-
ditional preparation. The family was poor and
could ill afford the expense of sending Louis to such

8 LOUIS PASTEUR

a distance and supporting him in Paris. Besides
there was the fear in the hearts of the parents, who
were loth to be separated from their son, that the
temptations of the gay capital might overcome the
effects of their careful training.

Through the influence of a family friend, young
Pasteur secured the privilege of attending the pre-
paratory school of M. Barbet who consented to
receive him for reduced fees. This offer overcame
the scruples of his parents, and accordingly Pasteur
set out for Paris, accompanied by one of his young
friends, Jules Vercel, whose society served to miti-
gate the dreariness of the long journey by stage
coach. Young Pasteur, who was then sixteen years
of age, was not happy in his new surroundings.
Despite his heroic efforts to interest himself in
study, he was seized by the peculiar malady of
homesickness. Those who have suffered acutely
from this affliction may understand something of
the anguish of a young lad in a strange city sepa-
rated from a family circle in which he had known
only close and affectionate companionship. "If I
could only get a whiff of the tannery yard," he
said to Jules Vercel, "I should be cured." But his
case went from bad to worse until M. Barbet, who
feared that his pupil's health was becoming im-

HOME LIFE AND EARLY TRAINING 9

paired, wrote to his father. One morning a mes-
senger told the lad that some one wanted to see him
in a nearby cafe. Louis entered and found his
father who had come to bring him back home. As
Stephen Paget remarks, this was his first and last
failure.

After a few days of joy in the companionship of
his family he took up some work again in the col-
lege of Arbois. For a time he became interested
in art, and drew several portraits of friends and
acquaintances, some of which have been said to
possess real merit. Having obtained from the col-
lege of Arbois about all that this small institution
afforded, it was deemed wise that he should go to
the college of Besangon which was situated only
about thirty miles from his home. Besides, the
father visited Besangon occasionally in the course
of his business and could look after him from time
to time. If homesickness recurred while he was in
the college of Besangon Pasteur never complained
of it. Fortunately there were a few members of
the faculty who were enthusiastic and capable
teachers, and young Pasteur applied himself most
diligently to work. "Dear sisters," he wrote, "let
me tell you again, work hard; be loving compan-
ions. When one is used to work one can no longer

10 LOUIS PASTEUR

live without it. Besides it is upon that which
everything in the world depends. With the aid of
science one can rise above all competitors. But I
hope that this advice is not needed and I am sure
that you devote considerable time every day to
learning your grammar. Love each other as I love
you. I am looking forward to the happy day when
I shall be admitted to the Ecole Normale."

Pasteur's ambition to attend the Ecole Normale
now seemed nearer to realization, and he bent all
his energies to qualify himself to enter that great
school. His intellect was rapidly maturing, and in
addition to performing his assigned scholastic tasks
we find him reading books on philosophy, litera-
ture, and science in the endeavor to satisfy the
hunger of his mind for knowledge and understand-
ing. At Besancon he contracted a lasting friend-
ship with a fellow student, Charles Chappuis, whose
alert mind and wide intellectual interests afforded
him both stimulus and diversion. The two read
books together, and took long walks together in
which they discussed all sorts of topics from the
subtleties of theology to the peculiarities of chem-
ical reactions. Such friendships are among the
most valuable experiences of college life. The in-
fluence of a teacher, however great, can never take

HOME LIFE AND EARLY TRAINING 1 1

the place of the wholesome effect of the close and
sympathetic companionship of two young and eager
minds.

Pasteur's scholastic work in the college of
Besangon was creditable, but not brilliant. Twice
he was second in his class, and once he took the
first place in physics. He stood well in the esti-
mation of his teachers and he was entrusted with
giving some work to students in mathematics and
physical science. After graduation he was eligible

r

to take the examinations for the Ecole Normale,
but as he was only the fifteenth out of twenty-two
candidates, he resolved to give himself another year
of preparation. In 1842 we find him again at Paris
at the Barbet Boarding School, no longer homesick,
but full of energy, ambition and enthusiasm for his
work. Only a third of the regular fees were re-
quired of him on account of his giving instruction
in mathematics to some of the students from six
to seven in the morning. In one of his frequent
letters home he says, "I shall spend my Thursdays
in a neighboring library with Chappuis. He has
four hours to himself on that day. Sundays we
walk and work together. I shall do some philos-
ophy Sundays and perhaps also on Thursdays.
Then I shall read some literary works. You

12 LOUIS PASTEUR

should see that this year I am no longer home-
sick/'

During his year at Barbet's, Pasteur attended the
lectures on chemistry which were being given at
the Sorbonne by the celebrated chemist Dumas,
who was destined to have a strong influence upon
his future career. "You cannot imagine," Pasteur
wrote, "the popularity of this course. The room
is immense and always well filled. It is necessary
to go a half hour ahead of time to secure a good
place, just as in a theater. There is also much
applause. There are always six or seven hundred
persons." Dumas, noted for his important discov-
eries in chemistry, and the author of a series of
standard works in this field, was one of the com-
manding figures of the science of his day. The
lucidity and eloquence of his lectures aroused the
enthusiasm of young Pasteur, who listened with
rapt attention and admiration to the words of his
instructor. Pasteur soon set his heart upon becom-
ing a chemist, spoke of himself as a disciple of
Dumas, and resolved to devote himself to research
in his chosen field. In 1843 he realized his long

r

cherished ambition of entering the Ecole Normale.
This time he was fourth in the list of entrants.
At the Ecole Normale Pasteur plunged into work

f

HOME LIFE AND EARLY TRAINING 13

with feverish energy. Grave, quiet, and retiring, he
cared little for the usual sports and diversions of
student life, and he looked forward to holidays
chiefly as affording an opportunity to read in the
library. His friend Chappuis would sometimes
coax him for a walk when Pasteur would talk of
tartaric acid, racemic acid, crystals, and other
topics which had fascinated him and on which his
mind continually brooded. He loved to expound
subjects in which he was interested, and he found
time to give some lessons in the school of M. Bar-
bet in recognition of the kindness which the latter
had shown him during his early struggles in Paris.
"I am glad," his father wrote, "to see that you are
giving lessons at M. Barbet's. He has done us so
many favors that I am pleased to see you do some-
thing to prove your gratitude. Be therefore always
obliging to him. Not only do you owe this to your-
self, but you owe it also for the sake of others. It
may make him act as he has to you toward other
young men who perhaps without it would be
handicapped in their future career."

Jean Joseph Pasteur was highly pleased with the
progress of his son, but he was apprehensive that
the work of the school would prove too taxing.
"You know how much we are concerned about

14 LOUIS PASTEUR

your health," he wrote. "You are so lacking in
moderation in your work. Have you not already
injured your eyesight by your work at night?
Having arrived where you are you should be quite
happy and your ambition should be abundantly
satisfied." Chappuis, to whom Pasteur's father
had written, "Tell Louis not to work too hard,"
doubtless exercised a wholesome influence over the
young student of science in his endeavor to lead
him into a more nearly normal mode of life. Chap-
puis' interests were chiefly in philosophy and lit-
erature, but his active mind readily assimilated the
subjects upon which his friend was fond of dis-
coursing. Young Pasteur's mind was so full of his
science and mathematics that he must find expres-
sion somehow. Realizing his father's educational
shortcomings and his strong desire for knowledge,
the son became the teacher of his father and he
undertook to carry on a sort of course of instruc-
tion by correspondence. In his delicacy about
assuming this role Louis wrote, "It is that you may
be able to serve as teacher to Josephine that I am
sending the work that you request." The father,
who would sit up late at night over the work as-
signed by the son, was a willing and industrious
pupil. "I have spent two days over trying to com-

HOME LIFE AND EARLY TRAINING 15

prehend a problem/' his father wrote, "which I
afterwards found quite simple. When one must
learn in order to teach it is no easy thing." But
after a month he informed his son that "Josephine
does not care to rack her brains, as she says.
Nevertheless, I promise that her performances will
please you by your next holidays. "

There were several students in the Ecole Nor-
male who made better records than Pasteur. He was
placed seventh when he passed the license examina-
tions. Out of fourteen students who presented
themselves for an examination for recruiting candi-
dates for professors to teach in secondary schools
Pasteur stood third of the four candidates who
passed. Chappuis, always confident of his friend's
superior merits, was wont to declare, "You will see
what Pasteur will become." One of Pasteur's most
distinguished teachers, the chemist Balard, who
also appreciated his talents, made him a laboratory
assistant, a post which gave him greater freedom
and opportunity for carrying on his work in chem-
istry.

About this time (1846) a new chemist was added
to the faculty, a young man, August Laurent,
already known for the originality and importance
of his investigations. The theory of substitutions

16 LOUIS PASTEUR

which was then beginning to occupy the attention
of chemists was Laurent's especial interest. It had
been developed by Dumas, and it appealed strongly
to the imagination of Pasteur. According to this
theory, chemical changes may occur by the substi-
tution of one atom or group of atoms in a molecule
by another atom or group of atoms, while the rest
of the molecule remains unchanged. Nowadays
chemists can build up whole series of allied com-
pounds by substituting one element or group for
another, thereby building up compounds of greater
and greater degrees of complexity. The possibili-
ties of orderly constructive chemical transforma-
tion which the theory of substitutions suggests
were clearly seen by Pasteur who recognized the
great importance of this guiding principle in chem-
ical research.

For his doctor's degree he prepared and defended
two theses, one in chemistry entitled Researches
into the Saturation Capacity of Arsenious Acid.
A Study of the Arsenates of Potash, Soda and
Ammonia; the other in physics entitled A Study
of Phenomena Relative to the Rotary Polarization
of Liquids. Both were dedicated to his parents.
"Although we cannot judge your essays," wrote the
father, "our satisfaction is no less great. But as

HOME LIFE AND EARLY TRAINING 17

to the title of doctor I was far from expecting so
much. My ambition would have been satisfied
with the license to teach."

After the newly fledged doctor had spent a short
vacation in the midst of his admiring family, who
were perhaps somewhat over-awed by his academic
distinction, he is back again in his laboratory in
Paris. It is impossible for him now to keep away
for long from his crucibles and retorts. "I am
supremely happy," he writes soon after his return.
"I shall soon publish a contribution on crystal-
lography."

The Revolution of 1848 caused a temporary
interruption of Pasteur's labors. A popular up-
rising had dethroned the citizen king, Louis
Philippe, and proclaimed a Republic. Paris was
in a turmoil. Pasteur, full of enthusiasm for the
new republic, had joined the National Guard. The
ideas of liberty, equality, and fraternity thrilled him
as they thrilled so many others who thought they
were witnessing the dawn of a new era for France.
Pasteur writes, "There are great and sublime doc-
trines which are now being unfolded before our
eyes. If it were required I should fight coura-
geously for the sacred cause of the Republic."
Seeing in the midst of a crowd a structure entitled

18 LOUIS PASTEUR

Autel de la Patrie upon which citizens were invited
to place their donations to the popular cause, Pas-
teur hastens to the Ecole Normale, gathers all his
savings amounting to 150 francs and freely offers
them in behalf of liberty. This sacrifice won the
approval of his patriotic father, who with pardon-
able pride desired to have the gift recorded as com-
ing from "the son of an old soldier of the Empire,
Louis Pasteur of the Ecole Normale."

After resuming his regular studies Pasteur re-
ceived news of the death of his mother which left
him for weeks unable to carry on his work. Home
ties were always strong with Pasteur. Years after-
ward in the course of a celebration at Dole when
a memorial plate was being placed on the house
where he was born, he exclaimed, "Oh, my father,
my mother, dear departed ones who lived so hum-
bly in this little house, it is to you that I owe every-
thing. Your enthusiasms, my brave mother, you
have passed them on to me. If I have always
associated the greatness of science with the great-
ness of our country it is because I was imbued with
the sentiments which you have inspired. And you,
my dear father, whose life was as hard as your
hard trade, you have shown what patience in long
labors can accomplish. It is to you that I owe per-

Fig. i. Pasteur at the Age of Twenty-* ink

HOME LIFE AND EARLY TRAINING 19

sistence in daily tasks. Not only did you have the
qualities of perseverance which make useful lives,
but you have also the admiration for great men and
great things. To look upward, to learn more and
more, to seek always to rise, — these are the things
which you taught me. I see you now, after your
day of labor, reading in the evening some account
of a battle from one of those books which recalled
to you the glorious epoch of which you were the
witness. In teaching me to read, your care was to
teach me the greatness of France."

CHAPTER II

EXPERIMENTS IN CHEMISTRY AND
CRYSTALLIZATION

Pasteur's scientific career upon which we now find
him fully embarked presents a remarkably con-
sistent and logical development. As we follow it
in the succeeding chapters we shall see how each
step almost inevitably leads to the one which fol-
lows. Many scientists work in varied fields, but
for the most part their versatility is the product
of a variety of interests with no organic inter-
relationship. With Pasteur a single thread may
be discerned running through all his research.
From the study of crystals he is led to attack the
subject of fermentation, and then successively the
problem of spontaneous generation, the maladies
of wine and beer, the diseases of silk worms, the
germ theory of disease of animals and men, and
the production of vaccines for the prevention and
cure of infectious diseases. Between the early
studies of the crystalline form of the tartrates of
potash and ammonia and his final great achieve-
ment in the conquest of hydrophobia occur a series

21

22 LOUIS PASTEUR

of steps, each leading on to the other in a perfectly
natural sequence. There are perhaps few better
illustrations of the unity of nature and hence the
essential oneness of science than that which is
afforded by Pasteur's work.

All along the road traversed by Pasteur we meet
with discoveries of capital importance. During his
generation Pasteur was the central figure in a great
epoch in the history of biology and medicine. His
life work was destined to be devoted to revealing
the role in nature which is played by the micro-
scopic forms of life. If he became a biologist after
being a chemist, it was his work in chemistry that
determined the living forms on which he worked
and the kind of problems which he first endeav-
ored to solve. In order to follow Pasteur's early
studies it will therefore be desirable to say a few
words about crystals which began to arouse his
interest in the Ecole Normale.

Many chemical substances, when they are recov-
ered from the liquid in which they are dissolved,
assume a perfectly definite crystalline form which
is characteristic of their own particular kind of
material. Thus common salt crystallizes in cubes,
quartz in six sided prisms and the tartrates in eight
sided prisms. The angles between the faces or

EXPERIMENTS IN CHEMISTRY 23

sides of the crystals have a remarkable constancy,
regardless of whether the crystal is large or small.
During the process of crystallization the molecules
of the dissolved substance are added to the dif-
ferent faces of the crystal in definitely proportional
amounts, thus preserving the general form of the
whole. Crystals when broken may regenerate their
normal form if they are placed in a solution of their
own substance, material being added to the broken
surface much more rapidly than elsewhere until
the typical outline is restored.

Under conditions in which there is a limited
supply of the dissolved material the substance for
restoring the broken end of the crystal may even
be obtained by dissolving away a certain amount
of the substance from other parts of the surface;
thus by taking material from one place and adding
it to another a completely regenerated crystal of
smaller size may finally be obtained. What forces
regulate the behavior of chemical molecules while
they are building themselves up into these beautiful
and regular geometrical forms is a fascinating sub-
ject of speculation which has attracted many minds.
That the process is dependent upon the chemical
nature of the substances concerned seems evident
from the constant and characteristic form which

24 LOUIS PASTEUR

many chemical compounds assume. Besides, simi-
lar compounds such as the salts of a given acid
often have crystals of the same general shape.

As a rule, crystals are regular in form and may
be divided by a plane into two symmetrical halves,
but the crystals of some substances cannot be so
divided; they appear to exhibit a certain degree of
distortion, but they are distorted in a very definite
way. Some are spoken of as right-handed and
others as left-handed. Quartz has the peculiar
property of crystallizing in both forms. Its right-
handed and left-handed crystals are exactly alike
except that the one is like the mirrored image of
the other. They cannot be superposed; they are
related much as our right and left hands.

The asymmetry of crystals is evinced not only
by their form, but by their peculiar action on light.
Light passing in a certain direction through Iceland
spar or quartz, for instance, becomes polarized.
Physicists have shown that light probably consists
of very minute undulations or waves which are sup-
posed to occur at right angles to the line of trans-
mission although these waves may occur
at various angles to each other, thus: — 7\~~
When a beam of light is passed through a
polarizing prism it is found to be incapable of pass-

EXPERIMENTS IN CHEMISTRY 25

ing through a second prism held at right angles to
the first one, although it can pass through the sec-
ond prism when it is held parallel to the first. The
ray has acquired the peculiar property of polariza-
tion in passing through the first prism. This is ex-
plained as due to the fact that the molecular struc-
ture of the crystal has reduced the undula- —
tions of the ray of light to one plane, thus: EEEEE;
The polarized beam can therefore pass —
through a second prism held in the same position
as the first, but when it is placed at right angles
to the first the light is quenched.

Some crystals have the property of twisting or
rotating the plane of polarization of light which is
passed through them. If I have two prisms of
crystalline substance so arranged that the one cuts
off the light transmitted by the other one, and if
I place between them some substance which rotates
the plane of polarized light passing through the first
prism, it will be found that some of the light will now
pass through the second. The plane of polarization
has been changed and hence some light is able to get
through the second prism. The amount of rotation
can be determined by finding through how many
degrees the second prism must be turned in order
completely to cut off the light.

26 LOUIS PASTEUR

Some substances have been found to rotate the
plane of polarized light to the right and others
toward the left. Certain kinds of sugar (dextrose)
twist the ray to the right and other kinds such as
levulose twist it in the reverse direction, and the
amount of these substances in a solution may be
ascertained by means of the polariscope by meas-
uring the amount of rotation which the light has
undergone.

Is there any relationship between the asymmetry
of crystals and the direction in which they rotate
the plane of the polarized ray? The English
astronomer and physicist, Sir John Herschel, sug-
gested that such a relation might exist, but without
submitting the question to the test of experiment.
It was in regard to this question that Pasteur's
researches on the tartrates are of special signifi-
cance. It had been observed by Biot that the salts
of tartaric acid when in solution rotate the plane
of polarized light to the right, but that the so-called
paratartrates had no effect on the polarized ray.
Pasteur subjected the tartrates to a careful micro-
scopic study and succeeded in observing the con-
stant occurrence of small facets or surfaces which
gave the crystals a slight asymmetry which had
escaped previous observers. This asymmetry char-

EXPERIMENTS IN CHEMISTRY 27

acterized the tartrates of many substances, how-
ever different the form of their crystals might
otherwise be. Pasteur then turned his attention to
the paratartrates or racemates. These substances
had been proven by chemical analysis to be of the
same chemical composition as the tartrates. They
had the same specific gravity and many other
properties in common, and were held also to have

Fig. 2. Right-handed and Left-handed Crystals of

Tartaric Acid

the same crystalline form, differing only in their
action on polarized light. By a careful study of
the crystals of the paratartrates Pasteur observed
that some of them were right-handed and others
left-handed. He then carefully separated out these
two types of crystals, dissolved them, and examined
the solutions with a polariscope. To his great joy
he found that the solution made from the right-
handed crystals rotated the plane of polarization
to the right, and the solution of the left-handed

28 LOUIS PASTEUR

ones rotated it to the left. The paratartrate was
therefore a mixture of two substances, the right-
handed one proving to be in no way different from
ordinary tartrate. The paratartrates had no action
on the polarized ray because the rotary power of
one of the two ingredients neutralized that of the
other.

This neat discovery aroused the enthusiasm of
the chemists of the Ecole Normale. Balard told
of it at the Institute de France where it awakened
the interest of Dumas and Biot. The latter, then
a man of seventy-four, was among the most promi-
nent of French scientists. Distinguished both in
astronomy and physics, and especially for his in-
vestigations on crystallography and the polarization
of light, he was naturally impressed with Pasteur's
observations. He had previously discovered the
different rotary effect of different crystals of
quartz, and when Balard told him of Pasteur's
experiments, he remarked, "It would be desirable
to examine closely this young man's results."

Pasteur wrote to Biot whom he did not know
personally, but for whom he felt the admiration
which he was accustomed to cherish toward distin-
guished investigators in science, requesting the
pleasure of a visit in which he might exhibit his

EXPERIMENTS IN CHEMISTRY 29

discovery. He was received in Biot's laboratory.
The old scientist insisted on furnishing his own
materials for the demonstration, and Pasteur made
the required solutions in his presence. In the words
of Pasteur who has left us a description of this
interview, "The solution was then placed in his
laboratory and allowed slowly to evaporate; when
thirty to forty grams of the crystals had separated,
he again called me to the College de France to col-
lect and distinguish by their crystallographic char-
acter the right and the left rotating crystals from
one another, under his direct observation; he bade
me repeat the declaration that the crystals which
I had placed in his right hand would rotate the
plane of polarization to the right, and the others
would rotate it to the left.

"After this had been done, he declared that he
himself would complete the experiments. He pre-
pared the carefully weighed solutions and, when he
was ready to make the observations in the polariz-
ing apparatus, he called me again into his labora-
tory. He put first into the apparatus the most in-
teresting solution, the one which should rotate
toward the left. Without making a reading, but
upon the instant, he noted a change in color in the
two halves of the field of vision, and he recognized

30 LOUIS PASTEUR

an important leavo rotation. Then the excited man
seized my hand and said, 'My dear child, I have
all my life so loved this science that I can hear my
heart beat for joy.' " This seance was the begin-
ning of a friendship between the old man of science
and the younger one that lasted throughout the
former's life.

The relation between crystalline form and ro-
tary power discovered in the tartrates Pasteur was
eager to test upon other materials in order to ascer-
tain how generally this relationship might be found
to occur. It was not easy to find many forms with
asymmetrical crystals which proved at the same
time to have the power of turning the plane of
polarized light. Asparagin proved to be one of
these, and was found to have the peculiar power
of rotating the plane of polarization to the left in
alkaline or neutral solutions, but to the right in
acid solutions. Malic acid and its salts were found
to have both right-handed and left-handed crystals,
whose action on light was frequently the same as
that of the tartrates, but it sometimes behaved in
an apparently contradictory manner that Pasteur
was unable to explain. It is now known that in
dealing with the salts of aspartic and malic acids,
Pasteur fell into certain errors of detail, which pre-

EXPERIMENTS IN CHEMISTRY 31

vented him from following out the clue to his
original discovery. If he finally abandoned his
tentative view that there might be a constant re-
lation between crystalline form and rotary power,
he held firm to the idea of molecular asymmetry as
the basis for the action of dissolved substances on
polarized light.

Here are two substances, identical in chemical
composition, and in numerous physical properties,
but having opposite effects on the polarized ray.
How can such a relationship be explained? The
molecules themselves, thought Pasteur, must have
asymmetry, the one being, so to speak, the mir-
rored image of the other. This conception formed
the foundation upon which was built one of the
most important branches of chemical science,
namely, stereo-chemistry, which is concerned with
the relative arrangement in space of the constituent
parts of the chemical molecule. Is it possible,
asked Pasteur, to change one of these asymmetrical
forms into the other? Paratartaric or racemic acid,
which was a relatively rare form which had been
obtained as a sort of by-product of the manufac-
ture of tartaric acid, had suddenly ceased to appear
where Pasteur had previously obtained it. In
order to collect other samples, Pasteur visited

32 LOUIS PASTEUR

many chemical factories in Europe in search for
this precious substance. He traveled from country
to country, encouraged by reports of its presence
in this place and that, only to find, upon investiga-
tion, that the reports were baseless. "I will go
on for ten years if need be," he wrote; but while
he found traces of paratartaric or raoemic acid in
several of the tartars he studied, it occurred only
in quantities too small to be of practical service.

Then he set himself resolutely to work to pre-
pare it artifically, — a feat which he believed im-
possible; but, after numerous experiments, he
finally effected the transformation by keeping
cinchonine tartrate for several hours at a high
temperature. In June, 1853, he telegraphed to
Biot, "I transformed tartaric into racemic acid;
please inform MM. Dumas and Senarmont." For
this discovery, the Paris Pharmaceutical Society
awarded him a prize of 1500 francs. The Paris
Academy of Sciences devoted a whole sitting to his
discoveries, and after active efforts in his behalf
by his friend, Biot, he was given the Red Ribbon
of the Legion of Honor. "He had won it," says
Vallery-Radot, "not in the same way as his father
had, but he deserved it as fully."

The work on molecular asymmetry, and its rela-

EXPERIMENTS IN CHEMISTRY 33

tion to light and crystalline form consumed about
five years of very active investigation. During this
time Pasteur had changed his position from the

r

Ecole Normale, first to Dijon, where he remained
only a few months, and thence in 1849, to the Uni-
versity of Strasbourg, where he was made Professor
of Chemistry. Half of the 1500 francs prize he
received was spent in fitting up the chemical labo-
ratory of that institution. Scientific laboratories
at that time were rarely furnished with adequate
equipment. Claude Bernard, who made epoch-
making discoveries in physiology, worked in a sort
of cellar in the College de France. Deville, one of
the foremost organic chemists of his time, was lim-
ited to a miserable corner, and the room assigned
to Dumas at the Sorbonne was so unwholesome
that he supported a laboratory at his own expense
outside the University. When Pasteur began as
Professor at the Ecole Normale, he had to utilize,
as a laboratory, two attics close under the roof
with no laboratory attendant or assistant of any
kind. At a later period, he was given a small build-
ing in which he installed a drying oven under the
staircase, which he could reach only by crawling
on his knees.
Pasteur found Strasbourg a favorable place for

34 LOUIS PASTEUR

his work. He devoted much care to his lectures
in chemistry, but he found a good deal of time to
spend upon investigation. He was comfortably
situated in the house of his old school friend,
Bertin, the Professor of Physics, who would not
hear of his going elsewhere. A letter from his
father at this time contains the following remarks:
"You tell us that you will not marry for a long
time, and that you will take one of your sisters to
live with you. I could wish it for you, and espe-
cially for them, for neither of them could wish for
a greater good fortune. To serve you and to look
after your health is what both of them would wish
most of all."

But Pasteur had met the daughter of the Rector
of the Academy at Strasbourg, M. Laurent. He
had called upon the family soon after accepting
his new position, and the charm of the quiet and
united family circle and the attractions of Mile.
Marie, spurred him to a sudden resolve. We have
little record of the association of Pasteur and
Marie Laurent during the period immediately fol-
lowing their first acquaintance, but the mind of
Pasteur, usually so cautious and deliberate, had no
doubts about the young woman to whom he was
so strongly attracted. There are some natures

EXPERIMENTS IN CHEMISTRY 35

whose nobility and sweetness of character are so
transparent that they inspire, almost at once, a
perfect confidence. Mere time, as an element in
acquaintance and understanding, becomes an irrele-
vant detail. Only two weeks after Pasteur's ar-
rival, he sent, in accordance with prevailing custom
in such matters, the following communication to
M. Laurent:

Monsieur, a request of high import for me and for
your family will be made to you in the course of a few
days, and I believe that it is my duty to put you in
possession of the following facts, which may enable you
to grant or refuse this request:

My father is a tanner in Arbois, a little village in the
Jura. My sisters, in the care of the household and the
business, take the place of my mother, whom we had
the misfortune to lose during last May. My family is in
a comfortable position, but without fortune. I estimate
our possessions at not over 50,000 francs; and, as to
myself, I have long since decided to leave to my sisters
all that may fall to my lot. I have therefore no fortune.
All that I possess is good health, good principles, and
my position in the University. I graduated two years
ago from the Ecole Normale as an Agrege in Physical
Science. I took my doctor's degree eighteen months ago,
and I have presented to the Academy of Sciences some

36 LOUIS PASTEUR

productions which have been very well received, espe-
cially the last. A very favorable report which I have
the honor to send to you with this letter was made on
this work.

Such, Monsieur, is my present position. As to the
future, all that I can say is that unless my tastes com-
pletely change, I shall devote myself to researches in
chemistry. I have the ambition to return to Paris when
my scientific contributions shall have brought me some
reputation. M. Biot has spoken to me several times
about thinking seriously of the Institute. Within ten
or fifteen years, perhaps, I may think of it if I continue
to work assiduously. This is no more than a dream. It
is not this that makes me love science for science's sake.

My father will come in person to Strasbourg to make
this proposal of marriage. Accept, Monsieur, the assur-
ance of my profound respect and devotion.

I was twenty-six years old on the 27th of last De-
cember.

Somewhat more cautious than Pasteur, Laurent
deferred for a few weeks his reply to this request.
At last, a favorable answer came. The marriage
took place on May 29th, 1849. Like that of Pas-
teur's father and mother, it proved a happy one.
"All the qualities I could desire in a wife," Pasteur
writes to Chappuis, "I find in her. . . . But I do

EXPERIMENTS IN CHEMISTRY 37

not think I exaggerate at all and my sister, Jo-
sephine, is entirely of my opinion."

The compounds whose solutions had been found
to exercise a rotary power on the plane of polarized
light, had, up to that time, proved to be organic
compounds,— that is, compounds formed through
the agency of living organisms. Pasteur was led
to the veiw that molecular asymmetry is a pecul-
iarity of the compounds formed through the
agency of life, and that it represents a funda-
mental difference between the products of living
and non-living matter. At that time, chemists had
been able to produce artincally many of the chem-
ical substances formed by living beings. Begin-
ning with the synthesis of urea from its elements
by Wohler in 1822, organic chemists had formed
in the laboratory one organic compound after an-
other, using the simpler ones as bases or steps from
which to build up substances of greater and greater
complexity. Dessaignes, an able chemist of Ven-
dome, had transformed the optically inactive maleic
acid to malic acid and then to aspartic acid. As
the latter acid had been found to have the power
of rotating the ray of polarized light, the question
arose as to whether an optically inactive substance
had been changed into an optically active one.

38 LOUIS PASTEUR

Pasteur went to Vendome, obtained a sample of
the aspartic acid made by Dessaignes, and found,
as he had anticipated, that it possessed no rotary
power. The malic acid, which was made from the
aspartic acid was also optically inactive. Pasteur
concluded that there were four kinds of compounds
of identical composition, the symmetrical, the right-
handed, the left-handed and those arising from the
combination of right-handed and left-handed forms.
The artificial products were believed to differ from
the natural ones in being optically inactive. As
Pasteur says, "We recognize that when natural
organic bodies arise under the influence of vege-
table life, they are usually asymmetric in opposi-
tion to minerals and synthetical bodies. The ele-
mentary constituents of all living matter will as-
sume one or the other of the opposite asymmetries,
according as the mysterious life force, which causes
asymmetry in natural bodies, acts in one direction
or the other."

The barrier, which Pasteur attempted to erect
between the products of the living and the non-
living, like so many others that have been erected,
has now broken down. The optically inactive
malic acid, which Pasteur derived from asparagin,
was subsequently shown by Bremer to be a com-

EXPERIMENTS IN CHEMISTRY 39

bination of right-handed and left-handed acids.
But, although errors of detail in this difficult field
of research led Pasteur to an untenable deduction,
his general conception of molecular asymmetry has
proven to be a most fruitful one. Professor G. M.
Richardson, credits Pasteur with the first sugges-
tion that led to the development of stereo-chem-
istry. As Duclaux has stated in his admirable work
on Pasteur's discoveries, "Our knowledge has been
very much extended since Pasteur did his work,
but there has been no change in its source; and in
its immense development, it remains faithful to this
parent idea of Pasteur that all difference in the
grouping of the atoms of a molecule must be ex-
pressed externally in some way."

One of Pasteur's observations is of especial im-
portance, not merely for its scientific interest, but
for its possible influence on the course of his future
studies. It had been observed by manufacturers
that calcium tartrate, when contaminated by a
small amount of albuminous matter, undergoes a
process of fermentation, giving rise to a variety of
products. Pasteur endeavored to find if other
tartrates would behave in a similar manner.
Taking a solution of pure right-handed or dextro-
ammonium tartrate, he placed in it a small amount

40 LOUIS PASTEUR

of albuminous material. Like the calcium salt, it
was found to ferment. He tried the same experi-
ment with ammonium paratartrate which, it will be
remembered, is a mixture of right-handed and left-
handed tartrates. This solution, at first optically
inactive, was found, as fermentation went on, to
rotate the polarized ray more and more to the left.
When the fermentation stopped, the right-handed
tartrate had disappeared; only the left-handed tar-
trate remained. The fluid, originally clear, was
now clouded, owing, as was shown by the micro-
scope, to the presence of minute living organisms.
The microscopic forms of life selected as food the
one asymmetrical tartrate, and left the other,
thereby suggesting a peculiar asymmetry of their
own protoplasm, which made it possible for it to
act chemically on but one of the two constituents
of the solution.

Doubtless this discovery confirmed Pasteur in
his views regarding the asymmetry of the com-
pounds that are immediately concerned with vital
activity. What is of especial importance for his
future career is that it took him across the bound-
ary that separated chemistry and biology. Hence-
forth, it was the micro-organisms which were to
form the chief object of his research.

CHAPTER III

THE WORLD OF MICROSCOPIC LIFE

At this stage of our history it may be advantageous
to consider briefly some of the peculiarities of the
minute organisms to whose study Pasteur was des-
tined to devote the remainder of his life. Readers
who are familiar with microscopic organisms and
their ways will probably prefer to omit the perusal
of this chapter. In fact, they are advised to do
so. I am throwing this chapter in for the benefit
of those, — and my experience as a teacher of
biology has shown them to be very numerous, —
who have never been introduced to this vast and
important assemblage of living beings which have
remained so long unknown because they happen to
be so very small in size. But they make up for
their smallness by their prodigious numbers, their
variety, their rapidity of multiplication and the
magnitude of their mass effects.

Science has proven that microscopic organisms
play a very important role in nature which was

entirely unsuspected a century ago. We may

41

42 LOUIS PASTEUR

imagine the eager curiosity with which the old
Dutch investigator, Anton van Leeuwenhoek,
examined for the first time the minute creatures
which were revealed by his hand-made micro-
scopes. Leeuwenhoek lived in the seventeenth and
eighteenth centuries (163 2-1723) at a time when
the compound microscope was just coming into use
and was being applied by Malpighi, Grew and
others to reveal the finer structure of animals and
plants. He had used his microscopes to observe
the stings of bees, the scales of butterflies' wings,
and other favorite objects of the amateur micro-
scopist, but one day he chanced to examine some
drops of stagnant rain-water when, greatly to his
surprise, he found them swarming with a variety
of minute living creatures, swimming about in all
directions in the most lively manner. It was like
the revelation of the fauna of a new continent,
except that the animals were much more strange
and different from what we are familiar with than
any animals we should be apt to find in an unex-
plored part of the world. Leeuwenhoek sent many
notes describing these new and strange creatures
to the Royal Society at London which published
them in the early volumes of its transactions. Won-
derful revelations these! Inevitably they aroused

THE WORLD OF MICROSCOPIC LIFE 43

widespread interest, and attracted other observers
to turn their attention to this newly-opened field.

Knowledge of the world of minute organisms
progressed rapidly. Great improvements effected
in the compound microscope made it possible to
learn much concerning the structure of these small
living creatures and to bring into view forms of
life whose minute size had rendered them invisible
with the cruder instruments of the older observers.
Leeuwenhoek described the creatures he observed
as "animalcules," or little animals, and little ani-
mals many of them are; but many others turned
out to be minute plants. In these low forms, how-
ever, the plant and animal kingdoms draw nearer
together as if converging toward a common root,
and there are many forms about which it is very
difficult to decide to which kingdom they be-
long.

A much greater insight into the nature and rela-
tionships of these forms followed the establishment
of the cell theory which was originally promulgated
in 1838 and 1839. According to this theory the
bodies of higher animals and plants are made up
of living units, the cells, which may be compared
to the bricks which are used in the construction of
a house. The small living forms studied by the

44 LOUIS PASTEUR

older observers formed a most varied assemblage.
Many of them proved to be the minute represen-
tatives of higher groups of animals, such as worms
and crustaceans. Others, such as the wheel ani-
malcules, belong to groups of many-celled forms
characterized by their small size. But a large pro-
portion of this minute world is found to be com-
posed of organisms consisting of a single cell, the
one-celled animals being known as the Protozoa,
and the one-celled plants as the Protophyta.

The Protozoa form an extensive group, includ-
ing many thousand known species of the greatest
diversity of form, size, and behavior. The majority
live in water, but some, like the soil Amoebae, live
in earth; others are found in decaying organic
matter; some species live in the tissues of plants,
and many kinds are parasitic within the bodies of
animals. In the sea they are represented by very
numerous forms, many of which are furnished with
beautiful silicious or calcareous skeletons and cov-
erings, whose accumulation at the bottom of the
ocean is responsible for the formation of chalk,
many limestones, and other rocky deposits. To-
gether with the unicellular plants of the sea, which
are able to build up their living substance out of
the salts dissolved in the water, they afford the

THE WORLD OF MICROSCOPIC LIFE 45

food supply of over 99 percent of the animal life
of the ocean. The smaller animals, as well as some
of the larger ones, feed on them directly and serve
in turn as food for fishes and other larger forms.
The support of practically all the life in the open
sea from the jellyfish to the whales is afforded, in
the last analysis, by those minute forms of plant-
life which have the property of utilizing as food
the mineral substances found in the water in which
they are suspended.

The Protozoa, like the primitive plants, com-
monly multiply by dividing. An individual simply
constricts into two parts and each assumes the form
of the whole organism. As each two becomes four
in the same manner and each four becomes eight,
and so on in geometrical progression, and as the
divisions frequently follow within the limits of a
few hours, it is easy to see that in a short time
enormous numbers might arise from a single indi-
vidual. Many species, especially those that live in
fresh water or decaying organic matter, are able at
times to assume a spherical form and secrete a
covering or cyst of resistant material within which
they are able to tide over unfavorable conditions
of life. Within these cysts they may undergo pro-
longed drying after which, if placed in water, they

46 LOUIS PASTEUR

may subsequently emerge and begin the usual
course of their lives. A few forms have been kept
for several years in the encysted state and subse-
quently revived. Some of the soil Amoebae when
in these cysts are able to withstand several minutes
of boiling without being killed.

The ability of many Protozoa to withstand
drought while in the encysted state greatly favors
their wide dissemination. These cysts may be
blown in the dust of the air like the spores of mold.
If we make an infusion by boiling some animal or
vegetable material and then set it aside for a few
days exposed to the air, we shall probably find it
to be teeming not only with bacteria but with sev-
eral species of Protozoa. Or if I soak a bit of
dried hay in water for a few days and then examine
it with the microscope, I would probably observe
a veritable menagerie of small animal forms of the
most diverse kind. I well remember when as a boy
after becoming the proud possessor of a compound
microscope I used to make up all sorts of decoc-
tions, malodorous and otherwise, and examine them
for the living creatures that somehow mysteriously
came to develop in them. This world of life with
its rolling ciliated infusorians, swiftly darting
flagellates, and sluggish slowly-crawling Amoebae,

THE WORLD OF MICROSCOPIC LIFE 47

although composed only of forms well known to
science, was to my uninstructed vision as new and
fascinating as it doubtless was to Leeuwenhoek, the
Columbus of this new world.

Fig. 3. Forms of Protozoa. A, Amoeba; B, Amoeba dividing;
C, a flagellate, Haematococcus ; D, an infusorian, Para-
mcecium ; E, an infusorian cyst; F, trypanosomes ; G, a
foraminiferan.

The subject of protozoology, which deals with
these one-celled animals, has now become one of
the most important branches of biology. Not the
least of the roles played by these organisms is that

48 LOUIS PASTEUR

of parasites within the bodies of higher animals.
Some Protozoa in fact live within the bodies of
other Protozoa, and there are even protozoan para-
sites of protozoan parasites.

One of the primary divisions of this group, the
Sporozoa, is composed entirely of forms parasitic
in other animals. Hundreds of different species
inhabit the alimentary canal and other organs of
insects, crustaceans, and worms. It is a protozoan
of this group that causes pebrine, the destructive
disease of silkworms which was studied by Pasteur.
One whole subdivision of the Sporozoa, the Hemo-
sporidia, is peculiar in living within the red blood
cells of vertebrate animals; examples of this sub-
division are furnished by the Plasmodium causing
malaria in man and the parasite causing Texas
fever in cattle, a highly malignant disease, trans-
mitted from one animal to another by the bites of
the wood-tick.

The amoebas causing amoebic dysentery, the
flagellates causing various intestinal diseases, the
trypanosomes giving rise to the fatal sleeping-
sickness in Africa, are a few of the many Protozoa
that cause trouble in the human body. The species
afflicting the lower animals are much more numer-
ous and are found in the bodies of almost all ani-

THE WORLD OF MICROSCOPIC LIFE 49

mals down to and including the Protozoa them-
selves.

It is with the minute forms of plant life that the
researches of Pasteur were mainly concerned, and
the importance of these greatly exceeds that of the
Protozoa, great as this may be. There can be no
doubt that in the absence of these primitive plants,
all higher life on the globe would be impossible.
Like the Protozoa, the Protophyta or one-celled
plants, belong to many groups. There are the
minute green algae, which are common inhabitants
of both fresh and salt water, the more primitive
blue-green algae, the diatoms with their beautifully
sculptured silicious shells, the desmids, and the
many other forms which we cannot even mention
in this cursory sketch.

One group of primitive fungi, the yeast plants,
are, however, of more than usual interest to us in
this history on account of their relation to the
problem of fermentation studied by Pasteur. Man-
kind has made use of yeasts from the earliest times
without suspecting that their activity is due to the
life of minute plants. Examination of actively fer-
menting beer or wine, and especially the growth
that often appears floating upon the surface, re-
veals multitudes of spherical or oval bodies which

50 LOUIS PASTEUR

may be seen to put out buds which slowly increase

in size and finally constrict off as new yeast cells.

^ ^r^^ Sometimes the substance of the yeast
HP m^

q q cells breaks up within the cell wall

into (usually four) rounded bodies

called spores, and these bodies, which

Fig. 4 Cells of are more resistant to drought and

Yeast °

Showing bud- other destructive influences than the

onefcas11 f *r yeast plants themselves, may give rise
spores. to new individuals. There are many

kinds of yeast plants, each producing its own peculiar
kind of fermentation. The importance of yeasts
in making bread, alcoholic beverages, and other
products of industry has greatly stimulated the
study of their different varieties and modes of life.
The most important of all one-celled forms of
plant life are unquestionably the bacteria. These
are also the simplest and most primitive of all
living organisms. Their discovery dates back to
our industrious old Dutch observer, Leeuwenhoek,
who in 1683 in one of his notes to the Royal So-
ciety describes and figures several very small crea-
tures that undoubtedly belong to this group. Al-
though countless in the number of their species,
the bacteria present little variety of external form
as compared with the Protozoa. A very common

THE WORLD OF MICROSCOPIC LIFE 51

type is the rod-shaped form called bacilli (Latin:
bacillus — rod) ; then there are the spherical cocci,
and the spiral bacteria (the spirilli and spirochetes)
and sometimes forms of peculiar shape. Bacteria
have no clearly-defined nucleus and they present
but little differentiation of internal structure, al-
though their very small size would probably pre-

■ l D6°8

Fig. 5. Forms of Bacteria. A, staphylococci; B, streptococci;
C, bacilli of anthrax ; D, bacilli of the plague ; E, Spiroch&ta
pallida; F, tetanus bacilli showing spores in one end; G, the
typhoid bacillus.

elude us from observing it even were it present.
Sometimes there are whip-like appendages or
flagella, which are employed in locomotion, al-
though many forms move about actively without
possessing any external appendages at all.

All the bacteria are invisible to the naked eye.
It is impossible to specify their minimum size;
even with the most powerful microscopes there are
forms which can barely be seen, and it is practically
certain there are others which are too minute to be

52 LOUIS PASTEUR

seen at all. Some of the ultramicroscopic forms
pass through niters (the so-called filterable viruses)
and their existence is inferred only by the effects
which they produce.

Like most other unicellular organisms, bacteria
multiply by fission. At times some species such
as the hay bacillus and bacilli of tetanus and
anthrax may form spores which are very resistant
to heat, dryness, and destructive chemicals. The
fact that as spores some bacteria may withstand
boiling even for several hours, proved to be a very
troublesome circumstance in the controversy over
the spontaneous generation of life as we shall see
in a later chapter.

Under favorable conditions the multiplication of
bacteria may proceed with great rapidity. Since
divisions in some cases may follow one another
every twenty or thirty minutes, the number arising
from a single individual in the course of a few
days is enormous. Cohn estimates that if a bac-
terium divides once in an hour it would produce
over three and one-half million descendants at the
end of twenty-four hours. Assuming its size to be
that of a Bacillus proteus, which is about %oo of
a millimeter long by %ooo of a millimeter thick,
the volume of this mass of bacteria after twenty-

THE WORLD OF MICROSCOPIC LIFE 53

four hours would be about a fortieth of a cubic
millimeter; after two days the volume would be
about a half liter or about one pint; and after four
and a half days, however, the volume would more
than equal that of the water of the entire Pacific
Ocean !

The food material utilized by bacteria varies
with different species. A few forms are able to
build up their living substance out of purely min-
eral constituents. One of the sulphur bacteria can
subsist on a bill of fare made up as follows:

Ammonium sulphate

i gram

Potassium phosphate

i gram

Magnesium carbonate

i gram

Water

i liter

Here we have the food supply reduced to perhaps
its simplest possible terms. Most kinds of bac-
teria, however, demand some organic matter. A
great many species live upon compounds furnished
by the dead bodies of plants and animals whose
decomposition is brought about by the activity of
these minute forms. The large number of para-
sitic bacteria which subsist within the bodies of
plants and animals are still more specialized in

54 LOUIS PASTEUR

their food requirements. Different forms vary in
their reactions to oxygen, some requiring this gas,
while others (the anaerobes) will not grow if free
oxygen is present.

Bacteria differ not only as to the substances
which they take in but also as to the substances
which they give out. Just as our own bodies give
off carbon dioxide and other products of excretion,
so do the bacteria get rid of various substances
characteristic of different varieties. It is chiefly
with respect to the materials which the bacteria
eliminate that many of the characteristic effects of
their growth and activity are brought about. The
role of bacteria in ripening cheese, curing tobacco,
and many other industrial processes is due to the
products of metabolism of certain species employed
for these purposes. One very important effect of
bacteria in relation to agriculture, depends upon
the property possessed by a few species of con-
verting the free nitrogen of the air into a form
which may be used as food for higher plants. Some
of these bacteria live within the roots of legumi-
nous plants, such as beans, clover, alfalfa, vetches,
etc., and consequently crops of these plants are
grown in order to increase the supply of available
nitrogen in the soil.

THE WORLD OF MICROSCOPIC LIFE 55

The study of bacteria involves the use of an
especially refined technique. It is a study full of
pitfalls, and in which many errors have been made
in the past. One great difficulty arises from the
fact that it is often very difficult to isolate par-
ticular kinds and to keep them free from admix-
ture with foreign species. Even with the most
careful treatment our cans of fruit and vegetables
sometimes spoil, and the investigator occasionally
finds his material contaminated after all possible
precautions had been taken to prevent the entrance
of outside germs. Perhaps the difficulty in keep-
ing material free from outside bacteria can best be
realized by watching the dust particles revealed by
a beam of light entering a room. For each par-
ticle that we can see there are many others too
small to be seen, and even the smallest visible par-
ticle would appear under a powerful microscope to
be quite a large object many thousand times the
size of a bacterium. The floating matter of the
air, as has been shown by the extensive studies of
the great English physicist, John Tyndall, is widely
distributed even in the air at great heights. It is
responsible for the blueness of the sky and the red-
ness of the sunset. A beam of light is visible only
on account of the dust particles in its course. And

56 LOUIS PASTEUR

these are present even in ordinary air in astonish-
ingly large numbers.

It is no wonder then, even if only an occasional
dust particle contains a bacterium, that it is so
difficult to keep out all of these intruders. The
bacteriologist who wishes to have air admitted to
his materials employs plugs of cotton wool which
allow air to enter, but filter out all solid particles.
Bacteria may be grown in many kinds of media,
some species in one medium and others in other
media; a few forms cannot be cultured artificially
at all. A very convenient and much employed
method of culture is partly to fill a test-tube with
the culture medium, plug it with cotton wool,
sterilize it by heating, and then to introduce from
the point of a needle a minute amount of material
containing bacteria. The growth of the colony
may often be followed by observing the clouded
area in the culture medium. Colonies may be
transplanted from one tube to another and kept
going for an indefinite time.

The varied applications and refinements of the
technique of bacteriology would require a volume
to describe. Perfection of technique has been
brought about as bacteriology has progressed and
become applied to different fields. Undoubtedly

THE WORLD OF MICROSCOPIC LIFE 57

the enormous development of bacteriology is one
of the most striking features in the history of the
nineteenth century, a history especially noteworthy

, -. •»iJ.~'V.-;v\.-'.

• •-.,v-.>.-iV

Fig. 6. A Test Tube Plugged With Cotton and Showing
a Bacterial Colony Growing in the Culture Medium

for the advance of science. For over a century and
a half following their discovery by Leeuwenhoek,
the great importance of bacteria was practically

58 LOUIS PASTEUR

unknown. They were among the many other in-
teresting and curious forms of minute life whose
study occupied the attention of a few naturalists.
Now there are departments of bacteriology with
their several courses in most universities and
medical schools. Government bureaus, agricultural
experiment stations, institutes for medical research,
and many private industrial firms are carrying on
investigations in this field. A small army of in-
vestigators devote themselves to such subjects as
the bacteriology of milk, the bacteriology of water,
soil bacteriology, dairy bacteriology, and the bac-
teriology of sewage, to say nothing of the bac-
teriology of plant and animal diseases. Almost all
of the enormous development of bacteriology with
its numerous ramifications has taken place in the
last fifty years. What strides may be made in the
next half century we can only vaguely conjecture.
I have said a little concerning the relation of
bacteria to disease. This topic, which is of the
greatest importance for our human welfare, will
occupy us more or less in the succeeding pages.
There is one fact in regard to bacteria, however,
which is of fundamental significance in relation to
disease as well as to other practical aspects of bac-
teriology, and which has come to be established

THE WORLD OF MICROSCOPIC LIFE 59

only after a great deal of careful and critical work.
This is the specificity of these low forms of life.
Each kind of micro-organism breeds true to type,
maintaining, even amid considerable changes in the
course of its life cycle, certain structural features
characteristic of its species as well as its own pe-
culiar physiological activities. Several of the older
observers had very incorrect views concerning the
relationships and transformations of these primitive
forms of life. Thanks to the refinements and per-
fection of bacteriological technique the older errors
have been corrected. The most primitive organ-
isms fall into species just as the higher animals and
plants do. There is a certain amount of variation
or deviation from the type, to be sure, but this is
quite analogous to, and probably no more extensive
than the variability observed in higher organisms.
The more we know of primitive forms the more
closely are they found to resemble the highly de-
veloped types with which we are familiar. Life
is very much the same sort of thing wherever we
find it.

CHAPTER IV

STUDIES IN FERMENTATION

Pasteur had scarcely more than entered upon the

study of fermentation at Strasbourg when he was

appointed Professor and Dean of the Faculty of

Science at Lille. The faculty at Lille had just been

reorganized, and one of the innovations made in

the course of instruction was to grant to students

for a small fee the privilege of entering scientific

laboratories and carrying on experiments. This

improvement in education was warmly approved

by Pasteur. In his opening address as Dean he

spoke of the advantages of laboratory instruction

in the following terms: "Where will you find in

your families a young man whose curiosity and

interest are not awakened as soon as you put into

his hands a potato with which he will make sugar,

with this sugar alcohol, with this alcohol ether and

vinegar? Who would not be happy to tell to his

family in the evening that he was about to make

an electric telegraph?

"And, gentlemen, be convinced of this, such

61

62 LOUIS PASTEUR

studies are not readily forgotten, if they ever are.
It is almost as if, in order to teach the geography
of a country, one causes a student to travel in it.
That geography is preserved in the memory because
one has seen and been in contact with the places.
Similarly, your sons will never forget what is con-
tained in the air we breathe when they have
analyzed it, when in their hands and under their
eyes the admirable properties of its elements have
been revealed."

The relative merits of studies in pure and in
applied science have been the subject of no end
of learned disquisitions. Lille is in the center of
an industrial region and its inhabitants looked to
the University for scientific information of a prac-
tical kind. The words which Pasteur addressed to
the public on the appropriate occasion of his in-
stallation are well worthy of quotation. "Without
theory practice is but routine engendered by habit.
Theory only is able to cause the spirit of inven-
tion to arise and develop. It is important that
you, above all, should not share the opinion of
those narrow spirits who disdain everything in
science that has no immediate application. You
may recall the charming response of Franklin when
he took part in the first demonstration of a purely

STUDIES IN FERMENTATION 63

scientific discovery. When he was asked, 'What is
the use of it?' he replied, 'What is the use of a
baby?' Yes, gentlemen, what is the use of a baby?
And yet at this age of tender infancy there are
already unknown germs of the talents by which
you are distinguished. In your infants in arms,
in the little ones whom a breath would overthrow,
there are magistrates, scientists, heroes as valiant
as those who, at this time, are covering themselves
with glory under the walls of Sebastopol. Simi-
larly, gentlemen, theoretical discovery has only the
merit of existence. It awakens hope; that is all.
But let it be cultivated, let it grow, and you will
see what it will become." One sentence of this
address stands out as expressing a truth of which
his own career was destined to form a striking
illustration. Speaking of the role of good fortune
in discovery, Pasteur says, "In the field of obser-
vation chance favors only the mind which is pre-
pared."

Pasteur's duties at Lille as teacher and dean
were discharged with that energy and capacity
which he applied to all the tasks that fell to his
lot. He did much to improve and enliven labora-
tory instruction. He took his students to visit the
factories in neighboring towns. And he frequently

64 LOUIS PASTEUR

devoted the services of his laboratories to the solu-
tion of the practical problems that presented them-
selves in the industries of the surrounding region.
Although fully aware of the importance of the
search for knowledge regardless of its practical
applications, Pasteur was not one of those who dis-
dained to spend his time upon matters of practical
economy. In fact, a considerable part of his re-
searches has been devoted to economic problems.
The maladies of wine and beer, the production of
vinegar, the diseases of silkworms, and the epi-
demics of fowl cholera, swine plague, and splenic
fever in sheep and cattle, are all matters whose
economic importance had much to do with enlist-
ing his interest. He was ever ready to respond
when the industries of his country called upon
science for help. That a problem is an economic
one does not detract in the least from the scientific
importance of its solution. If it may be said in
behalf of pure science that it leads to valuable prac-
tical results, it may also be said that investigations
carried on with purely practical aims frequently
yield discoveries of the greatest theoretical import.
In most of the researches of Pasteur theoretical
and practical considerations were very closely re-
lated. The solution of the practical problems

STUDIES IN FERMENTATION 65

which he attacked involved the answer to theo-
retical questions. Whether we are studying the
souring of milk, the fermentation of sugar, the
maladies of beer and wine, or the diseases of ani-
mals and men, the thing of fundamental importance
to get at is the cause of the phenomenon we are
dealing with. We may learn much about all these
things by observation and the collation of facts;
but if we wish to get at the root of the matter we
must discover causes. Knowledge of the widest
general import frequently comes from getting at
the real root of particular problems. When we
thoroughly understand the reasons for lactic acid
or alcoholic fermentation our knowledge is of great
service in understanding fermentation in general,
and the demonstration of the cause of one infec-
tious disease opens the way to the discovery of the
causes of many others. If Pasteur occupied him-
self with particular economic problems such as how
to keep wines from spoiling and silkworms from
dying of a destructive epidemic, he solved his prob-
lems in such a way that by getting at the real causes
in these particular cases he threw a flood of light
upon related phenomena that has illuminated whole
new fields of enquiry.

It was a combination of theoretical and practical

66 LOUIS PASTEUR

considerations that determined Pasteur's point of
attack upon the subject of fermentation at Lille.
His observations on the relation of the molecular
asymmetry of the tartrates to fermentation and
the fact that this fermentation was accompanied
by the appearance of multitudes of minute organ-
isms impressed him profoundly. The thought that
fermentation is essentially a vital phenomenon and
not a mere chemical transformation due to decom-
posing substances became more deeply impressed
upon his mind as he continued to investigate the
subject. It was one of those "preconceived ideas"
which he frequently alluded to as guides to the
investigator in the discovery of truth. In his case
it was an idea that was ever-present during the
years which he devoted to the study of fermenta-
tion.

When Pasteur began his studies on fermentation
the prevalent ideas on the subject were very ob-
scure. One peculiar feature of the chemical trans-
formations occurring in a fermenting body is that
they may be set up in the same kind of material
by transferring to it a small part of the fermenting
substance. The Swedish chemist Stahl held that
fermentation is the result of a peculiar "internal
movement" which may be communicated from one

STUDIES IN FERMENTATION 67

substance to another. Through the labors of
Lavoisier, Gay-Lussac, Thenard, and others, a good
deal had been learned of the chemical changes that
occur during the fermentation of sugar into alcohol
and the transformation of the latter into vinegar.
The part played by yeast in converting sugar into
alcohol and carbon dioxide seemed quite* mysterious.
An important step was taken when Cagniard-Latour
showed that yeast consisted of small oval or
rounded bodies which had the power of growth and
multiplication by budding and fission. This ob-
server and the German biologist Schwann held that
fermentation is produced by the growth and activi-
ties of these small organisms, and Schwann gave
reasons for believing that these organisms are of
vegetable origin. But the chemists, as a rule, were
averse to attributing fermentation to the influence
of living forms; they sought for a purely chemical
explanation of the process and regarded the asso-
ciation of fermentation with the mysterious vital
activities of the living organism as a backward step
calculated to obscure rather than to elucidate the
phenomenon.

The illustrious Liebig who called attention to the
fact that sugar can be caused to undergo alcoholic
fermentation by adding to it almost any decom-

68 LOUIS PASTEUR

posable nitrogenous compound, held that it was the
death and decay of the yeast which causes the
breakdown of the molecules of sugar, fermentation
being a consequence of death and decomposition
rather than of life. "In what respect," argues
Liebig, "does the explanation of fermentation ap-
pear more clear to you when you have introduced
a living organism? What if they are everywhere
present? But you see yourself that there are none
in the putrefactions. Let us admit, if you will,
although this appears very extraordinary, that the
meat and the sugar are destroyed by different
agencies. But the sugar may undergo various fer-
mentations very similar to alcoholic fermentation
and even accompanying it; lactic fermentation,
butyric fermentation, etc. Do you find in these
fermentations anything that resembles yeast? Do
not these behave absolutely like the putrefaction
of meat? Your explanation limps and encounters
obstacles at every step. For me, on the contrary,
these transformations present a common character,
that is, of taking place in the presence of organic
matter in course of decomposition. One may start
a lactic or a butyric fermentation by means of old
cheese or rotten meat. For alcoholic fermentation,
Colin showed in 1828 that one may bring it about

STUDIES IN FERMENTATION 69

by means of a number of organized nitrogenous
substances, different from the yeast of beer, pro-
vided that they are in a state of decomposition.
It is these dead substances which are the ferments.
I do not forget, moreover, the experiments of
Thenard on the almost constant production of yeast
in fermenting fluids. ... But this yeast does not
embarrass me; it enters my system. If you admit
that it lives you also admit that it dies. Then it
is in dying that it acts, as a consequence of the de-
composition that it undergoes at this time, and of
this Thenard furnishes us the proof."

This passage read in the light of our present
information is most instructive in reflecting the
most advanced knowledge of its day. That it con-
tains a number of errors both in statement of fact
and in conclusions was made apparent by the later
observations of Pasteur. Liebig held that albu-
minous substances in a state of decomposition im-
parted a sort of "molecular movement" whose in-
fluence is to break up sugar into alcohol and
carbon dioxide, or in the case of putrefaction, to
effect destructive changes that give rise to other
products. This view was defended by Liebig with
energy and ability and it became the most widely
accepted doctrine of the time.

70 LOUIS PASTEUR

Pasteur, as we have seen, had been brought,
through his studies of molecular asymmetry, into
contact with the problems of fermentation. Mo-
lecular asymmetry as revealed by its rotary effect
upon light, he looked upon as a characteristic of the
products of life. His observation that the right-
handed tartrate of ammonia would ferment while
the life-handed one would not, suggested a relation
between the asymmetry of the tartrate and the
asymmetry of some of the compounds of the living
substance of the yeast plant which has been com-
pared to the relation of a lock and key. In regard
to the agents causing the decomposition of organic
products a number of pertinent questions suggested
themselves to his fertile mind. Are fermentations
in general caused by living organisms, or may they
be provoked by various kinds of albuminous mat-
ter? Is putrefaction due to living germs, or does
it occur in material that is quite free from them
as stated by Liebig? Is each kind of decomposi-
tion produced by a specific organism? In what
relation does the yeast plant stand to the decom-
position with which it is associated? Is fermenta-
tion due to the life of the yeast plant or is it a
result of death and decomposition? Here are sev-
eral questions which have a close relation to the

STUDIES IN FERMENTATION 71

views of Pasteur in regard to molecular asymmetry
and life. Moreover, fermentation being a method
of splitting up organic compounds is a valuable
instrument for studying the relationship of the
asymmetry of an organic compound and the asym-
metry of its derivatives if they possess any. In
fermentation Pasteur surmised there might be fur-
nished the clue to many problems not only in chem-
istry, but also in biology, if only the confusion and
obscurity surrounding the subject could be dis-
pelled.

Pasteur's early studies were made on lactic acid
fermentation, the process which is responsible for
the souring of milk. His memoir on the subject,
though short, is very noteworthy, not only in estab-
lishing for the first time some important facts, but
in containing the expression of several of the lead-
ing ideas which guided him throughout his future
investigations. Pasteur observed that the little
gray patches which appeared on the bottom and
sides of the vessels of fermenting fluid were com-
posed chiefly of minute organisms, much smaller
than yeast plants, and that these organisms in-
creased in number as fermentation proceeded. Are
they the agents that cause the souring of milk, as
yeast plants produce alcohol from sugar? Pasteur

72 LOUIS PASTEUR

made up a medium composed of a solution of sugar
to which was added a small amount of chalk and
the boiled and filtered extract of the yeast of beer
to furnish the albuminous material needed for car-
rying on fermentation. In this mixture he placed
some of the gray material composed mostly of the
small organisms just mentioned, and set the fluid in
a warm place. The next day revealed an active
fermentation. The liquid originally clear was now
turbid or clouded. Bubbles of gas, which proved
to be carbon dioxide together with variable amounts
of hydrogen, rose to the surface and escaped. The
chalk, which had settled on the bottom, disap-
peared. After fermentation had ceased, the fluid,
when evaporated down, gave a residue chiefly of
lactate of lime. The sugar had been transformed
into carbon dioxide and lactic acid, and the latter
had combined with the chalk (which is carbonate
of lime) and crystallized out. Here was revealed
a process very similar throughout to alcoholic fer-
mentation; with the same materials which would
form alcohol upon the addition of ordinary yeast;
we obtain quite different products solely by the
substitution of a different ferment.

Lactic acid fermentation, like alcoholic fermen-
tation, was found by Pasteur to arise in suitable

STUDIES IN FERMENTATION 73

material to which its special ferment had not been
added. Both kinds of fermentation often occur in
the same material in which bits of cheese or other
decomposable substances are placed or which have
simply been exposed to the air. Still other kinds
of fermentations might occur, the products ob-
tained varying greatly according to circumstances
and often for reasons that appear quite accidental
or capricious. Pasteur recognized in these varied
phenomena the influence of mixtures of different
organisms which might have been introduced in
different proportions from the floating matter of
the air or from the rotten cheese or meat used to
start up the fermentation. He observed in such
cases yeast plants along with the organisms found
in lactic acid fermentation, and also other organ-
isms, some of which were bacteria, while others
were forms that he referred to as "infusoria."

"We may compare," Pasteur says, "what goes on
in fermentation with what is produced in a field in
which one sows no seed. One soon sees it inhab-
ited by diverse plants and insects which are mu-
tually destructive." Pure fermentations were found
to contain predominantly but one characteristic
kind of organism, while the mixed fermentations
contained two or more kinds in variable propor-

74 LOUIS PASTEUR

tions. "The purity of a ferment," observes Pas-
teur, "its homogeneity, its free development with-
out any restraint with the aid of a nutriment appro-
priate to its peculiar nature form one of the essen-
tial conditions of good fermentation." One may
obtain mixed fermentations of a given material at
will by sowing in it diverse kinds of organisms.

Lactic acid fermentation, then, is not a process
occurring independently of minute organisms, as
stated by Liebig. Pasteur had discovered that it
was due not to yeast plants, but to bacteria which
had not been noticed by previous observers. A
knowledge of the cause of this kind of fermentation
gave the key to its control. The memoir on lactic
acid fermentation showed the conditions under
which the small bacteria concerned could best be
grown and kept reasonably free from contamina-
tion. The mind of Pasteur was naturally led on
to the general conclusion that the different kinds of
fermentation in nature have each its own peculiar
organisms whose nutrient needs and metabolic
products determine the characteristic chemical sub-
stances arising from their activity.

The illuminating investigation of lactic acid fer-
mentation was followed two years later by a
memoir on alcoholic fermentation. Pasteur showed

STUDIES IN FERMENTATION 75

that in the fermentation of sugar, other substances
besides alcohol and carbon dioxide, namely glycerin
and succinic acid, were regularly formed in small
amounts, and that these substances were formed
at the expense of sugar. The alcoholic fermenta-
tion of sugar cannot be adequately represented
by the simple equation in which chemists were
accustomed to express it. It is a complex, many-
sided process in which sugar yields several prod-
ucts, among which, as Pasteur proved, is the cel-
lulose constituting the substance of the cell wall
of the yeast plant. This suggested the intimate
role played by the life of the yeast cell in the
process of fermentation. Pasteur held that this
process was dependent on the vital activity instead
of the death of the organisms found in ferment-
ing matter, and he sought to ascertain the role
of the nitrogenous matter which must be added to
dissolved sugar if it is to transform into alcohol.
The chemists held that it acted through its decom-
position or merely by its presence. Pasteur, on the
other hand, believed that it served simply as food
for the yeast plants which, in common with all
living creatures, require nitrogenous matter for
building up their living substance. But the ques-
tion was how to put the matter to the test?

76 LOUIS PASTEUR

It occurred to Pasteur to see if yeast plants could
derive their nitrogen from simple inorganic salts
instead of albuminous matter of uncertain compo-
sition. Accordingly, he made up media consisting
of sugar, water, ammonium salts, phosphates, and
a few other inorganic ingredients to which he added
a minute amount of yeast. After experimenting
for some time he succeeded in making up solutions
in which yeast plants would grow and which would
undergo at the same time a typical alcoholic fer-
mentation. The yeast plants require several sub-
stances as food, but organic nitrogenous material
was proven unnecessary both for fermentation and
for the growth of the yeast cells. The theories of
Liebig and other chemists were dealt a severe blow.
Brought to the test of experiment they were found
wanting. On the other hand, it became more ap-
parent that it was owing to the growth and activity
of microscopic organisms that fermentations were
brought about.1

1 Although Liebig was in error in attributing ordinary
fermentation to decomposing nitrogenous substances, there is
an element of truth in his chemical theory. It has long been
known that enzymes of organic origin produce fermentation.
Micro-organisms may effect the decomposition of surround-
ing substances by giving rise to enzymes. In fact an enzyme
has been extracted from ordinary yeast that has the property
of converting sugar into alcohol and carbon dioxide. Fer-

STUDIES IN FERMENTATION 77

Pasteur's position was strengthened, also, by the
study of other ferments. It was found that, after
lactic acid fermentation had ceased, the lactate of
lime was capable of undergoing fermentation in
turn if a drop of material were added which is
undergoing butyric fermentation. Butyric acid is
the acid that makes its appearance in rancid butter.
Upon searching for the organisms in material un-
dergoing butyric acid fermentation, Pasteur was
surprised to find active rod-like bodies which he
classed as vibrios and which he believed, on ac-
count of their activity, to belong to the animal king-
dom. In this Pasteur was misled by the imper-
fect knowledge of his day, for it is now well known
that many one-celled plants, and especially bacteria,
move about in a most lively manner. During his
examination of these so-called vibrios Pasteur made
an interesting observation that led him eventually
to further generalizations on the nature of fermen-
tation. Taking a drop of the fermenting solution,
he placed it on a glass slide, covered it with a thin
glass cover-slip, and proceeded to study it under
the microscope. The organisms at first active

mentation is not a vital process in quite the sense that Pasteur
thought it was, although it remains true that living organisms
play an essential role in ordinary fermentations. They pro-
duce the enzymes that do the work.

78 LOUIS PASTEUR

throughout the fluid were found to become immo-
bile near the edges. This is quite the reverse of
what often happens with other forms, because it is
near the edge that there is the most abundant
supply of oxygen. Can it possibly be that oxygen,
the great supporter of life, checks the movements
of these forms? Ready as always to put his ideas
to the test of experiment Pasteur passed a current
of air through a flask of liquid containing active
vibrios, thus supplying the material with an abun-
dance of oxygen. The activities of the vibrios
ceased, and the butyric acid fermentation that was
going on was brought to a close. Pasteur was thus
led to the conception of anaerobic life, or life with-
out free oxygen, and the organisms which devel-
oped best in a medium devoid of oxygen and whose
activities are checked in the presence of this sub-
stance he called anaerobes.

The nature of the changes undergone by a de-
composing substance may be determined, therefore,
by the amount of oxygen with which it is supplied.
If it contains a variety of micro-organisms, then,
under conditions of free supply of air, certain or-
ganisms that require oxygen will develop and pro-
duce their characteristic effects. If, on the other
hand, the oxygen supply is limited, the anaerobic

STUDIES IN FERMENTATION 79

forms will thrive and produce different effects.
Frequently one change follows another, the ordi-
nary aerobic organisms using up the available
oxygen in the material, and thus creating a condi-
tion in which the anaerobes may take their turn.

Some organisms, as Pasteur found in the case
of common yeast of beer and wine and some species
of molds, may live either with or without free
oxygen. In any case they need oxygen for their
life, and if they cannot secure it directly they take
it out of some of the compounds in which it is
chemically combined. Pasteur found that the
ordinary yeast of beer, if given abundant oxygen,
would grow rapidly, but would produce very little
alcohol. If its supply of oxygen were limited, it
would ferment much more of the sugar into alcohol
and carbon dioxide. By being forced to wrest
away its oxygen from sugar it becomes thereby a
ferment. Fermentation depends, therefore, in his
view, on the capacity of an organism to live with-
out air.

What is called putrefaction was proven by Pas-
teur to be essentially like the phenomena which
had been described as fermentations, only it is pro-
duced, as a rule, by different kinds of organisms
and gives rise to different products. What we com-

80 LOUIS PASTEUR

monly designate as putrefaction is simply fermen-
tation which generates substances having a bad
smell. Commonly, but not necessarily, putrefac-
tions are caused by anaerobic bacteria.

The result of Pasteur's numerous labors on fer-
mentation was to bring order out of chaos. No
longer were the phenomena obscure or mysterious.
Fermentation was shown to be associated with the
functioning of minute living organisms instead of
with the decomposition of dead nitrogenous matter.
Different kinds of organisms were proven to cause
each its own peculiar kind of fermentation in a
given substance such as sugar. The products of
one ferment, it was shown, might be split up again
by another kind of an organism. The influence of
these living ferments was shown to be specific or
limited to certain kinds of transformation. The
loose ideas which then prevailed concerning the
ready transformation of one type into another were
proven to be based on faulty observation or incon-
clusive experiments. We now know that micro-
organisms produce their own kind as faithfully as
do cabbages or turnips, and a transformation of a
bacterium into a yeast plant, or an infusorian would
nowadays be no more expected than the conversion
of a cow into a horse, or a maple into an oak tree.

STUDIES IN FERMENTATION 81

The great progress that has been made in our
knowledge of fermentation is based on the sound
foundations laid down by Pasteur. Brewers are as
careful of their special varieties of yeast as stock-
raisers are of their breeds of cattle. Poor yeasts
produce undesirable fermentations. Many of the
impurities of "home brew" and the various alco-
holic liquors that are now secretly made and ped-
dled are due to the influence of micro-organisms
which regular manufacturers had learned how to
exclude. The doctrine of the constancy of specific
types has proven to be a guide of great value in the
solution of problems of fermentation both theo-
retical and practical. We shall see further indica-
tions of its far-reaching import when we come to
consider its relation to infectious disease.

It was when Pasteur was in the midst of his
studies of fermentation that he had an opportunity

r

to join the Faculty of the Ecole Normale of Paris.
He decided to accept the new position, and in 1857
we find him installed as a professor in the institu-
tion which it was once his dream to be able to at-
tend. Although his duties in the school were many>
he made a laboratory out of the attic which we
have previously mentioned and began work on the
fermentation of alcohol. During a part of the

82 LOUIS PASTEUR

summer the heat of the attic made it impossible to
work there. "I see with regret," he wrote to
Chappuis, "the longest days of the year lost for my
work. Nevertheless I am growing used to my gar-
ret and I shall find it hard to leave it. I hope to
enlarge it during the next holidays."

During the year 1859 he was studying fermen-
tation. In the latter part of the year he met with
a great sorrow, for he had lost his eldest daughter
who had died of typhoid fever in September. He
wrote his father, "I am unable at present to think
of anything except my little girl, so good, so full of
life, so happy in living, whom the fatal year that
has just passed has taken from us. In a little time
she would have become such a loving companion
for her mother, for me, and for us all . . . but I
beg pardon, my dear father, for recalling to you
these sad memories. She is happy. Let us care
for those who remain and make ourselves keep
from them, as much as in our power, the bitterness
of this life."

CHAPTER V

CONTROVERSIES OVER SPONTANEOUS

GENERATION

Pasteur's studies on fermentation inevitably
brought him face to face with the problem of the
origin of those minute forms of life through whose
activity the process of fermentation is caused. The
minute organisms found in decaying substances
were regarded by many scientists as arising, by a
process of spontaneous generation, out of organic
matter in a state of dissolution. Pasteur , who had
traced specific kinds of fermentation to specific
organisms, and had shown that these organisms
reproduced their own kind true to type, and more-
over possessed extraordinary powers of dissemina-
tion through the atmosphere, was very skeptical in
regard to their alleged origin, de novo, out of or-
ganic matter. Realizing the futility of the meta-
physical discussions and a priori arguments on the
subject, which had been so frequently indulged in,
and convinced that it is only by careful and critical

experimentation that the question could finally be

83

84 LOUIS PASTEUR

settled, he resolved to devote himself to the task.
In January, i860, he wrote to his friend, Chappuis,
"I am doing my best with these studies on fermen-
tation, which have a great interest on account of
their relation to the impenetrable mystery of life
and death. I hope to make soon a decisive step by
solving, without the least confusion, the celebrated
question of spontaneous generation. Already I
could speak, but I want to perform still more ex-
periments. There is so much passion and so much
obscurity on both sides, that it will require nothing
less than the cogency of an arithmetical demon-
stration to convince my adversaries of my conclu-
sions. I intend to accomplish even that."

Biot, who had followed Pasteur's career, with
a sort of fatherly interest, endeavored to dissuade
him from an investigation which he believed would
prove fruitless. Dumas, less decided in his remon-
strance, remarked that he "would counsel no one
to occupy himself too long with such a subject."
But Pasteur, who doubtless had a clearer vision
in this field than either of his elder counselors, per-
ceived that the problem of spontaneous generation
lay, as it were, across his path. To attack it, was
the next logical step in his scientific career.

The belief in the spontaneous origin of living

SPONTANEOUS GENERATION 85

forms is a very old one. Formerly, caterpillars
were supposed to arise spontaneously from leaves;
and frogs, fishes, and eels were said to be produced
from mud and ooze. Virgil has described how bees
arise from the carcass of a dead bull, and Van
Helmont, although a scientist of eminence, tells us
that mice may be engendered by putting some dirty
linen in a container along with a few grains of
wheat.

The first to perform real experiments in regard
to the origin of living things was Francesco Redi,
physician to the Grand Dukes of Tuscany. Re-
flecting on the origin of the maggots observed in
decaying meats, he set himself to trace their source.
Noticing that blowflies frequently hovered about,
and often alighted on, decaying meat, he thought
that these flies might possibly be responsible, in
some way, for the appearance of the maggots.
Accordingly, he placed pieces of meat in jars cov-
ered with gauze to exclude the flies. Although the
meat so protected was found to putrefy, no mag-
gots made their appearance. Moreover, Redi ob-
served that the flies laid eggs, and that from these
eggs small maggots arose which grew rapidly as
they devoured the decaying flesh. By many obser-
vations and experiments, Redi conclusively showed

86 LOUIS PASTEUR

that maggots do not arise spontaneously, but de-
velop from eggs laid by flies.

Other naturalists extended these observations
and experiments, and finally banished from science
the notion that such creatures as worms, insects,
fishes or frogs arise spontaneously. Closer investi-
gation of the life history of these forms revealed
the fact that they arise from eggs of members of
their own species. To-day nothing could seem
more incredible to a trained biologist than that an
angleworm or an insect should arise by a process
of spontaneous generation. He would as soon
expect that a Westminster Abbey should sud-
denly build itself out of the paving stones of the
street.

With our present knowledge, we easily perceive
that the older notions of spontaneous generation
were exceedingly crude. In the light of the scien-
tific knowledge that accumulated during the seven-
teenth and eighteenth centuries, it was impossible
for them long to persist. But when the compound
microscope revealed myriads of minute living crea-
tures in a drop of stagnant water, the question of
spontaneous generation presented itself anew. That
these strange simple organisms might arise by a
transformation of organic matter was a conclusion

SPONTANEOUS GENERATION 87

that did not appear to be unreasonable. It was
observed that they made their appearance in infu-
sions previously boiled, and exposed to the air. As
boiling was held to kill all living matter, it was
inferred that the organisms appearing in boiled
infusions must have arisen by spontaneous genera-
tion. Moreover, these minute organisms seemed so
very different from higher forms of life, and as
very little was known of their life history, their
spontaneous origin was all the more readily ac-
cepted. The Irish priest, Needham, had heated
flasks of organic infusions, corked them up while
hot, and found, in the course of a few days, that
the liquid became turbid from the multitude of
minute organisms which were engendered within it.
The origin of these living forms was attributed to
a "vegetative force" operating on the organic sub-
stances of the infusion.

These experiments aroused the interest of an-
other priest, the sagacious Abbe Spallanzani, who
attacked the subject by somewhat more rigorous
methods. He made infusions in flasks whose con-
tents were thoroughly boiled. Being suspicious of
corks, he sealed his flasks by drawing out their
necks and fusing them, thus absolutely excluding
all air, and hence any germs which might be car-

88 LOUIS PASTEUR

ried by it. His flasks, unlike those of Needham,
remained clear for a long time, and showed no
trace of living organisms. Spallanzani concluded
that organisms appearing in boiled infusions do not
arise spontaneously, but are brought in from the
atmosphere. Needham objected that the heat used
by Spallanzani altered the vegetative force of the
infusions, and that boiling drove off the air neces-
sary to produce life. The controversy came to no
decisive issue, and parties to both sides of the ques-
tion continued their discussions.

Schulze, in 1836, conceived the idea of supply-
ing boiled infusions with air which had been drawn
through sulphuric acid in order to rid it of any
living germs which it might possibly carry. Infu-
sions supplied with air in this way remained several
months free from decay. Schwann, in the follow-
ing year (1837) varied the experiment by supply-
ing his infusions with air which had been passed
through a heated tube. As these infusions re-
mained free from organic life, he concluded that it
is not air that causes life to develop, but something
in the air which is destroyed by heat. In 1854,
Schroeder and Dusch obtained the same results by
drawing into their infusions air which had simply
been filtered through a plug of cotton wool. Thus

SPONTANEOUS GENERATION 89

originated a method which is now an every-day
procedure in every bacteriological laboratory.

These experiments, which were distinctly unfa-
vorable to the theory of spontaneous generation,
were not permitted to go unchallenged. Their
most noteworthy opponent was Prof. F. A. Pouchet,
Director of the Museum of Natural History at
Rouen, a man celebrated as a naturalist and of
high standing among the scientists of his coun-
try. In 1859, Pouchet published a large work en-
titled "Heterogenic" in which the experiments of
his opponents are subjected to a searching criticism,
and in which many new experiments are described
which, in the opinion of the author, prove conclu-
sively that life develops in boiled infusions under
conditions which completely exclude the entrance
of germs from the outside. Pouchet threw himself
into this work with much vigor and enthusiasm.
He repeated the experiments of Schulze and
Schwann, and obtained living organisms where they
had obtained none. If germs exist in the air in the
abundance which would be necessary to produce
the effects ascribed to them, Pouchet maintains, the
air would be quite obscured. The extensive re-
searches of Pouchet, carried on with the appear-
ance at least of careful control, and set forth in a

90 LOUIS PASTEUR

confident and impressive manner, tended to make
opinion more favorable to the theory of the spon-
taneous origin of life.

Naturally, these researches were closely followed
by Pasteur. Although their results were contrary
to his own experience and the conclusions to which
he was led, he refrained from any discussion of
the subject until he had carried out many investi-
gations of his own. No one was better prepared
than he to realize the difficulties that beset the
investigator in this field. Even with the most
scrupulous care, one may, quite unsuspectingly,
make little slips that entirely vitiate his results.
Pasteur strongly suspected the adequacy of the
technique employed by Pouchet, and he set himself
to repeat the experiments of his opponent and to
devise others which would afford a conclusive an-
swer to the much controverted question with which
he was grappling. Pouchet affirmed that suitable
infusions supplied with oxygen would develop living
organisms when every care was taken to exclude
outside germs. Pasteur, on the contrary, found, in
agreement with Schulze, that if air were drawn
through a heated tube before supplying the infu-
sions, no life would develop.

One type of experiment which is particularly

SPONTANEOUS GENERATION 91

significant was the following: Pasteur placed infu-
sions of many different organic substances in glass
flasks whose neck was drawn out into a long curved
tube. After thorough boiling, the air which was
sucked in to take the place of the condensed steam
after the liquid gradually cooled, would deposit

Fig. 7. Flask with Curved Neck Used for Keeping Boiled
Infusions Supplied with Air Free from Germs

nearly all its floating matter along the sides of the
tube. Although supplied with air, the contents of
the flask were found to remain for a long time per-
fectly clear and free from decay. If now the flasks
were tilted so that some of their contents came in
contact with the walls of the tube, putrefaction
would invariably be set up. The material in the
flask was able to develop life. The only thing
lacking was not air but something which was caught

92 LOUIS PASTEUR

in the long narrow neck. When this was added,
living forms appeared in abundance. What was
this something?

Pasteur affirmed that it was germs floating in
the air, and he set himself to demonstrate that
germs actually do float in the air. To show this,
he caused air to be drawn through a tube, plugged
with gun cotton to act as a sort of filter. After a
given volume of air had been drawn through the
tube, the gun cotton was dissolved in alcohol and
ether. A residue was deposited which, under the
microscope, was seen to be composed of many kinds
of particles, among which were bodies indistin-
guishable from the spores of mold, the cysts of
infusorians, and various kinds of bacteria. That
the cotton actually contained the germs of organ-
isms was shown by another experiment. Taking a
flask of sterile infusions, Pasteur, under precautions
to keep out the entrance of matter from the out-
side, placed a small bit of the cotton in the neck
but without allowing it to come into contact with
the liquid; then the neck of the flask was sealed.
So long as the cotton remained in the neck of the
flask, the liquid kept clear. After fifteen days, or
a month or longer, the flask was tilted so as to bring
the liquid in contact with the cotton. Soon the

SPONTANEOUS GENERATION 93

liquid became turbid, and teeming with living or-
ganisms. "What reply," asks Pasteur, "do you
make to this experiment? Will you claim that the
cotton, being an organic substance, generates life?"
Even this possibility was met. Pasteur replaced
the cotton by the purely mineral fiber of asbestos,
and obtained precisely the same results. These

Fig. 8. Flask with Sealed Neck Partly Filled with

Boiled Infusion

were crucial and clear-cut experiments and their
answer was decisive.

Pasteur's instinct for thoroughness led him to
make a detailed study of the atmosphere of dif-
ferent localities, in order to ascertain whether or not
it possessed uniformly the same power of generating
life. In this investigation, he used small straight-
necked flasks (Fig. 8), partly filled with an infu-

94 LOUIS PASTEUR

sion, and after bringing the contents to a boil, he
sealed the necks by fusing the glass with a blow
pipe while the steam was escaping. He then car-
ried these flasks to where he wished to study the
atmosphere, sterilized the necks, snipped them off
with sterilized pincers, thereby allowing the air to
rush into the flasks; then he re-sealed them. As
a rule, some flasks remained clear, and others not,
depending upon whether or not germs happened to
be present in the sample of inrushing air. Of the
ten flasks opened in the calm air of the cellar under
the observatory at Paris, only one showed any signs
of contamination. Of the eleven flasks opened in
the yard of the same institution, all gave evidences
of the development of life.

During his vacation in i860 Pasteur decided to
experiment with the pure air of the Alps. On Sep-
tember 20th of that year we find him ascending the
Montanvert, near Chamounix, with a mule laden
with cases of flasks. In his first experiment, being
unable to close the necks of his flasks until he re-
turned to the inn where he was stopping, he found
that nearly all of his infusions became contami-
nated. His next experiment was carried out on the
Mer de Glace glacier. After sterilizing the neck
of each flask he raised the flask high above his

SPONTANEOUS GENERATION 95

head to avoid the entrance of germs from his
clothes and broke the neck with a sterilized forceps
and quickly re-sealed it. Of the 20 flasks so
treated only one gave signs of life. By these and
other experiments Pasteur showed that air is by
no means uniform in its power to generate life in
infusions. Where the air is pure and relatively
free from floating matter it rarely gives rise to
living forms. It is therefore not air that generates
life, but something in the air, as Pasteur repeat-
edly affirmed.

The publication of these results stirred Pouchet
and his colleagues to renewed efforts in support of
their cause. They had affirmed that air taken from
anywhere would give rise to life when brought into
contact with a proper sterile solution of organic
material. They resolved to meet Pasteur on his
own ground, and accordingly they also set out for
the Alps with a supply of flasks. A party of three
investigators, Pouchet, Joly, and Musset, made a
somewhat perilous journey to a height considerably
above the Montanvert, for they must outdo Pas-
teur in the excess of their precautions to obtain
pure mountain air. Their flasks which had been
partly filled with a boiled infusion of hay (a note-
worthy point as we shall see later) were opened

96 LOUIS PASTEUR

and sealed again with the most careful precau-
tions. In a few days the investigators were re-
warded by finding all of their flasks turbid and
teeming with life. Even the purest air of the moun-
tains, Pouchet triumphantly claimed, is capable of
generating life in putrescible material.

Here we have a most curious situation! Differ-
ent investigators of high standing and unquestioned
integrity performing what they deemed to be the
same experiment under as nearly as possible the
same conditions arrive at diametrically opposite
results. What is the explanation? Who is right?
Did Pouchet and his adherents commit some ex-
perimental error which allowed germs to gain en-
trance without their knowledge into their infusions?

In order to resolve this apparent deadlock Joly
and Musset made the fair and reasonable proposal
that the Academy of Sciences appoint a commis-
sion, before whom both parties to the controversy
should repeat their experiments. Pasteur, con-
vinced of the truth of his position, readily acceded
to this proposal. The Academy therefore ap-
pointed five men, Flourens, Dumas, Brongniart,
Milne-Edwards, and Balard. Pasteur wished the
discussion to occur as soon as possible, but his
opponents plead for delay on account of the cool-

SPONTANEOUS GENERATION 97

ness of the weather. But when warm weather
came they refused to comply with the conditions
laid down by the Commission, which presented a
report favorable to Pasteur.

The heterogenesists still continued the discussion,
and it was a number of years before the question
was cleared up to the satisfaction of the most com-
petent judges. In the light of what is now known
it is not improbable that Pasteur's opponents would
have been able to repeat their experiments before
the Commission of the Academy with the results
which they had predicted, and Pasteur, although
right in his fundamental contention, would prob-
ably have been unable to refute them. Truth is
sometimes very elusive, and nowhere more so than
in this field. The positive results obtained by
Pouchet and his co-workers under conditions in
which Pasteur was unable to obtain any traces of
life were probably not due, as Pasteur thought, to
faulty technique, but to a fact then unknown to
both parties, i.e.; that certain forms of life may
resist prolonged boiling without being killed. This
is demonstrably true of the spores of the hay
bacillus, and it is significant that Pouchet worked
with infusions of hay, while Pasteur employed a
decoction of yeast and various other infusions.

98 LOUIS PASTEUR

The controversy was somewhat analogous to the
celebrated discussion of the color of the two sides
of the shield.

This fact was brought out only several years
later in the course of a discussion with the cele-
brated English champion of the doctrine of spon-
taneous generation, Doctor Charlton Bastian. Bas-
tian, who was well known in medical circles in
England, had written a large, two-volume work
entitled "The Beginnings of Life," in which he
brought forward much experimental evidence for the
spontaneous origin of living organisms, and con-
tended that many of the low forms of life passed
readily into species of a quite different character.
Although his work is full of wrong conclusions
based on inaccurate observations, Bastian per-
formed several experiments which have been the
means of materially advancing our knowledge of
the propagation of minute forms of life. Bastian
claimed that urine boiled to free it from germs,
then rendered alkaline by a solution of boiled
potash and set aside to incubate, became swarming
with bacteria in nine or ten hours. It is not germs,
he claimed, that give rise to the bacteria, but the
alkali which supplies a condition necessary for
spontaneous generation.

SPONTANEOUS GENERATION 99

The experiment was repeated by Pasteur who
confirmed Bastian's observations, although he
sought to explain them in a different manner. It
cost Pasteur and his co-workers, Joubert and
Chamberland, much work to get at the real solu-
tion of the difficulty. Chamberland showed that
in an acid medium some germs may be heated to
the boiling point, but will remain inert until the
medium is rendered alkaline when they again de-
velop. Again, germs, such as the spores of the hay
bacillus, may endure a temperature in an alkaline
medium several degrees higher than in a neutral or
acid medium. By heating to 1150 or 1200 C, the
materials used by Bastian it was found that all
bacterial development in alkaline urine was effec-
tually checked. Nowadays a practice is made of
heating to i2o°C. materials which it is important
to thoroughly sterilize. As Duclaux remarks,
"Bastian rendered a service to science; he lashed
it on its weak side, but he compelled it to ad-
vance."

The interest aroused by these controversies and
the importance of the question involved drew sev-
eral investigators into the field. Many facts of
importance in regard to the vitality of germs under
different conditions were brought out as a result

100 LOUIS PASTEUR

of efforts to arrive at a definite settlement of the
problem. It was found that in a dried condition
germs may resist degrees of heat considerably
above the boiling point. Bacteria may lodge upon
the sides of glass vessels or the necks of glass re-
torts and remain there in a living condition while
the fluid contents have been subjected to boiling.
As Duclaux observes, "The heating to 1200 C. of
a flask half full of liquid may sterilize only the
moistened part, allowing life to persist in the
regions which are not in contact with the liquid.
In order to destroy everything, it is necessary to
subject the dry walls to 1800 C. Hence the utility
of flaming all the receptacles used in microbiology,
and behold once more a practice arising, like the
autoclave, from the laboratory of Pasteur, and
which, along with it, established a good technique
and made the future secure."

As knowledge of micro-organisms became more
extensive and precise, the position of the opponents
of spontaneous generation grew steadily in strength.
In England the problem was investigated with great
ability and manipulative skill by the physicist,
John Tyndall, who approached the problem by a
route very different from that of Pasteur. Tyndall
was led to it from his investigations of the way in

SPONTANEOUS GENERATION 101

which light is affected by minute particles in the
air and other media which it traverses. The blue-
ness of the sky and the blue color of the sea and
the water of deep lakes he explained as due to
minute particles held in suspension which, on ac-
count of their very small size, reflect chiefly only
the shortest light waves of the visible spectrum,
or those near the violet end. It was necessary for
him in the course of his experiments to obtain air
free from floating matter. Light passing through
ordinary air reveals its course by being reflected
from a multitude of minute particles. Tyndall
showed that a beam of light sent through air free
from floating particles is absolutely invisible. I
have often noticed in the shade of the dense red-
wood forests of northern California how beams of
light reveal their path, high up among the trees,
by delicate hazy streaks in the exceptionally pure
air of that region. Even there the air is charged
with floating matter. Of what does it consist?

Tyndall studied the question in samples of the
air of London by an ingenious method. A coil of
platinum wire which could be heated to redness by
an electric current was enclosed in a glass vessel
into which air could pass only by going through a
dense plug of cotton. A beam of light passing

102 LOUIS PASTEUR

through the vessel could be traced by the illumi-
nated motes in the air. After the platinum coil
had been heated to redness for some time the
course of the beam was no longer visible. The
floating matter had been burned; it was therefore
organic matter. The same result was also obtained
by passing air through the flame of an alcohol
lamp. Examination of floating matter in several
places has shown that it contains as a rule only a
small proportion of inorganic dust. The more
persistent floating matter is composed mostly of
organic material which when dried and finely
divided is very light and readily wafted to great
heights by even a very gentle breeze.

Occasionally inorganic particles, if very small
and of light material, may be carried to great dis-
tances in the air. Several years ago after the
eruption of the great volcano of Krakatao, it was
estimated that the dust was carried several times
around the world in the higher levels of the atmos-
phere, causing the striking red sunsets which were
observed for several weeks after that event.

Tyndall found that passing air through sulphuric
acid as Schulze had done failed to make it "op-
tically pure." Some of the motes in the bubbles
failed to come into contact with the liquid and

SPONTANEOUS GENERATION

103

passed through unaffected. Such air he showed
was occasionally able to develop organic life in
sterilized infusions, but for reasons quite different
from those given by Pouchet.

Is there any relation between the optical purity

B

I* 1

1 1

i 1

, —

«

%

f

•

r

• * «

@. ;

> :

.

.© :

(

Fig. g. Apparatus Designed to Free Air from Germs by
Drawing It Through Sulphuric Acid Contained in B

Air sucked through in the direction of the arrows causes it
to bubble through the acid, but some of the germs, repre-
sented by dots, may escape coming into contact with the
fluid and pass into the infusion is the flash A.

of the air and its power of causing putrefaction?
Tyndall attacked this problem with his usual thor-
oughness and skill. Like Pasteur he experimented
with sealed flasks containing infusions which were
opened and closed again in different kinds of air.
He also experimented upon the air in his favorite

104 LOUIS PASTEUR

vacation ground in the Alps with results corrobo-
rating those obtained by Pasteur. Many experi-
ments were carried on with an apparatus constructed
as follows: A case with glass front and a glass
window in either side (Fig. 10) is provided with a
bottom having holes in which glass test tubes are
fixed, air tight, with their open upper ends in the
chamber. Through the top is a funnel tube passing
through an India rubber disc. This tube is movable
and is used for filling the tubes with liquid. Two
tubes are fitted for admitting air, but they are bent
several times to intercept any floating matter that
might be carried by the slow exchange of air be-
tween the inside and the outside of the chamber.
The inside of the chamber is coated with glycerine
to catch any floating motes which come in contact
with it.

A powerful beam of light sent through the glass
windows revealed the existence of floating particles
in its course. After a time the beam became less
and less visible as the motes in the air settled to
the bottom or were caught by the coating of glyc-
erine on the top and sides. In three days the beam
within the box was quite invisible, but before it
entered the box and after it emerged its track was
"vivid in the air."

SPONTANEOUS GENERATION 105

Fig. io. Apparatus Designed by Tyndall for Freeing Air

from Floating Matter

a and b curved tubes for admitting air ; p, tube used for filling
the test tubes in the bottom. /, source of light passing
through the windows, W and W.

106 LOUIS PASTEUR

Various infusions were poured through the fun-
nel tube into the test tubes and brought to a boil
by a burner placed below them. Similar sets of
tubes, filled with the same material, were boiled for
the same length of time and exposed to ordinary-
air as a control experiment. In the one case the
tubes were protected from floating matter, in the
other they were exposed to it. Otherwise the con-
ditions in the two sets were the same.

Hundreds of experiments were tried with all sorts
of substances; urine, infusions of beef, haddock,
sole, codfish, hare, grouse, liver, oysters, turnips,
hay, and many other materials in varying degrees
of strength. Tyndall was nothing if not thorough.
And what was the outcome? "There is no shade
of uncertainty," says Tyndall, "in any of the re-
sults. In every instances we have within the
chamber perfect limpidity and sweetness — without
the chamber, putridity and its characteristic smells.
In no instance is the least countenance lent to the
notion that an infusion deprived by heat of its
inherent life, and placed in contact with air cleansed
of its visibly suspended matter, has any power
whatever to generate life anew."

The hay infusion employed had been heated to
i2o° C. for four hours as the spores of the hay

SPONTANEOUS GENERATION 107

bacillus were proven to be exceptionally resistant
to heat, especially in an alkaline medium, but all
of Tyndall's protected tubes "remained for more
than three months as clear and healthy as they
were on the day the infusion was poured into
them."

That several kinds of micro-organisms remain
alive in boiling water is a fact that has proven a
fertile source of error in experiments on spon-
taneous generation. It was but natural that in the
earlier experiments on this subject it was generally
assumed that boiling must be fatal to all living
substance. Gradually it became manifest that dif-
ferent species vary greatly in their power to resist
destruction by heat. The bacteria causing the sour-
ing of milk, for instance, are easily killed, and in
Pasteurizing milk it is only necessary to heat it to
about 6o° C. Other organisms in milk are not
killed by this temperature, and some of these may
cause milk to putrefy without becoming sour. Only
a few forms can withstand boiling, and they do so
commonly in the form of spores. Their protection
by a resistant coating which prevents their proto-
plasm from being softened is probably one reason
for the high resistance of the spores of several
forms. For a similar reason a high resistance to

108 LOUIS PASTEUR

heat is shown by the seeds of several plants. Seeds,
like the germs of micro-organisms to which they
are analogous, vary greatly in their resistance to
heat. Most of them are destroyed by temperatures
far below the boiling point; some, like mustard
seed, may withstand a few seconds exposure to
boiling water. A few kinds of seeds have been
found to resist boiling for several hours without
destroying their power of germination.

Another very deceptive circumstance consists in
the relation of the development of some germs to
oxygen. In some cases infusions have been boiled
and found to remain clear so long as they were
kept from the air. When supplied with oxygen,
under the most careful precautions to prevent con-
tamination, they were nevertheless found to develop
life. Here seems to be the kind of proof required
for the theory of the spontaneous origin of life.
More searching investigation, however, solved the
problem in a different way. It was shown that the
germs in question were not killed by boiling, but
remained alive, though inactive, in the sealed tubes
because they required oxygen for their develop-
ment. When this was supplied under conditions
that kept out any germs from the outside, life de-
veloped in the infusion. By bringing the infusion

SPONTANEOUS GENERATION 109

to a temperature several degrees above the boiling
point no life developed even with an abundant
supply of oxygen. It was not the germs alone that
were required as Pasteur at first thought, nor
oxygen alone as the champions of spontaneous gen-
eration thought, but germs plus oxygen as Pasteur
later came to discover.

I have been able to give but a brief sketch of
the numerous experiments which the battle over
spontaneous generation called forth. Few problems
in science have proven so baffling. The difficulties
and the pitfalls besetting the investigators of this
question have led many into errors, and Pasteur
himself was not entirely free from them. But the
conquest of the difficulties has added much to our
knowledge of the world of microscopic life. To-
day the scientific world is convinced that spon-
taneous generation, in the sense in which it was
formerly believed, does not occur. That it has not
occurred, or may not occur under precisely the
right conditions, the cautious scientist would not
assert. How the gap between the inorganic and
the organic was bridged is a problem still far from
solution.

The more we know of minute organisms the
more their propagation is found to resemble that of

110 LOUIS PASTEUR

higher plants and animals. Their species breed as
true as those of sheep or cattle. Their form may
vary in different parts of their life cycle, but we
often meet with profound changes of form in the
life history of highly organized creatures. So far
as our experience goes it corroborates the truth of
the dictum, "Omne vivum e vivo," — all life from
antecedent life. And not only this, but it may
be said that all life comes from antecedent life
of approximately the same kind. The establish-
ment of this doctrine for minute forms of life in
the sense that it holds true for higher forms is an
achievement of far-reaching importance in many
relations. Pasteur was early convinced of its truth.
He did more than any one else to establish it. And
this principle served him as a most valuable guide
in grappling with the problems with which he was
destined to be occupied during the remainder of
his life.

CHAPTER VI

THE DISEASES OF WINE AND VINEGAR

The years devoted to the problem of spontaneous
generation were years of growing fame. The con-
troversies in which Pasteur engaged attracted the
attention not only of the scientific world, but of
the wide circle of people who were naturally curi-
ous in regard to the beginnings of life. A lecture
on spontaneous generation delivered by Pasteur on
August 7, 1864, drew a large and eager audience
in which were such celebrities as George Sand,
Duruy, Alexandre Dumas and the Princess Ma-
thilde. The subject was discussed in the popular
press and became a favorite topic of chatter in
polite society.

As always occurs with great scientific issues
there were many people whose chief concern with
the question was over its possible bearing on re-
ligion. Spontaneous generation was regarded by
some as tending toward atheism, while the opposed
view was considered to be more in accord with the
traditional account of creation as narrated in

Genesis. Pasteur's work was, therefore, quite

111

112 LOUIS PASTEUR

orthodox in its supposed theological bearings. For
this reason it was received with favor by some and
suspicion by others. Pasteur felt called upon to
declare, "This is not a matter of religion, phi-
losophy, atheism, materialism, or spiritualism. I
might even add that as a scientist these things do
not concern me. It is a question of fact; I took
it up without preconceived ideas, and if experiment
convinced me that way I was as ready to maintain
the existence of spontaneous generation as I am
now persuaded that those who affirm it are blind-
folded."

The purely scientific attitude of mind is hard for
many persons to appreciate. The true scientist
endeavors to exclude all kinds of bias which may
obscure his vision of the truth, to follow humbly,
without regard to preference or desire, wherever
evidence may lead, regardless of consequences to
his preconceived opinions. To close his eyes to
evidence against his cherished convictions is, from
the point of view of the seeker after truth, not only
unwise, but immoral. But how often do we sin
against the cause of truth, preferring to adhere to
our opinions, rather than to bring them to the test,
and to give them up if the balance of evidence
turns against theml

DISEASES OF WINE AND VINEGAR 113

In the realm of scientific fact Pasteur endeav-
ored to maintain an open mind, and to be always
ready to acknowledge error and to retrace his steps
when he found himself on a wrong track. This
trait is essential to a man of science, who is, so to
speak, a professional seeker after truth. In the
ordinary walks of life people may be unreasonable,
pig-headed and intolerant in regard to matters of
opinion without exciting much comment, — in fact
this is to be expected. But even in ordinary life,
matters of great importance may hinge upon the
correctness of our judgments, and we may pay
dearly for our disregard of the principles of right
thinking. And there is no lot nor occupation in
which adherence to these principles will not mate-
rially add to the effectiveness of our lives.

Although Pasteur endeavored never to allow his
mind to be swayed by prejudice or inclination, his
work was far from being carried on in a cold and
dispassionate spirit. Few men worked under
greater emotional stress. Of an intense nature,
fired by a lofty enthusiasm for discovery, ambi-
tious to throw light on fundamental problems in his
fields of research, inspired by a vision of the far-
reaching importance of his investigations, and con-
scious that he was opening the door to discoveries

114 LOUIS PASTEUR

of highest value to mankind, Pasteur threw him-
self into his work with feverish energy and entire
absorption. Readily aroused by opposition he ex-
hibited a vigorous pugnacity in controversy that is
attributable less to irritability of temper than to
the intense seriousness of his concern with the
problems before his mind.

His family life was a singularly happy one. For-
tunately, Madame Pasteur could appreciate her
husband's scientific work and ambitions, and she
betrayed no jealousy on account of his extreme
devotion to his tasks. If she suffered an occasional
pang, as doubtless she must have done, she loyally
concealed it under a guise of cheerfulness and
encouragement. In 1884 she wrote to one of her
children, "Your father, always much preoccupied,
talks little, sleeps little, rises at dawn, and, in a
word, continues the life which I began with him
thirty-five years ago to-day."

One of Pasteur's characteristics, which offers
the strongest testimony as to his sterling qualities,
was his capacity for making true and devoted
friends. Men were drawn to him not only by his
ability and achievements, but on account of per-
sonal traits that inspired their respect and affec-
tion. It was Pasteur's privilege to number among

DISEASES OF WINE AND VINEGAR 115

his close friends such men as Balard, Dumas, Biot,
Deville, Senarmont, and Claude Bernard, and it
was his pride to have drawn around him as pupils
and assistants men such as Roux, Joubert, Cham-
berland and Duclaux, who have made themselves
famous by researches in fields opened up by his
labors. When these men speak or write of their
master it is in a tone which reveals the great ad-
miration and devotion with which he inspired them.
Pasteur's essay on organized corpuscles existing
in the atmosphere gained the prize which the
Academy of Sciences offered for the best experi-
mental investigation of the question of spontaneous
generation. Several of his scientific friends endeav-
ored to have Pasteur made a member of the
Academy. As this learned body is one of limited
membership, a new member is elected only when
a vacancy arises through the death or resignation
of one of its number. In 1857 a vacancy arose in
the section in mineralogy and Pasteur was urged
to present himself as a candidate on the basis of
his researches on crystallography, for which he had
already received the Rumford medal from the
Royal Society of London. Although ardently sup-
ported by Biot, who had been his steadfast friend
ever since his demonstration of right-handed and

116 LOUIS PASTEUR

left-handed tartrates, and in spite of a most flat-
tering account of his work by the mineralogist,
Senarmont, Pasteur received only sixteen votes,
thirty being required for election. Again in 1861
he stood for election, this time in botany on ac-
count of his researches on minute forms of plant
life. Championed by Balard and again by Biot he
obtained 24 votes and failed again. The fact that
he was a professional botanist doubtless counted
against him. Moquin-Tandon, who was urged by
Balard to support Pasteur, replied, "Let us go
to Pasteur's and if you find a botanical work in
his library, I shall put him on the list." It would
not be surprising if the quest should have been
unsuccessful. In 1862, through the death of his
friend, Senarmont, a vacancy was again created in
the section on mineralogy, and this time Pasteur
was elected.

The battles over spontaneous generation had
taught Pasteur many things which he was able to
turn to good account in his efforts to solve several
practical problems which now engaged his atten-
tion. Nearly a year was devoted to studying the
manufacture of vinegar and in endeavoring to
obviate several of the difficulties and mishaps that
beset the makers of this useful article. Vinegar,

DISEASES OF WINE AND VINEGAR 117

as is well known, is derived from the fermentation
of alcohol. Wine, cider, and other liquids contain-
ing not too high a percentage of alcohol, turn sour
under the proper conditions, owing to the trans-
formation of alcohol into acetic acid. The city of
Orleans in France was a great center for the manu-
facture of vinegar and those engaged in this occu-
pation frequently suffered great losses, because the
fermentations failed, for some unknown reason, to
proceed in the proper way. Ordinarily in the half-
filled casks of partly ripened vinegar and wine
which were used, a thin film developed on the sur-
face which the manufacturers knew, from experi-
ence, was important for the proper fermentation of
the underlying liquid. When the film sank, or
became dislodged, fermentation was checked. It
was known that the film required air for its devel-
opment, although it was not known why. Pasteur,
in making a microscopic examination of this film,
found it to consist of minute organisms, about
twice as long as wide and %oo of a millimeter in
length. He called this form Mycoderma aceti, and
he showed that it had the property of taking
oxygen from the air and oxydizing the material
below. One gram of these minute organisms was
proven to be capable of transforming ten thousand

118 LOUIS PASTEUR

times its weight of alcohol into acetic acid in five
days.

It is now known that several species of micro-
organism may ferment alcohol into vinegar, but for
the most part they closely resemble each other and
may readily be distinguished from other organisms
that are frequently associated with them. The
vinegar-producing organisms multiply at an almost
incredible rate. So long as alcohol is present they
transform it to acetic acid, but when their preferred
food is exhausted they may attack the acetic acid
itself and transform it into carbon dioxide and
water. Vinegar exposed to the air often, therefore,
becomes weaker and its acid may in time entirely
disappear. Not only wine should be shielded from
air to keep it from turning sour, but vinegar should
be similarly protected to keep it from growing
weak. Pasteur found that if vinegar is heated, thus
killing its organic life, it may be kept clear and
pure for a long time.

Pasteur's studies introduced several improve-
ments in the methods of producing vinegar which
were the means of saving millions of francs to the
manufacturers. In a lecture before the Chamber
of Commerce at Orleans, which was largely attended
by vinegar makers, doctors, and students, he gave

DISEASES OF WINE AND VINEGAR 119

a general summary of his investigations. He told
his audience of the work of the minute organisms
that are responsible for fermentation, the condi-
tions necessary for their life, the real reasons for
the procedures followed in vinegar-making, the
sources of failure so frequently encountered in this
industry, and the means by which these failures
may be avoided. "Nothing," he said in concluding
his lecture, "is more agreeable to men devoted to
a scientific career, than to increase the number of
discoveries, but when the practical utility of their
observations is demonstrated by practical utility
their joy is complete." To Pasteur it was a great
satisfaction to grapple with a troublesome problem
and after mastering it, to set forth his discoveries
before his grateful hearers.

Pasteur's studies on vinegar afforded a natural
introduction to his investigations of the maladies
of wines. Wine-making has always been one of
the important industries of France, and French
wines enjoyed a reputation which caused them to
be sought after all over the world. But the wine
industry had come to suffer from several diseases
which occasioned much financial loss. Even the
best of wines sometimes went bad, and wine-
makers were quite in the dark as to the causes of

120 LOUIS PASTEUR

their misfortunes and the methods by which they
might be avoided. From England a business man
wrote to Pasteur, "In France people are astonished
that trade in French wines has not been more ex-
tensive in England since the commercial treaty.
The reason is quite simple. At first we received
these wines with eagerness. But we soon had the
sad experience that the business led to great losses
and to much embarrassment on account of the
maladies to which they are subject."

The Emperor Napoleon III, who had followed
Pasteur's career with interest and appreciation,
called upon him for aid in this emergency. Pasteur
entered upon this investigation with his accustomed
energy. The volume of Studies on Wine (Etudes
sur le Vin), which is the product of his labors, was
dedicated to his royal patron in the following
terms :

Sire, Your Majesty, concerned with reason over the
prejudice against the trade in French wines which has
caused the alterations to which they are subject has
deigned to invite me, now two years ago, to seek the
causes of the diseases of wines and the means of pre-
venting them. Since the day on which I was honored by
this important mission I have not ceased to devote my-
self entirely to this work.

DISEASES OF WINE AND VINEGAR 121

If time, the necessary and infallible judge of all the
productions of science, confirms, as I hope, the exactitude
of my work, I shall have received, Sire, the satisfaction,
the most enviable for a scientist, of having performed a
useful service to my country in responding to the desire
of the Emperor.

I am, Sire, with the most profound respect, the very
humble and faithful servant and subject of Your Majesty.

L. Pasteur.

French wines suffered from several different dis-
eases, more or less characteristic of wines of dif-
ferent kinds and localities. Sometimes they be-
come acid; again they may become turbid, gen-
erate gas, and acquire a flat taste. Such wines
were spoken of as turned (tourne). This change
was particularly apt to occur after the warm
months of summer. One malady which was very
troublesome was the development of bitterness
(l'amertume) which was prone to attack all red
wines and especially those of Burgundy. Again,
wines may become ropy, as occurred in the wines
of Champagne. Pasteur's first procedure was to
subject wines suffering from these several diseases
to a microscopic examination. He found that each
disease was accompanied by characteristic organ-
isms differing from those producing normal vinous

122 LOUIS PASTEUR

fermentation. The acid wines contained an abun-
dance of the Mycoderma aceti. In the "turned"
wines there were slender filaments resembling those
found in the fermentations that form lactic acid.
Bitter wines were found to contain larger filaments

A B

0® m j^

©0

■tf if

»V*«

E

\w

b^?/5"

Fig. ii. Organisms Found in Diseased Wine

A, Cells of normal vinous fermentation ; B, acid wine in early
stage of deterioration ; C, a later stage of the same mal-
ady; D, ropy wine (maladie de la graisse) ; E, bitter wine
(maladie de l'amertume).

which were sometimes branched. As the diseased
condition became more pronounced the character-
istic organisms became more abundant.

And the remedy? It was very simple. At first
Pasteur tried antiseptics but without much success.
Then he tried heat. After considerable experimen-
tation he found that heating wine to about 55 ° C.

DISEASES OF WINE AND VINEGAR 123

sufficed to kill all of these troublesome living fer-
ments. There was a natural prejudice against heat-
ing wines, but the treatment in no wise injured
their flavor nor interfered with the slow process of
ageing which Pasteur showed was due largely to
oxidation. Once the cause of the trouble was
known the remedy, as in so many other cases, was
much more readily thought of.

A Commission was formed to try out the results
of the new treatment. Five hundred liters of
wine, placed aboard an outgoing vessel at Brest,
were divided into two parts, one half being heated,
and the other half left in the usual manner. After
the return of the vessel from a ten months' cruise
the heated wine was found to be in excellent flavor,
while the non-heated wine was astringent and acid,
and in a fair way to be soon entirely spoiled.
Other trials turned out in much the same way, and
soon the practice of heating became very prevalent
and proved to be the means of enormous savings
to the wine industries of France. In 1867 a jury
of the Universal Exposition offered Pasteur a grand
prize for his services to the wine industry. These
successful efforts to check the diseases of wines
evoked the gratitude of the Emperor who expressed
surprise that Pasteur had not taken advantage of

124 LOUIS PASTEUR

his discoveries to enhance his own wealth. Pas-
teur replied that, "In France scientists would feel
that they lowered themselves by such a procedure."
Napoleon III, as well as the Empress, conceived
a personal liking for Pasteur and occasionally had
him at the palace. They enjoyed having him ex-
pound the mysteries of the world of minute life, and
sometimes the scientist would show them and their
guests some of his organisms under the microscope.
On one of these visits he required for one of his
demonstrations some live frogs which he carried
in a bag. Absent-mindedly he forgot the bag
when he went away, and during the night some of
the frogs made their escape and wandered about
freely through the palace, some of them invading
the bed chamber of the Empress. The Empress,
happening to get up in the night, set her foot upon
the cold and clammy back of one of these innocent
wanderers and experienced a fright which only a
person of feminine sensibilities can imagine. Not-
withstanding this experience, so unusual in the
royal circles, Pasteur continued to be in favor at
court.

CHAPTER VII

THE DISEASES OF SILK WORMS

While still at work on the diseases of wine Pas-
teur received from his old friend and teacher,
Dumas, an urgent appeal to investigate a peculiar
malady which was creating great havoc in the silk
industry of France. Dumas represented as Sen-
ator a region in the south of France, which was
particularly infested by this disease. Knowing in-
timately Pasteur's career and how successfully he
had grappled with the diseases of wines and vari-
ous other scientific problems, Dumas picked out
Pasteur as the one man who would be most likely
to bring relief to an important industry which was
threatened with ruin. Dumas wrote, "I attach the
greatest importance to seeing your attention fixed
on the question which interests my poor country;
the distress is beyond anything you may imagine."
Pasteur had his misgivings about interrupting the
work on which he was engaged and entering a field
with which he was unfamiliar. "Consider, I pray

you," he wrote to Dumas, "that I have never even

125

126 LOUIS PASTEUR

touched a silk worm. If I had a part of your
knowledge on the subject I should not hesitate; it
may perhaps lie within the sphere of my present
studies. The recollection of your many favors to
me would always leave me bitter regrets if I were
to refuse your pressing invitation. Do with me as
you like." To Pasteur's complaint that he was
entirely ignorant of the subject Dumas only replied,
"So much the better ! For ideas you will have only
those which will come to you as a result of your
own observations."

Pasteur with mingled feelings of self distrust and
hope soon left for Alais, a town in the thick of the
silk worm epidemic. He little suspected that he
had embarked upon one of the most arduous and
perplexing investigations of his career. The great
French naturalist Fabre, well-known for his fasci-
nating writings upon the habits of insects, gives an
amusing account of a visit which he received from
Pasteur upon his arrival in the silk worm district
in which Fabre happened to reside. Pasteur sought
some instruction from the celebrated entomologist
regarding the habits and life history of the silk
worm, and requested to see some of the cocoons.
"Nothing could be simpler," said Fabre who
stepped out and soon returned with a pocket full

THE DISEASES OF SILK WORMS 127

of cocoons. Pasteur took one and turned it around
and around in his fingers as he attentively exam-
ined the unfamiliar object. Shaking it before his
ear he exclaimed in surprise:

"It rattles; there is something inside of it!"

"Yes, certainly," said Fabre.

"But what is it?"

"The chrysalis."

"The chrysalis! What is that?"

"I might say it is a sort of mummy into which
the caterpillar transforms before becoming a moth."

"Is there one of these things in every cocoon?"

"Certainly. It is to protect the chrysalis that
the caterpillar spins."

"Ah!"

It is somewhat curious to find this celebrated
man of science ignorant of simple facts of natural
history which children usually learn in the gram-
mar school. If there are any advantages in
attacking a problem in entire ignorance of what
has been previously done upon it Pasteur certainly
possessed them. But he possessed what was in-
finitely more valuable than information and that is
a fertile and resourceful mind trained in the
methods of experimental investigation and endowed

128 LOUIS PASTEUR

with rare patience, determination, and energy. His
work on fermentation and spontaneous generation
with the many deceptive sources of error involved,
and his conquest of the diseases of wine had given
him a training in critical methods, in comparison
with which his ignorance of entomology was but a
trifling and easily remedied drawback. And yet in
this work Pasteur was destined to be deceived and
to labor on the basis of false hypotheses, but as he
put them to the test of crucial experiments, he
came finally out of darkness and confusion into
clearness and order.

The disease in question had been introduced
about twenty years previously and had been
gradually becoming more widespread. It attacked
the worms in all stages of their development, some
dying before the first molt, or shedding of the
skin; others succumbed in later stages. Commonly
growth was checked, and the worms, ordinarily vora-
cious, would eat little or nothing. One common,
but not universal symptom was the appearance of
black spots upon the skin which resembled grains
of black pepper; this caused the disease to be
called pebrine. Often the afflicted worms would
begin a cocoon but would weaken and die before
it was completed. Others would spin normally,

THE DISEASES OF SILK WORMS 129

but the disease would attack the chrysalis, which
might die in the cocoon or pass through its usual
metamorphosis and emerge as a diseased moth.
Silk worm moths mate soon after they emerge, and
then the female lays her eggs. It was found that
eggs from diseased moths produced diseased worms,
so that the malady was spoken of as hereditary.
It is, in fact, one of the very few diseases which
may be transmitted through the germ cells from
parent to offspring.

The disease had made such tremendous inroads
upon the silk industry that France was producing
but a small fraction of her previous yield of silk.
In 1853, France produced 52,000,000 pounds of
cocoons; but there were only 8,000,000 pounds, or
less than one-sixth as much, produced in 1865.
The distress in the silk-producing district was acute.
"The traveler," wrote Pasteur, "who fifteen years
ago had gone through the mountains of Cevennes,
and who retraced his course to-day, would be sur-
prised and shocked to see the changes of all kinds
which have occurred in so short a time in that coun-
try. Formerly he would see, on the slopes of the
hills, active and robust men breaking up rock in
order to construct solid walls for the support of the
fertile but laboriously prepared soil and raising ter-

130 LOUIS PASTEUR

races planted with mulberry trees even to the sum-
mit of the mountain. These men in spite of the
fatigue due to their rough work were then contented
and happy because plenty reigned in their domestic
firesides.

"To-day the mulberry plantations are entirely
abandoned; the tree of gold no longer enriches the
country, and the faces formerly happy are now
downcast and sad. Where abundance once reigned
there is now poverty and distress."

There were all sorts of theories as to the cause
of the disease. All sorts of treatment were tried
in vain. The unfortunate worms were dusted with
ashes and charcoal, treated with chlorine gas and
with fumes of nitric and sulphuric acid, sprinkled
with rum, sugar, and quinine, and doped with creo-
sote and copperas. Remedies of reputed efficacy
were sold to the luckless growers, only to be used
without the slightest success. There was nothing
but groping in darkness and the empirical trial of
remedies much after the style of old-fashioned
medical practice upon afflicted humanity.

Pasteur, in his characteristic fashion, went
straight after the cause of the disease. This must
first be discovered beyond all else. When the
cause is known, he thought, we shall at least know

THE DISEASES OF SILK WORMS 131

what we are dealing with, and we shall be in a
better position to grapple with it. In the search
for the cause for the disease previous investigators
had made some observations which gave Pasteur
a point of attack. Guerin-Meneville in 1849 nad
seen in blood of silk worms some small, oval cor-
puscles which subsequent observers discovered in
various parts of the body and even in the eggs. It
was found that these bodies increase in number as
the disease progresses, but there was much doubt
as to what relation they bear to the disease.

When Pasteur began his investigations he was
unaware of most of these previous findings, and he
rediscovered a number of things already known.
On the evening of his arrival at the scene of action
he had observed the oval bodies in the tissues of
diseased worms. He soon made himself familiar
with the occurrence of these minute bodies in all
stages of the life history of their host from the egg
to the mature moth. The question which naturally
occurred to Pasteur in the light of his previous in-
vestigations was, What relation do these small oval
bodies bear to the disease? The supposed para-
sites do not occur, at least in abundance, in healthy
worms; they increase in numbers as the disease
progresses, and worms dying of pebrine are often

132 LOUIS PASTEUR

swarming with them. Pasteur found that the dis-
ease was contagious, that healthy worms could be
infected by feeding upon leaves on which diseased
worms had been crawling. They could be given
the disease by a mere scratch from an infected
worm or by the prick of a needle smeared with
infectious material. Eggs containing the supposed
parasite were found to give rise to diseased larvae,
and on this fact, a method of egg selection was
practised in order to obtain healthy progeny. Ex-
amination of eggs, however, was soon replaced by
an examination of the couples that produced the
eggs. The procedure recommended by Pasteur in
1865 was as follows:

After the mating, the female, set apart will lay her
eggs; then one will open her, as well as the male, in order
to search therein for the corpuscles. If they are absent
from both male and female, he will number their laying
which shall be preserved as eggs absolutely pure, and
bred the following year with particular care. There will
be eggs diseased in various degrees according to the
greater or less abundance of corpuscles in the male and
female individuals which have furnished them.

Pasteur himself became a raiser of silk worms
in order to be able to furnish pure "seed," as the

THE DISEASES OF SILK WORMS 133

eggs were called, to the growers. The method he
recommended, however, sometimes failed, and Pas-
teur was led to conclude that diseased progeny
might arise from moths possessing no corpuscles.
Often worms sickened and died from what he con-
sidered pebrine, without having any corpuscles at
all. He was therefore led to regard the corpuscles
as a sort of product of the disease instead of its
cause, — a product, like certain other symptoms of
diseases, which might or might not appear accord-
ing to various circumstances which are little under-
stood. He believed that the disease preceded the
existence of the corpuscles, and that feeding worms
with corpuscular matter would sometimes give them
the disease without the appearance of corpuscles in
the infected worms. He was also unable to find
evidence that the corpuscles reproduced themselves
like the bacteria and the yeasts by either fission
or budding.

Thus far, in spite of some success, the disease
proved to be baffling. Duclaux, one of his co-
workers in the silk worm investigation, remarks,
"In 1867 Pasteur had distributed by small lots the
healthy eggs prepared in 1866, and the success, we
knew, had been general. Meanwhile, as the letters
came announcing the results of the cultures, we

134 LOUIS PASTEUR

found our master more and more disturbed. He
kept us so far from his thoughts that we did not
understand his inquietude until one day he ap-
peared, almost in tears, and settling himself dis-
couraged into a chair exclaimed, 'Nothing has been
accomplished. There are two diseases.'

This fact, which Pasteur had suspected for some
time, made it apparent that the investigations had
been proceeding on the basis of a wrong assump-
tion. It was necessary for Pasteur to retrace his
steps and to repeat many experiments in the light
of a new viewpoint. But notwithstanding the dis-
concerting effects of this discovery, the recognition
of the existence of a distinct malady hitherto con-
fused with pebrine had its reward in resolving
many contradictions and inconsistencies in Pas-
teur's previous results.

This disease now recognized as distinct for the
first time is commonly designated by the name of
"tnorts-flats" or "flacherie." Like pebrine it is a
peculiarly fatal disease, readily contagious, and
having its peculiar complex of symptoms. It is
primarily an intestinal infection accompanied by
the development of enormous numbers of its char-
acteristic bacteria in the alimentary canal.

Going back over previous work it became evident

THE DISEASES OF SILK WORMS 135

that cases of pebrine without the corpuscles were
not pebrine at all, but flacherie. The eggs without
corpuscles which were supposed to produce pebrine
were found to produce the other disease instead.
In all cases of true pebrine there were the charac-
teristic corpuscles, and in all cases of flacherie the
characteristic bacteria. The discovery of two dis-
eases where there was supposed to be only one re-
moved most of the objections that prevented Pas-
teur from concluding that the corpuscles were the
cause of the disease instead of its product. It was
clearly established that without the corpuscles no
pebrine could occur. The difficulty in regard to
the mode of multiplication of the corpuscles is now
resolved. As this parasite is now known to belong
to the Sporozoa, a group with which Pasteur had
little familiarity, it is not surprising that no evi-
dence of fission was discovered, as the members of
this group multiply by the formation of spores
within the body of the parent organism.

The discovery by which Pasteur was at first so
upset resulted in bringing order out of chaos, and
it also resulted in perfecting methods for checking
not only pebrine but flacherie as well. Diagnosis
of both diseases now became certain. It could now
be ascertained by examination of moths which ones

136 LOUIS PASTEUR

would be almost certain to produce eggs free from
both maladies. Pasteur produced and distributed
eggs which he could guarantee to be free from in-
fectious diseases, and which would give rise to
healthy worms provided they were protected from
new infection from the outside.

"Would you like to find," Pasteur asks, "whether
a lot of cocoons will give you healthy eggs? Take
a part of them and heat them so as to hasten by
four or five days the hatching of the moths, and
see if they are corpuscular. ... If the moths are
infected send the cocoons to the spinning mills.
. . . But would you have the brood sound up to
the very end and give healthy eggs? In this case
take absolutely sound eggs derived from entirely
healthy parents and hatch them in clean and iso-
lated places to which infection cannot spread. But
if, unfortunately, the disease should arise, I still
give you the means of making a selection, and of
separating infallibly the sound eggs from the dis-
eased ones.''

By following Pasteur's directions the growers
found that they could check the destructive disease
of pebrine and also flacherie. The silk industry
soon felt the benefit of the improved methods.
The Lyons Silks Commission had asked Pasteur

THE DISEASES OF SILK WORMS 137

for a sample lot of healthy eggs. Pasteur sent
them several lots concerning which he made the
following predictions:

i. One lot will produce healthy worms.

2. One lot will perish exclusively from pebrine.

3. One lot will perish exclusively from flacherie.

4. One lot will perish partly from pebrine and partly

from flacherie.

Pasteur desired that these predictions be recorded
in the minutes of the Commission and that the re-
sults be reported on. They turned out exactly as
he had predicted.

After six years of labor the silk worm diseases
were conquered and the silk industry of France
was brought back to prosperity. Pasteur's meth-
ods were applied in other countries into which the
diseases had extended (for they had become almost
world-wide in their distribution) and they met with
similar success. The work had been peculiarly
taxing and full of difficulties and discouragements,
but a dogged perseverance had brought it to a
triumphal ending. Pasteur succeeded where so
many others had failed, not only because of the
fertility and ingenuity of his mind, but because
he sought first, as he always did in attacking a

138 LOUIS PASTEUR

problem, the cause of the phenomenon with which
he was dealing. The results of his investigations
are collected in a work of two volumes entitled
"The Diseases of Silk Worms" (Les Maladies
des Vers de Soie), which he liked to have his stu-
dents read because of the examples of scientific
method which they contain. These volumes are of
permanent value not only for the information they
afford, but perhaps more as a record of an elabo-
rate experimental research which, despite many
false assumptions and errors of detail, led finally
to a clear understanding of an intricate subject.

During the years spent upon the diseases of silk
worms Pasteur was occupied intermittently with
several other matters. He wrote an account of the
scientific work of his friend Claude Bernard, and,
at the request of Dumas, an article on the great
chemist, Lavoisier. He also continued some of his
investigations on wines, to which I have previously
alluded, and he devoted considerable attention to
the administration of the Ecole Normale.

In 1865 he lost his father, and soon afterward
his youngest daughter, then two years old. The
following year an older daughter, Cecile, who was
twelve years of age was taken with typhoid fever
and died suddenly after a period of convalescence

THE DISEASES OF SILK WORMS 139

which promised recovery. Deeply afflicted by these
sorrows Pasteur sought consolation in work. The
intense and arduous life which he had been leading
brought on in 1868 a stroke of paralysis that seri-
ously threatened his life. Beginning with a strange
tingling on the left side followed by a chill, the
attack did not prevent Pasteur from reading a
paper before the Academy which he was especially
desirous of presenting. In the evening a more
severe attack followed which for a time deprived
him of speech. The best medical aid was sum-
moned, and for several days his family and friends
watched him with the greatest anxiety. Intermit-
tent states of paralysis alternated with intervals in
which his mind was clear. Despondently he said
to Deville, who was watching by his bedside, "I
am sorry to die; I wanted to render many more
services to my country." "Be assured," replied
Deville, "you are going to recover; you will make
still more marvelous discoveries; you will live
happy days. You will live longer than I, for I am
your senior. Promise me that you will pronounce
my funeral oration. ... I wish you would, be-
cause you would speak well of me." Pasteur did
not then know that he was to perform this sad
service.

140 LOUIS PASTEUR

It was a period of great solicitude for many
friends who were anxious to be of service to the
sufferer and his family. "All scientific Paris,"
wrote Pasteur's cousin, "comes with anxiety to in-
form itself concerning the condition of the patient;
intimate freinds take turns in waiting by him.
Dumas, the great chemist, insisted yesterday in the
most affectionate manner on fulfilling the same
duty. Every morning the Emperor and Empress
send a footman to obtain news."

Recovery was slow. A laboratory whose con-
struction had been authorized by the Emperor for
Pasteur's researches had been started, but work on
it was discontinued, apparently on account of the
probability that Pasteur might never be able to use
it. During his illness the patient would enquire
anxiously how the building was getting on, but he
was put off with various evasive answers. Pasteur
soon became aware of this and expressed himself
with some bitterness. The Emperor hearing of
Pasteur's disappointment wrote the following note
to the Minister of Public Instruction:

My dear Monsieur Duruy:

I have learned that, doubtless without your knowledge,
work was suspended on M. Pasteur's laboratory on the

THE DISEASES OF SILK WORMS 141

day when he became ill. This circumstance has strongly
affected him, because it seemed to point to his non-
recovery. I beg you to give orders that the work under-
taken shall be continued. Rest assured of my sincere
friendship.

Napoleon.

The work on the building was immediately re-
sumed, and later as Pasteur improved he could see
from his window the rising walls of his new labora-
tory.

It was several months before Pasteur was able
to return, even partially, to his work. But as soon
as his strength permitted he was back to Alais
superintending work on silk worms. He was soon
given an opportunity of testing out his methods of
silk worm culture on a large scale. The Prince
Imperial owned an estate, the Villa Vicentina, near
Trieste, upon which there were many mulberry
trees; but for several years, owing to the diseases
of silk worms, its yield of silk had greatly fallen
off. Pasteur was offered a lodgment at the Villa
with facilities for experimentation. He soon in-
stalled himself there with his family and began to
superintend the culture of silk worms raised from
healthy eggs which he had supplied. The result

142 LOUIS PASTEUR

was that the Villa yielded a net profit of 22,000
francs, the first time it had paid anything in ten
years. Pasteur remained at the Villa eight months
completing there the Studies on the Diseases of
Silk Worms which he dedicated to the Princess
Mathilde.

CHAPTER VIII

THE DARK DAYS OF THE WAR: STUDIES

ON BEER

When Pasteur returned to Paris the air was full
of rumors of an approaching war with Prussia.
Feelings of hostility on both sides had reached an
acute state, and many perceived that the coun-
tries were being carried inevitably toward conflict.
Many were confident of victory, but others, who
had followed the elaborate, well-planned prepara-
tions of Prussia for this event and who realized
the inadequate defenses of France and the demor-
alized condition of her army foresaw only unavoid-
able disaster. With the outbreak of hostilities most
of the students of the Ecole Normale, although
exempt from military service, volunteered as sol-
diers. Pasteur desired to join the National Guard,
but his half paralyzed condition caused him to be
rejected. The rapid successes of the Prussian
army greatly oppressed him. He desired to devote
himself to work that might be of value to his coun-
try, but as the deserted Ecole Normale had been

143

144 LOUIS PASTEUR

converted into a hospital he was deprived of his
usual facilities, and yielding to the entreaty of his
friends who reminded him that he would be only
an extra mouth to feed during the siege, he de-
parted with his family for his old home at
Arbois.

There he tried to interest himself in his favorite
books and to make plans for future investigations.
"His reading," says Radot, "afforded Pasteur a
means of consoling himself in his sadness and
anxiety, and he was wont to repeat one of his
favorite sayings 'Laboremus.' But at times in the
midst of hours passed with his wife and daughter
there would sound one of those peals of the trum-
pet with which the public crier of Arbois would
announce the receipt of news. The universal order
of things now no longer existed. Full of anguish
Pasteur concentrated himself upon that imper-
ceptible point in the Universe which is called
France. He descended the stairway and mingled
with the crowds which gathered on the little bridge
of the Cuisance. He listened anxiously to the
official communications and then sadly returned to
his room where certain souvenirs left by his father
emphasized by contrast the present situation of his
country."

THE DARK DAYS OF THE WAR 145

In the old home his eye fell at almost every turn
upon busts, pictures, or other souvenirs of the first
Napoleon, which his father had collected with de-
voted zeal. Not improbably, in common with many
of his countrymen, he wished that the little cor-
poral might be recalled to life and lead again the
now disorganized armies of France. "I wish,"
Pasteur wrote, "that France may fight to her last
man, to her last fortress." The brother-in-law with
whom Pasteur shared the old home continued the
trade of a tanner and Pasteur began some studies
on the fermentation of tan. As Radot states, "He
enquired continually seeking to learn the scientific
reason for each custom and routine procedure.
He excelled in devising projects for research from
the most common and apparently insignificant
facts. Everything about him became a subject for
study. When his sister made bread, he studied the
rising of the dough, the influence of the air in the
kneading of the dough, and his imagination pro-
ceeding always from a small point to problems of
great import sought to obtain a more nutritive
bread and consequently a bread of lower price."

The bombardment of Paris stirred him deeply.
Prussian shells had crashed into the Ecole Normale
and the Museum of Natural History. In 1868 the

146 LOUIS PASTEUR

University of Bonn conferred upon him the diploma
of Doctor of Medicine, in acknowledgement of his
work on the role of micro-organisms, but unwilling
to retain a parchment in which his own name ap-
peared along with that of the German Emperor he
returned the diploma with a caustic letter explain-
ing the reasons for his action. His bitterness was
probably all the more intense because of his in-
ability to take an active part in the defense of his
country.

Having had no news of his son, now a young man
of 1 8 serving in the Army of the East, Pasteur
went to seek him and was overjoyed at finding him
safe among the disorganized retreating soldiers.
He accompanied his son to Geneva and then went
to Lyons and soon afterward to Royat where he
stopped with his old collaborator Duclaux who was
now Professor of Chemistry in the Faculty of Clere-
mont-Ferrand. Shortly before this Pasteur had
written to Duclaux in the following terms: "My
head is full of the most beautiful projects for re-
search. The war has compelled my brain to lie
fallow. Now I am ready for new productive
labors; but alas, I may be laboring under an illu-
sion! In any case I shall try. Oh, why am I not
rich, a millionaire] I would say to you, to Raulin,

THE DARK DAYS OF THE WAR 147

to Gernez, to Van Tieghem, etc.. Come! we shall
transform the world by our discoveries. How for-
tunate you are to be young and full of vigor. Oh,
that I might begin a new life of study and work.
Poor France, dear country, what would I not do to
relieve your distress!"

Near by at Chamalieres there was a brewery
which Pasteur began to visit, interesting himself in
all the details of brewing beer and the reasons for
the various procedures followed in this industry.
Here he was brought into contact with the many
difficulties encountered in beer making. Germany
had hitherto excelled in the manufacture of beer,
and Pasteur conceived the idea of perfecting the
brewing industries of his own country so that
France would no longer pay tribute to her enemy
by importing German beers. Why should not
France produce as good beers as Germany! If
Pasteur could not perform military duty he could
at least aid his country in the field of industrial
rivalry. Beers, like wines, suffered from several
diseases. Some beers became sour, others ropy, and
others putrid. As in the case of wines, Pasteur
showed that these diseases were accompanied by
characteristic foreign micro-organisms. Through
the selection of pure yeasts, which could be tested

148 LOUIS PASTEUR

by microscopic examinations, the contamination of
beers by foreign micro-organisms could be largely
avoided. In this and in many other ways Pasteur
was able to control the process of beer making so
as to improve the flavor and keeping qualities of
the product, and his methods came to be widely
adopted in French breweries.

Wishing to extend his knowledge of beer making
he paid a visit in 1871 to the great breweries of
London. In one of the largest of these in which
he was being shown about he requested a sample
of the porter then being made and examined it with
a microscope. Finding in it a considerable amount
of foreign ferments which he pointed out to the
managers; he remarked that the product must be
considerably inferior to what was desired and
would probably bring complaint from some of its
purchasers. The managers, surprised at this criti-
cism, admitted that they had just decided to re-
place their yeast by a new supply. A visit to the
same brewery a week later showed that they had
installed a microscope and were beginning to test
with this instrument the purity of their supplies of
yeast. On his return to France he inspected many
breweries and initiated their managers into methods
by which they might improve their products and

THE DARK DAYS OF THE WAR 149

keep them from the intruding organisms that caused
them to deteriorate. He could usually predict by
a microscopic examination the particular defect
from which a beer was suffering. Pasteur inves-
tigated not only the diseases of beer, but many
phases of the process of brewing. He did not like
beer, but he had friends enough who were not un-
willing to pronounce upon his various samples.
"Give me a good bock," said his friend Bertin,
"and you can discourse learnedly afterward."

The results of his elaborate researches are
brought together in a volume entitled, Studies on
Beer, which was dedicated to his father. The
practice of heating bottled beer to kill its many
ferments dates from these investigations. The
French speak of "pasteurizing" beer and wine as
we speak of pasteurizing milk. French beers be-
came practically as good as the beers produced in
Germany and the Congress of French Brewers
meeting in 1889 gave to Pasteur the credit for the
great improvements which had been made in the
brewing industry. Nowadays brewers are as care-
ful of their strains of yeasts as an agriculturist is
of his breeds of cattle and sheep.

CHAPTER IX

ANTISEPTIC SURGERY, FOWL CHOLERA

AND ANTHRAX

We have now come to a turning point in Pasteur's
career. For several years Pasteur had pondered
over the possible relation of his researches to the
spread of human infections. He had often recalled
to mind the prophetic remark made over two hun-
dred years ago by the English chemist Robert
Boyle, that "He that thoroughly understands the
nature of ferments and fermentations shall prob-
ably be much better able than he that ignores them
to give a fair account of the diverse phenomena of
several diseases." Pasteur's work on spontaneous
generation, the diseases of wine and beer, and the
diseases of silk worms, naturally disposed him to
look with favor upon the idea, which had gradually
been growing more clearly defined in his mind, that
contagion might be caused by micro-organisms, and
in 1863 he remarked to Napoleon III, in the
course of an interview at the Tuileries, that it was

his great ambition to arrive at the cause of putrid

151

152 LOUIS PASTEUR

and infectious diseases. Would it be possible, he
thought, to check the diseases of human beings as
it was possible to check the maladies of wine, beer,
and silk worms?

Pasteur's imagination inspired him with concep-
tions of the wonderful possibilities of discovery in
the field of disease through the application of the
same methods which had proven so successful in his
previous work. With the loss of his own children
through disease fresh in his mind, and deeply im-
pressed with the fearful suffering of French troops,
not only from epidemics, but from gangrene, blood
poisoning, erysipelas, and the other scourges that
were the common accompaniment of wounds and
operations, Pasteur was stirred by the ambition to
do something which would obviate some of the suf-
ferings which disease and infections inflict on hu-
manity. Provided now with a new laboratory
exceptionally well equipped for carrying on bac-
teriological research he was eager to enter upon
this new field.

In Pasteur's time the cause of infectious diseases
was as little known as it was in the Dark Ages.
Pestilences and epidemics have always excited in
the human race a kind of superstitious awe.
Primitive peoples quite generally look upon disease

ANTISEPTIC SURGERY 153

as the result of possession by an evil spirit, and the
practice of the medicine man, who is frequently also
the priest, commonly consists in inducing the evil
spirits by supplications, bribes, or threats to leave
the body of the afflicted person. There has come
down to us from primitive times as a part of the
intellectual heritage of the race, a semi-supersti-
tious attitude in regard to the healing art that even
now betrays itself in a variety of ways. Epidemics
a half century ago were entirely mysterious. Medi-
cal men in general vaguely conceived of disease as
due to some subtle "morbid matter," which could
be spread by contact or through the air and which
had the power of multiplying itself in the body.
Many had from time to time speculated on the pos-
sibility that diseases might be caused by living
germs, but in the absence of any thorough-going
experimental tests the doctrine remained as a mere
plausible conjecture. Pasteur's work on fermenta-
tion and spontaneous generation brought the "germ
theory," as it was called, more prominently before
the public. The germ theory had been demon-
strated for the maladies of wines and beers and
later for those of silk worms and the analogy of
these phenomena to infectious diseases of man and
the higher animals could scarcely be overlooked.

154 LOUIS PASTEUR

There were other analogies. The disease popu-
larly known as the itch had been shown to be
caused by a minute mite which had the disagreeable
habit of burrowing into the skin and setting up a
peculiarly annoying type of irritation. This mal-
ady, which is highly contagious, was formerly much
more prevalent than is happily the case now. A
medical treatise written as late as 1833 stated that
the cause of the itch is entirely unknown and,
Hahnemann, the celebrated founder of homeopathy,
affirmed that three-fourths of human ills were
nothing more than the itch struck in ("gale
repercutee"). Here was a perfectly definite and
clearly demonstrated case of a contagious disease
caused by minute organisms which could be dug
out of the skin by a needle and observed to scram-
ble about in the field of the microscope. Another
"disease" caused by an animal parasite had been
made known through the discovery of the minute
worm, Trichina spiralis, which has the habit of
burrowing into muscular and other tissues and
lying coiled up in its so-called cysts. A disagree-
able disease of the scalp called favus, was shown
to be caused by a fungus growing in the skin. The
rapidly growing knowledge of the numerous para-
sites, large and small, that infest animals and

ANTISEPTIC SURGERY 155

plants created a certain presumption in favor of
the germ theory of disease, which is simply an ex-
tension of the notion of parasitism to more minute
forms of life. From the grosser parasites such as
lice and bed bugs, which are spread from person
to person, the smaller itch mites and worms respon-
sible for itch, trichinosis, and hook-worm disease,
down to the minute one-celled animals and plants
we have a graded series of attacking forms bent
upon the common aim of getting their living at the
expense of another organism.

Disease from the standpoint of the germ theory
is simply a result of the very common and wide-
spread biological phenomenon of predatory activity.
From this standpoint the mystery of contagion
vanishes. The period of incubation common to all
contagious diseases receives an almost obvious ex-
planation as due to the time required for the enter-
ing pathogenic organisms to multiply until they are
numerous enough to provoke disturbing symptoms.
And the course of a disease is a consequence of the
varying outcome of the struggle between the body
and its invading enemies.

In 1873 Pasteur became a candidate for mem-
bership in the Academy of Medicine and was
elected by a majority of one vote. He valued his

156 LOUIS PASTEUR

connection with this body chiefly as a means of
creating interest in the germ theory of disease and
he attended the meetings, dry as he doubtless found
many of them, with considerable regularity. Op-
portunities not infrequently presented themselves
for discussing the germ theory, as this doctrine was
scouted at by several of the foremost representa-
tives of the medical profession, many of whom be-
lieved in the doctrine of spontaneous generation
and thought that the bacteria sometimes observed
in diseased conditions of the body were created by
the body itself. As Pasteur was not a medical man,
being as was said, a "mere chemist," his incursions
into the field of medicine were regarded as not
entitled to much consideration. Little did his
medical colleagues then realize that they were deal-
ing with the man whose discoveries with regard to
disease were to be of greater value than those of
all the academies of medicine in the history of the
world.

The first successful applications of Pasteur's dis-
coveries were made in surgery. The transforma-
tion which surgical methods have undergone as a
result of these discoveries is, as Osier has remarked,
"one of the greatest boons ever conferred upon
humanity." The mortality from surgical opera-

ANTISEPTIC SURGERY 157

tions was appalling. It was the rule that wounds
became charged with pus, and it was fortunate if
they were not followed by gangrene and general
blood poisoning. Hospitals as places for operating
were simply hotbeds of infection, and many hospi-
tals had reputations that led them to be regarded as
mere portals to death. The leader in the effort to
eliminate infections from surgical operations was
Joseph Lister, Professor of Surgery in the Univer-
sity of Edinburgh. Lister, whose name is now so
frequently coupled with that of Pasteur, was a
medical man of unusually broad training and an
investigator of note in the science of physiology.
Primarily he was a man of science. He had fol-
lowed with great interest Pasteur's work on fer-
mentation, putrefaction and the problem of spon-
taneous generation, and he became convinced that
the mischievous agents of infection which give the
surgeon so much trouble are bacteria, which gain
access to wounds from the outside. If this were
true it should be a part of surgical technic to get
rid of these offending organisms. Accordingly
Lister thoroughly disinfected everything used in an
operation; the hands of the surgeon, instruments,
bandages and other apparatus were washed in a
solution of carbolic acid, and at first, a fine spray

158 LOUIS PASTEUR

was sent out around the seat of operation, in order
to kill possible germs that might be floating in the
air. The wound was frequently washed with the
same solution and the dressings employed were
changed with great care.

Although Lister was criticized by his colleagues
for the employment of these curious procedures,
the success of his operations as compared with
those carried on by the old methods spoke so elo-
quently and forcibly that they compelled convic-
tion. In 1874 Pasteur received the following letter
from this celebrated surgeon:

My dear Sir. Permit me to present to you a paper
sent herewith which gives an account of some investiga-
tions of a subject upon which you have shed so much
light. . . . Let me take this occasion to extend to you
my most cordial thanks for having shown to me, by your
brilliant researches, the truth of the germ theory of
putrefaction and for having thus furnished me with the
sole principle by which the antiseptic system could be
perfected.

If you should ever come to Edinburgh you would be
rewarded, I think, by seeing at our hospital how greatly
humanity has profited by your labors. I need hardly
add what a great satisfaction I should experience in show-
ing you here how much surgery owes to you.

ANTISEPTIC SURGERY 159

Excuse the freedom which is inspired by our common
love of science.

Believe me, I am, with profound respect,

Very sincerely yours,

Joseph Lister.

Lister's letter afforded Pasteur much gratifica-
tion. I do not know whether it was read before
the Academy of Medicine, but at any rate it should
have been. Other surgeons who were led to em-
ploy antiseptic methods were rewarded by an un-
usually high percentage of successful operations.
Pasteur pleaded for the employment of antisepsis
in surgery before the Academy of Medicine, and
the more open-minded members of this body came
to realize that there was much to be learned from
this non-medical member of their organization, for
he had much to tell them of micro-organisms, their
tenacity of life and means of spread. Antiseptic
surgery, the spontaneous generation of germs, and
the germ theory of disease provoked continued and
warm discussion. In the field in which he had car-
ried on investigations Pasteur had the advantage
of extensive and accurate knowledge based on most
carefully controlled experiments, and he took a
peculiar pleasure in defying his adversaries to

160 LOUIS PASTEUR

prove their case. He had much prejudice to over-
come, but he drew about him a following, espe-
cially among the younger men, who perceived the
great value of his discoveries and were anxious to
apply the newer knowledge to the healing art.

In 1874 the National Assembly rewarded Pas-
teur's services by an annual grant of 12,000
francs. Paul Bert, a prominent scientist who was
a member of the National Assembly (for the
French, unlike ourselves, sometimes honor scientific
men with political office), said, in presenting the
recommendation of the Commission, "Pasteur's dis-
coveries, gentlemen, after having thrown new light
on the obscure question of fermentation and the
mode of appearance of microscopic organisms, have
revolutionized certain branches of industry, of agri-
culture, and of pathology. One is struck with ad-
miration on witnessing so many important results
proceeding, by a chain of facts, followed step by
step, in which nothing is left to hypothesis, from
theoretical studies on the manner in which tartaric
acid turns the polarized ray. Never has the famous
saying, 'Genius consists in taking pains,' received
a more striking confirmation.

"It is this admirable collection of theoretical and
practical achievements which the Government pro-

ANTISEPTIC SURGERY 161

poses to honor by a national recompense. Your
Commission unanimously approves the proposal."
The bill was passed by a vote of 523 to 24.

This annuity was particularly acceptable to Pas-
teur, as he had been compelled on account of ill-
health to give up his academic positions. Although
his physician had strongly advised him not to un-
dertake serious work and notwithstanding the
counsel of his friends that he rest from his labors,
Pasteur, who thought that if he did not work he
might as well not live at all, was actively engaged
in his laboratory.

The disease anthrax or splenic fever was then
engaging the attention of the medical world. This
disease had been for many years a scourge of cattle
and sheep causing an annual loss of several million
francs. Occasionally it attacks human beings who
have come into contact with infected animals or
their products. As far back as 1850 Davaine and
Royer had seen small rod-shaped bodies in the
blood of animals dying of anthrax, but they were
quite unaware of the significance of their observa-
tion. Stimulated by Pasteur's studies Davaine re-
curred to the subject in 1863 and proclaimed these
"bacteria" as he had named them, to be the sole
cause of the disease. This conclusion was disputed

162 LOUIS PASTEUR

by a number of investigators who claimed that in
many cases of anthrax the bacteria could not be
found. Davaine replied by showing evidence that
the bacteria had been overlooked or that the disease
had been wrongly diagnosed as anthrax. Davaine
found that rabbits inoculated with the blood of ani-
mals suffering from anthrax would take the disease
and die. But if the blood had been passed through
a filter so as to remove its corpuscles and bacteria
it could be inoculated into rabbits with no ill-
effects.

But the disease presented many puzzling prob-
lems. Davaine adduced evidence that the bacteria
of anthrax disappeared from the blood of dead
animals after it began to putrefy, but he also ob-
served that dried blood retained its virulence for a
long time. It had long been known that fields over
which diseased animals had grazed might infect
healthy animals after a lapse of several years.
Much confusion and difference of opinion prevailed,
therefore, as to the mode of transmission of this
disease.

Much light was thrown upon the problem by the
labors of Robert Koch, a German investigator who
was then at the beginning of his famous career,
Koch had studied the germ of anthrax in its various

ANTISEPTIC SURGERY 16

o

phases of development and observed that in the
presence of oxygen, and at not too low a tempera-
ture, there appeared in the rod-like bacilli several
small round bodies or spores. These frequently
became liberated from their bacilli, and Koch
proved that they were very much more resistant
than the bacteria and were capable of producing
anthrax when inoculated into healthy mice. Koch
also succeeded in cultivating the bacilli of anthrax
in blood serum and aqueous humor by inoculating
one drop with a minute amount of material taken
from another drop* After making eight successive
transfers in this way, the bacteria multiplying in
the meantime, he found that the cultures would
convey the disease to new animals.

These experiments of Koch resolved some of the
difficulties that had troubled Davaine. The per-
sistence of anthrax germs; despite the fact that the
bacilli disappear soon after death, was shown to be
explicable through the vitality of the spores; and
the fact that the blood of animals dying of anthrax
is sometimes infectious and sometimes not, was
very readily accounted for as due to the circum-
stance that the spores appear or fail to appear
owing to varied conditions of temperature and the
supply of oxygen.

164 LOUIS PASTEUR

All of this work lent strength to the hypothesis
that it is the germ that is the cause of the disease.
But it was possible for objectors still to urge that
it is not germs that cause disease, but something
that goes along with germs, a sort of virus that
may not appear in the fluid part of the blood, but
which may nevertheless be a product of the body.
The culture experiments of Koch could be inter-
preted as simply diluting this something without
getting rid of it. It was this problem to which
Pasteur in his studies on anthrax first directed his
attack, and he attacked the problem in a thorough-
going way that left no reasonable doubt as to the
issue between the two rival theories. He began by
making culture experiments using sterile urine in
which the bacillus of anthrax grows very well, and
also various other culture media. He inoculated a
relatively large amount of culture fluid with a drop
of blood from an animal with anthrax. The char-
acteristic bacteria of the disease were soon swarm-
ing throughout the culture medium. Then a drop
of this culture was introduced into a fresh lot of
fluid, and when this was teeming with bacteria, a
drop from the latter was introduced into a third
lot. If the first dilution is i to 1,000, the second
would be i to 1,000,000 and the third 1 to

Fig. 12. Pasteur in His Laboratory

ANTISEPTIC SURGERY 165

1,000,000,000. After ten such transfers the
amount of material originally present would be
diluted so that it would be like a drop in the ocean,
but Pasteur kept on diluting and diluting until he
had made forty successive transfers. Any material
associated with the original germs would have been
diluted until not an atom of it could on the average
be left in the final flask of the culture medium.
Yet Pasteur showed that a drop of this culture
injected into a rabbit or guinea pig would cause
the animal to die with symptoms of anthrax.
"Anthrax, therefore," said Pasteur, "is the disease
of the bacteridium, as trichinosis is the disease of
the trichina, as itch is the disease of the itch mite,
with this difference, moreover, that in anthrax the
parasite, in order to be seen, must be observed with
a microscope of high power of magnification." The
evidence that anthrax is caused by the bacillus is
of the same kind and is just as conclusive as the
evidence that trichinosis is caused by the trichina
or itch by the itch mite.

Pasteur delighted in perfectly rigid, clean cut,
and demonstrative experiments, and in face of the
attacks on the germ theory, he took a peculiar
satisfaction in bringing forward arguments which
left his opponents no loop-hole by which they

166 LOUIS PASTEUR

might squirm through. Paul Bert, had claimed
that animals might be given anthrax if inoculated
with blood subjected to compressed oxygen which
could be seen to destroy the bacteria of this disease
as well as the septic vibrios which are sometimes
associated with it. It must be something beside
the bacilli, he argued, that caused the disease. The
explanation, as Pasteur showed, is that although
oxygen may destroy the bacteria it is not delete-
rious to the spores. Bert visited Pasteur's labora-
tory and became convinced of the correctness of
this interpretation and acknowledged his mistake,
acting, as Pasteur observed, "like a loyal French-
man."

Anthrax is a disease which attacks different
species of animals with different degrees of viru-
lence. Rabbits and guinea pigs are very suscepti-
ble; rats and dogs are relatively immune to it.
Fowls ordinarily do not take the disease. What is
the reason for the immunity of the fowl? It oc-
curred to Pasteur that since the temperature of
fowls is several degrees higher than that of mam-
mals, it might be that the temperature of the fowl's
blood is unfavorable to the development of the
anthrax bacillus. To test this supposition Pasteur
immersed a hen in a bath of cold water in order to

ANTISEPTIC SURGERY 167

lower its temperature. Then he inoculated it with
a culture of anthrax bacilli. The next day the hen
died. "All its blood," said Pasteur, "the spleen,
lungs, and liver, are rilled with the bacilli of an-
thrax susceptible of further cultures either in inert
liquids or in the bodies of animals. Up to the
present time we have not met with a single excep-
tion."

There had been considerable controversy in the
Academy of Medicine over the cause of anthrax,
and the question of the immunity of the fowl had
been under dispute. The Academicians were prob-
ably somewhat surprised to see Pasteur come into
one of the meetings with a cage containing four
hens which he placed on the desk. In his account
of his curious exhibit he stated that the dead hen
had been inoculated, after being chilled, with five
drops of a culture of anthrax three days before.
To obviate the objection that the cold bath and not
the germ had been the cause of death, another hen,
which was perfectly healthy, was exhibited, which
had been chilled but not inoculated. The third
hen, also in good spirits, had been inoculated with-
out having had its temperature reduced and was
enjoying the effect of its natural immunity. The
fourth hen was reserved for a further experiment.

168 LOUIS PASTEUR

It was inoculated, placed in a cold bath, and kept
there until symptoms of the disease became clearly
apparent. Would it recover if restored to its nor-
mal temperature? The hen was wrapped in cotton
wool and put into a warm container at 35 ° C. and
soon made a complete recovery. Here is a most
instructive experiment in proving that the natural
resistance of the body to infection may be broken
down by unfavorable conditions and allow an in-
vasion of bacteria which would normally be over-
come.

At this time anthrax was causing serious losses
among cattle and sheep in several districts of
France, and Pasteur was commissioned by the Min-
ister of Agriculture to make a study of so-called
spontaneous anthrax which broke out without ap-
parent cause. This feature of the disease made it
particularly difficult to cope with. When herds
were infected they were commonly taken to some
other locality, as it was held that it might be the
water, dampness, or dryness of the soil, or some
peculiarity of the pasturage that was responsible
for the outbreak. Pasteur visited one of the in-
fected regions in the vicinity of Chartres accom-
panied by M. Roux, one of his devoted collabo-
rators, who was destined to attain a prominent

ANTISEPTIC SURGERY 169

position in bacteriological research. Going over
one of the fields Pasteur noticed a part in which
the soil had a color somewhat different from the
rest. This part the owner explained was where the
sheep, which had died of anthrax, had been buried
the year before. Observing the little pellets of
earth which had been brought to the surface by
earthworms Pasteur thought that some of this earth
might contain spores of anthrax carried from near
the bodies of the buried animals. The pellets
therefore must be tested. Inoculated into guinea
pigs this earth produced anthrax. "One should
insist," says Pasteur, "that animals are never
buried in fields intended for growing hay or pas-
turing sheep. Whenever it is possible, one should
choose burying grounds on sandy or chalky soils,
infertile, readily dried, and unsuitable to the life
of earthworms."

Pasteur's crowning achievement in the battle with
anthrax had to wait upon a very remarkable dis-
covery which he made in connection with chicken
cholera. Poultry raisers, the world over, have long
had experience with this fatal malady. Fowls pre-
viously healthy may be stricken and die in only a
few days. The ruffed up feathers, drooping head,
and drowsy aspect of the fowls, as they sit quietly

170 LOUIS PASTEUR

or move about in a sluggish manner are the char-
acteristic symptoms of this malady which often
carries off ninety percent of the infected brood.
The few which recover seem to be immune to fu-
ture attacks. The disease is highly contagious and
may be conveyed by food contaminated with the
excreta of infected birds.

Very minute bodies described as "granulations"
had been observed by Moritz in the blood of
chickens suffering from cholera. Are they the
cause of the disease? Toussaint, who had brought
forth evidence of the causal role of these organisms
had made rather unsuccessful attempts to cultivate
them. Pasteur, after having tried a number of cul-
ture media which proved unsuitable, discovered that
in a sterilized broth made of chicken gristle the
organisms would multiply with almost incredible
rapidity. Successive cultures were made, the one
from the other. Fowl inoculated with these
speedily contracted the disease. Pasteur found
that chicken cholera, like anthrax, affects different
animals in different ways. Rabbits are quite sus-
ceptible, but guinea pigs are much less so; the in-
oculations producing only a local abscess, in which,
however, the germs multiply and from which they
may be recovered and inoculated again into fowl

ANTISEPTIC SURGERY 171

with fatal results. These animals, although be-
traying no obvious signs of the disease, may never-
theless transfer it to fowl, thus playing the part
of what we now would call "carriers" of the disease.
Pasteur's experiments had to be interrupted for
several weeks and when he recurred to his old cul-
tures which had been set aside and attempted to
carry them on by inoculating new media and fresh
fowl he found that growth in the new media was
very slow or absent, and that the inoculated fowl
were apparently unaffected. Being about to throw
the old cultures away and begin anew it occurred
to Pasteur to inoculate these fowl with a fresh,
virulent culture of the bacilli. To his surprise
nearly all of these fowl withstood the disease,
whereas new fowl recently purchased, which were
inoculated with the same fresh culture, succumbed
in the usual way. The idea immediately suggested
itself that the first lot of fowl had been rendered
immune by their previous inoculation with the old
cultures of the germ. We may well believe that
there was excitement in the Pasteur laboratory over
this striking and unexpected result! Further ex-
periments which were made served to confirm the
conclusion that by proper culture the chicken
cholera germ could be weakened so that when it was

172 LOUIS PASTEUR

inoculated into healthy fowl it would not only do
them little harm, but would protect them against
the disease in a virulent form. Pasteur had made
his great discovery — the attenuated virus.

The results naturally recalled the celebrated vac-
cination for smallpox discovered by Jenner, and
Pasteur believed that he had hit upon the explana-
tion of the success of that procedure which had
hitherto been a complete mystery. Visions of
great possibilities in the control of epidemic dis-
eases flashed before his mind, and he was filled
with enthusiasm over the prospects of further dis-
coveries in the fields which were now opened up.

That germs could be modified, that modified
germs were less deadly when injected into animals
and that animals so treated became protected
against attacks of virulent strains of the same kind
of germs was a discovery whose generality he was
eager to put to the test. Being occupied more or
less with anthrax while he was working with
chicken cholera, and being familiar with the
method of cultivating the germs of that disease,
the next object of attack was, as it were, marked
out for him. He set out to attenuate or weaken
the germs of anthrax.

The culture of the anthrax bacillus under con-

ANTISEPTIC SURGERY 173

ditions unfavorable for its life presented difficulties
owing to the formation of spores, but Pasteur
found, after considerable experimenting, that if it
were grown in neutral chicken bouillon at 42-43° C.
the spores would not develop. A month of this
regime usually suffices to kill the bacilli; they be-
come weaker and weaker apparently, and after ten
or twelve days they may be injected into rabbits,
guinea pigs, and sheep without producing fatal re-
sults. If the weakened bacteria were grown at
35° C, thus allowing them to form spores, the
bacteria subsequently emerging from these spores
were found to produce the same mild effects as the
bacteria from which they were derived. This is a
fortunate circumstance, as it enables one to pre-
serve the attenuated virus in a relatively permanent
form. Pasteur found, as in chicken cholera, that
the inoculation of animals with attenuated virus
would produce mild effects which would render the
animals immune to inoculation with the unmodified
bacilli of this disease. After making sure of the
success of his vaccine he announced his discovery
to the Academy of Sciences. "I could not be con-
soled," he remarked to his family, "if this dis-
covery which my collaborators and I have made
had not been a French discovery."

174 LOUIS PASTEUR

This discovery which was of so much promise
to the owners of cattle and sheep naturally excited
much comment. Some received it with enthusiasm
and others regarded it with distrust. The Society
of French Agriculturists offered Pasteur a medal of
honor, but as extensive experiments on the larger
animals had not been carried out, the general atti-
tude on the subject was one of suspended judg-
ment.

An opportunity of performing an experiment on
an extensive scale soon presented itself through the
instrumentality of M. Rossignol, one of the editors
of the Veterinary Press. Rossignol represented a
typical attitude on the germ theory of disease. A
short time previously he had written, "Micro-
biolatry is now the fashion, it reigns as a sovereign;
it is a doctrine which one must not discuss; one
must accept it without objections, especially when
its chief priest, the learned Pasteur, has pro-
nounced the sacramental words, 'I have spoken.'
The microbe alone is and shall be the characteristic
of a disease; this is understood and agreed to;
henceforth the theory of germs should take prece-
dence over pure clinics; the microbe only is eter-
nally true and Pasteur is its prophet."

Shortly after making this characteristically edi-

ANTISEPTIC SURGERY 175

torial pronouncement Rossignol began an active
campaign for funds for the purpose of purchasing
animals for his proposed experiment. Pasteur's
alleged discovery of a vaccine for anthrax should
not remain as a mere laboratory procedure. Would
Pasteur dare to subject his vaccine to a public test?
"The excitement which these experiments will nec-
essarily arouse/' said he, "will strike all minds and
end by convincing those who are still skeptical; the
evidence of facts will have the result of dispelling
all uncertainty." The Agricultural Society of
Melun endorsed the proposal, and its chairman was
delegated to wait upon Pasteur with the proposal,
or perhaps we should say the challenge, that he
carry on a public demonstration under the condi-
tions laid down. The conditions had been printed
and widely distributed by Rossignol.

Pasteur was game. He prepared his attenuated
virus and made the preliminary inoculations at the
farm Pouilly le Fort, near Melun, where the trial
was to be staged. A large crowd had assembled,
for the test had been widely advertised. Doctors,
farmers, and veterinarians turned out in numbers
and were speculating on the probable success or
failure of the experiment. Many were secretly
rejoicing over the prospect of a humiliating failure,

176 LOUIS PASTEUR

and Pasteur's friends and followers were filled with
anxiety over the outcome of the bold step which
their leader had taken. It was specified that
twenty-five sheep were to be inoculated with an-
thrax vaccine and afterwards inoculated with
anthrax. Twenty-five unvaccinated sheep were to
be inoculated with anthrax alone. Six cattle were
to be inoculated and four others kept as controls.
Two weeks after vaccination the sheep and cattle
vaccinated and unvaccinated alike were to be given
an injection of virulent germs of anthrax and three
days later the meeting was to be called to witness
the results. The preliminary inoculations were
carried out on May 5, 1881. "These experiments,"
wrote Rossignol, "are solemn ones and should be-
come memorable, if, as M. Pasteur affirms with so
much conviction, they confirm all that he has
already claimed. We express the ardent hope that
M. Pasteur will succeed and depart as victor from
a contest which has now lasted sufficiently long.
If he succeeds, he will have conferred upon his
country a great benefit, and his adversaries should,
like the ancient captives, wreathe their brows with
laurel, and prepare to follow, chained and bowed
down, the chariot of the immortal victor; but he
must succeed; that is the price of triumph. How-

ANTISEPTIC SURGERY 177

ever, M. Pasteur should not forget that the Tar-
pean rock is close to the Capitol."

On June 2nd the crowd again assembled to wit-
ness the results. As Radot remarks, "When Pas-
teur arrived at 2 o'clock in the afternoon at the
farmyard of Pouilly le Fort, accompanied by his
young collaborators, a murmur arose which soon
became a burst of applause ending in loud excla-
mations from all lips. Delegates from the Agri-
cultural Society of Melun, from medical societies
and veterinary societies, representatives from the
Central Council of Seine et Marne, journalists,
small farmers who had been influenced in diverse
ways by laudatory or injurious newspaper articles
and who were in doubt whether to accept or deny
a great discovery — all were there. The carcasses
of 22 unvaccinated sheep were lying side by side;
two others were dying; the last of the sacrificed
lot still living presented all the characteristic
signs of anthrax. All of the vaccinated sheep
were in perfect health. The cows which were un-
protected by vaccination were all showing severe
symptoms of splenic fever. In the vaccinated
cows there was not even an elevation of tempera-
ture and their appetite seemed unimpaired."

The conclusiveness of the experiment could not

178 LOUIS PASTEUR

be gainsaid. The skeptical Rossignol pronounced
it a "stunning success," and made a handsome
acknowledgment of his previous errors in regard
to microbiology. He assisted at the examination
of the blood of two of the dead sheep. This
showed an abundance of the bacilli of anthrax.
The last unvaccinated sheep died in the evening of
the day of the demonstration.

Further trials of Pasteur's protective vaccine
yielded additional evidence of its efficacy. There
was a wide demand for vaccine, and about 34,000
animals had been vaccinated by the end of 1881,
and about 500,000 by the end of 1883. The
method became widely used in stock raising coun-
tries throughout the world, and has resulted in
saving millions of dollars and the lives of many
thousands of animals.

CHAPTER X

THE DAWN OF A NEW ERA IN MEDICINE

The idea of conquering contagious diseases by
preventive inoculation filled Pasteur with an intense
ardor to apply to other maladies the methods
which he had found so successful in chicken
cholera and anthrax. What may not be hoped for
in the battle with contagious diseases in general?
It may even be possible some day, he thought, to
banish contagious diseases from the earth. The
secret of transmissible disease had now been re-
vealed. A method had been discovered by which
two of these diseases, the first two in which it had
been tried, could be checked. What wonderful
possibilities lay ahead!

News that yellow fever had been brought by a
vessel into Bordeaux caused Pasteur to hasten to
that city in the hope of finding the microbe of this
disease. To the warnings he received of the
danger of infection he only replied, "What does
it matter? Life in the midst of danger is the life,
the grand life, the life of sacrifice, of example, of

fruitfulness." The vessel had lost 18 persons,

179

180 LOUIS PASTEUR

but the patients who did not die had recovered
when Pasteur and his associates arrived. It is not
likely that Pasteur would have discovered the
germ of yellow fever, and he certainly ran no risk
in coming in contact with those afflicted by it. It
was many years later that the remarkable mode of
transmission of this malady was revealed; and the
mosquito convicted of being the agent of its trans-
mission,— a discovery which has led to the almost
complete, extermination of this widespread and
deadly scourge, and the saving of thousands of
human lives.

In the intervals of his work on anthrax Pasteur
interested himself in various human diseases. A
minor discovery was made in 1880 as to the cause
of boils. Duclaux, then one of Pasteur's collabo-
rators, was suffering from a series of these afflic-
tions. When Pasteur's attention was called to
them, he had one of the boils pricked open, for he
was averse to performing any kind of operation
himself, and he succeeded in making a culture
from its contents. In this and in other cultures,
a small, rounded organism, now known as a
staphylococcus, was discovered, which is at present
recognized as the common cause of these infec-
tions.

DAWN OF A NEW ERA IN MEDICINE 181

"Seek the microbe/' became Pasteur's motto.
Pasteur made many visits to hospitals with his
medical colleagues in order to familiarize himself
with the problems of the physician. Witnessing
an operation on a little girl for osteomyelitis he
gathered some pus from the inside of the bone and
found it to contain numerous rounded microbes
susceptible of culture like those of boils from which
they could not be distinguished. Somewhat boldly
he affirmed that the two infections were essentially
the same; it is only the place in which the germs
find lodgment and multiply that causes the dif-
ference between these very dissimilar afflictions.

Visiting patients and observing operations and
autopsies was very repulsive to Pasteur. Roux, who
was his frequent attendant in those days, remarks
that "His sensibility was extreme, and he suffered
morally and physically from the pains of others;
the cut of the bistoury which opened an abscess
made him wince as if he received it himself. The
sight of cadavers and the sad necessity of autop-
sies filled him with disgust. We have often seen
him come away ill from those operating rooms of
the hospital. But his love of science, his desire
for truth, were the stronger; he returned the next
day."

182 LOUIS PASTEUR

Puerperal fever, the great affliction of child-
bearing women, enlisted his particular interest.
For a long time it was not recognized that this
trouble was contagious, and it is one of the services
of Dr. O. W. Holmes, who is so well known as a
man of letters, and so little known as a physician
and professor of anatomy, that he brought forward
convincing evidence that puerperal fever is a trans-
missible disease and is frequently conveyed through
the hands and instruments of the physician. Cer-
tain lying-in hospitals had an unenviable record for
fatalities among child-bearing women. In 1856
The Paris Maternity Hospitals had in less than six
weeks 64 deaths out of 347 confinements. Epi-
demics of puerperal fever frequently swept through
maternity hospitals which were commonly the worst
possible places for bearing children.

Pasteur had discovered, in cases of puerperal
fever, characteristic rounded microbes appearing
commonly in chains like a string of beads, and he
affirmed them to be the cause of this disease.
"One day," says Roux, "in a discussion on puer-
peral fever at the Academy of Medicine one of
his most distinguished colleagues was eloquently
discoursing upon the causes of epidemics in lying-
in hospitals; Pasteur interrupted him from his

DAWN OF A NEW ERA IN MEDICINE 183

seat: 'What causes the epidemic is nothing of the
sort; it is the doctor and his staff that carry the
microbe from an infected woman to a healthy-
one.' And as the speaker replied that he feared
that one would never find the microbe, Pasteur
went to the blackboard and drew a picture of the
chain-like organism, saying, 'There, that is what
it is like!' His conviction was so strong that he
could not keep himself from expressing it for-
cibly. It would be difficult now to describe the
state of surprise and even stupefaction into which
he would throw the doctors and students when, at
the hospital, with a simplicity and assurance which
appeared disconcerting in a man who was entering
a lying-in ward for the first time, he criticized the
methods of dressing wounds and declared that all
the linen should be put into a sterilizing stove."
Through the adoption of strict antiseptic proce-
dures in assisting child-birth, puerperal fever has
now become a rarity, and a case of it would be
regarded as a disgrace in any well-regulated hos-
pital.

There were many controversies in the Academy
of Medicine. Several physicians and surgeons
were adopting Pasteur's ideas, but a considerable
number of conservatives regarded them with dis-

184 LOUIS PASTEUR

dain. At an open meeting attended by medical
students and the public Pasteur, apparently de-
spairing of many of his medical colleagues, thus
addressed the students: "Young men, you who sit
on those benches, and who are perhaps the hope
of the medical future of the country, do not come
here to seek the excitement of polemics, but come
and learn method." Never was wiser advice given.
Never in the history of medicine had there appeared
one so thoroughly qualified to give medical stu-
dents instruction in method; and never had the
value of scientific method been more clearly exem-
plified than in the work of this lay member of
the Academy.

Pasteur had a passionate love of science. He
had an equally strong love of humanity. But with
him it can hardly be said that science and humanity
were two separate objects of affection, for he saw
in science the means of performing the greatest
service to his fellow man. Serious, tremendously
in earnest, a man of deep feelings, and intensely
patriotic, he lived a life of severe labor with a
devotion to his work which was essentially reli-
gious. "Happy is he," he says, "who carries with
him his own ideal and lives in obedience to it."
To a rare degree he possessed that faculty which

DAWN OF A NEW ERA IN MEDICINE 185

his friend and admirer Tyndall has so well extolled,
— the scientific imagination; but it was an imagi-
nation held down to facts with a strong tether. As
Poincare remarks, "he had sudden inspirations
which bore him on toward unexpected discoveries;
he had instincts of divination which pushed him
forward along unexplored paths; he had swift,
headlong rushes of thought that overleaped and
anticipated the establishment of truth, prepared
the way for it, made its attainment more rapid, and
more sure. But when a scientific problem had
taken shape before him, in one of those general
flashes of illumination, he never considered it solved
until he had questioned all nature, until he had
classified or eliminated all the facts; until he had
forced them each and every one to give him an
answer."

Pasteur's remarkable series of discoveries brought
him many honors. In 1881 the Republic offered
him the Grand Cordon of the Legion of Honor.
Feeling that much of the credit for his recent
achievements was due to his able collaborators,
Roux and Chamberland, he imposed one condition
upon which he would receive this mark of distinc-
tion; it was that the Red Ribbon of the Legion of
Honor should go to his two collaborators; and he

186 LOUIS PASTEUR

wrote to his friend Paul Bert to "intervene most
warmly in their favor." The request was granted
and the news was conveyed to the laboratory.
"Hearty congratulations," wrote Madame Pasteur,
"were exchanged in the midst of rabbits and
guinea pigs."

In the same year Pasteur was asked to repre-
sent France at the International Medical Congress
in London. Upon his arrival at the well-filled
hall in which the Congress was held he was invited
to the platform, and as he passed along the aisle
there was a great outburst of applause. "It is
doubtless the Prince of Wales who is arriving,"
Pasteur remarked to his companions, "I should have
come sooner." "But it is you that they are all
cheering," exclaimed the President as Pasteur
reached the platform. The Prince of Wales and
the German Crown Prince entered later. In the
opening address of the President, Sir James Paget,
the mention of the name Pasteur brought such ap-
plause that Pasteur had to rise and bow to the
enthusiastic audience. "I was very proud," he
wrote to Madame Pasteur, "not for myself, — you
know how I regard success, — but for my country,
in reflecting that I was exceptionally distinguished
in the midst of that immense concourse of for-

DAWN OF A NEW ERA IN MEDICINE 187

eigners, especially Germans, who were there in
considerable numbers, much greater than those of
the French, of which the total did not reach 250.
Jean-Baptist and Rene were in the hall. You can
judge of their emotion.

"After the meeting, lunch with Sir James Paget,
with the Prince of Prussia on his right, the Prince
of Wales on his left. Afterwards, an assemblage
of twenty-five or thirty guests in the salon. Sir
James presented me to the Prince of Wales, to
whom I bowed saying that I was happy to greet
a friend of France. 'Yes,' he replied, 'a great
friend.' Sir James Paget had the good taste not
to ask me to be presented to the Prince of Prussia;
although there was no place under such circum-
stances for anything but courtesy, I could not
bring myself to appear to have requested such an
introduction. But who should approach but the
Prince himself, saying, 'M. Pasteur, permit me to
present myself to you and to say that I have just
been applauding you'; the rest of his conversation
was very cordial."

Invited to give a lecture before the general meet-
ing of the Congress, Pasteur described his experi-
ments with attenuated virus and paid a tribute to
the English physician, Doctor Jenner, the great

188 LOUIS PASTEUR

precursor of his own discoveries. Doctor Daren-
berg, the correspondent of the Journal des Debats,
wrote that, "Pasteur was the greatest success of
the Congress," proud that it was the representative
of France that received such hearty applause.

On his return to Paris several of the friends of
Pasteur belonging to the Academie Franchise en-
deavored to induce him to become a candidate for
the vacancy in that body created by the death of
the great scholar, Littre. It was the custom for
candidates to call on members and solicit their sup-
port. Alexandre Dumas, the dramatist, refused to
allow Pasteur to call on him, declaring, "It is I,
who will go and thank him for consenting to be-
come one of us"; and M. Grandeau wrote that,
"When Claud Bernard and Pasteur consent to
enter the ranks of a Society, all the honor is for
the latter." Pasteur, who had declared, "I have
never in my life contemplated the great honor of
entering the Academie Frangaise," was duly elected
and began his preparation for the formal ceremony
that marked the initiation of new members. Radot
in his life of Pasteur has given us a most inter-
esting description of the ceremonies of this occa-
sion and I may refer to his book for fuller details.
Ernst Renan, to whose lot it fell, as President of

DAWN OF A NEW ERA IN MEDICINE 189

the Academy, to welcome the new member, spoke
with his usual charm of style. After modestly dis-
claiming any competence of the Academicians to
pass judgment on Pasteur's scientific labors, he con-
tinued in the following words: "But apart from
the basis of the doctrine, which is not within our
province, there is a mastery, Sir, in which our
experience of the human spirit gives us a right to
express an opinion. There is something which we
can recognize in the most diverse applications,
something which belongs in the same degree to
Galileo, to Pascal, to Michael Angelo, to Moliere,
something which gives sublimity to the poet, pro-
fundity to the philosopher, fascination to the orator,
divination to the scientist. This common basis of
all beautiful and true work, this divine flame, this
indefinable spirit, which inspires science, literature,
and art, we have found it in you, Sir, — it is genius.
No one has traversed with so sure a step the regions
of elemental nature; your scientific life is like a
luminous track across the great night of the infi-
nitely small, in the last abysses of being in which
life is born."

Shortly after his reception at the Academy, the
town of Aubenas, in the midst of the silk produc-
ing region, honored Pasteur by the formal presen-

190 LOUIS PASTEUR

tation of a medal. "His arrival," according to
Radot, "was a triumphal affair; there were deco-
rations at the station, music, triumphal arches of
flowers and shrubs in the streets, speeches from the
Mayor, presentation of the Municipal Council, of
the Chamber and Tribunal of Commerce. All the
village was en fete. The music of the band was
almost drowned by the acclamations of the peo-
ple." "For us all," the President of the Aubenas
Silk Syndicate said, "you have been the kindly
genius whose magical intervention conjured away
the curse which was ruining us; in you we salute
our benefactor."

Before he could return to Paris the Agricultural
Society of the Gard gave a banquet in his honor
at Nimes and presented him with a medal for his
services to agriculture. A demonstration of the
efficacy of the anthrax inoculation was planned
(for there were still many doubting Thomases)
and the next day the experiments were carried out.
The plan of the experiments was practically the
same as those conducted at Melun and the results
were equally decisive and convincing. The Agri-
cultural Society of Herault, before whom Pasteur
gave a lecture, desired him to turn his attention to
a disease prevalent in the region termed "the rot."

DAWN OF A NEW ERA IN MEDICINE 191

The remark of the Vice-President, "He will surely
find the remedy for it," illustrates the confidence
which the people had come to place in his ability
to grapple with problems of disease. After return-
ing to Nimes to witness the final results of his
experiments on anthrax inoculation, he took the
train for Paris with the remark, "Now let us go
back to work."

Further recognition of his services had been
planned by the Academy of Sciences which had
enlisted the cooperation of the Scientific Societies
of France, in presenting him with a medal engraved
by the artist Alphee Dubois. On Sunday, June
25, 1882, a delegation called upon Pasteur who was
living with his family at his home in the Ecole
Normale. Heading the delegation was Pasteur's
old teacher, Dumas, who in presenting the medal
spoke in the following words: "My dear Pasteur,
it is forty years ago when you entered as a student
into this building. From your first appearance
your masters have foreseen that you would be an
honor to them, but none of them dared to predict
the brilliant services that you were destined to
render to science, your country, and the world."
And after speaking briefly of Pasteur's discoveries,
Dumas continued: "My dear Pasteur, your life has

192 LOUIS PASTEUR

known only success. The scientific method of
which you make so sure a use, owes to you its most
beautiful triumphs. The Ecole Normale is proud
to count you among the number of its pupils; the
Academy of Sciences is proud of your work; France
ranks you among its glories. At this time when
marks of public recognition are coming to you
from all parts, the homage which we come to offer,
in the name of your admirers and of your friends,
may seem to you worthy of a particular attention.
It emanates from a spontaneous and universal sen-
timent and it preserves for posterity the faithful
image of your features.

"May you, my dear Pasteur, long enjoy your
glory and contemplate the ever more abundant and
rich fruits of your labors. Science, agriculture,
industry, humanity will retain for you an eternal
gratitude, and your name will live in their annals
among the most illustrious and the most beloved."

Pasteur, listening with bowed head to these words
of his revered master and struggling to control his
deep emotion, replied, "My dear Master, it is in-
deed forty years since I had the good fortune to
know you and since you have taught me to love
science. I came from the country. After each of
your lessons I came away from the Sorbonne trans-

DAWN OF A NEW ERA IN MEDICINE 193

ported and often moved to tears. From that time
your talent as professor, your immortal works, your
noble character, have inspired me with an admira-
tion which has only grown with the maturity of my
mind. You have been able to divine my senti-
ments, my dear master. There is not a single im-
portant circumstance of my life or of that of my
family, happy or painful, which you have not in
some way blessed with your presence. To-day
again you take the first place in the expression of
the testimony, which I consider very excessive, of
the esteem of my masters, who have become my
friends.

"And what you have done for me, you have done
for all your pupils. It is one of the distinctive
traits of your nature. Beyond the individuals you
have always considered France and her greatness.

"What shall I do henceforth? Until the present
great praise inflamed my ardor and inspired me
with the idea of making myself worthy by new
efforts; but that which you have come to address
to me in the name of the Academy and the Scien-
tific Societies is in truth beyond my courage."
Pasteur had received the honor which he had
valued most, — praise from his scientific colleagues
and especially from his esteemed teacher.

194 LOUIS PASTEUR

In 1883 recognition of a substantial character
came in the form of an additional stipend from the
Government, an annual grant of 25,000 francs.
Both Senate and Assembly passed the bill by an
unanimous vote. Paul Bert, who was again instru-
mental in Pasteur's behalf, quoted in his report the
remark of Professor Huxley before the Royal So-
ciety of London, "Pasteur's discoveries alone would
suffice to cover the five millards paid by France
to Germany in 1870." We now recognize that
this was a very modest estimate.

Of the honors which were being showered on
him at this time, the one which perhaps touched
Pasteur most was the celebration at Dole, in which
a memorial plate was placed upon the house in
which he was born. In behalf of the Municipal
Council, the Mayor read the following words:
"M. Pasteur is a benefactor of humanity, one of
the great men of France; he will remain for all
the inhabitants of Dole, and especially those who,
like him, have come from the ranks of the people,
an object of respect as well as an example to fol-
low. We believe that it is our duty to perpetuate
his name in our village." There was a represen-
tative of the Government present, Mr. Kaempfen,
Director of Fine Arts, who said: "In the name of

DAWN OF A NEW ERA IN MEDICINE 195

the Government of the Republic I salute this in-
scription which recalls the fact that in this little
house on this little street there was born on De-
cember 27, 1822, one who was to become one of
the foremost scientists of this century, which is so
great in science, and who has by his admirable
labors added to the glory of his country and de-
serves well of all humanity." Proud little town
of Dole!

Amid all the praises which Pasteur received
from his grateful countrymen, there were several
attacks which lent at least variety to his eventful
life. Koch had attacked Pasteur's culture experi-
ments, claiming that pure cultures were not in most
cases made. He also minimized the value of Pas-
teur's work on anthrax and claimed that the inocu-
lation experiments with dirt brought up by earth-
worms were of no scientific value. In regard to
the purity of Pasteur's cultures Koch was probably
right. The method of cultivating bacteria on solid
media which was first introduced by Koch has been
of great service to bacteriology, because it makes
it possible to isolate particular strains of bacteria
from an originally mixed culture. At the medical
congress held at Geneva, in which Pasteur defended
his position, Koch failed to reply to the challenge

196 LOUIS PASTEUR

of Pasteur, stating that he would submit his reply-
later in writing. When the reply appeared Koch
did not deny the principle of attenuation but spoke
of it as a most important discovery. Nevertheless
he expressed doubt of the practical benefits of vac-
cination for anthrax. In response, Pasteur sub-
mitted, among other evidences, data supplied by
the veterinary surgeon, Bontet, in regard to 79,392
vaccinated sheep, with a mortality of less than one
percent, whereas in the same district in the last
ten years the mortality had been more than nine
percent. Equally favorable results were reported
also for cattle. Time and fuller experience, how-
ever, have now settled all controversy over the
efficacy of inoculation for anthrax.

Being pressed by some veterinarians to study the
disease known as swine plague or rouget, Pasteur
began by seeking to cultivate the microbe of this
disease. Thuillier, in 1882, had discovered numer-
ous very small bacteria in swine afflicted with
rouget, and Pasteur, who succeeded in cultivating
the germs in a suitable medium, found that these
cultures inoculated into healthy swine would set up
the disease. The next step was to develop an at-
tenuated virus. In experimenting on the behavior
of the disease in several small animals it was found

DAWN OF A NEW ERA IN MEDICINE 197

that when inoculated into pigeons it becomes in-
creased in virulence as it becomes transferred from
pigeon to pigeon, killing the birds more and more
quickly the longer the inoculations are continued.
Introduced from pigeons to the pig the germs be-
came more frequently fatal to these animals, thus
proving that they had become more virulent while
in the bodies of the birds.

On the other hand, it was found that in succes-
sive inoculations into rabbits the severity of the
disease becomes reduced. When the germs that
have been passed through a series of rabbits are
introduced into the pig they produce only a mild
attack of the disease, and after recovery the ani-
mals are immune to future attacks. The treatment
founded on these experiments has proven success-
ful in checking swine plague, which is a very
destructive malady. Unfortunately swine plague
was at first confused with hog cholera, a deadly
disease, now known to be caused by a filterable
virus and which has been greatly reduced by the
administration of a protective serum. The fact
demonstrated by these and other experiments that
virulence is not a fixed property of micro-organ-
isms, but something which may be increased or
decreased, and to a certain extent manipulated at

198 LOUIS PASTEUR

will in the laboratory, has proven of capital im-
portance in later work on disease. Like so many
of Pasteur's discoveries its value is attested by the
great benefits that were to flow from it in the
future.

In the Academy of Medicine the reactionaries
still kept up the battle over the germ theory of
disease. A Dr. Peter was particularly active and
persistent in his attacks. "The excuse of M. Pas-
teur," he exclaimed, "is that he is a chemist, who,
inspired by the desire of being useful, has tried
to reform medicine, to which he is a complete
stranger," and he prophesied a victory to the "old
medicine" over the new-fangled notions which were
misleading so many of his colleagues. This "old
medicine" had made little progress since it incurred
the delightful and well deserved ridicule of Moliere.
Pasteur, who, wearied by its sterile squabbles, had
not been present for some months at the Academy
of Medicine, returned and defended his position,
but he might have made a better use of his time.

From some professors of the Veterinary School
at Turin there had come the report of a complete
failure of an inoculation against anthrax. All the
sheep vaccinated and unvaccinated alike died after
being inoculated with the blood of a sheep which

DAWN OF A NEW ERA IN MEDICINE 199

had died of this disease. Pasteur wrote immedi-
ately to the Director asking how long the sheep
had been dead before its blood was used for inocu-
lation. Upon learning that the animal died the
day before, Pasteur affirmed that the inoculated
animals probably died of septicemia instead of
anthrax. This led to a controversy more or less
drawn out and finally to a challenge from Pasteur
who offered to go to Turin and demonstrate publicly
that blood in sheep dying from anthrax would after
twenty-four hours give rise to septicemia in healthy
and in vaccinated sheep. Pasteur's challenge was
not accepted. The professors at Turin contented
themselves with continuing their arguments and in
publishing a pamphlet entitled On the Scientific
Dogmatism of the Illustrious Professor Pasteur.

In a field requiring a refined and perfected tech-
nique and in which there lurk unexpected sources
of error it is easy for experimenters who are not
particularly well trained for their work to get dis-
cordant results. Pasteur, if he failed to convince
his opponents, pointed out many errors of proce-
dure which vitiated their conclusions. His strong-
est ally, however, was the growing evidence that
his methods were yielding tangible results. He
had the satisfaction of observing a remarkable de-

200 LOUIS PASTEUR

cline in the mortality from surgical operations to
about one-tenth the rate which obtained before the
application of antiseptic methods. Lying-in hos-
pitals that witnessed the death of more than ten
percent of their child-bearing women showed a
death rate of less than one percent. Erysipelas
and gangrene had been almost abolished from hos-
pitals in which they formerly ran riot. France
became relatively free from certain diseases of
animals, against which a battle had long been
waged in vain. All these facts spoke more elo-
quently than any words of controversy concerning
the great value of Pasteur's labors and the work
which he inspired.

CHAPTER XI

THE CONQUEST OF HYDROPHOBIA

The annals of hydrophobia form a curious chapter
in medical history. This disease was recognized
in animals by the ancient Greeks and its transmis-
sion from one animal to another through bites was
commented on by Aristotle, although he was ap-
parently unacquainted with hydrophobia in man.
Its uniformly fatal termination after its symptoms
became manifest and the frequently horrible suffer-
ings that attend its last stages made the disease an
object of unusual dread. Remedies for it, like
most remedies for most diseases, were entirely use-
less. Pliny, in an unconscious approach to the
guiding principle of homeopathy, recommended as
a cure the liver of a mad dog; and Galen pre-
scribed a preparation made from the eyes of cray-
fishes. For a time, sea bathing enjoyed a reputa-
tion for its curative influence, and various other
remedies were employed in the vain hope of allevi-
ating the sufferings of the patient. As a boy in
Illinois I not infrequently heard stories of people

201

202 LOUIS PASTEUR

cured of hydrophobia by the application of a so-
called mad stone which was believed to have the
curious property of clinging to the wound to which
it was applied, drawing the poison from the system
and dropping off after it had done its work. I
have never seen any one who had actually seen a
mad stone, but many people had heard of some
one else who knew of some one who had known it
to effect a cure. People commonly thought that
hydrophobia was caused by hot weather, and,
despite the fact that this supposition has been
definitely disproved, it still prevails more or less
in the popular mind. For a long time it was
thought that the disease could be communicated by
touch or through the breath, and in the fear that
its unfortunate victims might be sources of con-
tagion to others they were sometimes smothered
between mattresses or otherwise disposed of. A
person suffering from hydrophobia was smothered
as late as 1819.

The term hydrophobia owes it origin to the dread
of water which is a not uncommon symptom of this
disease in man. This dread of water apparently
is not shown by rabid dogs or other animals, and
consequently the term rabies has now come to be
employed as not carrying the misleading implica-

THE CONQUEST OF HYDROPHOBIA 203

tion of the older designation. It is, however, of
little importance which term is used so long as it
is well known what is meant, and despite possible
protests I shall use whichever word seems the
more suitable and euphonious.

Pasteur had long pondered over this mysterious
disease. M. Bourrel, a veterinarian, who had
sought for a means of preventing the spread of
hydrophobia in dogs and who had found nothing
more effective than filing down their teeth, sent two
rabid animals to Pasteur in the hope that this in-
vestigator might succeed where his own efforts had
failed. One of the dogs was half paralyzed, his
jaw hanging down and his tongue covered with
foam. The other was in the furious state more
typical of the disease, biting ferociously at every-
thing within reach, and giving utterance to the
most doleful howls. From these and other rabid
animals subsequently obtained, Pasteur took some
of the saliva and inoculated it into rabbits. He
did the same with saliva drawn from a human sub-
ject, a little girl of 5 years of age who had just been
admitted to a hospital. She was suffering from
spasms, thirst with inability to swallow, and fits of
furious mania; after twenty-four hours of agony
she died. Saliva from the little girl and also that

204 LOUIS PASTEUR

from rabid dogs was found to cause the death of
rabbits in about two days. A micro-organism was
observed in the blood of these rabbits, and it was
found that it could be cultured in veal broth and
that the cultures, when injected into other rabbits,
would cause their death. Pasteur was too cautious
to jump to the conclusion that he had found the
germ of hydrophobia. The incubation period, or
period between the first inoculation and the devel-
opment of symptoms of hydrophobia, is a relatively
long one, varying from about two weeks to, in some
cases, several months. It was more probable,
therefore, that the rabbits died from the effects of
some organism associated with the saliva of rabid
animals instead of the germ of hydrophobia, a sup-
position which was confirmed by inoculating rab-
bits with saliva from human beings with other dis-
eases and also with saliva from healthy persons.
This commonly proved fatal to rabbits. Saliva,
even in a healthy person, contains a multitude of
different kinds of bacteria as may readily be seen
by examining a drop of it under a microscope.
Some of these while harmless in our own mouths
are deadly when they gain access to the blood of
rabbits or guinea pigs. Consequently efforts to
induce rabies by the inoculation of saliva from

THE CONQUEST OF HYDROPHOBIA 205

rabid animals was a very uncertain procedure.
Experiments with the blood and tissues of rabid
dogs were equally unsatisfactory, as were Pasteur's
efforts to obtain a culture of the supposed microbe
of hydrophobia in the usual artificial media.

Not daunted by these failures, Pasteur simply
said, "We must try other experiments." On ac-
count of its characteristic symptoms it occurred to
Pasteur that hydrophobia might have its principal
seat in the nervous system. Accordingly some of
the matter of the brain of dogs that had died of
rabies was removed and injected, with precautions
to exclude all outside contamination, under the skin
of rabbits. In most cases the inoculated animal
died of hydrophobia. "The seat of the rabid
virus," Pasteur concluded, "is therefore not in the
saliva only; the brain contains it, and it is found
there in a degree of virulence at least equal to what
it has in the saliva of rabid animals."

The next step was to inoculate the nervous
matter from rabid animals directly into the brain.
A dog was placed under chloroform, a circular disc
was sawed out of his skull, and a small amount of
nervous substance from a rabid animal was intro-
duced directly into the dog's brain. The wound
was dressed and soon healed. After coming from

206 LOUIS PASTEUR

under the anesthetic, the dog behaved in a per-
fectly normal manner, but in about two weeks it
developed unmistakable symptoms of hydrophobia
and died. By similar experiments on dogs and
rabbits Pasteur showed that hydrophobia could be
produced, in practically every case, by the direct
inoculation of the virus into the nervous system.
Not only is the transfer of the disease by this
method practically certain, but its period of incu-
bation is shorter than when it is introduced by
means of saliva. Moreover, Pasteur found that in
rabbits the incubation period became shorter and
shorter with successive inoculations from brain to
brain. The virus had apparently been increased in
virulence as it is sometimes known to do in other
diseases. After a time, however, when the incuba-
tion period was shortened to a little less than seven
days, it could be reduced no more. The virus had
reached its maximum potency; it had become, as
it is now called, a fixed virus. Here, at last, the
disease, instead of being of uncertain transfer and
indefinite incubation period, was made a thing
which could be definitely controlled, and whose
time of appearance in an inoculated rabbit could
be accurately predicted.

Efforts to cultivate the virus obtained from nerv-

THE CONQUEST OF HYDROPHOBIA 207

ous tissue proved fruitless. How then could one
apply the principle of attenuation in this disease
and obtain a vaccine as in chicken cholera and
anthrax? Pasteur attacked the problem by at-
tempting to weaken the virus in its favorite seat,
the nervous system. The spinal cord of a rabbit
with hydrophobia was removed and suspended in
a sterile tube. Into this the air was admitted
through a plug of cotton wool, and was kept dry
by a piece of caustic potash in the bottom of the
tube which absorbed the moisture. After fourteen
days an emulsion of the cord injected into a dog's
brain showed that the material had lost its power
of producing rabies. Then an injection from a
cord dried for thirteen days was tried, followed by
an injection from a cord dried only twelve days,
and so on until finally material was used from a
rabbit that had died on the same day. Several
dogs that had been put through this treatment were
allowed to be bitten by rabid animals. The brains
of other protected dogs were inoculated directly.
All of the protected animals failed to develop
hydrophobia.

The success of these experiments was very en-
couraging. Realizing that his conclusions would
probably be attacked, Pasteur desired that his dis-

208 LOUIS PASTEUR

covery be verified by a Commission. Accordingly
one was appointed consisting of several of the fore-
most medical authorities in France and the Di-
rector of Agriculture. The Commission performed
many experiments according to the method of Pas-
teur, subjecting dozens of treated and untreated
dogs to the bites of rabid animals and to intra-
cranial inoculation, and finding that the treated
ones failed to develop hydrophobia, while those
that had not been previously protected generally
developed characteristic symptoms of the disease.
A report was drawn up substantiating Pasteur's
claims and recommending that further provisions
be made for more extensive experiments.

Soon after the Commission reported favorably
upon his new discovery, a meeting of the Inter-
national Medical Congress was held at Copen-
hagen and Pasteur was chosen as a representative
of France and he was invited to read the first
paper. The presentation of the results of his ex-
periments on hydrophobia was followed with the
greatest interest. At that time he attacked the
doctrine of the spontaneous origin of hydrophobia.
As this doctrine was then widely held, Pasteur
thought it desirable to correct this erroneous
opinion. "No matter what the physiological or

THE CONQUEST OF HYDROPHOBIA 209

pathological conditions may be under which dogs
are kept they never contract hydrophobia," accord-
ing to Pasteur, "except when bitten or licked by a
rabid animal. This is why several countries are
free from hydrophobia, and it is only necessary
to follow the procedure of Australia, which compels
every imported dog to be held for several months
in quarantine so that it would have time to develop
hydrophobia if it had been infected by it, in order
to keep the country entirely free from the disease."
Pasteur's account of his success in the preven-
tive inoculation against hydrophobia aroused the
keenest interest and it was followed by enthusiastic
applause. Among the entertainments planned for
the members of the Congress by the hospitable
Danes was a visit to the large Carlsberg Brewery.
Several years before (1879), the philanthropic
owner of this brewery, J. C. Jacobson, had engaged
the artist, Paul Dubois, to make a marble bust of
Pasteur, and had it placed in the Carlsberg Labora-
tory in honor of Pasteur's services to science. The
visit to the brewery showed the application of many
of the processes which Pasteur had recommended
as a result of his studies on beer, and Pasteur was
gratified to see a bronze bust of himself placed in
a niche near the entrance. In the Carlsberg labora-

210 LOUIS PASTEUR

tory Hansen was studying the influence of different
strains of yeast upon the flavor of beers and per-
fecting methods of obtaining these strains in pure
cultures.

Returning to France Pasteur plunged again into
his studies upon hydrophobia. He had perfected a
means of preventive treatment against this disease.
Could the treatment be made to cure the disease
after it had already been introduced by the bite
of a rabid animal? The great value of Pasteur's
discovery thus far lay more in its promise than its
actual utility. With most diseases preventive
inoculation after infection with virulent microbes
would probably be of little avail, as there would
hardly be time for the former to establish immunity
before the virulent, unmodified organisms would
gain the ascendancy. In any case it is a race be-
tween immunization and the development of infec-
tion. In hydrophobia, however, one circumstance
favors the immunizing process in this race, and
that is the slow incubation period of the disease.
It is believed now that the virus of rabies enters
the central nervous system along the course of the
nerves. This accounts in part for the length as
well as the variability of its period of incubation.
There is a further advantage in hydrophobia be-

THE CONQUEST OF HYDROPHOBIA 211

cause, in most cases, the time of infection is defi-
nitely known, whereas with such diseases as
diphtheria, scarlet fever, or tuberculosis people are
quite unconscious of when they may have picked
up the infection.

Pasteur's next step was naturally that of apply-
ing his treatment to animals after they had been
infected with hydrophobia. His procedure was to
take two dogs and allow them both to be bitten by
a mad dog; one he would vaccinate; the other
would be left without treatment. The vaccinated
dogs proved to have been protected against hydro-
phobia, while the others commonly succumbed to
this disease. The immunizing process thus won in
its race against the slower but more deadly onset
of the unmodified disease. Here was a discovery
which could be directly applied to saving the lives
of animals which had been bitten by rabid dogs.

The interest and hope kindled by this discovery
of a cure for hydrophobia became widespread. The
Emperor of Brazil wrote to Pasteur enquiring anx-
iously about the progress of the investigations and
especially when the treatment for hydrophobia
could be applied to man. Similar enquiries came in
from various other quarters, but Pasteur felt great
hesitancy about risking the treatment upon human

212 LOUIS PASTEUR

beings. To the Emperor of Brazil he wrote, "Even
when I have multiplied examples of prophylaxis of
rabies in dogs, I believe that my hand will tremble
when it comes to deal with man." He had thought
of proposing that experiments be tried first on con-
demned criminals, giving the criminal the option
between suffering his sentence and inoculation with
hydrophobia, subsequent treatment, and his free-
dom if the treatment were successful. There was,
however, no way in which this could be done in
accordance with existing laws. What dangers
might attend the introduction of the attenuated
virus into the new soil of the human body could
not be foreseen. The preparation used doubtless
contained the living though weakened germs of this
horrible disease. Persons bitten by a rabid animal
do not always contract rabies; in fact statistics
placed the proportion developing the disease from
sixteen to twenty-five percent. There was the
possibility that the person treated might be given
hydrophobia by the preventive inoculations, and
that he would not contract it if he were let alone.
The responsibility of applying the treatment to a
human being was therefore a grave one. A failure
would be a calamity which could not fail to arouse
public condemnation. And yet people were not

THE CONQUEST OF HYDROPHOBIA 213

infrequently dying in the hospitals of Paris from
this horrible and painful disease. "I have not yet
dared to treat human beings after bites from rabid
dogs," Pasteur wrote to Jules Vercel, "but the mo-
ment is perhaps not distant, and I have almost
decided to begin by myself, — that is, inoculating
myself with rabies, and then arresting the conse-
quences, for I am beginning to feel better and am
growing very sure of my results."

While Pasteur was making more sure of his
methods a circumstance occurred which overcame
his indecision. A little nine-year-old boy, Joseph
Meister, was brought by his mother to Pasteur's
laboratory. Two days previously the boy, while
on his way to school, had been furiously attacked
by a mad dog, thrown to the ground and severely
bitten about the face and hands. He was rescued
by a laborer who happened to be near, and the dog
was subsequently shot. An examination showed
that its stomach was filled with hay and bits of
wood which the infuriated creature had devoured
in its mania for biting. The boy's wounds (he had
been bitten in fourteen places) were covered by
saliva. Doctor Weber, who was consulted in the
evening, washed and cauterized the boy's wounds,
and advised the parents to take him to Paris for a

214 LOUIS PASTEUR

consultation with Pasteur. The position and num-
ber of the bites, their severity, and the obvious
contact of the dog's saliva; together with the cir-
cumstance that so long a time had elapsed between
the bites and the application of cauterization, made
the case a particularly dangerous one.

Pasteur secured quarters for the mother and
child, and consulted Doctor Vulpian, in whose
careful judgment he had much confidence, as to
what should be done. Both Doctor Vulpian and
Doctor Grancher, when they had examined the
bites, decided that the first inoculation should be
performed as soon as possible. They administered
the fourteen-day preparation of spinal cord, and
followed this by the inoculation with cultures of
decreasing age according to the usual method. The
boy, who had looked with alarm upon the approach-
ing ordeal, finding that it amounted to little more
than a pin prick, soon lost his fear and was quite
happy during the subsequent days of his treat-
ment.

As the inoculations increased in strength Pasteur's
anxiety became greater as he counted the days
until the period of danger should be passed.
"Your father has had another bad night," Madame
Pasteur wrote to her children; "he can hardly

THE CONQUEST OF HYDROPHOBIA 215

bring himself to make the last inoculations of the
child. And yet it is necessary to go on with it
now! The boy continues to be very well." "Pas-
teur," says Radot, "passed through a series of di-
verse and contrary emotions, all equally intense, —
hopes, fears, anguish, and an ardent yearning to
snatch little Meister from death. He could no
longer work. Every night he was troubled with a
fever, dreaming of little Meister whom he had seen
playing in the garden suffocating with hydro-
phobia, like the dying child he had seen at the
Trousseau Hospital in 1880. In vain did his ex-
perimental genius assure him that the virus of this
most terrible disease was about to be conquered,
that humanity was about to be delivered from this
horror, but his human tenderness was stronger than
all else. If he made the sufferings and anxieties of
others his own, what were his feelings in the pres-
ence of 'the dear lad!'"

The last inoculation having been given, the lad,
after claiming a kiss from "dear Monsieur Pas-
teur," as he had come to call him, went to sleep in
the evening, quite unconscious of the anxiety which
his benefactor was suffering in his behalf. For
many days after the completion of the treatment,
Pasteur had little rest until time gradually abated

216 LOUIS PASTEUR

his fears and finally assured him that his little pa-
tient was entirely safe.

It was not long before Pasteur was confronted
with another case as urgent as that of Joseph
Meister. A mad dog in the Jura district had at-
tacked a group of six shepherd boys, the oldest of
whom, J. B. Jupille, a boy of fourteen, in order to
save his comrades, courageously attempted to beat
off the animal with a whip. The dog seized the
boy's left hand, but the lad, after some severe
bites, succeeded in throwing the dog down, and
with the aid of his comrades, tied the animal's jaws
with the lash of his whip. Subsequent examination
of the dog convinced veterinary surgeons that it
was certainly rabid. Pasteur was communicated
with, and the lad, with the consent of his parents,
was sent to Paris for treatment. In this case treat-
ment was begun six days after the boy had been
bitten. But nevertheless it proved to be completely
successful.

The history of these two cases was communicated
to the Academy of Sciences. Many people who
had been bitten by rabid dogs now flocked to Pas-
teur's laboratory. A regular service for giving
treatments had to be organized. Success continued
to follow the preventive inoculations, but it was

THE CONQUEST OF HYDROPHOBIA 217

too much to hope that every case which presented
itself could be saved. As we have said, the success
of preventive inoculation depends upon the out-
come of the race between the processes of immuni-
zation and infection. If a patient comes too late
after the deadly virus has gained headway it is
hopeless to attempt to stay its course. On one
occasion a little girl of ten was brought thirty-
seven days after she had been severely bitten about
the head. Pasteur thought the case hopeless and
daily expected the appearance of hydrophobia;
nevertheless, in response to the urgent appeal of
the father and mother, the treatment was applied.
The inoculations were hardly completed before the
dreaded symptoms of hydrophobia began to ap-
pear; the little girl was seized with spasms and
inability to swallow, and soon died. Pasteur,
moved to tears as he watched by her bedside, said
to the grief-stricken parents, "I do so wish I could
have saved your little one!" The cruel disease had
too long a start, and its claim to its victim could
not be successfully disputed.

By means of a subscription started by the New
York Herald, four children of workingmen were
sent across the Atlantic to Pasteur's laboratory.
Although they arrived at the end of their long

218 LOUIS PASTEUR

journey many days after they had been bitten by
rabid dogs, the treatment was in every case suc-
cessful. Pasteur, a great lover of children, took a
keen interest in the young people who had been
under his care. The following letter to Jupille, the
lad previously mentioned who so bravely fought
with the rabid dog, is characteristic of Pasteur's
sympathetic attitude:

My dear Jupille:

I was glad to receive all your letters. The news you
have given me of your good health has afforded me much
pleasure. Madame Pasteur thanks you for remembering
her. She and I and all the staff of the laboratory hope
that you will continue to be well, and that you will make
the most rapid progress in reading, writing, and arith-
metic. Your writing is already much better than it was,
but make more efforts to improve your spelling. How
are you getting on in your classes? Who gives you les-
sons? Work by yourself as much as you can. You
know that Joseph Meister, the first to be vaccinated,
writes me often. I find, although he is no more than
ten years old, he has made more rapid progress than you
have. Apply yourself then as much as you can. Do not
lose time with your playfellows, and follow in all things
the advice of your teacher and of your father and mother.
Remember me to M. Perrot, the Mayor of Villers-Farlay.

THE CONQUEST OF HYDROPHOBIA 219

Probably without his foresight you would have been ill,
and to be ill of hydrophobia means certain death. You
owe him, therefore, a great obligation. Good-bye and
keep well.

Among the various people who came to Pasteur's
laboratory were nineteen Russians who had been
bitten by rabid wolves. Some of them were in a
very bad condition on account of the severity of
their wounds. The percentage developing hydro-
phobia after being bitten by rabid wolves was
known to be very high, being on the average of
about eighty-two per hundred. Two weeks had
passed since the unfortunate Russians were bitten,
and it was therefore very doubtful if they could be
saved. Two inoculations a day, a morning and an
evening one, were given in order to speed up the
process of immunization. Greatly to Pasteur's
grief, three of the Russians soon died, but the
others, who were followed with the greatest
anxiety, recovered, and were sent back to their
native country. In behalf of these and other Rus-
sians who had been saved, the Tsar presented to
Pasteur a diamond cross of the Order of St. Anne,
and a hundred thousand francs for the Pasteur
Institute for which funds were then being collected.

220 LOUIS PASTEUR

The reports of the success of the Pasteur treat-
ment caused the British Government to appoint a
Commission to make a first-hand investigation of
the facts. On this Commission were several men
of international fame, such as Lauder Brunton,
Quain, Joseph Lister, Burdon Sanderson, Victor
Horsley, and Sir James Paget. Delegates visited
Paris, observed the methods followed, and took
account of the results. Looking over Pasteur's
records of ninety persons who were treated within
the neighborhood of Paris, they visited all of them
in their own homes. Further experimental work
was carried on by the Commission in both France
and in England. Fourteen months were spent in
a most exhaustive and critical investigation, and
for this reason it was all the more gratifying that
the Commission fully verified all of Pasteur's re-
sults. "It may be considered as certain," says the
report, "that M. Pasteur has discovered a preven-
tive method against hydrophobia comparable to
that of vaccination against smallpox. It would be
difficult to overestimate the utility of this discov-
ery."

The support of this Commission was much ap-
preciated by Pasteur who in spite of his striking
successes was, as in most periods of his career, not

THE CONQUEST OF HYDROPHOBIA 221

lacking in opposition and hostile criticism. Part
of this came from certain reactionary members of
the Academy of Medicine, but they were becoming
less numerous, and Pasteur's cause was defended
by an increasing number of the most influential
members of this organization. Rabid newspaper
attacks, and insulting anonymous letters, disturbed
Pasteur more than he should have allowed them to,
because he was always easily stirred by opposition.
"I did not know that I had so many enemies," he
said; but if he had enemies, he soon had on his
side the almost unanimous support of competent
scientific men.

Among Pasteur's antagonists there were several
people who were opposed to any form of experi-
mentation that involved the infliction of pain upon
dumb animals. There are many persons who have
the same attitude to-day. The claim is frequently
made that it is morally wrong, for any purpose, to
inflict suffering on a defenseless creature, and it is
maintained, by some extremists, that no results of
value to science or humanity have come from such
procedures. There are organizations in several
countries whose object it is to secure legislation
that would greatly restrict or entirely prevent ex-
periments involving vivisection, even when pain-

222 LOUIS PASTEUR

lessly performed, as well as all experiments on in-
oculation or the production of protective serums and
vaccines.

In so far as these organizations aim to check the
infliction of useless cruelty, reasonable people can-
not fail to sympathize with their efforts. Unfor-
tunately, the opponents of animal experimentation,
however good their intentions, are much more im-
pressed by the sacrifices of a few laboratory ani-
mals than by the saving of thousands of human
and animal lives that has resulted from the knowl-
edge so secured. Pasteur employed a few sheep
and rabbits in his experiments on anthrax, but he
discovered a preventive vaccine for this deadly
disease that has saved thousands of sheep and
cattle. It required the sacrifice of several rabbits
and dogs to discover the cure for hydrophobia.
Any one who had a pet dog given this disease for
experimental purposes might be indignant at the
investigator. If he had a child who had been saved
from a horrible death because of the knowledge
gained through the death of the dog, he would prob-
ably have a different feeling. Were our intellectual
vision limited to the discomforts of a few animals
which the investigator uses in his research, we
might be inclined to stay his hand. But if our

THE CONQUEST OF HYDROPHOBIA 223

vision reaches beyond to the multitude of other
animals saved from cruel death by disease, the case
appears in an entirely different light. What might
appear to our limited vision as cruelty becomes,
when seen in its wider bearing, an act of mercy.

Many naturally sympathetic persons who have
little knowledge of how animal experimentation is
conducted have been led to oppose it by the mis-
representations and greatly exaggerated tales of
cruelties that are often circulated by those who
have allowed their fanaticism to overcome their
scruples. Most animal experimentation that is
now carried on is conducted in a humane manner,
the animals being given an anesthetic for all
operative procedures. And the men engaged in this
research, far from revelling in wanton cruelty as
they are sometimes accused of doing, are laboring,
as best they can, to check the suffering of animals
and men alike. I have been closely associated with
experimental laboratories for many years, but I
have never witnessed anything but the considerate
treatment of the rabbits, guinea pigs, or the occa-
sional stray dogs which are used for experimental
purposes. At times cruelties may occur, but they
are infinitesimal in amount as compared with what
is inflicted by hunters, trappers, and careless or

224 LOUIS PASTEUR

callous owners of live stock. On the other hand,
no one with the least knowledge of modern biology
and medicine can deny that the information gained
by animal experimentation has resulted in an
enormous saving of human and animal life, and
the prevention of untold suffering through dis-
ease.

Even the giving of anesthetics, incredible as it
may now seem, met with violent opposition from
fanatical persons who thought it was wrong to
check pain which the Creator had designed to
inflict. The opponents of animal experimentation
are analogous to those who, for humanitarian rea-
sons, would spare a child the discomfort of a sur-
gical operation only to condemn him to a life of
suffering afterward for want of the relief which
the operation would bring. They would allow ani-
mals and human beings to go on suffering and
dying of lingering and painful diseases as they
have done in the past, rather than employ a rela-
tively few animals for the increase of our knowl-
edge. A humanity that would sacrifice the many
to save the few is no humanity at all, and those
who are guilty of the real cruelty to animals and
human beings alike are not the investigators, who
are laboring to reduce the field of useless suffering,

THE CONQUEST OF HYDROPHOBIA 225

but the misguided individuals who would stop the
progress of experimental research.

The career of Louis Pasteur affords a striking
illustration of the truth that the cause of science
and the cause of humanity are one. Nothing would
have been more repugnant to this kindly man than
the infliction of useless pain. He shrank from
operations, and he sometimes forced himself to
carry on work in his investigations on hydrophobia
which was painful for him to perform. But he had
visions of the possibility of conquering disease and
abolishing needless suffering and death that made
his natural sympathies an aid rather than an
obstacle to research. As the treatments for bites
of rabid animals increased in number he was re-
warded with the certain knowledge that he had
saved many persons from a death that is frequently
of the most painful kind. Such persons scattered
about through many countries became object les-
sons to the people around them of the efficacy of
the Pasteur treatment, and when the project was
started for creating a great institute for the work
of Pasteur and his colleagues it was supported by
an unparalleled burst of generosity. Not only
from France, but from Italy, England, Russia, the
United States, and many other countries, contribu-

226 LOUIS PASTEUR

tions were sent in for the benefit of this institution.
The long list of subscribers included workmen,
students, and poor women, as well as millionaires
and the members of royal families. To a great
extent the Pasteur Institute, as it came to be called,
was an expression of the interest and generosity of
the common people. Among the subscribers from
Alsace-Lorraine, Pasteur noted with peculiar emo-
tion the name of little Joseph Meister, who eleven
months before, received the first treatment for
rabies administered to a human being.

The Pasteur Institute became a great research
institution which was devoted not only to the treat-
ment of increasing numbers of people bitten by
rabid animals, but also to carrying on investiga-
tions in bacteriology and the control of epidemic
diseases. The Institute since its foundation has
published in its annals the results of the treatment
for all of its cases of rabies. Up to 19 12 it had
treated over thirty thousand cases of rabies with a
mortality of less than one percent. The relatively
small percentage of failures include several cases in
which treatment was administered several days or
even some weeks after the bites were inflicted.

In order to avoid sending persons over long dis-
tances to Paris, as was formerly done, branch in-

THE CONQUEST OF HYDROPHOBIA 227

stitutes have been created 'in many other countries.
There were over forty of them in 19 14. In the
course of eighteen years they had treated over
100,000 persons with a mortality of 0.73 percent;
if we exclude the probably hopeless cases who
died within two weeks after treatment, the mor-
tality was 0.54 percent. Even though hydro-
phobia is not a common disease these figures in-
dicate a saving of many thousands of human lives.
I happened to live near an institution, the State
Hygienic Laboratory at the University of Cali-
fornia, which makes and administers the mate-
rials used in the Pasteur treatment. California
was practically free from hydrophobia before 1909,
but at this time some rabid dogs gained entrance
into the state and the disease rapidly spread. In
parts of the state it became prevalent among the
coyotes which did considerable damage by biting
sheep and cattle. Efforts were made to check it by
having dogs muzzled, but this aroused lively oppo-
sition among many people, who are always unrea-
sonable in such matters, and muzzling was not
thoroughly carried out. The people of the state
paid dearly for their failure to take prompt meas-
ures to stamp out the disease. Many people were
bitten by rabid animals, but, fortunately for them,

228 LOUIS PASTEUR

preparations for meeting the emergency were
quickly made at the Hygienic Laboratory. Up to
July, 1923, the Pasteur treatment was administered
to 1,490 persons with a mortality of about one
percent. If we were to exclude the obviously
hopeless cases in which the disease set in very
quickly or in which treatment was delayed the
mortality would be considerably less.

CHAPTER XII

LAST DAYS

The conquest of hydrophobia was the crowning
achievement of Pasteur's career. In the Pasteur
Institute, which afforded unrivalled facilities for
research, an efficient corps of well-trained co-
workers carried on investigations in the fields
opened up by Pasteur's genius. After 1888, Pas-
teur devoted most of his time to the work of this
institution and to superintending the treatments
given to patients for hydrophobia. It was his
habit to go the rounds of the patients in the morn-
ing, inquiring how they were progressing and
cheering them with words of encouragement. The
children enlisted his especial concern. "When I
approach a child," he says, "he inspires me with
two sentiments; that of tenderness for what he is
now, and respect for what he may hereafter be-
come."

After perfecting his treatment, which was now
administered by the efficient staff of the Institute,

Pasteur could rest with the assurance that all had

229

230 LOUIS PASTEUR

been done for hydrophobia that one man could well
do. He looked forward to new fields to conquer, —
to diphtheria, cholera, tuberculosis, the plague, and
many other diseases which afflict mankind, but his
strength did not permit of further active investiga-
tions. The work on rabies had been peculiarly
taxing. Added to the intense labor devoted to the
struggle with this disease, there was the anxiety
over the outcome of the treatments which gave him
many sleepless nights and robbed him of much
nervous energy. He was frequently called upon to
address or preside at public meetings, and his cor-
respondence, which was punctiliously attended to,
took much of his time. In 1889, despite his fail-
ing strength, he went to Alais to take part in the
ceremony of raising a statue to J. B. Dumas for
whose memory he cherished the deepest reverence.
The silk growers of that region, in memory of Pas-
teur's control of the silk-worm disease, presented
him with a token of their gratitude in the form of
a silver branch of heather adorned with the golden
cocoons of the silk worm. In his acknowledgment
of the gift, Pasteur said, "In the expression of your
gratitude, by which I am deeply moved, do not
forget that the role of initiator was played by
M. Dumas."

Fig. 13. Pasteur and Madame Pasteur

LAST DAYS 231

Tokens of respect and gratitude came to Pasteur
from many quarters. The Canadian government
gave his name to a district adjoining the State of
Maine. The Governor-General of Algiers informed
Pasteur that his name was given to a village in
Algiers, adding that, "I am happy to have been
able to render this slight homage to your illustrious
person." Streets bearing Pasteur's name were laid
out in several cities and towns, and letters full of
expressions of gratitude for some one near to the
heart of the writer who was saved by Pasteur's dis-
coveries, gave him a deep satisfaction that more
than offset the effect of other letters roundly abus-
ing him for the sacrifice of the animals which made
these discoveries possible.

Pasteur is regarded by his countrymen with min-
gled feelings of gratitude and pride. He is one of
the few men of science whose name has become a
household word. His work, directly or indirectly,
has touched every home. It has called forth the
homage of the people, not so much because of its
revelations of the secrets of nature, as because, in
many thousands of homes, it has meant the saving
of human lives. There is consequently little ground
for surprise over the results of the popular vote
which was conducted a few years ago by an enter-

232 LOUIS PASTEUR

prising Parisian newspaper as to who was the great-
est man whom France had produced. The great
Napoleon who probably would have been awarded
this distinction a generation before stood well down
the list. The first place was given to Louis Pasteur
whose discoveries have probably saved more lives
than Napoleon had destroyed.

As Pasteur approached his seventieth birthday,
preparations were made for a fitting celebration.
Norway, Sweden, and Denmark took the initiative
in this movement, which was enthusiastically sup-
ported by the Academy of Sciences in France. The
meeting was held in the large theater of the Sor-
bonne on December 27, 1892, and was presided
over by the President of the Republic, Sadi Carnot.
On the platform were the Ambassadors from Eng-
land, Russia, Austria-Hungary, Denmark, Belgium,
Holland, Sweden, Norway, and of Bavaria, and
also the chief officials of the French government.
There were representatives of the Academy of
Sciences, the Academy of Medicine, the Ecole
Normale, the Ecole Politechnique, the School of
Pharmacy and many other scientific societies in
France and in foreign countries. There were dele-
gations from many nations, consisting of their fore-
most men of science, — Lister, Burdon Sanderson,

LAST DAYS 233

Ray Lankester from England, Haskovek and
Schottelius from Germany, Metchnikoff from Rus-
sia, and distinguished representatives from Bel-
gium, Denmark, Holland, Italy, Poland, Greece,
Switzerland, and Spain. Masses of students com-
posed a large part of the great audience which was
stirred by a deep enthusiasm for the man whose
life-long labors were being so signally honored.
As Pasteur entered, leaning upon the arm of the
President of the Republic, the band of the Repub-
lican Guard played a triumphal march, and the
entire audience rose and greeted him with pro-
longed applause. It was, as Kein and Lumet have
remarked, "the supreme homage."

The opening ceremonies over, M. Dupuy, Min-
ister of Public Instruction, addressed Pasteur, re-
counting his great achievements and concluding in
the following words: "Who can say at this hour
how much human life owes to you, and what it will
owe to you in the years to come? A day will come
when some new Lucretius will sing in a new poem
of Nature the immortal master whose genius has
engendered such great benefits. He will not pic-
ture him a solitary and unfeeling man as the Latin
poet has portrayed his hero; he will show him
mingled with the life of his time, the sadness and

234 LOUIS PASTEUR

joy of his country, dividing his life between the
severe pleasures of scientific research and the sweet
intercourse of family life, passing from his labora-
tory to his fireside, finding among his dear ones
who knew him and who therefore loved him, the
encouragement in daily work and comfort at all
times, without which so many troubles would per-
haps have diminished his ardor, checked his per-
severance and enervated his genius. May France
possess you for many years to come and show you
to the world as a worthy recipient of her love, her
gratitude, and her pride!"

A large engraved golden medal was then pre-
sented to Pasteur, and after a few words from
M. Daubree, a former colleague of Pasteur's at
Strasbourg, an address was made by Lord Lister,
who was chosen with peculiar appropriateness as
the representative of the Royal Societies of London
and Edinburgh. "M. Pasteur," he said, "the great
honor has been accorded me of bringing you the
homage of the sciences of medicine and surgery.
As a matter of fact, there is no one living in the
entire world to whom the medical sciences owe so
much as they do to you. Your researches in regard
to fermentation have shed a powerful light that has
illumined the fatal darkness of surgery and changed

LAST DAYS 235

the treatment of wounds from a matter of em-
piricism, uncertain and too often disastrous, to a
scientific art of assured beneficence. Thanks to
you, surgery has undergone a complete revolution
which has robbed it of its terrors and extended its
efficacious powers almost without limit. Medicine
is indebted no less than surgery to your profound
and philosophic studies. You have lifted the veil
which for centuries had overhung infectious dis-
eases. You have discovered and demonstrated
their microbic nature. Thanks to your initiative
and in many cases to your special and personal
labors, there are already a number of these perni-
cious disorders of the causes of which we have a
complete knowledge. . . .

"Infectious diseases constitute, as you know, the
great majority of the maladies which afflict the
human race. You can therefore well understand
that the sciences of medicine and surgery are
eager upon this solemn occasion to offer you the
profound homage of their admiration and grati-
tude."

At the close of this address, the greeting of Pas-
teur and Lister, the two great figures in the crea-
tion of a great epoch in medicine and surgery,
brought tumultuous applause. No one in that re-

236 LOUIS PASTEUR

markable audience could ever forget the sight of
these two men. The Academy of Medicine, the
scene of so many controversies, paid its homage
through its Dean, who said, "More fortunate than
Harvey and Jenner, you have lived to see the tri-
umph of your doctrines, and what a triumph!"

Gifts, expressive of the admiration and esteem
of several organizations, were presented to Pasteur
on that occasion, but one which perhaps touched
him most was an album containing the signatures
of all the inhabitants of his native village of Dole,
a photograph of the house in which he was born,
and a facsimile of his birth certificate at the end
of which was the signature of his father. One
wishes that the old soldier, who sacrificed so much
in his ambition for his son's success, might have
been brought back to life and given a seat of honor
on the platform during the impressive celebration
of that day.

Pasteur, whose voice was weakened by his broken
health, had his address read by his son. After
expressing his appreciation for the honors con-
ferred upon him, he said, in addressing the foreign
delegates, "You who have come from so far to give
a proof of sympathy to France, you bring me the
deepest joy that a man can experience, who believes

LAST DAYS 237

invincibly that science and peace will triumph over
ignorance and war; that peoples will come to a
common understanding, not to destroy but to build,
and that the future will belong to those who will
have done most for suffering humanity. . . .

"Young men!" he continued, addressing the stu-
dents, "have confidence in that sure and powerful
method of which we do not yet know the funda-
mental secrets. . . . Live in the serene peace of
laboratories and libraries. Say to yourselves, first
of all: What have I done for my instruction?
and as you go on further, What have I done for
my country? until the time comes when you may
have the immense happiness of thinking that you
have contributed in some way to the progress and
to the welfare of humanity."

Although Pasteur could no longer endure the
strain of active labors, he followed with keen in-
terest the experiments of his associates at the
Institute. Metchnikoff, destined to be known
throughout the world for his investigations on
immunity and the role of the white corpuscles of
the blood, came to join the staff of the Institute.
The able, energetic, and ambitious men, whom Pas-
teur drew around him, regarded their master with
unfailing devotion. Pasteur's dream of a great

238 LOUIS PASTEUR

research institution, devoting itself to the conquest
of disease, was realized, and as he followed the
work of its able staff, he had reason to feel a pro-
found satisfaction in its achievements and promise.
Roux and Yersin had made a discovery of the
highest importance in regard to diphtheria. The
bacillus of this disease had been discovered by
Klebs in 1883, and isolated and cultured later by
Loeffler. Roux found that the liquid filtered from
cultures of the diphtheria bacillus was highly poi-
sonous. A very small amount of this injected under
the skin of small animals caused death with many
of the symptoms of diphtheria, although, of course,
without the presence of the bacilli of diphtheria in
the body. Roux drew the conclusion that the
germs of diphtheria and presumably other germs
also produce their deadly effects through the pro-
duction of poisons or toxins.

This discovery paved the way for another which
was made by Behring and Kitasato, the discovery
of antitoxins or substances produced by the body
which have the property of combining with and
neutralizing the toxins, and hence of relieving the
body from the poisonous effects which the latter
produce. The Pasteur Institute began to make the
antitoxin for diphtheria. By injecting gradually

LAST DAYS 239

increasing doses of diphtheria toxin into a horse,
the blood of the animal comes, after a time, to con-
tain a quantity of antitoxins. After this occurs,
some of the blood of the horse is withdrawn, the
serum is extracted and preserved in vials with a
small amount of antiseptic. It is then ready to use
for cases of diphtheria.

The gratifying results of the use of diphtheria
toxin are well known. If given early in the course
of the disease, it effects a cure in a very high per-
centage of cases, and the mortality of all cases
treated with antitoxin, as compared with the mor-
tality of untreated cases, is relatively low. Diph-
theria is a treacherous disease; it sometimes
snatches away its victims before the nature of the
malady is determined. Highly contagious and
often carried by persons not themselves affected, it
is remarkably persistent and still ranks among the
principal causes of death in the period of child-
hood. The work of Roux on diphtheria antitoxin
was suggested by some of the earlier experiments
of Pasteur on chicken cholera. Pasteur found
that the liquid obtained by filtering a culture of
the bacteria of chicken cholera would produce
some of the symptoms of this disease if injected
into a healthy fowl. He did not follow up the line

240 LOUIS PASTEUR

of enquiries to which the experiments pointed, as
he was then chiefly interested in establishing the
important principle of attenuation. This was left
for others, and the investigations thus started and
continued in the Pasteur Institute and elsewhere
have led, step by step, to the most striking results
in serum therapy and allied procedures.

In 1894, Yersin, who had gone from the Pasteur
Institute to China, discovered the germ of the
plague, and found that it could be cultured in arti-
ficial media, and inoculated into rats, mice, and
guinea pigs. The subsequent discovery of the role
played by rats in harboring the germs of the plague,
and its transmission from animal to man and from
man to man by fleas, has made it possible to stamp
out this disease in several places in which it had
gained a foothold. The epidemics that formerly
swept over nations carrying away thousands in
their course may now be controlled. Where plague
occurs war is made on the rats and fleas, the pa-
tients are strictly quarantined and the epidemic
dies.

Pasteur was profoundly gratified by the discov-
eries of his co-workers. They were bringing nearer
to realization his dream of the conquest of disease
though the methods which he had discovered and

LAST DAYS 241

so successfully applied. In 1895 he had almost
ceased to visit the laboratories of the Institute.
His growing weakness apprised him of the ap-
proaching end. Alone one evening with his grand-
children, who were playing about his knees, he took
them in his arms and affectionately kissed them
while tears rolled down his careworn face. To the
anxious questions of the children he replied, "I am
weeping, my children, because I am so soon to leave
you." The paralysis which had affected him years
before began to recur, and made it more difficult
for him to speak. The loving care of his family
and the solicitude of many friends did everything
possible to cheer his declining days. On September
27, 1895, holding in one hand a crucifix, for he had
always lived in the Catholic faith, and with the
other resting in the grasp of Madame Pasteur, he
passed away.

At the request of the French Government the
body of Pasteur was placed in a beautiful chapel at
the base of the Pasteur Institute. Its marble walls
bear the names of the chief fields of investigation in
which he had won renown, — molecular asymmetry,
fermentation, spontaneous generation, studies on
wine, studies on silk worms; studies on beer, the
cause of contagious diseases, curative vaccines, the

242 LOUIS PASTEUR

prophylaxis of hydrophobia. In the decorations of
his tomb are wreaths and garlands of grape vines,
mulberry leaves and figures of cattle, sheep, dogs,
and poultry, whose diseases he did so much to con-
quer. And on the vault above his grave are four
angels watching over him, Faith, Hope, Charity,
and Science. In the laboratories above his tomb
his great work is going on.

INDEX

Academie Frangaise, 188, 189
Academy of Medicine, 155,

156, 159, 167, 182, 184, 198,

221, 236
Academy of Sciences, 35, 96,

115, 116, 173, 192, 216, 232
Aerobic organisms, 79
Alcohol, fermentation of, 67-

69, 72-76, 79
Amoeba, 44, 46-48
Anaerobic organisms, 78-80
Animal experimentation, bene-
fits of and opposition to,

221-225
Anthrax, 51, 52, 161-170, 190,

195, 196, 198, 199
Antitoxins, 238, 239
Arbois, 6, 7, 9, 144
Aristotle, on hydrophobia,

201

Bacilli, 51 ; of anthrax, 51, 52,
161-173, 178; of diph-
theria, 238; of fowl chol-
era, 170, 171, 239; of the
plague, 51, 240; of typhoid
fever, 51

Bacteria, 50-59, 73, 156, I57»

161-173
Balard, 15, 28, 96, 115, 116

Barbet, M., 8, 11, 12, 13
Bastian, Dr. C, 98, 99
Beer, diseases of, 147-149
Behring, discovery of diph-
theria antitoxin, 238
Bernard, Claude, 33, 115, 138,

188
Bert. P., 160, 166, 186, 194
Bertin, M., 34, 149
Besancon, college of, 9-1 1

243

Biot, J. J., 26, 28-30, 32, 36,

84, 115, 116
Boils, germs of, 180, 181
Boyle, Robt., on fermentation

and disease, 151
Bremer, on malic acid, 38
Butyric acid fermentation, 77,

78

Cagniard-Latour, 67
Chamberland, M., 99, 115,

185

Chappuis, Chas., 10, 11, 13,

14, 15, 36, 82,84

Chemistry, work in, 31 -40
Cholera, of fowls, 169-173,

239; of swine, 197
Colin, G., 68
Crystals, work on, 21-33

Davaine, C, on cause of an-
thrax, 161-163
Dessaignes, 37, 38
Deville, H. S. C, 33, 115, 139
Diphtheria, cause of and treat-
ment for, 230, 238, 239
Dole, 3, 18, 194, 195, 236
Duclaux, E., 39, 99, 100, 115,

133, 180

Dumas, A., no, 188

Dumas, J. B., 12, 16, 28, 32,
33, 84, 115, 125, 126, 138,
140, 146, 191-193, 230

Dupuy, C, 233

Duruy, M., in, 140

ficole Normale, 7, 10, n -13,
15, 18, 22, 33, 35, 81, 138,
143, 145, 191, 192

Enzymes, 76, 77

244

INDEX

Fabre, H., 126, 127
Fermentation, 39, 40, 49, 50,

61-81
Flacherie, 134-138
Flagellates, 46-48

Galen, on a cure for hydro-
phobia, 201
Gay-Lussac, 67
Germ theory of disease, 153,

155, 156, 159, 174
Grancher, Dr., 214
Grandeau, M., 188

Hahnemann, Dr., 154

Herschel, Sir J., 26

Holmes, O. W., on conta-
giousness of puerperal
fever, 182

Huxley, T. H., on the value
of Pasteur's discoveries,
194

Hydrophobia, 201-230

Infusoria, 46, 47

Itch, cause of, 154, 155, l65

Jenner, Dr., 172, 187, 236
Joly, N., on spontaneous gen-
eration, 95

JOUBERT, 99, 115

Jupille, J. B., treatment for
rabies, 216, 218

Kaempfen, speech on Pasteur

at Dole, 194
Koch, R., 162-164, 196

Lactic acid fermentation, 68,

71-74, 107
Laurent, A., 15, 16
Laurent, M., 34-36
Lavoisier, 67, 138
Leeuwenhoek, A. van, 42, 43,

47, 50, 57
Liebig, 67-70, 74, 76
Lille, 61-63

Lister, Jos., 157-159, 220, 234,
235

LlTTRE, l88

Malic acid, 30, 37, 38
Mathilde, Princess, hi, 142
Meister, Jos., treatment for

rabies, 213-216, 218, 226
Metchnikoff, E., 233, 237
Milne-Edwards, 96
Moliere, 189, 198
Moquin-Tandon, 116
Moritz, on chicken cholera,

170
Musset, C., on spontaneous

generation, 95-96

Napoleon, I, 4, 5, 145, 232
Napoleon III, 120, 121, 123,

124, 140, 141, i5i
Needham, on spontaneous

generation, 87, 88

Osler, Wm„ 156
Osteomyelitis, germ of, 181

Paget, Sir James, 186, 187,

220
Paget, S., 9

Pasteur Institute, 219, 225,

226, 229, 237, 238, 240-242

Pasteur, Jean Joseph, 4-7,

13-15, 18, 19
Pasteur, Josephine, 15, 37
Pasteur, Louis,
At Arbois, 6, 7, 9, 144
At Besancon, 9-1 1
At Bordeaux, 179
At Copenhagen Medical

Congress, 208, 209
At Dijon, 33
At the ficole Normale, 11-

13

At the Geneva Medical Con-
gress, 195, 196

At Lille, 61-63

At London breweries, 148

INDEX

245

Pasteur, Louis,

At London Medical Con-
gress, 186

At Strasbourg, 33, 61

Birth, 3, 5

Controversy with Bastian,
98, 99; with Koch, 195,
196; with Liebig, 68-70,
76, 77; with Pouchet, 89,
90, 95-97 ; with Turin
professors, 198, 199

Death, 241

Letter, to Chappuis, 36, 37,
84; to Duclaux, 146, 147;
to Dumas, 125, 126; to
his father, 11, 34, 82; to
the Emperor of Brazil,
212; to Jupille, 218, 219;
to Laurent, 35, 36; to
Madame Pasteur, 186,
187; to his sisters, 9, 10;
to Vercel, 213

Marriage, 36

On the cause of anthrax,
165 ; of puerperal fever,
182, 183

On crystalline form and
rotary power, 28, 29

On fermentation, 73, 74

On laboratory instruction,

61, 62

On pure and applied science,

62, 63

On silkworm diseases, 129,

130, 136
On spontaneous generation,

93, 112
Paralytic stroke, 139-141
Pasteur, Madame J. J., 5, 18
Pasteur, Madame Louis, 34-

37, 114, 186, 214, 241
Pasteurizing, 107, 149
Pebrine, 48, 128-138
Peter, Dr., 198
Plague, 230, 240
Poincare, on Pasteur, 185
Pouchet, F. A., 89, 90, 95-97,

103

Protophyta, 44, 49

Protozoa, 44-49

Puerperal fever, cause of, 182,

183
Putrefaction, 68-70, 79

Rabies, 201-228

Racemic acid, 13, 31, 32

Redi, on spontaneous genera-
tion, 85

Renan, E., speech of welcome
to Pasteur, 188, 189

Richardson, G. M., on
Pasteur's work on stereo-
chemistry, 39

Romanet, M., 7

Roqui, J. E., 5

ROSSINGNOL, M., I74-I78
ROUGET, I96-I97

Roux, 115, 161, 181-183, 185,

238, 239

Schroeder and Dusch, 88
Schulze, on spontaneous

generation, 88-90, 103
Schwann, 67, 88, 89
Senarmont, 32, 115, 116
Silkworm diseases, 125-138,

141-142
Spallanzani, Abbe. 87, 88
Spontaneous generation, 52,

83-112
Sporozoa, 48, 135
Stahl, on fermentation, 66
Swine plague, 196, 197

Tartaric acid, 13, 26-32
Texas fever, 48
Thenard, 67, 69
Thullier, L., 196
Toussaint, on germs of fowl

cholera, 170
Tyndall, J., 55, 100-107, 185

Vallery-Radot, R., 32, 144,

145, 177, 188, 190, 215
Van Helmont, 85
Vercel, J., 8, 213

246

INDEX

Vinegar, work on, 116-119
Virgil, on spontaneous origin

of bees, 85
Vivisection, benefits of and

opposition to, 221-225
Vulpian, Dr., 214

Weber, Dr., 213

Wine, diseases of, 1 19-123
Wohler, artificial synthesis
of urea, 37

Yeast plants, 49, 50, 68-73, ?6>

79
Yellow fever, 179, 180
Yersin, Dr., 238, 240