il^^

yiii.iiii)|/||,ii:

LOUIS PASTEUR

(1S22-1895)
(From a bronze by Theodore Riviere.)

PASTEUR

THE HISTORY OF A MIND

BY

EMILE DUCLAUX

Late Member of the Institute of France

Professor at the Sorbonne and Director

of the Pasteur Institute

TRANSLATED BY

ERWIN F. SMITH and FLORENCE HEDGES

Pathologists of the U. S. Department of Agriculture

ILLUSTRATED

PHILADELPHIA AND LONDON

W. B. SAUNDERS COMPANY

1920

Copyright, 1920, by W. B. Saunders Company

PRINTED IN AMERICA

CONTENTS

Introduction v

Author's Preface xxxi

FIRST PART
WORKS ON CRYSTALLOGRAPHY

Chapter Page

I. The Predecessors of Pasteur: Hauy, Weiss, Delafosse 1

II. Biot and J. Herschel 7

III. Pasteur: The Tartrates 12

IV. The Paratartrates 16

V. Aspartates and Malates 20

VI. Molecular Dissymmetry 23

VII. Dissymmetry of Cellular Life 28

VIII. Substances Inactive Through Loss of Dissymmetry 32

IX. Combinations Between Active Molecules 39

X. Means of Separating the Right- and Left-handed

Substances 43

XI. General Conclusions 46

SECOND PART
LACTIC AND ALCOHOLIC FERMENTATIONS

I. The Knowledge of Fermentations before Lavoisier 51

II. From Lavoisier to Gay-Lussac 56

III. Cagniard-Latour, Schwann, Helmholtz 59

IV. Liebig 64

V. Pasteur: Lactic Fermentation 67

VI. Alcoholic Fermentation 73

VII. Aerobic Life and Anaerobic Life". 79

i

11 CONTENTS

THIRD PART
SPONTANEOUS GENERATIONS

Chapter Page

I. ^Spontaneous Generation and Fermentation 85

II. BuFFON, Needham, Spallanzani, Schultze, Schwann,

SCHROEDER AND DuSCH 87

III. Pouchet, Pasteur: The Germs of the Air 91

IV. In the Air There are Living Germs 9.5

V. Response to the Arguments in Favor of Spontaneous

Generations 100

VI. Distribution of Germs in the Air 101

VII. Discussion with Pouchet 104

VIII. Discussion with Fremy Ill

IX. Discussion with Bastian 114

FOURTH PART

WINES AND VINEGARS

I. Industrial Methods in the Manufacture of Vinegar 121

II. The Mycoderma of Vinegar 124

III. Discussion with Liebig 128

IV. The Diseases of Wine 133

V. Action of Oxygen on Wine 136

VI. The Heating of Wines 141

FIFTH PART

STUDIES ON THE DISEASES OF SILKWORMS

I. Orientation toward Pathology 145

II. The Corpuscular Disease (P^brine) 149

III. Studies of 1865 154

IV. Studies of 1866 158

V. Is THE Corpuscle the Cause of the Disease ? 162

VI. Studies of 1867 168

VII. The Disease of the Morts-Flats (Flacherie) 173

VIII. Studies of 1808, 1869, 1870 178

SIXTH PART
STUDIES ON BEER

I. Studies on Brewing 187

II. Tuansfor.\i.\tion of One Species into Another 190

III. Anaerobic Life of Aerobic Species 198

CONTENTS 111

Chapter Page

IV. Aerobic Life of Anaerobic Species 202

V. Ideas of Claude Bernard on Fermentation 206

VI. Discussion of the Ideas of Claude Bernard 210

VII. Origin of the Yeasts of Wine 214

SEVENTH PART

STUDIES ON THE ETIOLOGY OF MICROBIAL

DISEASES

I. The Ideas on Contagion Prior to 1866 225

II. Causes of the Sterility op the Ideas Upon Contagion .... 230

III. Anthrax: Pollender, Brauell, Delafond 233

IV. Davaine 237

V. Koch: The Spore of Anthrax 241

VI. Objections to the New Doctrine 244

VII. Pasteur: The Bacteridium is the Sole Cause of

Anthrax 250

VIII. Conflict of the Microbe with the Organism 253

IX. The Septic Vibrio 257

X. A Common Microbe may be Pathogenic 263

XI. New Examples of Physiological Conflicts 269

EIGHTH PART

THE STUDY OF VIRUSES AND VACCINES

I. Microbial Diseases and Virus Diseases 273

II. Chicken Cholera 276

III. Discovery of Vaccines 280

IV. Anthrax is also a Virus Disease 285

V. Studies on Rabies 294

VI. The Problem of Immunity 299

VII. Virulence and Attenuation 304

VIII. Return to Virulence 308

IX. Chemical and Humoral Theories of Immunity 312

X. Cellular Theory of Immunity 317

Annotated List of Persons Mentioned in this Book 323

Index ' 353

EMILE DUCLAUX

^About 1897;
(From a photograph l\v Paul Rivos, Paris.)

INTRODUCTION

This book is more than a critique of Pasteur. It is a
contribution to the biological history of a swiftly changing
time, a very striking period in the development of science.
As such it should be of interest to all biologists, and
especially to all teachers and students of biology and of
medicine. For them it was written, and tiranslated. In
this time of world upheaval and readjustment, when our
young men are looking more and more to France for
moral and intellectual ideals, it seems peculiarly apropos
that the scientific life of one of her greatest sons, to whom
the whole world owes an enormous debt of gratitude,
should be set before them clearly and interestingly.

This life of Pasteur was published in 1896, and
its author has been dead fifteen years. The book speaks
for itself, but in giving to the public an English edition
it seems fitting to say some words respecting its author:
'^Cette grande et belle intelligence, si simple et si rohuste"
(Yourievitch).

The senior translator still remembers with what un-
expected and keen pleasure a dozen years ago he saw the
title of this book in a German catalogue of second-hand
books. For some unexplained reason he had never come
across the book in any library or seen any notice of it in
any review, nor could he find any of his fellows who had
read it, or seen it, or even heard of it. Once, only, since
then has he seen it mentioned in a catalogue of second-
hand books. Indeed, it seems almost as if it must have
died still-born, so little notice has been taken of it, at
least outside of France. Duclaux's name was enough,
however, and it was ordered straightway, with the fear,
oft renewed during the next few weeks, that like many a

V

VI INTRODUCTION

coveted treasure mentioned in old-book catalogues, it
would be snapped up by another and never delight his eyes.
But such was not to be the case. In due time it came
(pages uncut) and then what keen delight was his as he
devoured page after page, marveling more and more at
the wonderful breadth and perspicacity of the presenta-
tion. Pasteur seemed alive in its pages, and Duclaux
not less alive. No book about a scientific man ever in-
terested him more, or could be written, it seemed, with a
more appreciative and discriminating touch. When the
last page was finished nothing was more natural, there-
fore, than to write on its margin: "The most useful book
I have read in a long time."

Going over these pages ten years later, the writer sees
no reason for modifying his first judgment. The next
impulse was to lend the book, and then to wish that it
might reach thousands of readers in a suitable English
dress. This idea disturbed his spirit so much that finally
he began a translation, dictating to a stenographer in the
odd minutes of a busy life. Later, it seemed better to
turn over a part of this work to an assistant. Eventu-
ally, about two-thirds of the rough draft from the French
was made by Florence Hedges. We then worked it over
together into its present English shape, but those who
can read it in the French are advised to do so, since, do
the best we could, Duclaux's wonderful idiomatic style
has lost somewhat in the translation.

If Pasteur be an incomparable genius, Duclaux, at
least, is his Boswell, but he is more than a mere Boswell
tagging around after a great man. He is himself a great
man. He has a genius of his own which burns with a very
clear flame — a genius that penetrates and illuminates
whatever it touches, and this has made him an incompar-
able biographer, and one of an unusual kind. He is no
blind ]iartisan or patriot. TTo thinks his own thoughts.

INTRODUCTION Vll

goes the shortest way to the heart of a subject, and im-
presses one everywhere as honest and fair in his scientific
criticisms. He is an ideal man of science and, moreover,
he has what many lack, a direct, forcible, and delightful
way of putting things. One would like to know more
about such a man, and Madame Duclaux in her inter-
esting book ("I like it best of all the books I have
written," she said) has opened the way. In the spirit
of her happ3^ motto Transire benefaciendo, and mostly
from this heart book,^ I have compiled the following
facts respecting the author of " Pasteur: Histoire d'un
EspriV

Duclaux was Auvergnaise. He was born in 1840 in
Aurillac in Cantal. Aurillac is a quaint, gray-stuccoed,
red-roofed town on a high plateau in the old volcanic
region of southern France. It is in a smiling, pastoral
country, overlooked by the great rounded flanks of the
extinct volcanoes. It is in latitude 45°, due south of
Paris 442 kilometers, and north of the eastern Pyrenees
275 kilometers. East and west it lies about midway be-
tween Bordeaux and the Rhone at Valence. Already
the population begins to be southern in its speech and its
manners.

On both sides Duclaux was descended from the great
middle class of France. His father was a clerk with
wandering and scholarly proclivities, a dreamy and silent
man. His mother was a good-natured, joyous, affec-
tionate country girl, the daughter of a small proprietor
and merchant. He was the first child. From his ear-
liest days he was brought up very strictly. His father,
Pierre-Justin Duclaux, gave nearly his whole time to his
education, himself teaching him at first, and later, when
he was under other instructors, going over all his lessons

1 La vie de Emile Duclaux, Par Madame Einile Duclaux (Mary Robin-
son). Laval. L. Barneoud and Cie Imprimeurs. 1906. 12mo, pp. 332.

Vlll INTRODUCTION

with him. Emile was the apple of his eye; on him was
lavished all his interest, rather to the neglect of the other
children who were allowed to play as they would while
Kmile must stick to his lessons, to become the scholar of
the family. In this respect the father was a second
James ]\lill or Etienne Pascal. ''Sometimes, Mamma,
taking pity, sent to inquire after the young recluse. The
little brothers entered the study softly and waited re-
ligiously until they were spoken to. Sometimes they
found the scrivener drawing up a legal paper, but more
often they saw him seated at the work-table of his son
explaining to him some old author. The opportune
moment come, the children clasped the knees of the
father and, while he stroked their heads with a distracted
hand, he said: 'You have come for Emile? but he can-
not go yet. Especially do not talk!' And the lesson
went on and on, until the two lads, desperate, withdrew
on tiptoe, leaving the elder to his endless task." * * * *
"Father dreamy, incommunicative; mother sensitive
and lively. Such without doubt is an excellent com-
bination for the production of a superior man. Such
at least were the parents of Louis Pasteur and such those
of Ernest Renan."

From his father he inherited a character of rare eleva-
tion, an absolute sincerity, and a spirit at once per-
spicacious and free, a little inclined to criticise, which
made him so "generous" in the sense of Descartes; but
it was from his mother, the amiable Agnes Farges, that
he inherited that overflowing goodness, the openness of
mind which he blended witli so fine a sagacity, the ban-
tering good nature, always tender so that it did not
wound. What he had of skillful and prudent in his
character came also from his mother.

The child loved his two parents equally, confided all
his thoughts to his father and drew the sweetness of life

INTRODUCTION IX

from contact with his mother. In return for a devotion
without bounds, the father exacted impUcit obedience
and the son never disobeyed him. If he felt at times the
constraint, which made of him an infant prodigy at the
expense of his liberty, he never mentioned it, but spoke
often of his father and always with tenderness and
veneration.

He entered college at Aurillac, where, in 1852, he
carried off the first prize for Spanish, as one might ex-
pect from a son whose father had wandered much in
Spain. Every evening he read some pages of Don
Quixote with his father, who was the authorized trans-
lator for the law courts. Through all his college studies
the father kept pace with him, rising at 4 or 5 o'clock in
the morning to study over Emile's college lessons. Again
in the evenings, the supper finished, the father and son
climbed up to the study, lighted the 3-wick lamp, the
antique liin, and began the evening's lessons. Once
the lessons were well learned, they read some good author
from the treasure of eld books the scrivener kept in his
little library. There were some volumes of the Magasin
Pittoresque from which Emile drew his first notions of
science, the Letters of Madame de Sevigne, the Memoirs
of Saint-Simon, the plays of Racine, a volume of travels
in Spain, a little history in two volumes of the Romans
in GauL and the like.

While he made excellent progress in his classical studies,
he was fortunate in falling under the influence of a good
teacher of mathematics and the sciences. Especially
in Balard's pupil, Emile Appert, who was at the same
time chemist, physicist and geologist, and who knew
everything and how to teach everything and turned the
boy's mind readily from the classics to science, he found
just the friend he needed.

Studies over, father and son, inseparable still, rambled

X INTRODUCTION

over woods and fields, mountains and valleys. To-
gether they discussed rural things and the old volcanic
lands. Emile collected pebbles and explained to his
father limestone and basalt, and together they read
M. Appert's summaries. The neighbors saw them pass:
the father tall, erect and stern, with energetic, wrinkled
features, the son meager and little, always holding on to
his father's arm, hitching up to be on a level, talking as
they went along. "What can they find to talk about so
much? It must be they are going to fish for crabs in
the valley of the Condamine?"

Such was the boyhood of this man. Between his
father and his dear M. Appert he early learned to love
nature and especially to look below the surface of things.

The supreme desire of the father was to see his son
enter a polytechnic school and become an engineer or an
officer of artillery. To enter a polytechnic more prepa-
ration was required than could be obtained at Aurillac.
Clermont-Ferrand and Toulouse were considered but it
was finally decided that he should go to Paris, although
it wrung the father's heart to be parted from him. Here
he studied under a certain M. Barbet, who predicted for
him a brilliant future and was always holding up to him
as a model a certain Louis Pasteur, a graduate twenty
years earlier from the same institution and the pride of the
school, who had just left the faculty of Lille to take charge
of the scientific studies of the Normal School in Paris.

For his pocket money at this time Duclaux had 50
francs a trimester. Out of this meager sum in the spring
of 1858 he took 35 francs for lessons in diction and for
drawing instruments, and for his nostalgia ordered an
English book, Scrope's Extinct Volcatioes of Central
France, which to his astonishment cost him another
30 francs and required dire economies but, in the delight
of possession, was worth much more than it cost.

INTRODUCTION XI

In 1859 Duclaux successfully passed entrance examina-
tions for both the Polytechnic School and the Normal
School, and M. Barbet had sufficient influence to cause
him to be sent to the latter.

At the age of 19, therefore, Duclaux entered the Nor-
mal School and came under the teachings of Louis
Pasteur. The father, meanwhile, had died. Each anni-
versary of the father's death the young man went to
pass with his mother in Aurillac. But another bond had
sprung up — an enthusiastic respect for the man of genius
who was now sub-director of scientific studies in the
Normal School. After Duclaux, father and son, it was
Pasteur and Duclaux. From the beginning Duclaux
ranged himself under his banner and experienced to the
depths an influence which modified his whole mind and
thought, as it was later to overturn all science. The
chemists of the Normal School of 1860 believed in Pasteur
as the romanticists of 1830 believed in Victor Hugo, and
these are the two great Gallic names of the 19th century.
Wlien Duclaux received his degree from the Normal
School in 1862 he entered the laboratory as assistant
to the master, assistant in a double sense, since the
authorities had not appointed any other assistant to
sweep up the dust or to wash the glassware. But as
Duclaux said later in his charming article on the labora-
tory of Pasteur which he contributed to the book on Le
Centenaire de VEcole norniale, "It is, moreover, a useful
apprenticeship for a young scientific man to keep things
clean. I will add, although it is perhaps a vanity to be
condemned, that I believe I have never had flasks as
meticulously cleaned as in that far off time when I
cleaned them myself."

Madame Duclaux has drawn a very pleasing picture
of him as he was at this time :

"I possess a photograph taken at this period which

Xll INTRODUCTION

shows him very young, slender and alert, with the supple
figure of a mountaineer. He is rather small, he has very
delicate members, especially his hands, which seem to
think. His manner of walking is full of a self-restrained
alacrity. His head is large with a good cranial capacity,
finely formed, bristling with dark brown hair cut close
and planted low and tufted around a perpendicular fore-
head which is ample but not high. The mask is a little
melancholy, elongated as in portraits of the sixteenth
century. In this thin visage there are fine eyes, very
blue, by turns dreamy, teasing, tender or profound but
always limpid. If the eyes suggest poetry, the long nose
stands for sagacity and goodness, although the fleshy
end trembles in moments of impatience. Fine ears,
elongated at the tip like those of a faun, give to this grave
oval head of the thinker a delicately rustic character.
Already he had the air which I loved so much, a modest,
ardent and good expression. Something of the harsh
accent of Cantal still vibrated in his voice in spite of the
lessons in diction taken at the Institution Barbet and at
the Normal School. 'Say terrrine, Duclaux,' Madame
Pasteur will often say to him, laughingly. The young
man spoke well and sometimes copiously, with charm
and spirit, but of his personal ideas he was not very com-
municative, being timid as well as independent. He
gave, however, an impression of joyousness when one
looked at him, going and coming from one piece of
apparatus to another, humming some arietta of IMozart
or the refrain of a popular song heard in the street."

At this time Pasteur worked in very cramped quarters
in the rue d'Ulm. From such quarters, hardly fit for a
rabbit hutch, as Duclaux said, started the movement
which was to revolutionize science. Here in the Nor-
mal School Duclaux was lodged, fed and received as
compensation 47 fr.-oO per month. But what arc wages

INTRODUCTION Xlll

when one can be with a master! Rauhn was his prede-
cessor, a ferocious anti-clerical. Mascart and Gernez
were also assistants in the Normal School at this time
and friends of Duclaux, especially the latter.

These were the heroic times of the Pasteurian struggle.
The master was in the forefront of the debate on crystals,
the campaign on fermentations and the great battle over
spontaneous generations.

In October, 1865, Duclaux left Paris for Tours, where
he had been appointed professor of chemistry in the sec-
ondary school. He now had the maintenance of the
family on his hands. He was the youngest professor in
the faculty of France, being only 26. From Tours he
was soon transferred to a better place at Clermont-
Ferrand, where a portion of his time could be given to
Pasteur's work. When Duclaux was seeking this trans-
fer Gernez interested himself in behalf of his friend and
was very much surprised and chagrined one day to learn
that he had himself been appointed to the place. This
appointment he would not accept nor would Duclaux,
under the circumstances, until Pasteur smoothed things
out by taking Gernez with him to Alais, which left
Duclaux free to accept the position at Clermont-Ferrand,
a fine old city, former capital of Auvergne and the birth-
place of Blaise Pascal.

At Clermont he had about a hundred students, mostly
medical students. The pick of these he admitted to
his own laboratory and initiated into the experimental
method. Sundays he went with these choice spirits on
long excursions through the volcanic lands. His most
distinguished pupil was Emile Roux, the present director
of the Pasteur Institute, who says, "During these hours
of life in the open air Duclaux was the most delightful
of companions, overflowing with a deep spontaneous
gaiety. The day ended around the hospitable table of

XIV INTRODUCTION

Mamma Duclaux in the apartment in the rue Alontlosier.
It was truly good fortune for a beginner in science to
meet a master Hke Duclaux." In connection with Roux,
as beginner in chemistry, we have the following story.
Duclaux had given out a pinch of some salt for analysis.
"What is it, my friend?" and the test made, the young
man replied, ''Sir, I think it is sulfate of copper." ''Ah,
you think so? Truly? Eh, well, do it over again."
At the end of some hours, the pupil returns, "Sir, I
believe it is sulfate of copper." "Begin again, my
friend." But the third time he returns with indignation
in his eyes and voice a little vibrant as he says: "Sir,
it is sulfate of copper." "So it is, my friend, but you
see in chemistry it is necessary to know, not merely to
believe or to think."

From Clermont-Ferrand, Duclaux went to Lyons,
where he remained five years as professor of physics, and
then to Paris (1878) as professor of meteorology in the
Agronomic Institute. Through all of these changes it
was bio-chemistry which held the first place in his ajffec-
tions, but he was geologist, physicist, meteorologist,
agronomist, and chemist, as well as learned in medicine,
in brewing and in the dairy industries. He loved to
contemplate one aspect of the universe as well as another.
To his friend M. Voigt he writes at this time from one
of his summer vacations in Fau. "I like the sohtude
where I Hve so well that I imagine it ought to have as
much charm for my friends. I find myself particularly
happy in the country. Free labor and not at all pressing,
an independent life, very few books, almost no journals,
see how I regain possession of myself."

At another time he wrote: "I am strongly attached
to the soil. I communicate with it. I think how many
generations of my fathers have hved in contact with it
and I take pleasure in asking it about them. I never

INTRODUCTION XV

come across a wall of big dry stones, a retaining wall
made to gain a few inches of earth, an irrigation ditch,
an old tree sensing decrepitude, a big rock in a field,
without thinking of all those who have builded and
planted and dug, or grumbled at having to pass around
the rock they could not remove. With such ideas and
impressions, there is no solitude. I live in communion
with my own, and with this soil, on which they have
left the powerful impression of their feeble intelligences,
and their vigorous arms."

At Paris he displayed incredible activity — mornings
and evenings at his work-table and the rest of the day
either at the Agronomic Institute or at the Sorbonne
(Roux). These were sad years and labor was an opiate.
He overworked and suffered from insomnia and for two
years from boils. During this time he wrote ''Ferments
et Maladies" (1882) which he dedicated to his wife who
had died of puerperal fever. ''To you, innocent victim
of the infinitely httle, I dedicate this book in which I
have attempted to popularize their history. May it,
sHght as it is, serve to hasten a httle the day wherein
the accomphshment of her sacred mission will no longer
cause the wife to fail her husband, and the mother the
new-born child." The book made a sensation and a
gold medal was struck for it by the Society of Agricul-
ture; also a number of medical men were won over to a
belief in microbes.

Duclaux loved to ripen a project for a long time in his
mind and to work it over and over on paper before
finally putting it into type, which is the secret of all
good expression. This was Tennyson's method and
Renan's. It was Beethoven's way in music. It is also
the method of Anatole France.

In 1882, apropos of "Ferments et maladies'' which had
just appeared, he wrote to his friend, M. Voigt, ''You
2

XVI INTRODUCTION

are very amiable to say so many good things about my
book * * * but physicians are those I would wish to
lay hold of and I begin to believe that I shall not suc-
ceed! I know very well that old physicians do not read
any more, and when they do read do not understand. I
know that students think only of their examinations,
when they think at all; but among the population of
hospital internes or externes and that of physicians who
have not yet obtained a clientele, I thought I should
find attentive readers possessed of good will. Experience
begins to demonstrate that I shall not have them."
Again he writes: ''When I read one of those byzantine
discussions of the Academy of IVIedicine always I ask
myself whether the speakers do not wish to understand
or simply cannot understand." In 1885 his book "Le
Microbe et la Maladie^' was completed and was published
the following year. This year he writes, ''My dear friend,
jMedicine is a strange terrain. It is an edifice where
nothing remains standing. Tradition still maintains
the plan and general arrangement, but it would be best
that everything should come down, because there is no
good to be derived from what exists except from the
materials. If I were a physician I believe I should give
the mattock blow which would make all crumble. Since
my manuscript is finished I have become more intimately
aware of the fragility of medical notions even those in
appearance best founded. Who knows? Perhaps a
section of wall will blow up somewhere and a little light
penetrate through the opening thus made."

From 1877 to 1896 Duclaux's time was largely de-
voted to a profound study of milk and dairy products.
These studies led him to attribute a preponderating role
to microbes in all the industries based upon milk. His
work in Cantal led to a revolution in cheesemaking and
to a great extension of the industry, due to tlie better

INTRODUCTION XVll

keeping qualities of the properly made cheeses. ''The
work of Duclaux inaugurated the scientific era in the
dairy industry" (Dr. Roux). In recognition of the im-
portance of these researches the Agricultural Society
awarded him its great gold medal in 1881.

Duclaux was also the first to gather together and
coordinate the scattered facts on the enzymes. This he
did in 1877 for Dr. Dechambre's " Dictionnaire des
sciences medicales.^' Some pages sufficed at this time,
but in 1899 when he took up the subject again for the
second volume of his "Traite," seven hundred and fifty
pages were insufficient. ''He returned to this subject
many times, showing how the same microscopic organism
secretes different enzymes, according to the food that is
given it. He classed the enzymes by the reactions
they cause and proposed the terminology^ adopted
to-day" (Dr. Roux).

He also devoted much time to the purity of w^ater
supplies and to analyzing, especially during vacations in
the latter part of his life, the water of springs issuing
from the volcanic lands, and said that he could tell
whether the water had percolated over limestone or
basalt.

Also toward the close of his life he became greatly
interested in community welfare, attended conferences,
presided at meetings, made addresses, and wrote the
charming book "L'hygiene sociale.'"

In 1888 when the Pasteur Institute was founded the
workers in the rue d'Ulm had only to transport their
microscopes and their balances to rue Dutot, but there
was need of someone not to make discoveries, all could
do that, but to disseminate them and to formulate a body
of doctrines. Duclaux was selected for this purpose. The
other colleagues of this time were Chamberland, Roux,
Nocard; Perdrix, assistant professor; Loir and Fernbach,

XVlll INTRODUCTION

assistants; Grancher, Chant emesse, and Charrin, physi-
cians in charge of the antirabic inoculations; and Eugene
Viala, devoted assistant in the rabies service. Also a
little later Metchnikoff and Yersen formed part of the
staff, but Strauss had gone earlier to a chair in the Med-
ical School. Pasteur was now 66, and the sole shadow
on the picture was the ill health of the master. If
Pasteur had not been weakened by his second attack of
paralysis in 1887, the new Institute might have been
very different from what it is to-day, namely, a great
cooperative research institution drawing the brightest
minds from all parts of France and all quarters of the
globe. It might have been greater, at first, but on the
death of the master all would have crumbled. Its pres-
ent form, so cohesive while at the same time so well
adapted to maintain the independence of the workers^
corresponds rather to the ideas of the collaborators than
to those of Pasteur and is due largely to the administra-
tive genius of Duclaux on whom fell nearly the whole
burden of the organization. Duclaux wished to make it
an immense college of international biology, whereas
Pasteur's idea was rather to make it a place where he
would work behind closed doors with rare and devoted
assistants, not explaining too fully the reason for his
demands but being, like an Indian god, one head with
many hands. Our good English poet has said :

"The old order changeth, yielding place to new

And God fulfils himself in numj- ways,

Lest one good custom should corrupt the world."

So it was to be here. The old master, the founder, was
not always in perfect accord with his friend. Duclaux
wished to open all the doors, call the faithful from all
corners of the earth, work in a large way, found a scien-
tific college for the future, where each one would be free

INTEODUCTION XIX

while laboring in a common cause. The professor and
the social apostle dominated in him. Pasteur was
especially a discoverer. Original, profound and slow,
he was made to walk alone. He said "we must seek."
His disciple added "we must organize and convince."
Roux understood both points of view, went from one to
the other, and effected a reconciliation, for each one
maintained his own ideas only in the interest of the
foundation. And so the years passed on, each year
giving more and more into Duclaux's shaping hand, until
the Institute became such as we see it to-day.

"To this great foundation Pasteur bequeathed a sci-
entific tradition but it was Duclaux who created its soul"
(Bloch).i

One of Duclaux's first efforts, begun even before the
Institute was opened, was the founding of a journal
which should be a worthy exponent of the new ideas.
Thus came into being in 1887 ^^Les Annales cle VInstitut
Pasteur,^' which has done so much for the advancement
of human and comparative pathology, and to which
Duclaux devoted all of his energy and ability. In this
journal, the first volume of which was organized around
the doctrine of immunity, he realized an old dream of
Raulin, his comrade of other days.

In many ways Duclaux's interests deepened and diver-
sified in these years. In 1888 he became a member of
the Academy of Sciences, in the section of rural economy.
In 1890 he entered the National Society of Agriculture.
In 1894 he was elected a free member of the Academy of
Medicine. And always there were his Annales.

"My journal (1892) gives me twice as much work since it threatens
to become twice as large as at the beginning. I have two laboratories
to conduct with two categories of students. In short I am driven:
0 rus quando tc aspiciam! "

^ Annuaire de I'Association des anciens eleves de I'Ecole Normale.

XX INTRODUCTION

Pasteur died September 28, 1895, and the Council of
the Institute elected Duclaux to be his successor. Noth-
ing less resembled the dreamy, intuitive nature of Pas-
teur, turn by turn combative and silent, than the modest,
passionate, devoted soul of his apostle. They were equal
only in a generous ardor of soul and in the patient tenac-
ity which both gave to the service of science. Never-
theless, it was Duclaux of all the Pasteurians, who
possessed most fully the entire tradition of the master,
since he had been more or less closely associated with him
and familiar with his ideas since 1858.

Nothing was more natural therefore than that he
should write a book on Pasteur. Even before the Insti-
tute was thought of, Duclaux wished to erect in his own
way another monument to the memory of his master.
For he realized how fragile is life and that already man}^
things had ceased to exist except in his memory. There-
fore, he wrote this book: "Pasteur: Histoire d'un Esprit."
In it the Pasteurian discoveries unfold in their harmo-
nious development with, perhaps, a little more amplitude
and coherence, a little less originality and vivid pro-
fundity than in the reality. He who has read this book
will understand the reach of the greatest scientific move-
ment in the nineteenth century, and at the same time will
appreciate how slowly the truth unfolds and how often
genius itself loses the thread of the labyrinth in traversing
it for the first time. Now that we have made of this
daedalus one of the boulevards of the modern mind, it
is good to recall what obstacles and what errors then
rendered it almost impracticable. The one who knew
best the founder of microbiology has written of the book
as follows: ''After having read this analysis of his work,
we understand Pasteur better, and find him greater still"
(Dr. Roux). We understand better both Pasteur and
Duclaux. Pasteur followed his idea as the magi their

INTRODUCTION XXI

star. "He was a priest; priest of the idea," said his
successor. In him, instinct or rather bold intuition,
dominated reason. "Therefore," says Duclaux, '-he saw
with a new vision and justly." His disdain for tradi-
tional knowledge and philosophical speculations was
scarcely concealed. Trusting only in experiments, he
knew how to outstrip them and more than once went far
beyond them. "That which puts him outside of com-
parison is the fact that he loved great horizons, knew
how to discover them and to make himself a part of
them; that he saw at a distance and through the mists,
more clearly than anyone else, the high summit he must
attain to dominate the unknown and promised land.
This was his rare gift and the secret of his power. But
once seen he had wings to reach it, no more than we.
One might believe, considering the originality, the sim-
plicity and the unexpected in his solutions, that they were
spontaneous and in the nature of happy discoveries. I
do not know whether there ever are any such easy dis-
coveries, accomplished without effort and by a sort of
divination. Such surely was not the case with Pasteur's.
If he was a discoverer it was first of all because he was a
silent man and an obstinate one.""^

Duclaux's spirit was patient and methodical but much
less concentrated than Pasteur's. He discovered rela-
tively little, but he excelled in understanding, observing
and comparing. Without pride, he loved obscure labor
— the only means that permits a great soul, unknown of
the multitude, to enjoy liberty and to enter into the de-
lights of meditation. There was something of Mon-
taigne in the vast and varied intelligence of Duclaux.
It made no difference to him whether a doctrine or a
theory was true, if it incited to labor and led to the
discovery of new facts. He made use of criticism and

1 Duclaux. Discours aux etudiants de Paris. 18 juiii. 1896.

XXll INTRODUCTION

hypothesis to interest and to arouse, as an electric cur-
rent to stimulate the too often inert substance of the
human brain. He said: Je voudrais voir tout marcher
autour de moi du mane train que moi. In his "Discours
aux etudiants^^ he has expressed himself also as follows:

"The free disinterested search for truth is useful, in
and of itself, from the delight it brings to the one who
follows it, from the independence of spirit it begets, from
the deep sentiment it develops of liberty and of respon-
sibility. I dare maintain even for this inner work that
it has no need of looking to or obtaining the suffrages of
other men. It is sufficient that we have the conscious-
ness of being in our place and of doing our duty honestly.
'Live,' said Pasteur, 'in the serene peace of the labora-
tories and the libraries.' I am sure of remaining faithful
to his thought in adding: You will not always find glory
there, you will never find fortune there, but you will
experience there the dehght of every day being something
more than the day before, and of having brought into
the world your share of the truth."

"Do not take my word for things but be enamored of
independence," he said. "The fruitful periods of science
are those in which dogmas are taken."

"You esteem me too highly," he writes. "There are
a hundred thousand Frenchmen who are as important as
I am. I differ from them only in that I have been helped
more by science. We must distinguish between those
who have rare qualities and those who march in the
ranks with cominon f[ualities, made productive by will
and labor."

The national instruction, he said, refiecting on the war
of 1870, is not only insufficient but false. Based on
rhetoric and on classical studies, it ornaments the mind,
but does not strengthen it much; rather we may say it
weakens it, since it instills the principle of authority,

INTRODUCTION XXlll

and makes all rest on the example of others, whereas
youth should be accustomed to see, to scrutinize, and to
feel for itself, aided to draw much from its own deeps,
and set in quest not of elegance, not of poetry, but of truth.
A method of teaching founded on science, preaching ex-
amination and research, not recoiling from the minutise
of analysis; seeking in all things to know the causes
and the consequences, leaving nothing to chance, culti-
vating in its proteges prudence and initiative, such a
teaching he thought would give to France a new existence.

"I have tried on the children the effect of abstract
reasonings (1886). Alas, they do not comprehend them,
and, if other children resemble them, the teaching of the
exact sciences in the lower grades is very chimerical.
They want the concrete, always the concrete."

He addressed himself to their understanding and their
conscience more often than to their memory. ''In an
old volume of Montaigne at Olmet I found the two
fine chapters on 4 'Institution des Enf ants' full of penciled
markings. Such an education, free, strong and healthy,
seemed to him well adapted to furnish those two solid
foundations of character — independence and sincerity.
But to this ideal of jMontaigne he added what had been
the ruling principle of his own existence; forgetfulness
of self and the capacity of devoting himself to a high
end. To be a free man; to look in all things beyond
selfish interests; to love the truth and to speak it; to
act conformably to what seems just; to be mutually
helpful. These, unless I am deceived, were his five
commandments. ' '

His ideas on many subjects are full of interest: "It
is precisely because science is never sure of anything
that it always advances."

"For the idea of specificity, still dominant ten years
ago when I wrote the first edition of my " Traite de Micro-

XXIV INTRODUCTION

biologie" has been substituted another, which is de-
veloped in my present book, that of cellular toleration."

"Besides, how is it possible not to see that the immense
edifice on which we all labor changes constantly in plan
and in foundations. We have lovingly hewn, dressed
and even sculptured our stone, with the thought that
it will remain perhaps a stone of the facade, and attract
the attention of visitors. Vain hope, new tiers of ma-
sonry will cover it and cause it to be forgotten. It mat-
ters not! It exists, and, if we have chosen it wisely
and built it solidly, it will serve as the foundation of new
discoveries" (Discours aux etudiants).

Apropos of the Dreyfus affair, in which he sided with
Dreyfus, took pubUc action and suffered correspondingl}^,
he writes :

"We also have rules, which have descended to us from
Bacon and Descartes — not to lose our heads, not to put
ourselves in a cave in order to see better, to believe that
probabilities do not count, that a hundred perhapses are
not worth a single certainty. Then, when we have sought
and believe that we have found the decisive proof, even
when we have succeeded in making it accepted, we
are resigned in advance to see it become invalidated
by a process of revision over which often we ourselves
preside."

"In all this we are very far from the Dreyfus affair;
and truly we have a right to ask if the State does not
waste its money on educational establishments, the pub-
lic spirit is so far from scientific." * * *

"If Dreyfus is on Devil's Island, it is only because
the Government has listened to the cries of the mob and
joined the majority instead of listening to the minority,
alone capable of imposing silence on the human brute."

"It has a tragic grandeur. Can you think of a like
drama, played by a nation, with that freedom of the

INTRODUCTION XXV

press which allows the whole people to take part in the
drama? It is two tragic choruses berating each other.
And the scene is France, and the theater, the world."

''The minister was long and diffuse. It is incredible
how much this cursed French language allows one to
speak without saying anything. There are a certain
number of words which straightway show the intellectual
poverty of those who use them. Ten times yesterday
[at the unveiling in Lille of a monument to Pasteur] the
rigid logic of Pasteur was mentioned. But, good people!
logic is a proof of mediocrity, and savants who have only
logic are not scientific men!"

"Nature loves diversity, education aims at repressing
it. Those who later break through into life, show origi-
nality and make a name for themselves, are recruited
chiefly from those who have escaped the sterilizing
influences of the first years."

"Toute douleur est bonne si elle sert a nous agrandir
Tame."

"On pent rever une humanite superieure a celle qui
s'incarne temporairement en nous."

"Soyons chacun soi-meme, soyons different mais
soyonsunis."

"Ce que la cellule vivante faisait, sans conviction ni
libre arbitre, il etait digne de I'homme de le faire, dans
Tinteret commun."

"There is no end to science. So long as there shall
be men, there will be savants, and so long as there shall
be savants there will be discoveries. Gradually the
spirit of men of science has been enlarged and has become
open to the idea that the world is immense, that the
forces which circulate in it are also immense in number,
that those of which we are ignorant considerably exceed
those we know. We are sure, from certain examples,
that there are circulating around us incessantly count-

XXVI INTRODUCTION

less forces of which we are ignorant^ and will remain
ignorant for a long time, things with which other beings
than ourselves may be perfectly familiar; for it is here
that we find that imperfection of our senses which does
not allow us to draw conclusions from ourselves as to
other beings which surround us.

''Do not defend yourself against faith and confidence.
Life would be an immense dupery, the world in the midst
of which we exist would be a colossal absurdity, if the
earth were the only abiding place and if what is best in
us and among us, should be lost in universal nothingness.
The heavens teach not only the glory of God, they teach
also hope to all those who are worthy of hope."

Madame Duclaux closes her account of Duclaux with
these words in which many ' f us will concur: "L'dme
la plus 77iodeste, la plui desinteressee, et une des plus justes
dece temps."

The following translation, which I have made from the
eulogy on Duclaux, published in the Annales de l' Insti-
tute Pasteur for Alay, 1904, and written, it is said, by
Dr. Roux, his former student and his successor as director
of the Pasteur Institute, will serve as a fitting close to
this introduction:

"Once more the Pasteur Institute is in mourning. The
third of this month died Emile Duclaux, the director of
this Institute, the founder of these Annates.

"In less than a year, Nocard and Duclaux have been
taken from us !

''All those who have frequented the Pasteur Institute

' How right he was must now 1)0 ai)pari'iit to every one. Since these
thoufrhts were expressed in liHIl lias come most of our knowledge of the
radio-active substances — uranium, ionium, radium, actinium, thorium
and their emanations — ami all of those revolutionary ideas on the nature
of electricity, the structure of matter and the constitution of the universe,
which now fill the minds of scientific men with awe and wonder.

INTRODUCTION XXVII

will understand our deep sorrow, for they know the sen-
timents which united the workers of this institution to
its director. They were the sentiments of confidence,
respect and affection which a true chief inspires.

"After Pasteur, no one knew better than Duclaux how
to direct this Institute, where are gathered together
young scientific men whose independence he knew how
to respect while directing their efforts toward a common
end. His authority was beloved, for it proceeded, not
from his position but from the qualities of his mind and
his heart. One went to him when he felt lost in the ob-
scurities of a scientific research, one went to him also
when he felt oppressed by the miseries of life. Confi-
dence was born from the beginning, so cordial was his
welcome, so much the luminous glance of his merry blue
eye expressed goodness. Duclaux soon learned what you
expected of him; his clear intelligence overcame the ob-
stacle which arrested you and his good heart always
found wherewith to comfort you. He never lost an
occasion to be obliging. On leaving him one always
felt stronger for scientific struggles as well as for moral
struggles.

"The conversation of Duclaux, simple, full of imagery,
full of original ideas, was charming; it was moreover
beneficent, because it allowed a character of rare beauty
to show through. Thus, this man so jealous of his inde-
pendence, so respectful of that of others, became, with-
out suspecting it, a director of consciences. None of us,
disciples or friends, would have had a tranquil spirit if
Duclaux had disapproved any of his actions.

"Duclaux owed this influence to the fact that his acts
were worth even more than his words. When he be-
lieved a thing just, nothing would have prevented him
from undertaking it. He went ahead without blowing
a trumpet, without considering the prejudices that would

XXVlll INTRODUCTION

be overturned any more than the blows that would be
received. He was one of those rare men who support a
cause, not for the advantages they expect to receive, but
simply because they beheve it is just. Duclaux sup-
ported those which he had adopted with the tenacity of
his Auvergnaise blood and also with a force of thought
and clarity, and a generous joyousness which rendered
his faith contagious. As to attacks against himself, he
bore them with an imperturbable serenity; this scientific
man with a slender body and frail members possessed
true courage, and he possessed it to the degree of giving
it to others in tragic moments.

''Goodness and the disinterested worship of justice and
of truth w^ere the rules of his private life as they were of
his scientific life. It was a delight to him to find in a
memoir new facts and well-conducted experiments. If
the pubhcation was that of a young man his joy was com-
plete. He showed this in his articles in the Annates,
which were marvels of exposition and of criticism. So
much so, that the author often found in the analyses of
Duclaux more than he had himself put into the original.

''In order to make the labors of a beginner useful,
Duclaux did not hesitate before the disagreeable task
of retouching the manuscript, pruning it, sometimes
even rewriting it, in order that the interesting point
might stand forth clearly, which point was not always
that one which the author had believed.

"His penetrating and just criticisms, with an original
and piciuant turn, never wounded; they guided into the
right pathway and kept from vanity.

"Correspondents from all countries sought the advice
of Duclaux and he passed a good part of his time in inter-
course with them. He excelled in discovering young
talents and in giving to them a knowledge of themselves.
He was truly a midwife of minds for he knew how to

INTRODUCTION XXIX

bring into the light of day that which was good in the
most confused conceptions.

"Duclaux was, above all things, an independent. He
esteemed scientific doctrines according to their fecundity
without believing them final and thought usually that
the fruitful periods of science are those wherein dogmas
are shaken. His knowledge was truly encyclopaedic;
Duclaux had studied to the bottom the mathematical and
physical sciences and was quick to understand all the
others. Thus he was capable of writing a book like his
Traite de Microbiologie, and of treating with competence
subjects pertaining to physics and to medicine. The
readers of these Annales have had the proof many times
in the critical reviews where he developed a question
with remarkable precision and ease. I need not recall
to them the qualities of Duclaux the WTiter. No scien-
tific man of his time has written better than he, no one
has better employed his talent.

"Duclaux was an incomparable professor. His facility
of speech never served to mask the difficulties of a sub-
ject; he went to the bottom of things without fatiguing
the attention, because with him everything became easy
to understand. His lectures have determined more than
one vocation and provoked numerous investigations.
He sow^ed ideas and rejoiced to see them germinate in the
fields of others.

''The regrets inspired by the loss of such a man will be
extinguished only with those who have know^n him.
But the esteem and the admiration for Duclaux will be
durable, for his works will be there to attest that he was a
scientific man of the first order and, what is much more
rare, a noble character."

I have ventured to add to the book a few footnotes
indicating progress in certain fields of research, an index,

XXX INTRODUCTION

an annotated list of persons mentioned, a portrait of
Pasteur made from a bronze in my possession, several
from middle-period photographs and one from a photo-
graph taken in his old age. To these I have added two
portraits of Duclaux, one from a photograph made a
year or two after he became director of the Pasteur
Institute (about 1897), the other from an admirable oil
painting made by Ernest Bordes in the last year of his
life and purchased by the French Government for the
Pasteur Institute, both through the courtesy of IMadame
Duclaux. For a third portrait of Duclaux the reader
may consult the Frontispiece in ^^ Bacteria in Relation to
Plant Diseases," Vol. I, Carnegie Institution of Washing-
ton, 1905, where also may be found another portrait
of Pasteur and one of Roux.

The greatest progress of bacteriology since this book
was written has been in the field that would have inter-
ested Pasteur most, namely, in that of immunology,
which now has its own text-books and journals. Read
in the light of the new knowledge, the Eighth Part of
this book seems very ancient history although it well
expresses the current ideas of twenty years ago and will
always serve as an important landmark.

E. F. S.

KMILE DICLAUX

(From a painting made during tlie last year of his life, by Ernest

Hordes.)

AUTHOR'S PREFACE

On opening this volume someone will say: "How is it
possible to make the history of a mind? One could
write an exact history of a man: he has spoken, he has
written, he has done things; we know where to lay hold
of him, and can follow him and judge him. But a mind,
especially that of a scientific man, is a bird on the wing;
we see it only when it alights, or when it takes flight.
When it is the mind of a genius, like Pasteur, the diffi-
culty seems almost insoluble. We may, by watching
closely, keep it in view, and point out just where it
touches the earth. But why does it alight here and not
there? Why has it taken this direction and not that
in its flight toward new discoveries? If it were possible
for you to know this and tell us, Pasteur would no longer
be a genius, escaping analysis; and if you do not tell us,
you will merely draw up a report, not write a history."

All this is true, and nevertheless I have written this
book. I have done so for two reasons: the first is that
Pasteur was not a savant like the others. His scientific
life had an admirable unity; it was the logical and har-
monious development of one and the same thought. Of
course he did not know when he made his first studies in
crystallography that he would end by discovering a
means of preventing rabies. But neither did Chris-
topher Columbus know when he set forth, that he would
discover America. He only divined that by going always
in the same direction he would find something new. So
with Pasteur. From the beginning of his studies he had
before him a problem of life, and, having found the road
to it, from that time he always traveled in the same di-
rection, consulting the same compass. Without doubt

xxxi

3

xxxii author's preface

he has traversed many different countries leaving foot-
prints, but he did not intend to explore them; they were
merely along his pathway and the grandeur of his dis-
coveries makes it possible for the history of his mind,
even though reduced to a report, to clothe these adven-
tures with all the air of a romance.

My second reason is that in its details this scientific
life is no less interesting than in its ensemble. As one
may readily conceive, Pasteur encountered many diffi-
culties and many obstacles. These obstacles we recog-
nize more clearly as such, now that they have been
surmounted and we see them behind us. It is interesting
to see how Pasteur outflanked or evaded them. He
employed for that purpose qualities of the first order.
At the same time audacious and prudent, deceiving
himself sometimes even for a long period but being
brought back constantly to the true path by that ex-
acting experimental method of which he has so often
spoken gratefully, he is always worthy of admiration
and worthy also to serve as an example. It is less for
the purpose of making an eulogy than for purposes of
instruction that I have attempted to write his history,
in which I set aside all that relates to the man, that I
may speak only of the savant. I have desired, in the
ensemble as well as in the particulars, to give the genesis
of his discoveries, believing that he has nothing to lose
by this analysis, and that we have much to gain. But
I found the task difficult. It is now for the skeptical
reader to say whether I have succeeded.

PASTEUR:
THE HISTORY OF A MIND

PASTEUR
(At Thii'fy.)

i

PASTEUR:

THE HISTORY OF A MIND

FIRST PART
Works on Crystallography

THE PREDECESSORS OF PASTEUR: HAUY, WEISS,

DELAFOSSE

If we wish to take exact account of the progress
brought about in science by the different studies of Pas-
teur, the first thing to do is to become acquainted with
the state of our knowledge up to the time when each one
of these studies advanced it. In order to understand
clearly the progress they have made, we must know from
what they started. But that is not as easy as we might
think. To get an idea of the general intellectual status
of any period one must not content himself with reading
the classical books and manuals of the epoch: these
books are always behind the knowledge of the labora-
tories, that which is in the air, that which one breathes,
and which arouses investigators. We encounter another
danger in resorting to sources and original memoirs;
viz., the danger of taking the opinions and ideas of their
authors for current opinions and ideas. A scientific
man worthy of the name is always in advance of his con-
temporaries: between him and them is a middle zone in
which one must take his stand in order to judge the under-
takings and the progress of a period; but where is one to

find this middle ground, and how, when he has found it,

1

2 PASTEUR: THE HISTORY OF A MIND

is he to see justly, that is to say, to judge with the judg-
ment of that time? How abstract oneself from what has
been learned since, and take on again the necessary
ignorance?

Nevertheless, I shall attempt to do this throughout
this volume; but, as it is easy to understand, the greatest
difficulties are at the beginning. Familiar as we are
to-day with the theories of molecular structure, we have
some difficulty in picturing to ourselves the chaotic
condition of these ideas among the scientific men of 1840.

They had a knowledge of the chemical molecule.
They knew it is formed by a grouping of generally quite
stable atoms, the number, weight and nature of which
are ordinarily very well defined. They knew, for ex-
ample, that there is one atom of chlorine and one of
sodium in marine salt, while in calcium carbonate there
is one atom of calcium, one atom of carbon, and three
atoms of oxygen. They had recognized that the different
compound molecules differentiated themselves ordinarily
by the number and nature of the atoms composing them;
that there are, nevertheless, some which contain the same
number of the same atoms without being identical, from
which one was led to suppose that they were arranged
somewhat differently. But in what did these arrange-
ments consist? How do the atoms dispose themselves
in relation to each other in a molecule? What is the
resultant form for this molecule? These were questions
on which no one had clear ideas.

Crystallography had given no answer, contrary to
what we might believe to-day, after the teachings which
this science has furnished us. It held to Hauy's narrow
and geometrical conception of the integral crystal mole-
cule. We know that he called by this name the little
soUd, the juxtaposition and superposition of which in an
infinite number resulted in the formation of the crystal.

THE PREDECESSORS OF PASTEUR

By breaking a cubic crystal of marine salt we reduce it
to many little cubes which, pulverized in their turn,
would bring us, if it were possible to push the division
far enough, to the integral molecule, which also we may
suppose to be a cube. By superposing, or placing in
juxtaposition a sufficiently large number of these invisi-
ble cubes we can form a cubic crystal of any volume
whatever, and this example suffices very well to repre-
sent to us the integral molecule of Haiiy. But, in the
mind of this savant, these integral molecules of the
crystal bore no necessary relation to the chemical mole-
cule. In order to make an integral molecule of marine
salt it sufficed that eight chemical molecules, each formed

?^^=^

c^

-o-

Fig. 1.

-Diagrams illustrating primitive conceptions of the distribution of
molecules in crystals.

of one atom of chlorine and one of sodium, should group
themselves into the form of a cube. What these chem-
ical molecules, themselves, might be, spheres (as repre-
sented in Fig. 1), cubes, tetrahedrons, etc., was a matter
of entire indifference; their form had nothing to do with
it; it was their grouping alone that determined the form
of the integral molecule of the crystal and, consequently,
that of the crj^stal itself.

This grouping, according to Haiiy, was determined by
the particular nature of the chemical molecule and
could only occur among molecules which were similar
and completely identical. The geometrical regularity
was evidence of the physical and chemical regularity.
The discovery of facts relating to isomorphism came

4 PASTEUR : THE HISTORY OF A MIND

shortly to change ideas on this point. By showing that
without changing the form of a crystal of calcium car-
bonate, Iceland spar for example, it was possible to re-
place as large a number as one wished of atoms of
calcium by an equal number of atoms of magnesium,
Mitscherlich introduced, in a form still vague, a struc-
tural conception of the crystal entirely different from
that of Haiiy. If atoms of calcium and magnesium can,
without any change of form, be substituted one for the
other in a crystal, it is because they are of the same form,
or what amounts to the same thing, because they act
at a distance in the same way. Thus the geometrj^ of
the integral molecule was abandoned to approach the
geometry of the chemical molecule, and one could say
that calcium, magnesium, iron, manganese, and zinc,
which give carbonates crystallizing in the same form as
Iceland spar, have atoms of the same form, while barium
and strontium, which give entirely different carbonates,
not isomorphic with the first, have atoms of another form.
As in the molecules of the carbonates of calcium, of iron,
of magnesium, of manganese and of zinc everything is
identical (except the metals, whose atoms are of the same
form), it was assumed that the chemical molecules
of these different bodies are also of the same form, and
by conceiving that the integral molecules of the different
crystals are also of the same form, the conclusion was
reached that between the crystalline form of any sub-
stance whatsoever and the constitution of its chemical
molecule a relation existed which, though still vague, was
most certainly much closer than the theory of Haiiy
assumed it to be.

Clearly not all of these deductions were based on solid
foundations, and one could almost as well have explained
these new facts on the doctrine of Haiiy by admitting
that the chemical molecules of different forms could

THE PREDECESSORS OF PASTEUR 5

balance themselves at the eight angles of a cube, and that
a molecule of carbonate of iron could displace without
disturbance at one of these angles a molecule of calcium
carbonate of an entirely different configuration. But
a new theory in order to be useful and fruitful does not
need to have a solid foundation. It is enough that it
should be sufficiently well founded to give a new point
of view, one which allows the investigator to see things
the other way around, and it even happens that some
inexact theories may claim an active part in progress.
The progress which the very original researches of
Mitscherlich brought about was incontestable.

Some years later, M. Delafosse, a pupil of Haiiy,
studying another phenomenon than isomorphism, that
of the hemihedron, advanced a step farther. The
beautiful geometrical laws stated by Haiiy were some-
times found lacking. They required, for example, that,
since the eight angles of a cube are identical from a
physical point of view, every natural modification which
acts on the one should also act on the other, for why
should there be any choice? If one of them is inter-
sected by a plane and is truncated, this truncation, what-
ever it is, must be repeated eight times. But it some-
times happens that only four of the angles of a cube bear
planes, and these are placed in such a way that no two
of them are ever at the extremities of the same edge of
the cube. The ensemble of these four faces prolonged in
the imagination form a tetrahedron. This is the case
with boracite which crystallizes in the cubic system.
Quartz likewise forms hexagonal prisms (Fig. 1) and the
twelve angles at its two bases are physically identical.
Nevertheless, it often happens that only six of these
angles, situated for example alternately above and below
the lateral edges, are intersected by facets which, joined
together, would forui a rhombohedron with six faces.

6 PASTEUR: THE HISTORY OF A MIXD

One finds analogous facts in the other systems of crystals.
Whence come these apparent exceptions to that regular-
ity which, really without knowing just why, we attribute
to the laws of nature?

Haiiy was very familiar with these phenomena of the
hemihedron and if he did not attribute to them any
great importance it is because his theory led him to
a somewhat distorted view of them, as I have just said.
According to his conception the form of the integral
molecule was, first of all, that which cleavage, the natural
division of the crystal, gave to it. A cubical crystal of
marine salt produces cubes by cleavage; a rhombohedral
crystal of Iceland spar gives in the same way rhombo-
hedrons. The rhombohedron was, therefore, for Haiiy
a primitive form. When we intersect the six lateral
angles by planes having the same angle of inclination
to the faces of the rhombohedron, we obtain by a
perfectly regular process of derivation, the hexagonal
prism of quartz. And so for the other cases. This
conception formed a logical and coherent whole, but left
Haiiy indifferent to the questions of the hemihedron.

In order to imderstand the hemihedral character
of the rhombohedron, it is necessary to reverse the
order and take the hexagonal prism as the primitive
form. Then the rhombohedron can be derived from
it only by way of the hemihedron. The same is true
in the other systems. Weiss, the mineralogist, did
this and straightway the hemihedron appeared to
be a phenomenon more frequent than was supposed,
and there arose a problem requiring solution. Why
this deviation from the law of symmetry?

This is what Delafosse tried to explain in 1840,
by the aid of a deceptive hypothesis which to-day
seems very childish. **In the prismatic quartz," he
said, ''the hemihedral constitution exists without being

BIOT AND J. HERSCHEL 7

visible externally, since this prism can be derived from
a rhombohedron. Some rhombohedrons may, very
easily, pile themselves up in such a way that they
form a hexagonal prism. In the same way some tetra-
hedrons may so adjust themselves as to give a cube.
Therefore, if we admit that the crystalline net-work
of prismatic quartz is formed of rhombohedral mole-
cules, as boracite is formed of tetrahedral crystals,
all difficulty vanishes between Weiss and Haiiy: the
molecular polyhedron will express the dissymmetry
by its form, but this dissymmetry will not necessarily
appear in the external aspect of the crystal."

This solution of the difficulty is, I repeat it, very
infantile. It is a pure invention and Delafosse did
nothing to give it a firmer foundation; nevertheless it made
for progress, by virtue of that which I have just pointed
out, for it introduced into the mind this idea that the
form of the integral molecule of the crystal is not as
closely bound up as Haiiy thought with the form of
the crystal itself. We shall soon see the influence
of this conception upon Pasteur, the pupil of Delafosse,
and, like him, passionately fond of questions of molecu-
lar structure.

II

BIOT AND J. HERSCHEL

The general law, just now stated, that a science pro-
gresses above all by changing its point of view, explains
the aid which it always derives from kindred sciences;
and it is especially because young minds search most
eagerly and are more open to these suggestions from
without, that youth is particularly the time when the
spirit of invention flourishes. In the case with which

8 PASTEUR: THE HISTORY OF A MIND

we are dealing the progress came by way of physics
from the introduction into the questions of mineralogy
of the power to rotate the plane of polarization.

We know that every impression of light is the result
of a vibration. It is as though a rigid rod, clamped in a
vise at one end, should vibrate at the other end, oscill-
ating about a position of equilibrium. If, on the moving
end, there is a pohshed button making a luminous point,
we can describe with this luminous point an ellipse,
a circle, or a straight line. Let us consider this last
case, the simplest one, and let us call, for sake of argument,
the plane of polarization the plane which contains
the vibrating rod and the luminous line which its
extremity describes. Let us suppose this plane verti-
cal, and the luminous point moving before us in the
line occupied by the hands of a clock indicating six
o'clock, i.e., in a vertical line. As long as only the
air intervenes between the luminous point and our
eye the vibration will not change direction, but there are
manv transparent substances which, when traversed
by the vibration, would make it project itself along
the lines of the hands of a clock indicating five minutes
of five for a certain thickness traversed, or ten minutes
of four for a thickness twice as great. In other words,
these substances rotate the plane of polarization to the
left an amount proportional to their thickness. We
call them substances having a left rotary power, or, to
abbreviate, left-handed substances. There exist, further-
more, right-handed substances, of which, mutatis mutandis,
the definition is the same.

Crystallized quartz, the hemihedral form of which
we have just seen, is typically one of these substances
endowed with rotary power; it rotates the plane of
polarization of a ray of light which traverses it in the
direction of the axis, and Biot, in the very careful study

BIOT AND J. HERSCHEL

9

which he made of the laws of this rotation, remarked
that certain quartz crystals, of a definite thickness, rotate
the plane of polarization as much to the right as other
quartz crystals of the same thickness turn it to the left.
He summed up the whole matter briefly by saying that
there are right-handed and left-handed quartz crystals.
But here a curious circumstance presented itself.
Haijy had observed at the angles of his prismatic quartz
crystals some hemihedral facets (x, x' Fig. 2) different
from those in the simple example which we have just

Quartz plagihedral left.

Fig. 2.

Quartz plagihedral right.

been considering, but which when prolonged would
still give a rhombohedron. He had also remarked that
these facets, which, in pursuance of sj^mmetry should
have been doubled for each of the angles which they cut,
were in the majority of cases single, that is to say that
only one of them was preserved and this facet inclined
according to the crystal, sometimes in one direction
sometimes in the other, to the edge which bore it.
When the inclination was in one direction with respect
to one edge of the prism it was in the same direction
with respect to the five other edges. He called plagi-
hedrons all crystals which had these hemihedral facets;
right-handed plagihedrons, those in which these facets

10 PASTEUR: THE HISTORY OF A MIND

inclined to the right, the crystal being oriented in a
manner agreed upon; left-handed plagihedrons, those
in which it inclined to the left. There he rested the
matter. His pupil, Delafosse, had likewise seen in
these crystal-facets only the confirmation of his ideas
respecting the tetrahedral character of the integral mole-
cule. If we imagine a series of tetrahedrons, threaded end
to end along a rigid rod, this thread will terminate at
one end in a point, at the other end in a plane; the one ex-
tremity corresponded, for Delafosse, to the corner which
was not truncated and remained pointed, the plane sur-
face to the other extremity bearing the hemihedral facet.
For some years the discovery of Biot and that of
Haiiy existed side by side in science without influencing
each other. It was John Herschel who applied to
this inert machinery the drop of oil destined to make it
go. He bethought himself of combining the purely
crystallographical observation of Haiiy on the right-
and left-handed plagihedrons with the purely physical
observation of Biot on the right- and left-handed
quartz. Since one defines arbitrarily the crystallo-
graphical position of the crystal of quartz which he
examines, it is possible to place the crystal in such a
way that the right-handed quartz shall be also the right-
handed plagihedron, and the left-handed quartz, the
left-handed plagihedron. Thus there appeared to be
a connection between the crystalline form and the direc-
tion of the rotation. Observe that this arbitrary
definition which we have just made is not at all obliga-
tory and may be replaced by the opposite one.
What is essential is that the existence of the rotary
power was put by Herschel into relation with the
inequalities in construction of the crystal, and that
alongside of the different but nevertheless similar
structures which the existence of the right-handed

BIOT AND J. HERSCHEL 11

and left-handed plagihedrons oblige us to admit as
present in the quartz, we can place the parallel, but
inverse, actions which it has on polarized light.

I have just spoken of structure. It is necessary
to make here an important remark: this action on
polarized light manifests itself only in crystallized quartz.
With the amorphous quartz, or silica in solution
in any liquid whatsoever, we no longer find a trace of
it. Furthermore, the action takes place only on a ray
of polarized light traversing the crystal in the direction of
its longer axis and parallel to that axis, or at least in a
direction very little inclined away from it. It dimin-
ishes rapidly in proportion to the augmentation of the
inclination, and there is no longer a trace of it when
the ray traverses the crystal obliquely and in the direc-
tion of its shorter diameter.

This circumstance, which connected the rotary power
with the molecular files of Delafosse, was so much
the more curious as it did not occur at all in the other
substances in which Biot had also discovered the rotary
power. Almost all of these substances were products of
animal or vegetable life: sugar, tartaric acid, different
essences, albumen, etc. But those which could crystal-
lize, the sugar and the tartaric acid, had no polarizing
action in the crystalline state. All, on the contrary,
when dissolved in water or any liquid whatsoever, rotated
the plane of polarization, some to the right, some to the
left. This rotation is always the same for the same solu-
tion when the density is the same, regardless of the direc-
tion in which the light ray is made to traverse the liquid
which is being examined, and we can agitate this liquid
during the observation without changing in any way the
quantity and direction of the rotation, a fact which well
demonstrates that it does not depend on the internal
arrangement of the active molecules in the solvent.

12 PASTEUR: THE HISTORY OF A MIND

This goes to show, and Biot was well aware of this
fact, that the action exerted by the solutions of tartaric
acid or of sugar is not due, as in quartz, to the arrange-
ment of the molecules in relation to each other, that is to
the form of construction, but to the shape of the molecule
itself, a form which must be related to its constitution.

It is a considerable stride which this conception forced
us to take. It enabled us to attack a question which
Haiiy had neglected and which Delafosse had scarcely
touched — the question of the form of the molecule. It
enabled us to see in the arrangement of the atoms of this
molecule dissymmetrical dispositions, analogous to that
of the integral molecules of the quartz crystal in the
arrangement of the crystal. As to the quartz itself, it
had awakened ideas, but its importance diminished much
in comparison with substances which had the rotary
power wdthin the molecule. With the watches in his
show-case a watchmaker can make regular geometrical
arrangements analogous to some of the crystalline
systems; these attract the eye and are subject to certain
laws, but as soon as we see that all these watches are
going and indicating the same hour we cease to think
of the arrangement in the show-case and reflect rather
on the movement of the watch. What connection could
there be between the arrangement of the atoms in the
molecule and the rotary power?

Ill

PASTEUR: THE TARTRATES

Such was the question which Pasteur must often have
put to himself, for it was at this juncture that he made
his appearance. Under Delafosse he had acquired the
taste for these researches, and as soon as he was out of

PASTEUR: THE TARTRATES 13

the normal school and able to enter the laboratory as
''preparateur/' he made ready to pursue them. In
order to accustom the eye and the hand to the things
with which crystallography deals, he conceived the ex-
cellent idea of taking as guide a rather extended treatise
on crystalline forms, proposing to repeat all the experi-
ments and all the measurements, and to compare his
results with those of the author whom he followed step
by step. He chose for this purpose a work by Provostaye
on the tartrates, a most fortunate choice, for among the
substances endowed with rotary power, the tartrates
are those which present in simplest form the phenomena
toward which the ambition of the young savant directed
him. With other salts he would have been obliged to
search much longer to find things not so clear, but he
would have found them in the end.

He had, in fact, constantly present in his mind, this
correlation between hemihedrism and the rotary power
discovered in quartz. It was useless to say that it had
no apparent connection with the case of tartaric acid,
that is, that it resided in the arrangement of the mole-
cules, instead of in the molecule itself; the ideas of his
master as well as his own, reverting constantly to this
subject, told him that there ought to be something exter-
nal indicating the mode of arrangement of the atoms.
One of the best proofs that he searched for this some-
thing which his imagination had glimpsed in the memoirs
of BiO/t and Herschel, is that he saw at once on the
crystals of tartaric acid and the tartrates those hemi-
hedral facets which neither Provostaye nor Mitscherlich
had observed. The former, a conscientious worker but
without inspiration (sans flamme), had certainly seen
them but he had disregarded them. The second, whose
fame is well established, was occupied in his study espe-
cially with showing the isomorphism of the tartrates,
4

14 PASTEUR: THE HISTORY OF A MIND

which have these facets, and of the paratartrates which
do not have them. He could not have much considera-
tion for these hemihedral facets which sometimes upset
a parallehsm, other^^ise so marked. With a shght
exaggeration we may say that MitscherHch did not wish
to see them and did not see them, while Pasteur, who
wished to see them, saw them at once.

It must be stated, however, that these facets are not
always very apparent in all the tartrates and in all the
crj'stals of the same tartrate, but we can ordinarily make
them more manifest by changing slightly the conditions
of crystallization. In short, as soon as attention is
called to them and we search for them, we find them in
all of the tartrates.

This confirmed the idea of a correlation between hemi-
hedrism and the rotary power, but this correlation was
still remote. In appearance at least not even here
was there that correlation between the position of the
facet and the direction of rotation which made the right-
handed quartz the right-handed plagihedron, and the
left-handed cmartz the left-handed plagihedron. The
crystals of the different tartrates belong to different
systems, and have therefore very different aspects, and
we do not find that beautiful harmony of forms which
makes almost twin brothers of the different prismatic
crystals of quartz. The confirmation which Pasteur
had just made would have remained fruitless without
another discovery to give it the life it still lacked, and
if the first discovery belonged to the man of reflection
and imagination the latter was due to the experimenter.

I have just said that the crystals of the different
tartrates have the most varied aspects; there are needles,
tabular crystals, and prisms; they are more or less
covered with facets which cut off their angles or then-
edges and mask their primitive form. But in spite

PASTEUR: THE TARTRATES 15

of the variety of their physiognomy there are some
features which remain immutable among them and con-
stitute their family mark. These features are three
facets which always succeed each other in the same
order and make between them very nearly the same
angles. These facets, which consist in the primitive
form of two contiguous faces, P and M
(Fig. 3), and a facet ¥, cutting off the
intersection of the first two, are parallel
to the same straight line which might re-
place for us that axis of the hexagonal
prism of quartz, which has been so useful
to us in establishing the correlation be-
tween the direction of the hemihedrism
and that of the rotary power in this ^tStr^e^c'r^tar
crystal.

Let us agree to place this right line vertically in our
tartrate crystals and to turn forward the group of three
facets which is that characteristic the different crystals
have in common. All the crystals can thus be
ranged, in spite of the variety of their forms, in an
oriented series like soldiers exhibiting in front the
same series of buttons. But when one has arranged
them thus he perceives with surprise that all of these
soldiers bear only one epaulet, turned in every case
in the same direction: I mean to say that all these tar-
trates have their hemihedral facet inclined forward to
the right of the observer.

If one turns them half-way around they are hke
children's lead soldiers, or like the god Janus, inasmuch
as the front cannot be distinguished from the back:
the hemihedral facet from the rear is now in front, but
it is always to the right. If one reverses them in order
to observe them from the other end they resemble
then the double figures on playing cards; their extrem-

16 PASTEUR: THE HISTORY OF A MIXD

ities resemble each other and however one places
them, provided that one puts in front the characteristic
group of the three faces that we have pointed out,
one of their four hemihedral facets comes again ob-
stinately to take up its position facing the observer,
and at his right.

Thus, a curious circumstance, all the tartrates so
varied in form, which Pasteur had studied to the number
of 19, have a rotary power in the same direction, and
also a hemihedrism in the same direction. This
correlation related them to the quartz but had a deeper
meaning, for here it could be no longer a question of
arrangement of the molecules in the cr3'stal, but of
arrangement of the atoms in the molecule. It is clear that
one can change the conventions, for example, examine the
crystals on the edge as is the custom in Germany, instead
of on the face, as is the custom in France. In that case
the hemihedral facets incline to the left when the rotary
power remains to the right, but it is the statement of the
phenomena which changes, and not its nature: all
the tartrates having a rotary power in the same direction
have also a hemihedrism in the same direction, and that
demonstrates a relation between the form of the molecule
and its mode of action on hght.

IV

THE PARATARTRATES

It is evident that we have made progress since the
study on quartz. Now we find ourselves studying with
Pasteur the manner of grouping of the atoms. And
here belongs an unforeseen discovery.

In the factories where tartaric acid is made one

THE PARATARTRATES 17

sometimes finds in the cavities between the large crystals
of this acid some Httle needle-like crystal forming
tufts which are visible as an opaque white mass on the
surface of the semi transparent tartaric acid and some-
times so much resemble oxalic acid crystals that in the
factory of Thann, where they were formerly very abun-
dant, they have been taken for oxalic acid crystals and
an attempt made to sell them as such. It was soon
recognized that they were formed of a particular kind
of tartaric acid, giving salts entirely similar to the tar-
trates. Mitscherlich, who made a comparative study
of the known tartrates and of these new salts,
which he called paratartrates, found them identical
in all their relations. They had the same crystal-
line form, the same specific gravity, the same double
refraction in the crystalline state, the same angle
of the optical axes, the same index of refraction when
they were dissolved in the same proportion of water.
In short, no method, either physical or chemical, made it
possible to distinguish them, and they seemed identical
in every respect, save this, that the tartrates acted on
polarized light while the paratartrates were entirely
without action.

Having arrived at this stage in his researches, Pasteur
could not fail to be impressed by this apparent contradic-
tion. ''Mitscherlich was deceived," he said, ''in affirm-
ing that the crystals of the tartrates and the paratartrates
resemble each other. There must be some external differ-
ences between them as regards the hemihedral facets.
Mitscherlich, preoccupied with his ideas on isomorphism
which made much of all the crystalline resemblances
between the different forms, would not have seen these
differences which he did not seek, but I, who have the
preconceived idea of their existence, am in a good posi-
tion to find them if they are there."

18 PASTEUR: THE HISTORY OF A MIXD

Experiment, questioned in this fashion, gave an imme-
diate response. All the paratartrates examined appeared
with their two epaulets, that is to say with all the faces
required by the laws of symmetry: there was no more
hemihedrism: the facet on the right had its corresponding
one on the left and, simultaneously, every trace of action
on polarized light had disappeared.

This was a confirmation of Pasteur's foresight, a re-
ward of his daring intuition. But, in addition to this
foreseen discovery, chance, one of those happy chances
which one rarely meets with save when he is constantly
in search of it, kept in store an unexpected discovery.
Among the paratartrates there were two which behaved
differently when they were crystallized. The others gave
crystals having hemihedral facets in pairs, and conse-
quently had no hemihedrism, just as he is no longer one-
armed who has two arms. On the contrary, the double
paratartrates of soda and ammonia on the one hand, of
soda and potash on the other, deposit in their mother
liquors crystals which are all hemihedroms, all one-armed;
only there are some of them which have the right arm,
and others the left.

What did this mean? If one regarded these facts as
a whole, the result was confusing, since it showed the
apparition of hemihedrism where there was no rotary
power. But Pasteur had advanced too far to go back.
He had already derived too much advantage from his
conception to lose confidence. ''In spite of all that was
unexpected in this result," said he,^ ''I followed none
the less my idea. I separated with care the right and left-
handed hemihedral crystals and observed separately
their solutions in the polarization apparatus. Then,
with no less surprise than joy, I saw that the right-

* Recherches sur la dissjTn<?trie moleculaire. Le^on professee a la
Soci6t6 chimique de Paris, 1860, p. 29.

THE PARATARTRATES 19

handed hemihedral crystals turned to the right and the
left-handed ones to the left the plane of polarization, and
when I took equal weights of each of these kinds of crys-
tals the mixed solution was neutral to polarized light
because of the neutralization of the two equal and oppo-
site individual deviations."

We can understand how in the presence of this un-
expected phenomenon, with its almost dazzling confirma-
tion of his preconceived idea, Pasteur received such a
shock that he quitted the laboratory, incapable of again
applying his eye to the polariscope. This was a clear
ray of sunlight coming to illuminate perspectives which
he had thus far examined only in shadow or half light.
Now that they were suddenl}^ illuminated it was not the
time to abandon them.

The more so as immediately there was a harvest to be
reaped. In removing chemically from the right-handed
hemihedral crystals the tartaric acid which they con-
tained, he found an acid which, when compared minutely
with the acid of the grape, was found to be absolutely
identical with it. The left-handed crystals furnished
him furthermore a tartaric acid also identical in every
respect with the acid of the grape, save in one point,
that is that it bore on the left the hemihedral facet which
the first bore on the right, and that its solutions deviated
to the left exactly the same amount as equally concen-
trated solutions of the tartaric acid of the grape deviated
to the right. When these solutions were mixed there
was no deviation, and one obtained a third tartaric acid,
the paratartaric acid inactive by compensation. Fur-
thermore, this acid did not result from a juxtaposition
of these two constituents but from their combination,
for properly concentrated solutions of right-handed and
of left-handed tartaric acids often give off much heat
when mixed, and the liquid solidifies on the spot with an

20 PASTEUR: THE HISTORY OF A MIND

abundant crystallization of a paratartaric acid identical
■wdth the acid of Thann with which we set out.

To summarize, there existed there tartaric acids iden-
tical from the point of view of all their physical and chem-
ical properties, save this, that they each had their
special hemihedral facets and the corresponding rotary
power. These differences persisted in all their com-
pounds and formed a part of their true nature. They
formed their distinctive marks, which were permanent
and deep.

ASPARTATES AND MALATES

This harmonious development from a single fertile
idea will become still more thrilling presently when we
go back, as we are justified in doing, to the chemical
molecule from which comes the initial influence. For
the moment we must ask ourselves whether we are here
in the presence of a general or an exceptional fact. Do
all these different organic substances, which Biot found
endowed with rotary power, present hemihedral forms
when crystaUized? Unfortunately, not many of them
give measurable crystals: asparagin and its different de-
rivatives, aspartic acid and malic acid do, however,
and Pasteur made haste to study them.^

Asparagin was at this time a rare substance. Pasteur
was obliged to plant vetch in the garden and cellars of
the Academy of Strasbourg. By known processes, from
the juice of these plants he extracted the asparagin which
he crystallized and which he showed at the same time
to be provided with hemihedral facets and endowed with

^ M6moire sur les acides aspartique et malique. Ann. de ch. et de
phys., 3e p., t. XXXIV.

ASPARTATES AND MALATES 21

rotary power. Like the tartaric acid it carries over this
last property into its solutions, whether acid or alkalin,
but it presents this unforeseen pecuHarity of rotating to
the left the plane of polarization when it is in a neutral
or an alkalin solution, and on the contrary of rotating
it to the right, and to a much greater extent, when it is
in an acid solution. In no case, however, has it ceased
to be asparagin unless the liquid has been heated or
the acids or alkalies have been too concentrated, and it
is possible by precipitation to recover it with all the old
properties. This proved that the rotary power of a
substance did not depend on itself alone and that if the
existence of this power had any significance for the ideas
on which Pasteur had taken his stand, its meaning and
importance were contingent and of a secondary order.

I have just said that, in order to leave intact the as-
pai'agin on which one is working, it is necessary not to
heat the liquids. Boiled with an alkalin solution, it is
transformed into aspartic acid. Does this acid keep
any of the rotary power of the asparagin? It is too little
soluble in water to make it possible to study it in aqueous
solutions. In solution in the alkahes it rotates to the
left: in chlorhydric or nitric acid it rotates to the right.

Another derivative of asparagin was still more interest-
ing to study; viz., the malic acid which one can obtain
from it by action of hyponitric acid. This malic acid
accompanies tartaric acid in the grape and therefore
should arouse curiosity. Experiment shows that in
regard to the rotary power it behaves a little like tartaric
acid, and that it sometimes even recalls it so much in its
properties that one is tempted to suppose for the two
acids origin from a common atomic grouping. Never-
theless, in their ensemble, the phenomena presented by
malic acid and the malates are more complicated than
those of tartaric acid and the tartrates. In the latter

22 PASTEUR: THE HISTORY OF A MIXD

we have several series of well-ordered crystals in which
the correlation between the two hemihedrisms and the
direction of the rotary power is always clear. In the
nialates, on the contrary, the inclination of the facets
and the direction of the rotation are sometimes contrary,
and thus there disappears, apparently at least, this beauti-
ful harmony which had so charmed us in the tartrates.

If Pasteur had commenced with malic acid he would
have needed all his perseverance in order to disentangle'
himself from the midst of so many contradictory facts.
But at the point which he had reached his ideas were too
well grounded and his experience already too great for
him to be astounded by these particular variations in the
direction of rotation of the malates. He had discovered
quite parallel phenomena in asparagin, which neverthe-
less remained always the same, and also in the aspartates.
He had even found examples of it in the tartrates, for
the left-handed calcium tartrate dissolved in chlorhydric
acid gives a rotation to the right.

It is under conditions like these, where the judgment is
wavering, that the discernment of the scientific man
reveals itself. Without being embarrassed by the
differences between the malates and the tartrates, he
saw and aimed at one thing only, the resemblances which
he had perceived and pointed out, and he concluded with
a fine tranciuillity that if there was a common atomic
grouping between the right-handed tartaric acid of the
grape and the malic acid of the sorb-tree, there must
also occur a common atomic grouping between the left-
handed tartaric acid and a malic acid still unknown,
which would be the left of the malic acid of the sorb-tree.
And thus little by little was born in his hands that science
of the arrangement of atoms which has since attained so
much importance. Wherever he went Pasteur was an
initiator.

MOLECULAR DISSYMMETRY

23

Before leaving this subject let us point out a last series
of facts and conclusions. Tartaric acid and malic acid
undergo changes due to the action of heat; the former
gives pyrotartaric acid, the second maleic acid and a fum-
aric acid identical with that which is derived from the
fumitory. Is the atomic grouping which gives to the
tartaric and malic acids the property' of acting on polar-
ized light preserved intact in their derivatives? Experi-
ment shows that this is not the case. All these acids,
pyrotartaric, maleic, fumaric, and their salts are inactive.
According to Pasteur's interpretation, the molecules of
tartaric acid, aspartic acid and malic acid, are dissym-
metrical; those of the pyrotartaric, maleic, and fumaric
acids are not: the atoms are differently grouped and a
new proof is this, that the. two tartaric acids, the right-
and the left-handed, give only a single pyrotartaric acid.

VI

MOLECULAR DISSYMMETRY

The moment has come to pursue more closely than
we have hitherto done these ideas of dissymmetry.

A? — ~____--^

. ^

/I — ^ — ^Q^

C^

— : Q^' /

• • *\ ./^

f

• * ^

f

/

* jr ■

L . ^#

/

• ^%'

/

' ^ ■' *.

^v *

/

/ / ^

/

1 ' X -'

■>^ \

vNc'

/

' Jr-''

•^ \

\ • X

/

' Jr "'

)

kQv

/ ,

*^^ » • — - ■ "

--'-^

t^

^""- r

c

f—

r

Fig. 4. — Diagrams illustrating molecular dissymmetry.

There is a fundamental difference between the hemihedral
forms coming from the cube, as in boracite, or from
the hexagonal prism, as in Iceland spar, and the
hemihedral forms realized in the tartrates. All the

24

PASTEUR: THE HISTORY OF A MIND

Fig
Right tartrate.

Left tartrate.

tetrahedrons which can be derived from a cube by
hemihedrism are identical and could fit into one another.
The two tetrahedrons represented in Fig. 4, passing
through opposite vertices of the cube, have the same
angles and edges; it is only necessary to reverse the
first in order to make it fit over the second: they are
superposahle, to speak in geometrical parlance. The
same thing is true for the different rhombohedrons
derived from the hexagonal prism. It is quite otherwise

for the hemihedrons of the
tartrates. The tetrahedron
which one obtains by pro-
longing and joining the hemi-
hedral facets which a right-
handed crystal of tartrate
bears, is not superposable on
the tetrahedron obtained in
the same way from the left-
handed tartrate. Their faces, it is true, are equal two by
two, but they are not arranged in the same order in re-
spect to the vertices.

Fundamentally, the difference amounts to this, that
the tetrahedron of the cube has several planes of
symmetry, to the right and left of which the elements
are regularly distributed. If one imagines a reflect-
ing surface passing through any given edge of the
tetrahedron and the center of the opposite edge, the
image of the rear half in this mirror coincides with that
of the forward half, and inversely: in more general
terms, the object is superposable on its image in a mirror.
We shall say that in this case there is superposable
hemihedrism. The hemihedrism of the tartrates gives,
on the contrary, tetrahedrons which have no plane
of symmetry, which are not superposable on their image,
and when we reflect upon it we see that ''all material

MOLECULAR DISSYMMETRY

25

objects, whatever they may be, regarded with respect
to their form, or the repetition of their identical parts,
resemble the tetrahedrons which we have just distin-
guished. Some placed before a mirror, give an image
which is superposable on them; others do not, although
the image reproduces them faithfully in all details.
A straight stairway, a branch with opposite leaves, a cube,
the human body, all these are objects belonging to the
first category. A spiral staircase, a branch ^\ith leaves
in a spiral, a screw, a hand, an irregular tetrahedron
are forms of the second group. These latter have no
plane of symmetr3^"^

Of all these comparisons that of the hand is the most

^

t\

c.\

d

iM

d]

Mi

Ki/

Fig. 6. — Tartaric acids,
right. primitive form.

c. Hemihedral facets.

left.

convenient and striking. The two hands are not super-
posable and one cannot put the right glove on the left
hand, nor inversely. On the contrary the image of a right
hand in the mirror gives a left hand. Well! The two
hemihedral tetrahedrons of the right- and left-handed
tartrates are like the two hands: they are not super-
posable nor is either superposable on its image, but
each of them is superposable on the image of the other
in a mirror (Figs. 5 and 6).

Let us recall now that we were led a moment since
to attribute forms of dissymmetry connected with the
non-superposable hemihedrism of crystals to the

1 De la dissymetrie moleculaire des produits organiques naturels.
Le^on professee devaiit la Societe chimique de Paris, 1860.

26 PASTEUR: THE HISTORY OF A MIND

arrangement of the atoms in the molecule, and thus
we come quite naturally to represent to ourselves the
molecules of the two tartaric acids, the right- and the
left-handed, not only as dissymmetrical individually and
\^•ith a non-superposable dissymmetry^ but also as
having an inverse dissymmetry one with the other. If
one is a right hand the other is a left hand. If one is a
corkscrew with a dextrorse spiral, the other is a corkscrew
with a sinistrorse spiral. In short, we know nothing
and we shall know nothing probably for a long time of
the mode of arrangement of the atoms in these two
molecules, but we remain faithful to logic and the laws
of induction in acknowledging that these two arrange-
ments, individually dissymmetrical, are reciprocally sym-
metrical in relation to a plane.

Once this conception is admitted, we can easily
represent to ourselves the effect of these groupings in a
water solution on a ray of polarized light which tra-
verses it. Let us suppose that this solution contains only
identical and superposable tetrahedrons, for example,
those of boracite: these molecules are present in very
great numbers in the path of the ray, even when
the solution is not of much thickness; they occupy, in the
medium in which they are free, all possible positions.
Consequently, if we suppose that one of them is inclined
in a certain direction with regard to the ray of light and
acts on it in a given direction, there will always be
another one, identical with it and in the inverse position,
which will produce an effect in the opposite direction.
The molecular effects will always counterbalance there-
fore in pairs, that is to say, the light ray will leave
the solution just as it entered it, except for the small
amount of absorption undergone in traversing it. If, on
the contrary, the tetrahedrons in solution are not
identical, if they cannot be superposed, it would be

MOLECUL,\R DISSl'lMMETRY 27

only in very exceptional positions that compensa-
tions like those which we have just pointed out
could occur, and, without being able to indicate in
detail the results or the direction of the general resultant,
we see, nevertheless, that the total effect could not be
the same as in the first case. The path of the ray of
polarized light where the direction of the vibration
is constant and unique must depend on the direction
in which the obstacles it encounters are placed. With
out going into this problem further, it is possible to admit
that the deviation of the plane of polarization depends
on the manner of distribution of the obstacles, and that,
according as the dissymmetry in the atoms is right or
left there will be a right or a left rotation.

Of less importance is the mechanism of the action,
which always remains a little hypothetical. It is suffi-
cient that the experimental study of the tartrates has
linked indissolubly these two ideas: the molecular rotary
power, and the dissymmetry of the molecule. This
suffices to give us the right to attribute dissymmetrical
molecules to all substances acting in solution on polar-
ized light, and when one considers that all these sub-
stances belong to the vegetable or animal kingdom,
that is to say, are the products of cellular activity,
this pecuharity of structure becomes curious, if regarded
closely. Guided by an imagination at once so adven-
turous and so well controlled as was that of Pasteur,
we are constantly on the border of new countries, but we
journey with security.

28 PASTEUR : THE HISTORY OF A MIND

VII

DISSYMMETRY OF CELLULAR LIFE

The plant, which is the great creator of organic matter
on the surface of the globe, is an organism continually
engaged in the work of synthesis. By the aid of sub-
stances of the highest degree of chemical simplicity,
carbonic acid, water and ammonia, it manufactures sub-
stances more and more complex, which it stores in the
new tissues that it forms according to its needs. As
soon as these substances attain a certain degree of com-
plexity we see appearing in them the molecular rotary
power, absent up to that time. Carbonic acid, oxalic
acid, acetic acid, ammonia, urea and glycocol, are with-
out action on polarized light: the sugars, tartaric, malic
and citric acids, cellulose, the gums, and the albuminoid
substances are active.

At the time when Pasteur made these studies the chem-
istry of synthesis was still little advanced: Berthelot was
just beginning his work. But organic chemistry was in
full swing, and inorganic chemistry was leaving the
hands of Berzelius and Wohler to fall into those of
Sainte-Claire Deville. Already, at this time, Pasteur
was in position to remark that, contrary to the majority
of natural organic products, all the artificial products
of the laboratories and all the mineral species met with
in nature were without action on polarized light, that is
to say, they possessed a superposable image. (Quartz
itself is not an exception, for, as we have seen, it is only
the arrangement of the molecules in the crystal which is
dissymmetrical. Individually these molecules are with-
out action on polarized light. In the same way one can
arrange cubes of wood, which are exactly alike, so as to
make a winding and dissymmetrical staircase; there

DISSYMMETRY OF CELLULAR LIFE 29

is dissymmetry of construction but not molecular
dissymmetry.

One could put in the same category as quartz other
minerals or salts, such as sulphate of magnesium and
formate of strontium, substances having crystals with
hemihedral facets but the solutions of which are not ac-
tive. In short, no product of inorganic nature or of the
chemistry of the laboratory deviates the plane of polar-
ization of light when in solution; it is only the products
of living nature which have this property but they possess
it to a very marked degree and carry it with them when
they enter into combination with other substances.

Since then, the chemistry of synthesis has made
progress, and today, starting, like the plant, \^dth water,
carbonic acid and ammonia, and putting into play only
the forces and ordinary resources of the laboratory, we
are able to manufacture artificially the majority of the
natural organic products. Is it necessary, therefore, to
change some of the conclusions which Pasteur announced
in 1850? Yes, one thing only which he did not foresee.
We are able now, by the aid of primitively inactive bodies
to rhanufacture active ones, to thus produce dissym-
metry and the rotary power in the molecule which we
construct. With inactive succinic acid we can ascend,
for example, to tartaric acid. But when a chemist
manufactures thus artificially the right-handed tartaric
acid he makes also necessarily and simultaneously the
left-handed form, so that the combination which comes
from his hands is inactive. Nature alone has the secret
of manufacturing one without producing the other. In
the grape, for example, she gives us commonly the right-
handed tartaric acid and not the left, or at least rarely
the left, since paratartaric acid, the combination of the
right and the left, sufficiently abundant at one time to
obstruct the works at Thann, has almost disappeared
5

30 PASTEUR: THE HISTORY OF A MIND

there today, as well as from the other tartaric acid
factories.

What is the mechanism of this production of a right-
handed substance without a trace of the left-handed one,
or inversely? Are the two forms produced simultan-
eously and is one of them utilized and consumed in
proportion to its production? In this case nature would
behave like a chemist who, after having formed at the
same time the two inverse substances, should separate
them and cast aside one of them in order to preserve the
other. Some facts which we shall soon encounter are in
accord with this view. Pasteur adopted another view
which, however, is not exclusive of the first. Possessed
as he was by this novel idea of dissymmetry, he boldly
connected the dissymmetry of natural products wdth the
dissymmetry of their source. The earth is round, it is
true, but, he thought, it is only when in a state of repose
that it is symmetrical and superposable on itself. As
soon as it turns on its axis its image in a glass no longer
resembles it, for that turns in a different direction. The
sun's rays, which strike and animate a leaf of a plant,
no longer have the same direction in the earth and in its
image. If there is an electric current circulating in the
direction of the equator and presiding over the distribu-
tion of magnetism, this current turns also in opposite
directions in the earth and its image in the mirror. In
short, the earth is a dissymmetrical whole from the point
of view of the forces which make it live, it and all that it
produces, and it is on this account that, as soon as they
have exceeded a certain degree of complexity, the sub-
stances which the earth's living creatures produce are
dissymmetrical and endowed with a rotary power.

With this idea in mind, Pasteur had tried to crystallize
the tartrates in the presence of dissymmetrical forces,
for example, the poles of a magnet, and to make a plant

DISSYMMETRY OF CELLULAR LIFE 31

push out shoots by changing the direction of the hght
rays which struck it. These attempts gave nothing,
either to him or to those after him. But it is possible
that, repeated with greater persistence and with more
powerful means, they would result in something, and
that this something would be so remarkable that it
would pay for all the trouble taken to produce it. We
cannot justly scorn any of these ideas of Pasteur when
we see how fruitful have been all those which he pursued.

VIII

SUBSTANCES INACTIVE THROUGH LOSS OF
DISSYMMETRY

We are going to discover a new proof of the certainty
of Pasteur's intuition. Starting with asparagin,. and
profiting by the labors of Piria, we have seen that we
can obtain products more and more simphfied: aspartic
acid, maUc acid, maleic acid, and fumaric acid. In
this continued degradation of the asparagin molecule
there is a point reached where the molecular dissym-
metry disappears, permanently: this is at the maleic
or fumaric acid boundary. But it happened in 1850
that M. Dessaignes, an able chemist of Vendome,
succeeded in following inversely the steps of Piria, and
of remounting by the chemical path from malic acid
to aspartic acid, then, some months later, from fumaric
and maleic acids to the same aspartic acid.

The passage from malic acid to aspartic acid had not
surprised Pasteur, both of them being active on polarized
hght, but the case was different with maleic acid. In
transforming this into malic or aspartic acid, Dessaignes
would have created an active molecule by a laboratory
operation. This would have been, in the eyes of Pasteur,
a great discovery. He must assure himself of the truth
of it at once.

Pasteur, therefore, hastened to Vendome to state his

scruples to Dessaignes, and obtained from him without

difficulty a sample of the new aspartic acid which he made

haste to study. As he had expected, he did not find

any rotary power: this acid was an inactive acid. But

it resembled so much, in all its physical and chemical

32

SUBSTANCES INACTIVE THROUGH LOSS OF DISSYMMETRY 33

properties, the acid derived from asparagin, that Des-
saignes, who had no preconceived idea to put him on
his guard, was very excusable for having confused the
two.

This synthetic aspartic acid is especially interesting in
that it can be transformed into malic acid by the methods
of Piria, and we may well believe that Pasteur was
curious to know what malic acid one would obtain with it.
Experiment shows that we obtain a malic acid identical
with the natural acid, save that it is inactive on polarized
hght, as are also its salts. This is not all; the field
grows more fertile as we cultivate it. The active malic
acid of the sorb-tree or of the grape corresponds to one
of the active tartaric acids. To what was this new malic
acid comparable? To the paratartaric acid inactive by
compensation? Pasteur had, against this interpretation,
an objection which is no longer valid. "Dessaignes,
the father of this malic acid, would," he thought, "in
this case have created two molecules endowed with
rotary power at the expense of one inactive molecule,
but it is impossible to create a single active molecule, to
say nothing of two." We know today, not only that
the thing is possible, but that it has been realized.
It is very probable, if not absolutely demonstrated,
that the aspartic acid manufactured by Dessaignes was
a combination of the right- and left-handed acids. It
is certain that the malic acid which Pasteur had had in
his hands was also a paratartaric acid. This error at
the outset vitiated the memoir which Pasteur had
devoted to comparing the aspartates and malates with
each other and with the tartrates. The majority of
the deductions which he had drawn from these compari-
sons are inexact, and must be abandoned. But there
are some which survive and which we should note.
Even in the early years of his life as savant, Pasteur

34 PASTEUR: THE HISTORY OF A MIND

always had the good fortune never to wander very
far from the right path. His adventurous spirit led
him sometimes to the right or to the left of it, as he
followed the trail, but he always recovered the true path.
It is in these moments when he walked hand in hand
\nth truth that we must lay hold of him: they are the
landmarks of his route and of his career.

The theoretical idea which I have just pointed out
prevented him from believing that the inactive malic
acid was a paratartaric acid. Consequently, it must
present a new atomic grouping in which the optical
inactivity results not from a compensation between
ec^ual and opposed forces but from the disappearance
of all dissymmetry in the active molecule. It was very
audacious to imagine a new theoretical grouping when
there were already three, but Pasteur had audacity and
this audacity had often served him well. The malic
acid which he studied was not, we have said, the com-
pound with the symmetrical structure, which he had
dreamed it to be. Nevertheless he was not absolutely
deceived, for this body with a symmetrical structure
exists in the tartaric series, as Pasteur himself was to
discover a httle later.

Here is another point where error did not prevent him
from arriving at the truth. Confident in his idea that
he had an aspartic acid and a malic acid with a sym-
metrical molecule not contorted, so to speak, he made a
careful comparison of these acids with the twisted and
dissymmetrical molecules obtained from asparagin and
the fruit of the sorb-tree. He wished to see how this
symmetry or dissymmetry of the molecule expressed
itself externally, in the physical and chemical characters
of the acids and their salts.

From this study he derived no definite knowledge for
two reasons. The first is that the substances to which he

SUBSTANCES INACTIVE THROUGH LOSS OF DISSYMMETRY 35

turned his attention were not fitted to answer the ques-
tion asked. But of tliat Pasteur was unconscious.
The second reason, which touched him closely, is that
they were contradictory in their responses. The active
and inactive aspartates resemble each other very much
chemically and sometimes differ entirely from the point
of view of crystallography, even to the degree of present-
ing absolutel}^ incompatible forms, while the active and
inactive malates, very similar also as to their chemical
composition, are sometimes indistinguishable in a
crystalline state. The active and inactive bimalates of
ammonia, for example, have the same crystalline form
and the same angles. One is often in danger even of
taking one for the other, for it happens that the active
bimalate does not have hemihedral facets and corre-
sponds exactly in form with the inactive bimalate.

In other words, all the order and harmony observed in
the tartrates disappeared, so that not only was Pasteur
obliged to abandon without an answer the question which
he had put to himself but he might have asked himself
anxiously whether in the tartrates he had not accident-
ally fallen upon an exceptional case, devoid of all general
bearing. But no! Not once, it seems, did this doubt
cross his mind. At least his wTitings show no trace of it.
From the contradictions which he had observed he con-
cludes with a tranquil assurance that the crystalline
form has only a secondary importance, since in the
aspartates and the malates it no longer shows the beauti-
ful accord with the optical properties which are so
striking in the tartrates. He, therefore, deliberately
threw overboard the correlation of the crystalline form
with the rotary power, which remains the most certain
and most constant evidence of molecular dissymmetry.

Let us pause an instant to observe the successive steps
which we have made. Herschel gives us the first idea

36 PASTEUR : THE HISTORY OF A MIND

of a relation, not only between the existence of a rotary
power and a dissymmetry of construction in the quartz
crystal, but also between the direction of this power and
that of this dissj^mmetry. Biot shows us subsequently
that the rotary power can exist in the molecule. Where-
from Pasteur concludes that there must be a dissymmetry
in the construction of the molecule, that is to say in the
arrangement of the atoms. He finds the external indica-
tion of this dissymmetry in the tartrates, which serve him,
furthermore, to state precisely the meaning of this word
dissymmetry, up to that time a little vague. In his
mind, then, after his studies on the aspartates and
malates, these tartrates become, as did the quartz,
merely empty shells, after yielding the idea which
they contained. This idea is that of the dissymmetry of
the molecular structure and of its constant relation to
the rotary power.

There we have the portion of truth which this memoir
contains! On reflection the conclusion to which we
arrive will appear curious from the philosophical point of
view, for here we have a work which had begun by estab-
lishing a close relation between the rotary power and the
crystalline form, and which ends by scorning this crystal-
line form. One might think that science had turned
about in its place without advancing. But he would be
deceived, for here we see clearly how much a matter of
indifference it is whether a theory or a doctrine is right,
provided that it incites to work, and results in the dis-
covery of new facts. We do not know exactly what is
the relation between the molecular structure and the
crystalline form, nor even if there is a relation which
makes it necessary that they should be subject one to
the other. Fundamentally a correlation between the
existence of certain crystalline facets and the arrange-
ments of atoms in the molecule, appears to us rather

SUBSTANCES INACTIVE THROUGH LOSS OF DISSYMMETRY 37

remote, and therefore as a contingent, but the fact that
the idea of this correlation has given us, through Pas-
teur, the idea of the dissymmetrical structure of the
molecule, suffices to make it beneficial, whether false or
true.

Here we have, in reality, the idea which has come forth
from it quite naturally, like the grain from the ear: a
molecule which possesses the rotary power is dissym-
metrical. But a dissymmetrical molecule cannot be
contained in one plane because this plane would be for
it a plane of symmetry. Therefore, the molecule must
form in space a geometrical solid of three dimensions.
That is the first conclusion. Here is another: as we are
familiar with the number and nature of atoms entering
into the molecule we may attempt to arrange them in
such a way that the dissymmetry of the solid which they
form corresponds to the direction of the rotary power of
the molecule. Summed up, such is the series of deduc-
tions drawn nearly simultaneously in France by Le Bel,
in Holland by Van't Hoff, and which have served to
found a new science, stereo-chemistry, of which Pasteur
is thus the forerunner.

Let us forget, then, all the false interpretations of this
memoir on aspartic acid, and note only the certainty
with which Pasteur, arrested by a conception, inexact in
the case to which he applied it, but the general justness
of which the future was to confirm, succeeded in tracing
a fourth plan of construction for an active molecule.
''We are here," he would have been able to say at this
moment, "thanks to the discovery of inactive substances,
in possession of a fertile idea. A substance is dissym-
metrical, right or left: by certain artifices of isomeric
transformations, which must be sought and discovered for
each particular case, it can lose its molecular dissym-
metry, be twisted, to use a rough comparison, and effect

38 PASTEUR: THE HISTORY OF A MI^TD

in the grouping of its atoms an arrangement with a super-
posable image. Thus each dissymmetrical substance
offers four variations or, rather, four distinct sub-species:
the right-handed body, the left-handed body, the com-
bination of the right and the left, and the body which is
neither right nor left, nor formed by a combination of the
two."i

I shall dwell no longer on the aspartic and malic acids
because, as I have just said, Pasteur had taken the wrong
route. This has been evident since, and it is singular
that its discovery has required no new methods; it has
only been necessary to employ those methods with which
he has made us familiar. By following them ]\I. Bremer
has shown that the inactive malic acid of Pasteur was in
reality a paratartaric acid, that is to say, a combination
of right- and left-handed acids. It has been discovered
also that there are three asparagins, three aspartic acids,
three malic acids, and that the maleic acid and fumaric
acid are more distinct than Pasteur believed them, and
possess a new dissymmetry which is not expressed by
the appearance of a rotary power. In short, our knowl-
edge has been very much extended since Pastern' 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 expressed externally in some
way. That Pasteur was sometimes self-deceived, and
that there are some defective stones in the foundation
which he has given to the edifice, is of no importance.
The essential thing is that the edifice rises without
crumbling, and that it does rise.

' De la dissj-niotrie molcculaire des produits orgauiques naturels.
Legon profcssee devant la Soci^te chimique. IHOO.

COMBINATIONS BETWEEN ACTIVE MOLECULES 39

IX

COMBINATIONS BETWEEN ACTIVE MOLECULES

If the ideas which we have just developed have served
as a foundation for stereo-chemistry, others in the same
group will lead us to the study of fermentations, that is
to say, to one of the most beautiful conquests of this cen-
tury of marvels. For this, let us go back to the study
of the tartrates. We have seen that any left-handed
tartrate is the twin brother of the corresponding right-
handed one. Save that they bear their hemihedral facets
in different ways, when they have them, and that they
have equal rotary powers but in opposite directions, the
two brothers are exactly alike not only in respect to their
geometrical form, solubility, density, etc., but also in
what one might call the physiognomy of the crystals.
These twin crystals are equally limpid or clouded, hard
or fragile, polished or striated; they have the same
internal fissures, in short, they cannot be distinguished
unless one subjects them to a very careful examination.
We have taken exact note of these resemblances in orde^
to convince ourselves that the molecules of these crystals
are identical in everything save their atomic arrange-
ment. The moment has come to consider this resem-
blance from another point of view.

Up to this time it has been manifest to us only in the
combinations of the right and left tartaric acids, with
certain mineral substances: potash, soda, ammonia.
Inactive on polarized light, as the minerals are, these
substances are content, so to speak, with diluting the
active power of the tartaric acid on entering into combi-
nation with it. But what happens if one combines these
tartaric acids with active substances? If the latter, as
is probable, maintain their power in the compound, this

40 PASTEUR: THE HISTORY OF A MIXD

power will be contrary to that of one of the tartrates,
and will exalt that of the other. "What will be the out-
come of this internal conflict on the physical and chem-
ical properties of the compound? It does not seem,
a priori, that it will be expressed externally in the same
way as the harmonious dissymmetry of the tartrates.
What does experiment say?

Impelled by this ingenious and original idea, which,
let us remark, w^as, moreover, from the point of view
of the history of his mind, a logical consequence of his
conceptions, Pasteur tried, in fact, to combine with
active malic acid and its compounds, the right- and left-
handed tartaric acids and their compounds, asparagin
\\dth the two tartaric acids, etc. Between the difTerent
substances thus produced he actually determined some
differences greater than those existing between the
corresponding substances formed by means of inactive
bodies. But the results are clearer when one combines
the tartaric acids with the organic alkalies of plants,
quinine, cinchonine, brucine, strychnine, etc., endowed
also ^\dth the rotary power. The identity of the chem-
ical properties which existed in the tartrates with
mineral bases disappears. The right- and left-handed
tartrates of the organic alkalies are no longer either equally
soluble or equally hydrated. They bear very unequally
the action of heat, and they lose more or less easily their
water of crystallization. If by chance their chemical
formula is the same their crystalline forms are difTerent
and incompatible. Finally, sometimes, with aspara-
gin, for example, combination is possible with the right-
handed body, im]iossible with the left. As for their
rotary powers, instead of being equal and opposite, as in
the case of the combinations of the tartaric acids with
mineral bases, there may be either addition or subtrac-
tion, and the resultant deviation is very different in the

COMBINATIONS BETWEEN ACTIVE MOLECULES 41

right- and left-handed tartrates in combination even with
the same organic alkah. In short, we observe some
differences which can be attributed legitimately only to
the reciprocal influences of the acid and the base in
combination.

And, thenceforth, we are authorized to philosophize
with Pasteur. It is ver}' probable that all natural,
active bodies present, like tartaric acid, at least three
forms, the right, the left, and the para. Then when we
combine two substances each of which has its right, left
and inactive form, it is possible to obtain nine different
combinations, identical as far as the number and nature
of the atoms is concerned, but different in their arrange-
ments. This difference of arrangement will admit
of the addition of an unequal number of molecules
of water of crystallization which will be more or less
difficult to drive away with heat. It will involve,
furthermore, differences in crystalline form, in solu-
bility, and in chemical stability. On the whole, it is
sufficient to constitute nine different substances, which
number could be increased to sixteen if we take into
consideration, in addition to the three forms pointed
out above, the form by nature inactive, which Pasteur
had not yet discovered in the tartaric acid.

Of a complete series there was no example at the time
when Pasteur worked, and I do not know whether there
is one to-day. Then, there were only some scattered
terms but these permitted the beginning of proof.
Precisely the combination of the right-handed tartaric
acid with the left appears in the forecasts above made,
and it is remarkable that one finds between the tartrates
and paratartrates difTerences of the same order as those
which we have just pointed out. The chemical com-
position is ordinarily not the same, the crystalline forms
are incompatible, the solubilities are different, etc.

42 PASTEUR: THE HISTORY OF A MIND

It is true that this is not always the case, and Pasteur
would have been able to find contrary examples in the
history of the malates if he had not made the error which
we have pointed out above. But, on the whole, one
can accept this way of looking at it as sufficiently ex-
act, and Pasteur was right to introduce it into science.
The marked differences which one observes between the
various sugars encountered in nature, for example be-
tween rock candy and its constituent sugars, are evidently
of the same order and have the same origin. I will ven-
tiu-e to add that it is reasons of the same kind which render
so baffling the study of albuminoid substances, in which
differences of molecular structure are expressed exter-
nally otherwise than by differences in crystallization.

If w^e now recall that the protoplasm of all living
cells is endowed \\dth the rotary power, that it con-
tains, therefore, dissymmetrical molecules, and that
this dissymmetry in relation to the stability or insta-
biUty of the compound, cannot fail to play a role in all
the chemical combinations of which the protoplasm is
the seat, we shall conclude that there are in these con-
siderations indications of a profound mechanism of life.
We encounter here one of those flights of imagination
which Pasteur permitted himself sometimes and which
were for him the recompense and the repose derived
from works of research. But when he had thus boldly
explored the horizon he made haste to regain the solid
ground of experiment. Let us follow his example and
enter the laboratory.

MEANS OF SEPARATING ROTARY SUBSTANCES 43

X

MEANS OF SEPARATING THE RIGHT- AND LEFT-
HANDED SUBSTANCES

We have to deduce from the preceding facts one of the
consequences which they allow. Now that we have
substances of the same composition into the molecule
of which we can introduce either an identity, or foreseen
and premeditated variations, let us ask ourselves if we
cannot impart to the two tartrates, right and left, which
precipitate at the same time from a solution of the double
paratartrate of soda and ammonia, a difference in solu-
bility great enough so that one will be deposited before
the other, when the liquid is left to evaporate. That
would be a great advantage. At present, we only know
how to separate them by hand, observing individually
their hemihedral facets in order to determine how they
are placed on the crystal. That demands time, patience,
and a profound knowledge of crystalline forms. Further-
more, when deposited, the crystals are generally in a
mass, and one is never sure that a right-handed crystal
which one detaches from the mass does not bear with
it fragments of a left-handed one. The separate crystal-
lization of the two salts would certainly yield them in a
much purer state.

Let us search then in this direction, Pasteur surely
said, and he soon found, in reahty, that in crystallizing
the paratartrate of cinchonine, the left-handed tartrate
which is less soluble was deposited first, and to such an
extent that by decanting at a given moment the mother
liquid, and evaporating it anew, there was found in it
only the right-handed tartrate. It was a natural separa-
tion of the two acids, otherwise so similar. I imagine
that when Pasteur performed this experiment for the

44 PASTEUR: THE HISTORY OF A MIXD

first time he was no less happy than when he saw the
double paratartrate of soda and ammonia break up
unexpectedly. That was an unforeseen discovery on his
pathway; here, on the other hand, the discovery was
searched for and foreseen, which doubled the interest of
it. The paratartrate of cinchonine is not, moreover,
the only one which lends itself to such a separation:
that of quinicine is similar, but in this case it is the right-
handed tartrate which is deposited first.

We are, then, in possession of a second means of
separating the active components of a paratartaric acid.
Let us say immediately that it is bj^ this method that
M. Bremer demonstrated the inactive malic acid of
Pasteur to be in reality a combination of the right- and
the left-handed acids. Let us say, also, that a third
means was conceived by M. Gernez in the laboratory
of Pasteur. It was incident to the preceding in that the
separate crystallization of the two tartrates was provoked,
not by differences in solubility, but by a suitable crystal-
line decoy introduced into the supersaturated solution.
With a decoy formed of right-handed tartrate one ob-
tained the crystallization of the right-handed tartrate;
with one of the left-handed tartrate, that of the left
tartrate. This was, then, under another form, it is true,
a dissymmetrical influence introduced to obtain the
separation.

Another means discovered by Pasteur is still more
curious and introduces us into the realm of life. It had
been known for a long time that lime tartrate left to
itself under water decomposes with the formation of
various products. One day Pasteur observed a solution
of right tartrate of ammonia placed in a flask in the
laboratory to be decomposing in the same way. The
liquid which was at first clear (let us keep this fact in
mind because we shall need it later) became clouded

MEANS OF SEPARATING ROTARY SUBSTANCES 45

as the result of the development of one of those organisms
which invade infusions, and then a drop of this clouded
liquid sufficed to induce a fermentation in a new flask.

Thus far nothing surprising: we have before our eyes
one of those phenomena of decomposition of organic
matter which are constantly taking place around us.
But here is where the investigator awakes and the origi-
nality begins. For others the fact was commonplace; for
Pasteur it was life engaged in a struggle with a compound
endowed with rotary power. This form of plant life
which grew and developed in the flask was composed of
cells giving birth to dissymmetrical products, as do all
living cells, and then there presented itself quite natur-
ally and imperatively the following question: how will
this organism behave in a solution of paratartrate?

Let us transfer a drop of the fermented liquid of right
tartrate of ammonia to a solution of paratartrate of
ammonia. Things follow their course, and nothing out-
wardly distinguishes these two fermentations. But let
us study them with a polarization apparatus. Let us
filter, at definite intervals, a portion of the solution of
paratartrate and pass through it a ray of polarized
hght, and we shall see that this liquid, inactive in the
beginning, has acquired a left rotary power which in-
creases Httle by little till it reaches a maximum. At
this moment fermentation is suspended, the liquid clears,
it contains no longer any of the right-handed salt which
is the only one the fermentation has attacked and trans-
formed. The left-handed salt has been respected and
can be recovered by evaporation.

The phenomena, it is true, do not always proceed
in just this manner. Everything depends on the micro-
scopic organism which is sown, and developed, in the
liquid. Pasteur has never described the one which he

observed; it would seem that he had been working with a
6

46 PASTEUR: THE HISTORY OF A MIND

species of PeniciUium. Since then Pfeffer has found a
bacterium which acts like the species studied by Pasteur,
On the contrary, a bacterium that developed spontane-
ously in the laboratory, in a solution of left-handed tar-
trate of soda and ammonia, consumes by preference
the left tartrate from a solution of paratartrate, although
it is quite able to attack the right also. Other living
species consume indifferently the two salts, and all
cases are possible. But we are none the less in possession
of this fact: that the nutritive character of a tartrate
may bear a relation to its molecular dissymmetry.

XI

GENERAL CONCLUSIONS

This fact merits special attention. The right- and
left-handed tartrates of ammonia are composed of ex-
actly the same elements, carbon, hydrogen, oxygen,
nitrogen, in the same quantity. The only difference is in
the arrangements of the atoms. Still this difference is
not great since the two arrangements are the image of
each other in the mirror, and nevertheless it is great
enough so that a living organism can respect one of the
two salts while it entirely destroys the other.

To understand this fact it is evidently necessary to
relate it to what we know on the subject of the difference
in chemical properties brought about by combination
of tartaric acid with an active substance. In the pres-
ence of potash and soda the right and left tartaric
acids behave exactl}^ alike and have the same stability.
This is no longer the case when they unite with sub-
stances having rotary power. Now it is just these which
they encounter in the living tissues where there are

GENERAL CONCLUSIONS 47

always active substances though it may be only the
albuminoid matter of the protoplasm.

On the other hand, all phenomena of nutrition are
protoplasmic, that is to say the food of any cell, whatever
that food and whatever the cell, must begin by forming
a part of the protoplasm before being consumed or
utilized. From this we understand that the two tar-
trates do not lend themselves with the same facility
to this combination, or, that once combined, they have
different stabilities. Thus it is that the active bimalate
unites with the right-handed bitartrate to give a crystal-
line combination unrealizable with the left-handed
bitartrate. Thus it is that the two tartrates of quinine
are quite dissimilarly resistant to the action of heat.

A living cell appears to us, therefore, as a laboratory
of dissymmetrical forces, where a dissymmetrical pro-
toplasm acting under the influence of the sun, that is to
say, under the influence of dissymmetrical exterior forces,
may preside over quite varied actions, may manufacture
in its turn new dissymmetrical substances which add
to or take away from its power, may utilize one of the
elements of a paratartaric acid without touching the
other, may manufacture crystallizable sugar at one
moment to consume it at another, make reserve foods
today and exhaust them tomorrow, in brief, may show
the marvelous plasticity which we know to be char-
acteristic of it, and all that very simply, without any
stir, by means of very small deviations of forces under
dissymmetrical influences.

The nature of the albuminoid substance of each cell, or,
to speak more generally, the direction of the dissym-
metry of one or several of the elements of its protoplasm,
exerts thus on its functions and therefore on its develop-
ment, an influence of the first order, the mechanism
of which, obscure up to this time, is a little clearer when

48 PASTEUR: THE HISTORY OF A MIND

seen in the light of Pasteur's work. What kind of a
world would it be in which one would replace the cellu-
lose and albumen in the actually living cells by their
opposites and, to recall to our minds that which we
have already gone over, what kind of a world would it be in
which the earth should turn around the sun in a direction
opposite to that which it now takes, an earth where the
electric current which makes of it a magnet should take
an opposite direction and where the point of the compass
needle which marks the north should mark the south?

We are right in thinking that it would be a world not
identical with the actual world. We may even believe
that it would differ very much, and behold therein the
profound thought of Pasteur, the bond which unites
our nature to cosmic phenomena. We are all the
children of the sun, as someone has said, vspeaking from
another viewpoint. We see here more than that. The
sun not only distributes the force, but it influences its
direction and its use.

We see also, at the same time, all the difficulty which
one would encounter in approaching the problem by
experiment. In order to introduce into a cell proxi-
mate principles different and opposite from those which
exist there, it would be necessary to act upon it at the
time of its greatest plasticity, that is, to take the germ
cell and try to modify it. But this cell has received
from its parents a heredity in the form of one or several
active substances, the presence of which is sufficient
to render it rebellious to certain actions and to make it
accept others, that is to say, to impart to its evolution
a definite direction. This cell contains in the beginning
not only its being but also its becoming, and it is therefore
an initial force which augments without ceasing by giving
its own direction to new forces which appear every
day in the little world it governs. Vires acquirit eundo.

GENERAL CONCLUSIONS 49

And the life of the whole results from the sum total of
these cellular lives.

Ah! If spontaneous generation were possible! If
one could create a living whole, could cause to evolve
from inactive mineral matter a living cell, how much
easier it would be to give it a direction, to make these
foreseen dissymmetries of which we have spoken
enter into its substance and thence into its vital mani-
festations! I am adding something to what Pasteur
has written on these captivating questions, but I do not
beheve that I have gone beyond what was in his thought
in my effort to show how the methodical and regular
study of the questions which ranged themselves before
him, as he advanced, was able to put him in the presence
of two of the problems which it was fated that he should
solve: the question of fermentations and that of spon-
taneous generations.

#<^

y

W

PASTET'R

(From nil old Lithog-raph.)

(Courtesy of Capt. J. C. Pryor, Naval Med. School, Washington,

D. C.)

SECOND PART
Lactic and Alcoholic Fermentations

THE KNOWLEDGE OF FERMENTATIONS BEFORE

LAVOISIER

At the time Pasteur approached it, the question of
fermentations formed such a confused mass that not only
is it difficult to picture to ourselves what the chemists
of the epoch thought of it but we doubt even whether
they had any clear idea of it, we find so many con-
tradictions and singular statements in their writings.
When we seek to discover whence came that embryonic
notion respecting fermentation, persistent to the middle
of the nineteenth century, we see that it was due not to
the difficulties of the subject, but to the fact that the
question had been a philosophical one before it became
a scientific one.

The phenomena of fermentation are as old as the
world, and the first that man learned to control and to
adapt to his needs are probably those which lead to the
production of bread and wine. More time and effort
doubtless was required to procure beer. Once found,
it was inevitable that the methods which yielded these
articles of food and drink should spread rapidly and
soon become common. The bubbling which takes
place spontaneously in the mass of vintage, or which is
produced in the barley wort by the addition of the yeast
of beer, the change of savor and texture which results
from the introduction of yeast into the flour paste are

51

52 PASTEUR: THE HISTORY OF A MIND

phenomena too curious not to have attracted, from
the beginning, the attention of philosophers, who con-
tented themselves with borrowing from them comparisons
and figures, and the curiosity of searchers for the philos-
opher's stone, who were less disinterested. Might
not a base metal be transformed into a precious one
by means analogous to that which derived a savory
bread from an indigestible paste? Is there not some
powder of transmutation acting like a ferment? Here
we have the question which the alchemists asked
themselves and which naturally they did not solve,
first because it is insoluble, second because though they
were experimenters, they were still more logicians,
beheving in the power of the idea, and inclined to sub-
ordinate experiment to it.

It is not that there do not exist in their writings
phrases in which, if one is so inclined, it is possible to
see, like the break of day, the forecast of recent discov-
eries. But in reading these ancient authors we must
always bear in mind that the word with them has often
preceded the idea because of the general mode of
education of the middle ages, and that in the sciences
the idea has almost always preceded the fact. The
word has no value of its own; an idea, so long as it
remains a view of the mind, is always balanced by an
opposing idea; the fact alone is convincing and brings
certainty. But facts are what the alchemists scared}^ ever
found on the question of fermentation. The defini-
tions of it which they have given are only obscure or
pretentious paraphrases of the phenomena observed in the
manufacture of wine or of bread. They make allusions
sometimes to the setting free of gas {exaUatio), sometimes
to the fact that the fermented bread can, in its turn,
act as a yeast {immutatio). But as they knew nothing
of the nature of the substance which ferments, nor of

FERMENTATIONS BEFORE LAVOISIER 53

that of the products of fermentation (save that of
alcohol, known for a long time), it is difficult for them to
escape glittering generalities.

The honor of having provoked serious studies by
showing the worthlessness of the little that was known
belongs to Paracelsus (1493-1541). Although of new
facts he himself contributed very few, his militant way,
his great mind, his disdain for traditions and the philo-
sophical speculations which at that time dominated
science, all these brilliant and substantial qualities,
could not fail to have a powerful influence on his con-
temporaries. To the attraction of the studies in them-
selves he added the allurement of a close personal in-
terest. To him, man was a chemical compound; diseases
were caused by some alteration in this compound; the
putrid fevers, for example, were due to excremental
substances, which instead of being rejected were retained
in the economy. Hence, the utihty of searching for
chemicals which could combat efficaciously these
maladies. Paracelsus, we see, might be cited as the fore-
runner of the theory of antitoxins. The truth in that
he argued well, but it was, after all, only argument.

This association between the phenomena of fermenta-
tion and disease does not really date from Paracelsus.
It influenced his predecessors: it furthermore influenced
his successors down to Pasteur, who gave it a precise
significance. We find it becoming more and more clearly
defined from the beginning of the seventeenth century,
which opens the era of work and discovery. It takes an
experimental turn with Van Helmont, who discovered
carbonic acid in respiration, putrefaction, digestion, and
in the fermentation of wine; with Becher, who passed
several years in the practice of fermentations and whose
writings profited by his long experience. Unfortunately
dissertation regained ascendancy with R. Boyle, in other

54 PASTEUR: THE HISTORY OF A MIXD

respects so original, and especially with Stahl, whose
influence on his century was so great. His was a high
intelligence, a powerful and generahzing mind, but he
believed in fencing with words, and was not a scientific
man.

He introduced into his theory of fermentation, sus-
taining them vnth his great authority, ideas already
professed by Willis. According to Stahl, "Every sub-
stance in a state of putrefaction easily transmits this
state to another body still free from decay. Thus it is
that a similar body animated already by an internal
movement (let us bear this idea in mind for we shall
find it again in Liebig), may, with the greatest facihty,
involve in the same internal movement another body
still in repose but disposed by nature to a similar move-
ment. * * * There are two periods in fermentation thus
considered as the result of an internal movement; in
the first, the different molecules of the fermenting sub-
stances are gently agitated, and some parts, more or less
attenuated, gather together; in the second, the parts
separate themselves from the mixture as a result of the
movement which animates them, and the analogous
parts reunite to the exclusion of the others."

According to Stahl, the ferment intervenes only to
communicate its movement to the analogous parts of
the liquor to be fermented. Its action, therefore, we
should say today, is purely dynamic. Let us hasten
to remind ourselves once more that we must not read
into the phrases of the ancients our modern ideas. The
conception of Stahl derives its fundamental origin from
two classes of facts, the manufacture of bread and of
wine: the first a transformation arrested at its beginning,
during which the agitation is feeble and in which the parts
in the vicinity of the ferment become fermented in their
turn; the second characterized, on the contrary, by a

FERMENTATIONS BEFORE LAVOISIER 55

violent movement, which communicates to the Uquid
the gas, or spirit, which is set free. Adjust these two
phenomena, end to end, generalize them, and you have
the definition, cited above, of Stahl and his predecessors.
If with Stahl it ended in assuming a more definite form,
it was because the atomic theories of Descartes had
penetrated into chemistry. Save for this addition from
without, which appeared rather in the way of stating
it than in the idea itself, the theory of Stahl says nothing
more than that of Lefevre and Lemery, and other
chemists on the time. It has been said of this theory
that it was philosophical and seducing. A theory does
not need to be philosophical and seducing; it does not
even need to be true in the absolute sense of the word,
as we have shown; it suffices that it be fertile. But
the theory of Stahl was not fertile.

Progress in the field of fermentation came from without
and had for its origin new facts observed in the study of
gas by scientific men who were contemporaries of Stahl.
Moitrel d'Element (1719) learned to make gases visible
by passing them through water; Hales (1677-1761)
showed how to manipulate them; Black (1728-1799),
how to distinguish them one from another. He isolated
especially carbonic acid, learned to know its properties,
and discovered, something which Van Helmont had not
been able to do, that, aside from alcohol, it is the sole
product of the transformation of sugar in the alcoholic
fertnentation. He placed thus in the hands of the
chemists all the principal elements for the solution of
the problem; it remained only to coordinate these ele-
ments and to establish their mutual relations: this was
the work of Lavoisier.

56 PASTEUR : THE HISTORY OF A MIND

II

FROM LAVOISIER TO GAY-LUSSAC

Here we are able to point out, as we have done with
respect to the introduction of polarization into chemistry,
the fruitful power of a new instrument entering into a
science which had previously not known it or had ne-
glected it. It is to the introduction of the balance
into chemistry that Lavoisier owes his glory ; it had served
him well in the solution of other problems: it solved
also the problem of fermentation, Lavoisier placed on
the pan of a balance a vessel filled with water to which
he had added a given weight of sugar and a little yeast of
beer. From the loss of weight undergone by this vessel
at the end of the fermentation, he inferred the weight
of the carbonic acid^ liberated during the process of the
phenomenon. He then separated the alcohol by dis-
tillation, weighed it, and found that the sum of the
weights of the alcohol and the carbonic acid gave very
nearly the original weight of the sugar. The conclusion
is easy to draw: the sugar simply breaks up into alcohol
and carbonic acid; there are no other normal products
of the transformation.

But there is more than that in the experiment of
Lavoisier. The relation whicii exists between the weight
of the sugar on the one hand and that of the alcohol
and carbonic acid on the other, ought also to be verified
individually for each one of the elements of these bodies.
The carbon of the sugar ought, for example, to be found
entire in that of the alcohol and the carbonic acid; the
same should be true for the hydrogen and the oxygen.

1 Following the usage of Pasteur and his opponents and all the older
writers, this book, which is an interpretation, calls the dissolved gas and
the free gas, indifferentlj', carbonic acid. Trs.

PASTEUR
(At Forty-five.)

FROM LAVOISIER TO GAY-LUSSAC 57

It is sufficient, therefore, to know the composition of
the sugar, of the alcohol and of the carbonic acid, in
order to prepare the balance sheet of the reaction, which
Lavoisier sums up in these clear terms: "The results
of the vinous fermentation are reduced, therefore, to
separating into two portions the sugar which is an oxide,
oxidizing one at the expense of the other to form car-
bonic acid, deoxidizing the other at the expense of the
first, to form out of it a combustible substance which
is the alcohol, so that, if it were possible to recombine
these two substances, the alcohol and the carbonic acid,
we should again obtain sugar."

Here, apparently, we have reached a truly scientific
ground, and it seems as though, from this point on,
progress will be made in great strides. But this problem
is unlike others; everything in its course has been un-
certain and laborious; it even exhibits this fact, not
rare, but always curious, namely, that its progress has
been due as much to error as to truth.

The conclusions of Lavoisier were exact but his work
was not. Because of the lack of good analytical methods
he was deceived in the composition of the sugar employed,
and in that of the alcohol produced. And if, in spite
of these errors, which should have vitiated everything,
he reached a conclusion correct in its general features,
it was due entirely to a chance compensation of errors.
Happy chance, one might say, providential chance, which
has had such enduring and useful consequences!

Useful, for Lavoisier had apparently so clearly ex-
plained the mystery of fermentation, had reduced it to a
formula so simple, that the idea of this simplicity has
never left the minds of scientific men. This became
apparent when Gay-Lussac and Thenard, after having
perfected the processes of organic analysis, determined
the exact composition of cane-sugar. It was then very

58 PASTEUR : THE HISTORY OF A MIND

easy to be convinced that all Lavoisier's conclusions
were overthrown and that the work must be done again
or the conclusions revised. But as for Gay-Lussac
himself, so convinced was he of the truth of the interpre-
tation of Lavoisier that he contented himself with search-
ing whether the formula of the sugar, as determined by
his perfected method, would not accommodate itself so as
to break up into alcohol and carbonic acid. This was
to admit as exact the short-lived conclusion of Lavoisier.
But the proof very nearly succeeded. Believing that
Lavoisier was entirely right, Gay-Lussac did not hesitate
even to give what is commonly called a coup de pouce,
and to modify from 2 to 3 per cent the figures which
his experiment had given him in order to make them
fit into the hypothetical outline traced by Lavoisier.
A singular spectacle ! the degree of confidence and security
of conscience to which a preconceived idea may lead!
A strange spectacle to see Gay-Lussac continue, but
happily only on this one point, the tradition of those
alchemists of the middle ages, who consented, it is true,
to inquire of experiment, but who did not question it
impartially, and listened only when it answered in ac-
cordance with their desires!

Starting from an inexact experiment, supported by
the figures of an analysis voluntarily perverted, the idea
of Lavoisier nevertheless made its way, because of its
simplicity. It naturally met with more credence when
Dumas and Boullay observed in 1828 that every in-
correct statement in the interpretation of Gay-Lussac
could be made to disappear by admitting that the cane-
sugar assimilates the elements of a molecule of water
before undergoing alcoholic fermentation. This inter-
pretation, supported by experiment, reestablished both
the truth of the idea of Lavoisier and the accuracy of the
calculations of Gay-Lussac; it had only one thing against

CAGNIARD-LATOUR, SCHWANN, HELMHOLTZ 59

it — it was entirely a work of calculation. It had no
other foundation than the experiment of Lavoisier which
was evidently not exact, and had not been the object of
any verification.

Any one who had wished, about 1850, to get an idea
of the degree of credence which the equation merited, the
equation of alcoholic fermentation accepted everywhere,
would have been justified in being entirely sceptical on
the subject, especially if he had asked himself why all
the chemists who were occupied with this question passed
by obstinately in silence this yeast which Lavoisier had
been obliged to add to make his sugar ferment, and with-
out which it was impossible to obtain any fermentation.
Why should this yeast, so necessary in the experiment,
disappear in its interpretation?

Ill
CAGNIARD-LATOUR, SCHWANN, HELMHOLTZ

This yeast was known in the vats of the brewery as a
kind of superficial scum, or as a precipitate on the bottom,
a scum or deposit in which resided an occult force. It
multiplied when introduced into a sweetened must and
caused it to ferment: apparently when it was not intro-
duced it formed there spontaneously, and Thenard had
shown, in 1803, that all sugared juices which ferment of
their own accord, give a precipitate having the external
appearance and the properties of the yeast of beer.

This yeast seemed, therefore, necessary to the fer-
mentation. In an experiment which perplexed Pasteur
too much for us to pass over it, Gay-Lussac had shown
that something else was needed. That able physicist
caused to mount to the top of a test tube filled with

60 PASTEUR: THE HISTORY OF A MIND

mercury, some grapes, the surface of which had been
washed many times with hydrogen in order to remove
all traces of air from the skins. Then he had crushed
them against the top of the tube with the aid of a curved
iron rod introduced under the mercury. No fermenta-
tion occurred, which might appear very surprising in
view of the facility and rapidity with which fermentation
ordinarily takes place in the vintage. When it was
thoroughly demonstrated that there would not be any,
Gay-Lussac brought into contact with the crushed grapes
some bubbles of oxygen and saw fermentation begin in
a very short time thereafter. From this he concluded
that oxygen was necessary to start a fermentation,
whatever might be the role of the yeast.

The experiment is accurate, although it does not
always succeed. Gay-Lussac tried it twice and failed
once. That should have been sufficient to make him
reflect on the accuracy of his conclusion, but it was
decreed that, in this question, suggestion should play a
great role. Oxygen was then at the height of its glory,
and by opening to it the domain of the fermentations
Gay-Lussac not only acted in accordance with the pre-
vailing belief, but explained at the same time the pre-
serving methods of Appert, who, in heating his bottles
and flasks, was seen to be driving out the oxygen, and,
in reality, did not leave any of it behind, as experiment
showed. Gay-Lussac explained also the very ancient
practice of interrupting fermentation by sulphuring casks
or the juice of the grapes. Consequently his interpre-
tation has entered into people's minds, has remained,
and has exercised even on the science of our own time an
unquestionable influence.

Hitherto, the question had been confined to the domain
of chemistry. Since Fabroni (1799), the yeast, whatever
its role, was considered as a gluten, and it did not occur

CAGNIARD-LATOUR, SCHWANN, HELMHOLTZ

61

to the mind of Thenard to consider it as anything but a
chemical compound. As for the intervention of the
oxygen, that also was only chemistry. But at this
time there appeared in science a new idea, founded on an
old observation, made for the first time in 1680 by Leu-
wenhoeck, then by Desmazieres in 1825, and renewed in.

Fig. 7. — -Top yeast of beer.

Young.

Old.

1835, almost simultaneously, in Germany by Kutzing
and Schwann, and in France by Cagniard-Latour.
Subjecting the yeast to a microscopical examination, all
these observers had seen that it consisted of ovoid or
spherical globules of an organized aspect (Fig. 7), which
Cagniard-Latour had the merit to consider as clearly
living beings, "Capable of reproducing themselves by

62 PASTEUR : THE HISTORY OF A MIND

budding, and probably acting on sugar only as a result of
their growth."

It was only a phrase. Schwann had brought argu-
ments and made experiments. He had shown in the
first place that, contrary to what Gay-Lussac had said,
oxygen was not sufficient to start a fermentation. When
heated air was admitted to sugared must, the sugar re-
mained intact, and no yeast was produced. But the
oxj^gen in the air had not been touched. That which was
lacking was a something contained in the air, which the heat
had destroyed. Schwann says clearly that this some-
thing is a germ; he even says it is a vegetable germ,
basing this statement upon the fact that he has found
the yeast sensitive to arsenic, like many vegetables, and
not to nux vomica, which is deadly to many animals.
He found the yeast in the precipitate of fermented bever-
ages; he assured himself that the fermentation begins only
when the yeast is present, and is arrested when the
yeast ceases to multiply. He recognized the existence
of a very close relation between the reproduction of the
yeast and the fermentation, and in closing, he expresses
the opinion that the plant nourishes itself on the sugar
and rejects in the form of alcohol everything that it
cannot use.

Almost word for word this is a statement of our
present ideas. So perfectly do we agree with it that
we ask ourselves why the contemporaries of Schwann
were not able to hear his voice. The reason is very
simple: they had their prejudices as we surely have ours.
They also loved new ideas less than we; they demanded
proofs before accepting new ideas, and it is unfortunate
that those of Schwann had not the desired clearness.
The very short memoir, in which they were set forth,
was given out as a preliminary communication, but
this was not followed by any more detailed publication.

CAGNIARD-LATOUR, SCHWANN, HELMHOLTZ 63

The experiments, when repeated, were not always
successful, especially when, instead of working with
sugared musts, organic infusions were used. But how
separate, in their causes and origins, phenomena so
evidently analogous as fermentation and putrefaction?
Opinion remained, therefore, a little hesitating, and the
best proof that the old ideas were not disturbed is the
work of Helmholtz published in 1843, the first work of
the illustrious physicist.

Helmholtz repeated with success the experiment
of Schwann, and asked himself what is this something
in the air which heat kills, or renders inactive.
It may be, he said, only a putrid exhalation coming
from a mass undergoing fermentation, and capable,
by virtue of an unknown power, of provoking a new
fermentation: or else it is a living germ. In the latter
case, the germ is insoluble in water. The putrid ex-
halation is, on the contrary, soluble and therefore dif-
fusible. Let us take, therefore, two vessels separated
by a membrane; in one let us place a liquid under-
going fermentation, or putrefying, in the other a liquid
of the same nature but not fermenting, and let us see
what will happen. If the fermentation does not
cross the membrane, then it is produced by living
creatures; if it does pass the membrane, it must be
attributed to something else.

Now the experiment is always successful with liquids
undergoing alcoholic fermentation, and rarely or never
with macerated meat. That is, the presence of the
membrane prevents the alcoholic fermentation from
passing, but does not arrest the cause of putrefaction,
whatever it may be. From this Helmholtz concludes
that there are two kinds of transformation of organic
matter, one which takes place with the concourse of
microscopic organisms, and the other without them.

64 PASTEUR : THE HISTORY OF A MIND

IV

LIEBIG

This, then, was the result of the first attempt of the vital-
istic theory of fermentation to range itself as an opponent
of the purely chemical theory. Cagniard-Latour, Helm-
holtz, Schwann, were forerunners, but no one listened to
them. The uncertainty of their experiments and argu-
ments accounted for this to some extent. There was
another and greater obstacle, namely, the general state
of the scientific mind of the time. Chemistry had just
done such beautiful things, that it believed itself, and
every one believed it, capable of doing still more. It
did its best to explain everything, down to the most
mysterious phenomena of life, by the simple play of
physical and chemical forces, and behold how, in a
remote corner and one little known to science, it sees
reappear in the form of an animate cause, those living
forces which it had expelled little by little from the
domain of physiology. That seemed to it a step back-
ward. "In what respect," said Liebig, apparently
with reason, ''does the explanation of fermentation
appear to you any clearer when you have introduced
into it a living organism, even if it is everj'^vhere in
it! But you see for yourself that they are not present
in the putrefactions. Let us admit, if you wish,
although it seems very extraordinary, that the meat and
the sugar are destroyed by different methods. But the
sugar can undergo diverse fermentations, very close to
the alcoholic fermentation, and even frequently accom-
panying it: the lactic fermentations, the butyric, etc.
Do you find in these fermentations am'thing resembling
the yeast? Do they not behave exactly like the macer-
ations of meat? Your explanation limps, and encoun-

LIEBIG 65

ters obstacles at every step. For me, on the contrary,
these transformations present a common character,
namely, that of taking place, every one of them, in
the presence of an organic substance in the process of
decomposition. We start a lactic or butyric fermen-
tation by means of old cheese, or putrid meat. As for
the alcoholic fermentation, Colin showed in 1828, that
this could be provoked by means of many organic
nitrogenous substances, different from the yeast of
beer, provided that they are in process of decomposition.
It is these dead substances which form the ferment.
I do not forget the experiments of Thenard on the almost
constant production of yeast in juices when in fermen-
tation; I do not forget, furthermore, the conclusions
of Cagniard-Latour and Schwann confirmed by Quevenne,
Turpin, and Mitscherlich. But this yeast does not
embarrass me, it enters into my system. If you admit
that it lives, then you admit also that it dies. Now,
it is in dying that it acts, as a result of the decomposition
which it undergoes at this moment and of that Thenard
furnishes us the proof."

That savant had seen, in fact, that by adding 20 parts
of yeast to 100 parts of cane-sugar in solution in water,
he obtained a rapid and regular fermentation, after
which the remaining yeast collected on a filter weighed
no more than 13.3 grams. Added to a fresh and equal
quantity of sugar, this residue produced a fermentation
more slowly than the first time, after which it was
reduced to 10 grams, and was incapable of producing
a new fermentation. What more fitting to demon-
strate that the yeast destroys itself and is consumed by
its own activity? The theory of Liebig finds a good
defense, therefore, from this point of view. As for the
undeniable multiplication of the yeast in the vat of the
brewery, in the manufacture of wine, especially of the

66 PASTEUR : THE HISTORY OF A MIND

white wines, Liebig, who had much imagination, had
an explanation all ready. All the fermentable liquids
contain what he called gluten, what we would call to-day
albuminoid substances. In contact with air this
gluten oxidized and was precipitated in the form of
yeast: this is the explanation of the experiment of Gay-
Lussac. Consequently, in proportion as one part of
the yeast destroys itself by acting on the fermentable
substance, another forms: if more is formed than is
destroyed we have the case of the brewery vats; if
more is destroyed than is formed, we have the case of
Thenard's experiments concerning which we have just
spoken.

For the fundamental explanation of the phenomena,
Liebig had only to take the ideas of Willis and of Stahl
on the internal movement of a mass in fermentation,
attributing the motive power to the ferment. ^'The
yeast of beer, and in general all animal and plant sub-
stances undergoing putrefaction, impart to other sub-
stances the state of decomposition in which they find
themselves. The movement which is imparted to
their own elements, as the result of the disturbance of
the equilibrium, is communicated equally to the elements
of the substances which are found in contact with them."
For example, sugar is a stable compound with respect
to a great number of external influences, air, light, even
heat. On the contrary, it is an unstable structure with
respect to the molecular movement of organic sub-
stances in decomposition: under their action it breaks
up easily into alcohol and carbonic acid.

Thus the theory of Liebig, without denying or accept-
ing formally the organization of the yeast globule,
confined itself to denying its vital role in fermentation,
and collected all these phenomena into one single
formula. From all sides, it presented a good face,

PASTEUR: LACTIC FERMENTATION 67

and as it was defended with energy and talent, it ended
by triumphing. Taught in all the books, accepted as
true in all the works published on fermentation, it had
become almost a dogma, that is to say, what in science is
the most difficult to overturn. We may attack facts by
showing that they are inexact, experiments by testing
their conclusions; but what can we do against a doctrine
to some extent philosophic, resting for the most part on
argumentation, an argumentation so voluminous that
one can demolish certain parts of it without weakening
the rest, and which is based on that half mystical con-
ception of an imparted movement?

This detailed exposition was necessary in order
to show the state of the question at the time Pasteur
approached it, and to understand the nature of the means
which he employed to solve it. We shall now be able
to go on more quickly: we have reached the level ground.

V
PASTEUR: LACTIC FERMENTATION

The point which I wish to make clear in the beginning
is this: if Pasteur immediately made decided progress in
his studies it is because he approached them with another
guiding idea than his contemporaries.

In his memoirs, especially in the introduction to his
Memoire sur la fermentation lactique,^ it is easy to find
what guided him, but it must be a little more developed.
Its origin is an observation made during the study of the
rotary power. In many of the industrial fermentations,
we meet, as a secondary product, amyl alcohol, a sub-
stance endowed with rotary power and capable, further-

1 Ann. de ch. et de phys., 3'' serie, t. LII. Paris, 1858, p. 404.

68 PASTEUR : THE HISTORY OF A MIND

more, of forming several crystalline combinations which
do not show any hemihedrism. It was the first exception
which Pasteur had encountered in this law of correlation
between hemihedrism and the rotary power. Now, ac-
cording to the current ideas of the epoch, fermentation
was a disintegration: it was the breaking up of a molecule
by decay, the debris of which, still voluminous, formed
new molecular edifices which were the products of the
fermentation. Consequently, by virtue of the theory
of Liebig, the edifice of amyl alcohol must form some
part of the framework in the molecule of the sugar in
order to resist dismemberment, and as it preserves the
rotary power its optical action must be derived from that
of sugar.

This idea was repugnant to Pasteur. He had seen,
for example, in malic and maleic acids, that the least
injury to the structure of the molecule made its rotary
power disappear. "Every time," he says, "that we
try to follow the rotary power of a body into its deriva-
tives we see it promptly disappear. The primitive
molecular group must be preserved intact, as it were,
in the derivative, in order that the latter may continue
to be active, a result which my researches permit me to
predict, since the optical property is entirely dependent
on a dissymmetrical arrangement of the elementary
atoms. But I find that the molecular group of amyl
alcohol is too far away from that of sugar, if derived from
it, for it to retain therefrom a dissymmetrical arrange-
ment of its atoms."

The origin of this alcohol must, therefore, be more
profound, and, recalling the before-mentioned fact that
life alone is capable of creating full-fledged new dissym-
metries, and thinking that his objection would no longer
have a raison d'etre, if between the sugar and the amyl
alcohol a living organism were interposed, Pasteur

i

PASTEUR: LACTIC FERMENTATION 60

found himself led quite naturally to think of fermenta-
tion as a vital act.

Instinctively, for it was still only instinct, he took his
stand by the side of Cagniard-Latour and the vitalists.
But, in order to defend his position, it was necessary for
him to resort to experiment.

In collating the dates of his different publications, it is
evident that he began at nearly the same time the study
of the lactic fermentation and the alcoholic. Why did
he devote his first work to the lactic fermentation, a
much less important one from the industrial point of
view? Without his telling us, it is easy to divine. In
the first place, when the fermentation becomes lactic
there is produced, in the greatest abundance, this mys-
terious amyl alcohol of which we have just spoken. But,
from his point of view, there is another deeper reason,
that is, that the alcoholic fermentation had already lost
its bloom. Liebig and the most determined of his
partisans had almost condemned it by admitting that
the 3"east was necessary, and that it might be a living
organism. Their great argument, as we have said above,
was always: what role would you wish us to attribute to
the yeast, when we see so many other related fermenta-
tions, the lactic fermentation for example, taking place
without it, and without anything which resembles it?

The lactic fermentation was, therefore, in a certain
sense, le champ clos on which he must struggle, and I
believe I am so much the more in the right in attributing
to Pasteur this order of ideas because his argument is
confined to the following: All that one does with the
yeast, I do with the grayish deposit which I find at the
bottom of my flasks in which lactic fermentation is going
on. The yeast has an organized aspect: my ferment has
also, but it is different and difficult to see, and you have
not been able to recognize it because, owing to your idea

70 PASTEUR : THE HISTORY OF A MIND

that the organic matter itself is the ferment, and so much
the more the ferment the less it is disorganized, you take
for the ferment the altered gluten and the rotted cheese
whose amorphous debris covers and obscures the organ-
ized ferment. As for me, I have another idea, accord-

FiG. 8. — Ferments of wine and beer: (I) Bacillus of turned wine; (2)
lactic fermentj (3) but3'ric ferment; (4) ferments of ropy wine; (5) ferments
of vinegar; (6) amorphous deposit; (7) sarcina. In all of the fields j-east
cells.

ing to which the organic matter is only the food for the
ferment. I offer this food to it in a liquid state in bouil-
lons or clear macerations, and then my ferment forms,
at the bottom of the flasks, a homogeneous layer where it
exists alone, or where, when mixed, one can dissolve with

PASTEUR: LACTIC FERMENTATION 71

a little acid the carbonate of lime which I have had to
add to it. And then it is easy to observe it and to recog-
nize it as an organized being, all the individuals of which
resemble one another.

Furthermore, this ferment reproduces itself. Just
make, as I did, a clear must containing sugar and chalk:
sow there a trace of the deposit from a former fermenta-
tion, as small an amount as you wish, and you will see
a new fermentation begin. The lactic ferment will
multiply, as does the yeast of beer. You will have more
of it than you sowed, and with this deposit you will be
able to start in different liquids as many lactic fermen-
tations of sugar as you wish, provided these liquids are
well chosen, for this ferment, being a living creature, has
its special requirements and develops well only when it
finds within reach all that it needs.

On the other hand, when this is the case, it accom-
plishes with rapidity the transformation over which it
presides. "The purity of a ferment, its homogeneity,
its free unrestrained development by the aid of food
substances well adapted to its individual nature, these
are some of the essential conditions for good fermenta-
tion." Here we have, let us say, in our turn, a revolu-
tionary phrase, one that goes out to meet the enemy,
drums beating and fuse lighted.

There is still more in this short memoir of 15 pages.
There is a very exact statement of the good or bad
influence, as the case may be, of the acidity or alkalinity
of the liquid. The yeast prefers sugared media which
are acid; the lactic ferment, neutral sugared media, and
it is for that reason we add to the cultures carbonate of
lime. There is also a hint, as it were an apparition,
of the effect of antiseptics. "The essential oil of onion
juice inhibits completely the formation of the yeast
of beer: it appears equally harmful to Infusoria. It

72 PASTEUR : THE HISTORY OF A MIND

can arrest the development of these organisms without
having any notable influence on the lactic ferment."
Thus one could use antiseptics, with a suitable culture
medium, for separating the ferments one from another.
This memoir then is full of suggestion, and, strangely
enough, all these propositions which were so new and so
bold for the epoch were announced de piano, almost
carelessly, with the tranquil confidence of a man sure
of his facts, and to whom, if one did not known him, one
might even have attributed malicious intentions, he
showed so much apathy. It is only at the end of his
memoir that he admits that nothing of all this has been
demonstrated. "If any one should say to me that in
my conclusions I go beyond the facts, I would reply
that that is true in this sense that I have taken my
stand unreservedly in an order of ideas which, strictly
speaking, cannot be irrefutably demonstrated." But
his system is so logical that he takes pleasure in believing
in it. Everything is so consistent in his conception
and in his mode of exposition. The idea of a specific
ferment associated with each fermentation, of dispro-
portion between the weight of the ferment produced
and the weight of the matter transformed, of vital com-
petition between two organisms which simultaneously
invade the same medium and ultimately leave it to the
one which is best adapted to the conditions it finds there,
— all these ideas, which the future was to develop so far,
are found not in embryo, but clearly set forth in this
paper, the work of exuberant youth, in which we still
see the thought bubbling and fermenting. Pasteur
ended it with a general profession of faith: "It is now
my opinion," he said, "as the result of the knowledge
I have gained on this subject, that whoever will judge
impartially the results of this work and those which I
shall publish in the near future, will recognize with me

ALCOHOLIC FERMENTATION 73

that fermentation is correlative with life, with the or-
ganization of globules, not with the death or putrefaction
of these globules, neither does it appear to be a phenom-
enon of contact where the transformation of the sugar
takes place in the presence of the ferment without
giving anything to it or taking anything from it. These
latter affirmations, one will soon see, are contradicted by
experiment."

This was the announcement of the memoir on alcoholic
fermentation, to which we are now come.

VI

ALCOHOLIC FERMENTATION

In the memoir on alcoholic fermentation^ the move-
ments and the tone differ wholly from those of the
memoir which precedes. The latter is not that tranquil
and almost ironical exposition of a new theory which
holds up its head and marches along easily over a land
where its competitors hobble and stumble, or where
they have need at every step of what Victor Hugo would
have called crutch hypotheses. It is a series of blows
straight from the shoulder, delivered with agility and
assurance.

Ah! You insist on thinking of alcoholic fermentation
as a simple breaking up of sugar into alcohol and carbonic
acid! Undeceive yourselves: there are also glycerin and
succinic acid formed in considerable quantities and almost
as constantly as the principal products of the fermentation.

Ah! So you are bound to ignore the j^east in this
phenomenon, or at the most will concede to it only the
role of an initiator! Very well! Learn that this yeast

1 Ann. de ch. et de phys., 3'' serie, t. LVIII, 1860.

74 PASTEUR: THE HISTORY OF A MIND

ahvaj's borrows something from the sugar, and makes
a part of its own tissues out of this food. Learn also
that it is only on the condition of keeping a little of the
sugar for itself, that it consents to give you the rest in
the form of alcohol.

Ah! Do you believe that you can write an equation
for the alcoholic fermentation as you write the equation
for the preparation of oxygen? Very well! Simply
to account for the production of the glycerin and the
succinic acid, the eciuation must be very complicated,
and if you wish to take into consideration the things
borrowed by the yeast from the sugar, it will become so
complex that it would be better not to write it at all.
Would you dream of writing in the form of an equation
the series of transformations which are undergone by
the sugar in the tea or coffee you drink? The yeast is a
living thing just as you are.

This is a resume of the attack directed by Pasteur
against the old ideas, and when he had demolished them,
he set about their reconstruction. Omitting some of
the less important details, and taking up the exposition
proper, the edifice, it must be admitted, is simple: it
amounted to this, to produce regular fermentation under
conditions in which none of the prevailing theories could
explain the phenomenon.

It is curious to see how the idea of this pertinent ex-
periment came to Pasteur little by little.

Thenard, we have seen, had determined that there was
a diminution in the weight of the yeast during fermen-
tation, which is true for the conditions of his experiment.
He had found, furthermore, that this yeast, when ex-
hausted in the presence of an excess of sugar, no longer
contained nitrogen. This last was an error, due to the
imperfection of the methods in use for the detection of
this substance.

ALCOHOLIC FERMENTATION 75

On this first error, Dobereiner grafted another by
affirming that the nitrogen lost by the yeast was found
in the fermented liquid in the state of ammonia. As
organic matters in decomposition also produce ammonia,
this affirmation of Dobereiner was, clearly, very favorable
to the ideas of Liebig, and the latter, a great collector
of fact and abstractor of quintessence, did not fail to
seize on this and make it serve to prop his doctrine of
fermentation.

For Pasteur, on the contrary, this fact was inexplicable,
since the ferment was not a dead substance in process of
destruction, but a living thing in process of organiza-
tion. In trying to discover whether the statement of
Dobereiner was true he found not only that the nitrogen
of the yeast did not leave it in the form of ammonia,
but, moreover, that the yeast in process of fermentation
caused the ammonia to disappear from ammoniacal
salts added to the liquid.

But how could the yeast do this? He then was very
bold to reverse the reasoning of Liebig and of Dober-
einer, and to say: the albuminoid substance of the fer-
ment does not give up ammonia; it is, on the contrary,
the ammonia which produces the albuminoid substance.

This way of looking at it was so new and the pre-
sumption seemed so ill-founded that Pasteur hesitated,
as he himself acknowledges. But it was in accordance
with facts and the logic of his ideas. In any case, the
only thing to do was to resort to experiment. After
some attempts, the latter succeeded, and it became the
critical experiment, the experimentum cruets, which
made it possible to judge the doctrines side by side.

This experiment was entirely new. The problem was
to grow the yeast in a liquid deprived of all organic
nitrogenous matter — one containing only perfectly pure
cane-sugar, various mineral salts to supply the yeast

76 PASTEUR : THE HISTORY OF A MIND

globules with the elements of their structure, and an
ammonia salt to provide them with nitrogen. If, in
this medium, completely robbed of that organic nitrog-
enous matter which Liebig declared to be necessary,
one obtains a fermentation, and if, at the same time,
the yeast multiplies and develops, deriving all the
complex elements for its tissues from the sugar and the
ammonia, it will certainly be impossible not to admit
a correlation between the fermentation and a phe-
nomenon of development and of life in this ferment
which Liebig considered a dead substance.

With the same blow by which the theory of Pasteur
triumphed there fell into ruin not only the theory of
Liebig, but another theory then much less flourishing,
namely that of Berzelius, according to which the ferment
exerted an action only by its presence, and provoked
the decomposition of the organic matter without deriving
anything from it or contributing anything to it, remain-
ing, furthermore, unchanged in quantity and quahty
throughout the process. In our experiment, the ferment
must, on the contrary, increase in weight, taking all this
increase from the sugar.

It is just because this experiment was so interesting
that it was difficult. It was necessary, in the first place,
for Pasteur to devote his attention to supplying the
yeast with a suitable mineral medium, and a rather com-
plex one too, including phosphates, salts of potassium,
magnesium, and ammonia. It matters not that the
cell of the j'east is small; its needs are great and varied.
It was the first time that Pasteur had run up against its
exacting requirements, and the lesson which he drew
from this contact was not lost. Furthermore, even when
one gives to the j^east all that it needs in the way of
mineral substances, it has much more difficulty in living
in this medium where it must form all the substances

ALCOHOLIC FERMENTATION 77

constituting its tissues, than in the juice of the grape or
the must of beer where it finds everything composed of
utilizable elements. Nevertheless, in his Memoire sur la
fermentation alcoolique Pasteur succeeded in giving an
example of fermentation accomplished under these
difficult conditions.

Later, feeling the importance of this experiment, he
returns to it, perfects it, and renders it surer by em-
ploying a more vigorous yeast than that of his first
experiments. It is scarcely 13 years later in his Etudes
sur la biere that he gives it the definitive form. But what
he says in his memoir of 1860 is sufficient to carry
conviction.

No, it is not true, he said in substance, that there is
need of organic material in decomposition in order to
start alcoholic fermentation. An imperceptible trace
of yeast, introduced into a liquid containing, in addition
to the pure sugar, only pure crystallized mineral salts,
makes this sugar ferment and, at the same time, the
yeast develops, buds and multiplies. All the carbon
of the new globules is derived from the sugar, all their
nitrogen from the ammonia, which destroys also the
theory of Berzelius, according to which the ferment
acts only by its presence, in the same way that a red-
hot cannon-ball would start a fire. Moreover, it is not
simply in the absence of already manufactured organic
nitrogenous matter that the yeast globules borrow from
the sugar what they need : on the contrary, there is every
indication that this borrowing follows exactly the same
laws when the liquid is more favorable to fermentation.

There is, nevertheless, a difference, namely that in
those rich liquids, the musts, the new globules which
form, finding themselves surrounded by nutrient sub-
stances, have no need of borrowing anything from the
globules already formed, while in an exhausted medium

8

78 PASTEUR : THE HISTORY OF A MIND

such as sugared water, the new globules live at the ex-
pense of substances which the older globules have
allowed to diffuse into the liquid. All are famished and
then the young consume the old. It is this work of
diffusion and of exhaustion of globules already formed
in order to feed the young, which caused the diminishing
weight of the yeasts sown by Thenard in the sugared
water in the experiments cited above, and which has
led to the belief that the yeast is destroyed in fermenting
the sugar. In reality, there were not enough of the
new globules formed to compensate for the loss of weight
which the old globules underwent as the result of the
diffusion but if we add to the weight of the globules the
weight of the soluble organic matter which the filter does
not retain, but which we can find and estimate in the
liquid, we see that this total weight always increases
during the fermentation, because there is always a little
sugar which becomes yeast.

In proportion as the fermentation is accomplished
under better conditions and the yeast is less exhausted
toward the end, the increase in weight is more notable.
We are aware of this from the fact that the yeast con-
tinues to give off carbonic acid at the expense of its own
tissues for some time after all the sugar has disappeared
from the liquid which bathes it. We would say to-day
that it consumes the reserve food which it has made,
for it is a provident little cell which stores up in a time
of plenty for a time of famine. How is it possible not to
see that all this is a question not of decomposition and
of death, but, on the contrary, of development and
of life?

AEROBIC LIFE AND ANAEROBIC LIFE 79

VII
AEROBIC LIFE AND ANAEROBIC LIFE

And Pasteur, in all the enthusiasm of his discovery,
adds or did add soon: It is not simply for alcoholic
fermentation that this is true. I can return now to
affirmations respecting the lactic fermentation, which
it is very easy to start in a purely mineral medium.
The lactic ferment is smaller and in appearance simpler
than the alcoholic ferment. It is a little cell constricted
in the middle (2, Fig. 8) and the whole interior of which
is filled with a mass that appears to be homogeneous,
whereas it is differentiated in the yeasts. But the needs
of this little cell are not less: they are different, that is
all. These two dissimilar ferments are, moreover,
specific, that is to say the alcoholic ferment does not
produce lactic acid, contrary to what is generally be-
lieved and taught, and the lactic ferment does not yield
alcohol when it is alone and unmixed with the alcoholic
ferment.

Do not believe, furthermore, with Boutron and Fremy,
that successive fermentations can take place in the same
medium with or without order, according to the mode
and progress of the decomposition of the nitrogenous
substance. That happens when your spoiled meat or
rotted cheese carries with it into the fermentation flask
the numerous organisms which ordinarily populate it:
it does not happen when you grow a pure ferment in
clear nutrient bouillons. You are told that the butyric
fermentation, the mannitic, etc., accompany or follow
lactic fermentation. It is not so, everything stops in
my flasks when all the sugar is transformed into lactic
acid, now become lactate of lime by contact with car-
bonate of lime introduced into the liquid.

80 PASTEUR : THE HISTORY OF A MIXD

But, while keeping them separate, we can make these
fermentations follow each other, although, according to
the ideas of Liebig, they are interblended. Take this
liquid in which the lactic ferment has grown, and in
which there are only lactate of lime and mineral salts
in solution: after having heated it to sterilize it, sow
there a drop of a liquid in which there has occurred
spontaneously a butyric fermentation, and. therefore,
one which is almost surely impure. Phenomena anal-
ogous to those of alcoholic fermentation occur: a gas is
liberated which is no longer a pure carbonic acid, but a
mixture of this gas and hydrogen. This mixture has
very little odor, because of the absence of sulphuretted
hydrogen. These are the indications of a fermentation.
Let us see now what is present in the liquid which has
become clouded. We find there only motile rods, very
agile, with undulating movements, sometimes ranged in
a series, like a string of boats, and then motile on their
articulations (Fig. 8, sec. 3), which testifies to the fact
that they reproduce and multipl}' b}' elongating and
segmenting across their longer axis; this is the mode of
reproduction called fission.

\Mien he observed for the first time those organisms
which he called vibrios, Pasteur had a great surprise,
the trace of which is visible in his note on this subject.
The yeast of beer and the lactic ferment were non-motile
globules; the butyric ferment was motile, and partook
of the nature [animal] of those organisms which Ehren-
burg and Dujardin had found in infusions. O the power
of words! Nothing was more natural than to find in
fermentations the same organisms as in infusions, since
Pasteur nourished his ferments with vegetable infusions;
he hesitates, however, on finding that the butyric ferment
belongs to the Infusoria. "I was so far," he said, "fi'om
expecting such a result, so far, indeed, that for a long

AEROBIC LIFE AND ANAEROBIC LIFE 81

time I thought it my duty to apply all my efforts to
dispelling the apparition of these little animals, from the
fear lest they nourished themselves on the vegetable
ferment which I supposed to be the butyric ferment, and
which I was trying to discover in the liquid medium that
I employed. But not able to find the origin of the bu-
tyric acid, I ended by being struck with the coincidence
which my analyses showed me to exist between this acid
and the Infusoria, and, reciprocally, between these
Infusoria and the production of this acid. We must
consider them the true butyric ferment."

Thus Pasteur's surprise came from the intervention in
a fermentation of an organism which he considered to be
an animal because it was motile, while the non-motile
alcoholic and lactic ferments were considered as vege-
tables. We can to-day scarcely understand this aston-
ishment and these scruples. But from 1850 to 1860, the
old barriers established between the vegetable and animal
world had scarcely begun to fall. Although admitting
in his Recherches sur les zoospores des algues, which
appeared in 1851, that the green Infusoria and the Vol-
vocaceae "present animal characters too pronounced and
too permanent for it to be possible to relegate them to
the vegetable kingdom," de Thuret insists, none the less,
on the difficulty of tracing an exact line of demarcation
between animals and the lower vegetables. '^4.t this
time," writes my excellent confrere, M. Bornet, " motility
appeared to be so evidently an animal character that
Rabenhorst published, between 1849 and 1852, a collec-
tion of Diatoms and Desmids as Ein Beitrag zur Fauna
von Deutschland.^^ Pasteur, who was not a naturalist,
was excusable for still holding this opinion in 1862, and
although astonished at his scruples, one must be pleased
with him for taking so much pains to efface them from
his mind. He did not suspect then that this discovery

82 PASTEUR : THE HISTORY OF A MIND

would open a new world, the world of the bacteria, a
world still more active and more densely populated than
the world of the yeasts.

There was, in this same Note which we are analysing,
a fact much more important than the animal or plant
character of the butyric vibrio: namely, that this organ-
ism lives in the absence of the oxygen of the air and even
fears its contact. Pasteur has often related how this
fact leaped, so to speak, into his field of vision. In
examining these liquids, he would take a drop, place it on
the slide, cover it quickly with a cover glass, which
spread it out in a flat layer, and put the preparation
under his microscope. But on examining, with the
care which he applied to everything, one of these little
flattened drops of liquid undergoing butyric fermenta-
tion, he was astonished to see that on the margins of the
little drop, wherever it was in contact with the air, the
bacteria had become non-motile and inert, although they
continued to move with agility in the central portions.
This was a spectacle quite the reverse of that which he
had had occasion to observe often in the case of the
animalcules of the infusions. Especially when we ex-
amine, under the microscope, those from the surface of
infusions, they voluntarily leave the central portions of
the drop to approach the margin, the only place where
there is enough oxygen for all. In the presence of this
obiiervation, Pasteur asked himself immediately: is it
true that these vibrios are trying to escape from the
oxygen? An experiment along this line was easy to
make. By passing a current of air through a flask in
which the butyric fermentation was going on, the fermen-
tation was retarded or arrested, and behold a new idea
was introduced into science, the idea of anaerobic life
as opposed to aerobic life which was believed to be that
of all the animals of creation. We shall see how Pasteur

AEROBIC LIFE AND ANAEROBIC LIFE 83

developed this idea later. For the moment we may
content ourselves with saluting its dawn.

This idea has, nevertheless, an indispensable com-
plement which we can and must give immediately.
There is oxygen everywhere, in the air and in the water.
It is in the liquid in which we have sown our bacillus
which is unable to bear the air, our anaerobic vibrio.
How is it that it can develop) in this aerated medium?
It is because we have, unawares, sown with it in the liquid
some aerobic organisms which have consumed its oxygen,
and, this being achieved, have fallen inert to the bottom,
permitting the butyric vibrio to take possession of the
medium. If the liquid is in contact with the air some
of these aerobic organisms have remained on its surface.
There they continue to live, to swarm, and they form a
gelatinous layer which is, for the oxygen, a barrier as
impermeable as a wall of glass; all of it that is able
to penetrate is absorbed in the" passage, and, thanks to
this aerobic life on the surface, the anaerobic life can
pursue its course in the depths without hindrance.

Having come to this simple and satisfactory concep-
tion, it was not the moment for him to stop. Up to
this time we have observed only the phenomena of the
fermentation of sugar, or of the lactate of lime. Let
us now turn our attention to an albuminoid substance,
beef bouillon, egg albumen, meat macerated in water.
Let us, as we have done hitherto, begin the operation
by introducing into it a drop of an organic liquid under-
going putrefaction: we shall see the same phenomena
begin again. There is formed once more on the surface
of our liquid a living layer which will absorb the oxygen
and will leave the interior of the mass free for the
anaerobic hfe. If our liquid is contained in a closed flask,
one or several aerobic generations will dispel the oxygen,
and will leave the field free to the anaerobes. There

84 PASTEUR : THE HISTORY OF A MIND

will be produced once more the gases, which this time
will have an odor, because in this reducing medium,
hydrogen is mixed with sulphuretted and phosphoretted
hydrogen, which are not formed in contact with air,
or, if formed, are oxidized immediately: we shall have,
therefore, a putrid odor. But the gases will have the
same origin as in the fermentation of lactate of lime.
Fermentation and putrefaction are synonymous terms,
and there is no reason for maintaining the old distinction,
which had not yet disappeared from the conclusions of
Helmholtz. In these two phenomena the liberation of
gases has the same origin, and it is due to organisms
living in the absence of air. It is opportune to ask
if there is not a close relation between the phenomena
of fermentation and of anaerobic life. Here we have a
great question which Pasteur put to himself immediately,
but which he did not solve until some years after.

I have thought best to present without detailed exami-
nation all these deductions, because in reality thej^ were
the work of some weeks of labor and meditation, and
also because we have in them an example of Pasteur's
insight, of his ability to discover and state a problem,
of the patience with which he gathered together the
elements of the solution. During the best years of his
life, this man lived in advance of his time, a pioneer lost
in the solitude, absorbed in the contemplation of the
vistas which he was discovering, and which his eye alone
was to scrutinize and survey. What less astonishing
than his apparent indifference to things of daily life!
He lived in his thoughts without being a dreamer, for a
dream which goes somewhere and which bears fruit is no
longer a dream.

THIRD PART

Spontaneous Generations

I

SPONTANEOUS GENERATION AND FERMENTATION

Pasteur's contributions to the study of fermentations,
which we have just seen going on under our eyes, may
be summed up in a few words. Fermentation is no
longer a vague transformation, indeterminate in its cause
and in its origins, capable of taking place under the
influence of any organic substance whatsoever: it is a
specific phenomenon, due also to the existence and
development of a specific organism, the study of which
under the microscope is facilitated in proportion as
we remove from the liquid undergoing fermentation
those insoluble organic substances which it was formerly
believed necessary to add to it. Since, by working
with a clear bouillon, it is possible to follow closely the
organism sown, and to be sure that the bouillon con-
tains this and this alone, the study of its nutrition be-
comes easy. Now, by acting on the nutrition of an
organism, we become the master of it; we can sow it and
cultivate it with as much certainty, and with the same
absence of weeds, as we can lettuce in a garden. We
can also banish it from liquids where there is no occasion
for its presence. In short, this infinitely small organism
becomes tangible and open to experiment: a capital
idea, which the whole life of Pasteur will henceforth be
spent in developing.

Nevertheless, the logic of his studies placed before him

85

86 PASTEUR: THE HISTORY OF A MI XD

a question which, with just reciprocity, these same studies
permitted him to solve. Whence come the ferments?
Are they organized spontaneously at the expense of
dead organic matter? Or, do they come in the regular
ways from organisms like themselves, and from pre-
existing germs? Here we have a question which had
been asked very often, ever since men had begun to reflect,
and which had been solved in very different ways. Pas-
teur, himself, at the close of his studies on crystallog-
raphy, had been very undecided, and I think also very
indifferent regarding the answer. He had no precon-
ceived ideas: he would accept the results of experi-
mentation. But at the point to which the study of
fermentations had led him, he could no longer believe
in spontaneous generation: it is too far removed from
the idea of specificity, which he had just introduced
into science. Everywhere around us the idea of species
accompanies the idea of continuance by the germ cell,
and it would be very astonishing if this order were changed
in the world of the infinitely little.

The ancients believed in the spontaneous generation of
eels from the ooze of rivers, and in that of bees in the
entrails of a dead bull. But these were the ideas of a
child who had never lived in the face of the progress of
knowledge. For a long time people had believed in the
spontaneous generation of worms in putrefying meat,
because in this case the experiment is more difficult or
the observation is more dehcate, and a Redi was neces-
sary to demonstrate that these worms come from eggs
laid by flies, and that one would no longer see them in a
piece of meat which was protected by a simple layer of
gauze. It is true that this piece of meat continued to
putrefy, to decay, and to nourish, no longer worms but
confused tribes of microscopic organisms. As long as
it was the belief that fermentation and putrefaction oc-

BUFFON, NEEDHAM, SPALLANZANI, ETC. 87

curred by chance, without any order or regulation, it
had been possible to believe that the organisms which
accompanied them were also due to the spontaneous
organization of the elements of the meat undergoing
putrefaction, or of the organic matter added to the
liquids of fermentation. But as soon as these fermenta-
tions and the organisms which produced them assumed
something of a specific nature, there was something
strange in making them come into existence spontane-
ously. Why should chance create species endowed with
hereditary properties? Why should it create certain
organisms and not others?

The knowledge of fermentations which Pasteur had just
acquired forced him, therefore, to deny the hypothesis of
spontaneous generations. He observed, furthermore,
that after having abandoned all pretense of explaining the
origin of animals visible to the naked eye, and thus
accessible to experiment, this hypothesis had limited its
domain to the realm of microscopic organisms whose
minuteness precluded all exact scientific research. But
in this quarter he had had some experience and could
hope to escape some of the difficulties which his predeces-
sors had encountered. In spite of the advice of M.
Dumas, he, therefore, approached this subject with
confidence.

II

BUFFON, NEEDHAM, SPALLANZANI, SCHULTZE,
SCHWANN, SCHROEDER AND DUSCH

Like the question of fermentations, the question of
spontaneous generations had for long years been the
subject of philosophical speculations and oratorical
dissertations. Buffon had treated it with solemnity.
How remain indifferent in the presence of the very

88 PASTErR : the history of a aiixd

sources of life, before this phenomenon which endows
with a new existence the organic atoms which death has
just dissociated and Hberated? There is no death, said
the behevers in this doctrine. When an animal dies,
the life of the whole vanishes but not the life of the
elements, not that of its ultimate molecules. Scarcely
are they set at liberty by death, than they at once begin
an independent life, become isolated, and then give birth
to vibrios, to monads, or else they join already formed
aggregations which attract them, and thus produce the
large Infusoria. "Therefore," said Buff on, ''it is in-
evitable that one should encounter all imaginable grada-
tions in this chain of organisms which descends from
the most completely organized animal to the simple
organic molecule."

We see the connection between these ideas and those
which during the same epoch explained the mystery of
fermentations. It was the same organic molecules,
dissociated by putrefaction, which provoked the decom-
position of fermentable substances by communicating
to them their own movement, and which, on the other
hand, became organized into living animalculae. Sin-
gularly, this idea of a common origin did not prevent the
fermentation of a liquor from being considered as some-
thing (juite independent of the Infusoria which might
appear therein, and these two kinds of evolution of the
organic molecule were even regarded as opposed to each
other, and the Infusoria as harmful to the fermentation
which was called the principal phenomenon.

AMiat a strange way of looking at things ! we might say
to-day. Why turn the carpet over in order to see the
design? AMien we know a little of the history of science,
we are no longer astonished at this kind of blindness.
Our conceptions of things are generally more compli-
cated than the things themselves. It is rare that the

BUFFON, NEEDHAM, SPALLANZANI, ETC. 89

human mind sees simply: it is experiment alone which
leads it to simplification by ways which are sometimes
very tortuous. But to attain that end it is necessary
that the mind allow itself to be guided, and that it forget
its conceptions and its formulas. Nature is kindly; it
is we who picture her as bristling and sulky!

In the domain of spontaneous generations, experiment
had been introduced for the first time in 1748 by an Irish
Catholic priest, Needham, whose active faith did not
prevent him from believing in an actual creation, that of
the animalculse of infusions. In order to prove this, he
had employed a mode of investigation destined to play
a great role in the controversies on the question. He had
enclosed some putrefiable substances in well-corked flasks
which he had then heated by plunging them into hot
ashes. The heat, he said, must kill all the living germs,
visible and invisible, which may be introduced into the
flasks, for none are known which resist boiling water.
Now, as my closed flasks withdrawn from the ashes be-
come clouded in a few days, and are peopled with micro-
scopic organisms, I am assisting at a phenomenon of
creation at the expense of dead matter, that is at a
spontaneous generation.

These experiments, accepted for a long time without
question, met in 1765 a redoubtable critic in another abbe,
the illustrious Spallanzani, who, by repeating the same
experiments, with only the precaution of heating the
closed flasks longer than Needham had done, suppressed
all production of Infusoria. Therefore, he concluded,
Needham did not heat enough, and as it was for him to
prove his theory, which, besides, is in disagreement with
the facts of science, it vanished of its own accord, the
only fact on which it could rest having been shown to be
inexact.

Not at all, replied Needham, although with much

90 PASTEUR: THE HISTORY OF A AIIXD

courtesy. If your infusions remain sterile it is because
you heat too much. You alter thus the air in the flasks,
or else you destroy the vegetative force of your liquids.
The first of these objections was acceptable, although it
lacked force and precision in an epoch when the composi-
tion of the air was still unknown. But what was to be
said of the second? The vegetative force of the hquid,
does not that recall invincibly the dormative property of
opium, ridiculed a hundred years before by Mohere?
This strange conception, nevertheless, met with favor,
and, if I recall it, it is because the idea served as a banner.
If, in the discussions on spontaneous generations, there
have always been savants, who, like Spallanzani, have
endeavored never to go beyond experiment, there also
have been always those who, like Needham, have not
hesitated, in a time of great need, to have recourse to
the vegetative force, to the creative power of infusions, or to
other conceptions not less vague and chimerical. There,
as everywhere, has been the tribe of those who love to
deceive themselves with words.

Be that as it may, the celebrated debate raised be-
tween Needham and Spallanzani was left without any
definite conclusion, each of the adversaries showing
clearly that the other was wrong on some points, but not
proving that he himself was right on all. However,
science in its onward march validated or invalidated
their arguments. We have said that Gay-Lussac, by
studying the conserves of Appert, which were nothing
more than the application to domestic economy of the
results of Spallanzani, found that the air in the tins no
longer contained oxygen: this seemed to justify the first
objection of Needham given above. But in 1836, it
occurred to Schultze to replace with ordinary air the air
in the flasks of Spallanzani. After having determined
that they are sterile, he shows that they remain sterile

POUCHET, PASTEUR: THE GERMS OF THE AIR 91

when he introduces air which he has simply made to
bubble through concentrated sulphuric acid. One of
these experiments lasted from May to August, but, al-
though this air was incessantly renewed, it never caused
any production of Infusoria: this proved that Gay-
Lussac was wrong, and Spallanzani right.

The following year Schwann obtained the same result
as Schultze by using air heated by passage through a
bath of fusible alloy. Later (1854), Schroeder and
Dusch replaced the heated air by air simply filtered
through cotton, and from them dates the introduction
into microbiology of cotton plugs for filtering air.

Reading to-day of their experiments, we ask ourselves
why they did not bring universal conviction. What
did they signify save this: that there was in the air a
principle of life which sulphuric acid, heat filtration,
through cotton, destroyed? This principle was, there-
fore, neither a gas nor a vapor, nor one of those solid
bodies which heat respects. It could only be an organic
substance. How is it that Schwann and Schultze did
not as resolutely bring the partisans of spontaneous
generation face to face with this dilemma, as Pasteur was
to do 10 years later: this organic substance which heat
and sulphuric acid destroy, which cotton arrests, can
only be living or dead. Why, being forced to choose, do
you take the hypothesis the most contradictory to that
offered by the best known branches of science?

Ill

POUCHET, PASTEUR: THE GERMS OF THE AIR

In order to assume this tone of authority, it would
have been necessary to confront the partisans of spon-
taneous generation with some experiments which were

92 PASTEUR: THE HISTORY OF A MIND

irreproachable and always successful, l)ut no such were
available. Experiments which had been the most con-
vincing often failed, \Aithout any one being able to tell
why. Even to-day, when our technic is better, we can
not be sure of obtaining the results of Spallanzani.
Tyndall, whose experimental skill was very great, has
often repeated in vain the experiments of Schultze. In
short, there were certain substances, milk, albumen,
macerations of meat, which neither filtration, nor heating
of the air preserved from alteration, and we have seen
that Helmholtz admitted for these substances a kind of
spontaneous generation. But to admit it in one case,
was to admit it in all. Wherever there was a doubtful
case, one flask remaining fertile in spite of the precau-
tions taken, spontaneous generation had the right to
seize upon this result, and to say '*It is I who have pro-
duced this. Life is a fragile thing to preserve; more
fragile still to produce. It is all to no purpose that you
train your fingers to manipulate it delicately; you thwart
it without knowing it, and it is sometimes just because
you are unskilful that j^ou see it appear."

And these were not the only reasons. The partisans
of spontaneous generation had the best of it in the dis-
cussion, and they could say: "We who do not know on
what life depends and who make it arise from nothing,
we are exempt from the obligation of showing you its
origin and causes. But you who attribute it to pre-
existing germs, show us then these germs! Above all,
show them to us in sufficient number and variety so
that each bubble of air can people with numerous and
varied organisms the various infusions which we may
ask it to fecundate. For, finally, specificity is one of the
consequences of your way of looking at things. But we
have not forgotten a certain experiment of Gay-Lussac
in which some grape juice, sterile at first, was made to

POUCHET, PASTEUR: THE GERMS OF THE AIR 93

ferment upon the entrance of some bubbles of air. You
say these bubbles brought with them some germs of
yeast, but they brought something else into an infusion
of hay, and still other germs into a meat infusion, etc.
That makes a great many germs!" And Pouchet, who
was a man of imagination, added: ''The air thus peopled
would have the density or iron."

To all these reasons for doubt, add this one, to which
we have referred above, and which was more profound
and more powerful, being more general, namely that, in
the phenomena of spontaneous generation, even more
than in fermentations, chance seemed to be master and
to dictate according to its caprice the kinds of population
of the infusions, and of destruction of their elements.
Spontaneous fermentations, spontaneous generations,
chance, all these words harmonized well and entered
en bloc the minds of the scientific men.

It is here that we again recur to Pasteur, and to that
quality of which I have just spoken — the superiority of
his equipment for entering the fray. The idea of speci-
ficity, born of his work on the fermentations, involved
that of hereditary characters, which in its turn led to that
of an ordinary kind of generation. Pasteur inclined,
therefore, logically toward the theory of germs. It was
only a question of proving it by experimentation, and for
that he was better equipped than any scientific man of
his time. He was familiar with the infinitely small
organisms; ke knew how to manipulate them. He had
a clear field: and he advanced with great strides.

"You pretend," he said to the partisans of spontaneous
generation, "that there are not enough living germs in
the air to explain the fertility of the infusions with which
this air comes in contact: what do you know about it?
You have examined the dust deposited on furniture and
on stones; you have gone to investigate it in the aban-

94 PASTEUR: THE HISTORY OF A MIND

doned towers of old cathedrals, and at the bottom of the
hypogea in ancient Egypt. Futile pains! It is not the
dust which falls and is deposited that interests us! You
will find therein only the heaviest parts of what the wind
carries, mineral particles, grains of starch or of pollen,
the spores of cryptogams or even bits of down, of cotton,
of wool from the living sheep or from our garments. It
is not these particles which we must study, but rather
those which we see dancing without repose in a ray of
sunlight, and which the air contains in the state of a
permanent suspension,"

''Furthermore, your study of the dust of cathedrals
gives you no indication of quantity. AVhat is the volume

_ ••'■• i',%';V.' V— 3fi^ :.- -

'■i■^f'^J>■:^^ ^■'■'fl'K\-:.&.

Fig. 9. — Dust of the air caught by aspiration in the meshes of gun-
cotton.

of air which has deposited the little mass which you have
studied, and subjected to microscopic examination?
You do not know, and consequently your experiments
may well open the question, but they do nothing to solve
it."

"Nevertheless how easy the thing is! Let us take
the cotton filter of Schroeder and Dusch, and replace
it only by gun-cotton, and when by it we have arrested
in its passage the dust in a determined volume of air,
let us throw the gun-cotton into a mixture of alcohol and
ether in which it is soluble. All the weft of the filter
is dissolved. The particles of dust which have been
caught in the meshes are set at liberty and fall to the

I

IN THE AIR THERE ARE LIVING GERMS 95

bottom of the liquid if one leaves it in repose. We may-
then decant the liquid above them, wash them, reunite
them finally in a little volume of water and study them.
And behold what we have ! Look and tell me if there are
not there present corpuscles, spherical globules (Fig. 9),
round or oval bodies, so like the spores of cryptogams
or the eggs of Infusoria that no micrograph could dis-
tinguish them. As for their number, we find many-
thousands in a little plug of cotton through which has
been passed for twenty-four hours a moderate current
of air, and as we count only the largest of these globules
figured here, those which have a clearly organized aspect,
while we leave aside the smallest, which are evidently
the most numerous, failing to distinguish them from
amorphous elements, you must conclude that there is
constantly present in the air in a floating state the means
of life for all the infusions which you put in contact
with it."

IV

IN THE AIR THERE ARE LIVING GERMS

''But," you will say, "what assurance have you that
these particles of dust which you have shown us are
living, or at least that they contain something living?
That is also easy to prove. We take the flasks of
Spallanzani, or of Schwann, for, mark it, I do not in-
troduce any new method of work, I am content with
operating well where others operated badly, with avoiding
causes of error which rendered the experiments of my
predecessors uncertain and contradictory. We take
then a flask containing a vegetable or animal infusion:
draw out the neck of it in a flame, then boil the liquid
in order to destroy by heat everything living that it

96

PASTEUR : THE HISTORY OF A MIND

contains (Fig. 10). We remove the air which it contains
by the current of vapor which the boiling produces:
we shall sterilize at the same time all the interior walls.
On leaving the neck of the flask, the vapor traverses
a platinum tube heated to redness in a gas furnace
(F, Fig. 10), and then escapes into the air. "When the
boiling has lasted some minutes, we extinguish the flame
under the flask; the liquid cools; the vapor condenses:
it is replaced by air w^hich will have traversed the red-
hot tube of platinum, where everything organic contained
in it will have been burned. When the flask is cold,
we separate it from the rest of the apparatus by fusing

Fig. 10. — Method of heating the air (to free it from germs) before intro-
ducing it into flasks.

its tapering neck in a blowpipe. We shall have there
a flask of Spallanzani, that is to say an organic infusion
in contact with air containing all its oxygen, but robbed
of everything living, and even organic, which it contained.
Very well, nothing will be produced there; the infusion
remains clear because we have allowed nothing living to
enter it.

"Now, for this is not the end, we take one of these flasks
which has remained sterile, and by a simple process,
which I shall not stop to describe, we pass into its neck,
always in the presence of air sterilized by heat, one of
these little pieces of cotton soiled by the dust of the air,
the living character of which you deny. As long as

IN THE AIR THERE ARE LIVING GERMS 97

this remains in the neck (Fig. 11), the Hquid of the flask
retains its first clarity. At the end of 15 days, or a
month, we make the cotton fall into the infusion by
simply inclining the flask, and we shall see that at the end
of 24 hours, the liquid will become clouded, and that
after 48 hours it will contain miflions of living organisms.
When birth is given there to cryptogamic growths, we
shall often see tufts of filaments growing out around
the cotton of the plug, testifying thus to their affiliation
with the germs which it contained.

''What reply will you make to this experiment? The
microscope has shown us in the bit of
cotton substances of an amorphous
aspect and substances with an organ-
ized aspect. This we can affirm as a
result of our first experiment. The Fig. ii.— Flask used
second, which I have just described, by Pasteur in his study

, ,, ii , ii 1 , of fermentations and

tells us that among the substances of the distribution of
on the cotton there are some that are ^^S? ^° ^^^ atmos-
living. You partisans of spontaneous
generation, you are condemned to seek by preference
in amorphous and dead substances the enigma of the
life which appears in the infusions. Behold the in-
consequence into which my experiments drive you,
for, mark it, they are no longer doubtful, irregular,
contingent experiments, but they succeed 100 times in a
100, provided a little skill is used in performing them.
They are obedient to the mind as though following to the
letter the excellent program drawn up by the Academy of
Sciences: 'They are freed from all uncertainty arising
from the experiments themselves.' Repeat them with
the details which I give you and you will succeed just
as I have done."

One can divine the eff"ect of an argument so concise,
and having the charm of a geometrical demonstration.

98 PASTEUR : THE HISTORY OF A MIXD

Pasteur did not stop midway. "Do you pretend/' he
continued, addressing the partisans of spontaneous
generation, "that the cotton, as such, plays some part
in the phenomenon? Never mind! We will replace it
with calcined amianthus, without in any way changing
the result. You pretend that the cotton would have
absorbed, by contact with the air which has traversed
it, some vapor, or I know^ not what subtile matter which
heat can destroy, and which, entering the infusion with
the cotton, would have brought there one of the condi-
tions necessary for life. Your hypothesis is somewhat
intangible. But there is nothing more mysterious than
life itself, and I will reply to it.

"After having introduced into the flask an infusion
capable of fermentation, draw out the neck in an enamel-
ler's lamp, in such a way as to make a bent and sinuous
tube, in the form of a letter S (Fig. 12). Then boil the
liquid. When vapor has issued from the orifice of the
neck for some minutes, drawing out all the air of the
flask with it, extinguish the flame and let the flask cool.
The flask becomes filled with ordinary air which will not
have been heated, and which will enter it with all its
elements, both known and unknown. As the neck
remains open, diffusion will produce incessant exchanges
between the air of the flask and the atmosphere outside.
Nevertheless, the flask remains indefinitely sterile. How
do you explain this result, you partisans of spontaneous
generation? There you have organic matter, water, air
incessantly renewed, and heat, nevertheless nothing
appears in the liquid. You will say that the genetic power
of the infusion has been altered by the boiling to which
we have subjected it. But if, without touching the
infusion, I cut off the neck of the flask which contains
it, in such a way as to leave it exposed to the fall of
atmospheric dust, it becomes clouded in two or three

IN THE AIR THERE ARE LIVING GERMS

99

days. Did the genetic power then wait for the disappear-
ance of this swan's neck in order to manifest itself?
WTiat is your explanation worth in the presence of this:
the curves of the neck, remaining moist at the moment
when the fire was extinguished, washed in its passage the
air which traversed them in a thin thread? In the
beginning when the entrance of the air was rapid, the
purifying action of this washing was doubled by that of

Fig. 12.— Swan-neck flask used by Pasteur in his study of spontaneous

generation.

the liquid, still hot and able to destroy the germs which
came in contact with it. Later, the wet walls of the
neck have held fast the germs of the air as they have
passed through the narrow opening. The proof of this
is that if you shake the flask in such a way as to introduce
into the curve of the neck a little drop of the infusion,
having previously closed the open end so that nothing
new will enter, this drop becomes clouded, and if you
then mix this drop with the rest of the liquid, the latter

100 Pasteur: the history of a mind

becomes populated just as if the neck had been broken
off. Another proof is this: when the neck is removed
one often sees (Fig. 12) the first development of growth
directly under the opening, where the germs from the air
have fallen in."

V

RESPONSE TO THE ARGUMENTS IN FAVOR OF
SPONTANEOUS GENERATIONS

"I am not content," Pasteur might have continued,
condensing his powerful argument, ''I am not content
with giving you convincing experiments which always
succeed. I do more "than that. I explain why my
predecessors have so often obtained those contradictory
results which have troubled them and stayed their
decisions. Thus, always, Schwann and the others have
seen their best-contrived experiments fail when they
placed their liquids, if only for an instant, in contact
with mercury. What imprudence! Is not the mercury
constantly and necessarily full of impurities? Those
particles of dust which come to it from the air, and
which collect on its surface, mingle with it and are
carried along with it everywhere. It is for this reason
that I have carefully excluded it from all the preceding
experiments, which, performed with its aid, might have
been easier to carry out, but which might have left us
uncertain as to the results,

"And then, to disturb our convictions, there is also the
history of this milk which curdles or putrefies under
conditions where beef bouillon, the must of beer, and
other infusions remain unaltered. There is this yolk of
egg, or this meat without water, which we cannot pre-
serve by heating to 100° C and keeping afterwards in

DISTRIBUTION OF GERMS IN THE AIR 101

air which has been heated or filtered through cotton.
There are those exceptions which haunted the mind of
Hehiiholtz, of Schroeder and Dusch, and made them
admit that there were some 'decompositions of organic
matter which needed only the presence of oxygen to
start them,' that is to say that spontaneous generation
was alone capable of explaining. Very well, there again
spontaneous generation has nothing to do with it. Only
carry up to 110° C. your milk, your yolk of egg, your
meat, and you will preserve them intact as easily as
the bouillon. The milk needs to be heated a little more,
and that is all there is to it. It is not that it contains
more resistant germs, but that it is shghtly alkalin,
and in an alkalin medium germs are more resistant
to the action of heat. The proof is that a decoction
of yeast, which is easily sterilized by a short boiling at
100° C. when it is slightly acid, needs to be heated to
105° C. or 110° C. when there is added to it a small
amount of carbonate of hne. It behaves then like the
milk."

We shall see later that there is in the interpretation of
this experiment an error brought to light by Bastian,
but which did not invalidate the conclusion, for Pasteur,
when he was deceived, had the art of never being deceived
more than half way. He approached the mark, when he
did not hit the bull's-eye. We shall find a new example of
this in the complementary demonstration which follows.

VI

DISTRIBUTION OF GERMS IN THE AIR

There was in favor of spontaneous generation one last
argument to which Pasteur had not yet replied. It is
the experiment to which we have referred, in which Gay-

102 PASTEUR: THE HISTORY OF A MIND

Lussac had seen some inert must of grape begin to fer-
ment as soon as he placed it in contact with some bubbles
of external air. Men had concluded from this, with
some appearance of justice, that there was in each bubble
of air something capable of starting all the fermentations
or putrefactions which could take place in the most varied
liquids in contact with air. This was, it is true, a little
too liberal an interpretation given to an experiment which
had been performed only twice and had succeeded only
once. But if it accorded well with the hypothesis of
spontaneous generation which saw in the oxygen the
only cause of the appearance of life, it could not accom-
modate itself to the theory of germs. It seemed difficult
that there should be sufficient in each bubble of air to
populate the most varied liquids with the most varied
microbes.

What degree of credence and of generality could be
attributed to the experiment of Gay-Lussac? This was
what no one knew, and what Pasteur was obliged to
study. It is this part of his work which has attracted
the most attention, not that it is the best: all of it is
valuable; but this is the most easily understood, and the
experiments in it are as simple as they are convincing.
Pasteur took again his flasks with a straight neck drawn
out. He brought to a boil the organic infusion which
they contained, and after having driven out all the air
from the interior, through the open extremity of the neck,
he closed this at the moment when the steam was given
off by melting the glass in the flame of a blowpipe. The
flask is thus practically empty of air when it is cooled.

He then took 20 or 40 of these flasks to the place where
he wished to make a study of the air, and broke the necks
with a long pair of pincers, having first taken the precau-
tion to pass the necks and the pincers through the flame
of an alcohol lamp, in order to kill all the germs which

DISTRIBUTION OF GERMS IN THE AIR 103

might have been deposited there. Furthermore, through-
out the operation he kept the flasks as high as possible
above his head, so as to avoid the dust from his clothing.
When the necks were broken, there was a hissing sound:
this was the air entering. The flasks were then re-
sealed in the flame of a lamp, and carried back to the
thermostat.

In some cases, the air which entered contained viable
germs, and the infusion became populated with various
organisms; in others, the air contained nothing, and the
infusion remained sterile. There were always some flasks
which remained intact, although each had received from
200 to 300 cc. of external air. To say that there are
germs in the air is not, therefore, to say that they occur
everywhere, or even that they are very numerous: it is
saying that there are some here and none there, that we
find more in a low and humid place, favorable to crypto-
gamic vegetation; that we find fewer in air which is in
repose, like that of the cellar of the observatory; that they
will be the more rare the farther we go from cultivated
land, and the higher we ascend a mountain; that there
will be almost none in the midst of the Swiss glaciers
where no vegetation can live. Pasteur opened a great
number of flasks in the air of these various places, and
he always found that some of them remained sterile, and
the greater the known purity of the air at the point
studied, the greater the number of these.

All the researches made since have confirmed the truth
of this conclusion. The air is much less populated with
germs than has been supposed, much less, even, than
Pasteur thought. To-day men carry on with security,
in this regard, either in the laboratories or in surgical
wards, operations which they would not have dared to
undertake in 1862, haunted as they were by the idea of
those germs in the air, to which Pasteur had just called

104 PASTEUR: THE HISTORY OF A MIND

attention so forcibly. Time was needed to recover from
this dazzling fact and to observe more accurately. We
shall see Pasteur himself working to harmonize things,
and to make that fit into his last theory of the air which
his work on spontaneous generation had put into the
first. Simultaneously, surgical science developed. After
Lister and Jules Guerin, who were preoccupied especially
with avoiding atmospheric contagion, came the present
day surgery which, neglecting the air, directs its attention
and precautions especially to liquids and solids, persons
and things, and thus it is that little by little we come
into possession of the truth. This work on spontaneous
generations has opened horizons whose profundity we
do not yet know.

VII

DISCUSSION AVITH POUCHET

We must not suppose that this demonstration, as ex-
act as it was, produced universal conviction immediately.
It became, on the contrary, the occasion, or rather the
pretext, for polemics which did not confine themselves
wholly to the scientific field, and from which neither
religion nor politics were excluded. The doctrine of
Pasteur contradicted certain philosophical doctrines; it
spoke to the same purpose as the Bible. In politics, or
rather the politics of the time, this was a conservative
doctrine; no one has ever been able to understand why.
Nothing further was needed to stir up against it certain
men and certain journals. On the other hand, scientific
men, even the greatest of them, do not always have un-
biased minds, or minds fitted to comprehend everything.
In short, there was a raising of bucklers, of which the
men of my generation have not lost the recollection.

DISCUSSION WITH POUCHET 105

Now that the dust of combat has fallen, it is curious to
pass in review the events of the strife, of which, further-
more, Pasteur bore the brunt. We shall discover a
Pasteur whom we have not yet known; a vigorous and
sometimes a hot-headed polemic, a cautious polemic
also, who profits by what his adversaries teach him.

I shall pass rapidly over the long discussion, opened
with Pouchet in the first place, then with Pouchet, Joly
and Musset. This discussion created a great deal of
stir in its time, but science did not derive from it any
new truth. In order to obtain a spark, it is necessary
to have the friction of iron against flint; here there was
only that of iron on punk. Pouchet was a conscientious,
erudite naturalist, animated by a desire to arrive at the
truth, but impelled by the nature of his mind outside
the only paths where it is to be found. He portrays
himself exactly in the second line of the preface of his
Traite de Vheterogenie, pubhshed in 1859. "When by
meditation," he says, "it became evident to me that
spontaneous generation was another one of the means
which nature employs for the reproduction of her crea-
tures, I applied myself to discover by what processes one
could demonstrate the phenomena." I picture to my-
self how Pasteur, as well as Tyndall later, must have
read these lines with stupefaction. Thus, behold a
scientific man who calls on experiment to prove a truth
which he considers in advance as certain— what shall I
say— as evident, although he has reached it only by
meditation! How much in accord here are this extra-
ordinary mind and extraordinary language! Tyndall
has remarked that it would have required a very powerful
bridle to hold in check a mind so strongly biased. Now,
not only was Pouchet incapable of profiting by the results
of a well-performed experiment, but he was a very medi-
ocre experimenter whenever he left the domain of natural

106 PASTEUR: THE HISTORY OF A MIND

history and entered a laboratory. We are nonplussed
before some of his pieces of apparatus. Thus, for ex-
ample, he did not hesitate an instant to send a current
of water vapor through a drying tube containing pumice
stone saturated with suli:>huric acid. But aside from
these defects as a scientific man, he had, as vulgariser
and polemic, some remarkable qualities^a wide knowl-
edge, a boldness of affirmation which betokened a sin-
cere conviction, and a ready pen which wrote without
growing weary.

In comparison with Pouchet, Joly, professor of zoology
of the Faculty of Sciences of Toulouse, and Musset, head
of an institution in the same city, were somewhat lost
to sight. Lesser metaphysicians than Pouchet, they
seemed quite as incapable of knowing what consti-
tuted a well-performed experiment. It was Joly, for
example, who, in order to prove that there was nothing
living in the scum of dust on the surface of the mer-
cury, introduced what he gathered into water (into
distilled water, he said gravely) and was astonished
to see nothing appear in the mixture, even when the
eye was ''armed with the best microscope."^ How
answer such experiments?

In the laboratory, we had great sport over these
details, but the master could not laugh. He would have
been wise to repeat philosophically: "We have not the
same sort of brain," but he was indignant to see the
truth unrecognized, and contested by such arguments,
and to encounter, even in the Academy of Sciences,
confreres who hesitated between him and his adversaries.
He forgot that science is not univocal, and that one
may have a very good mind and still comprehend
nothing of a mathematical demonstration, or of the

' Examen critique du memoire de M. Pasteur (Acad, des sciences de
Toulouse, 13 mai, 1863).

DISCUSSION WITH POUCHET 107

value of an experimental proof. Fortunately, on his
side Pasteur had Balard and Dumas, those confreres
whom he still called his masters, although he had already
gained the leadership himself.

Balard loved science. He had made very good early
progress in it, and his discovery of bromine, made in
his pharmacy laboratory at Montpellier, had placed him
above his peers. It sufficed to see him in a laboratory
managing a piece of apparatus, or making a reaction,
to know that he was a chemist to his finger-tips. But
he had a certain natural indolence, and he was thence-
forth satisfied with his share of glory. To the scientific
work which he would have been able to carry on, he
preferred that which he found done in the laboratories
he frequented. .AJthough each day having the intention
of returning to his own laboratory, the next day early
he yielded to the desire to see what was going on in the
laboratories of his friends. There he wished to see
everything, to know all the details, and we told him
everything, first, because he had an open mind and a
generous soul, then, because it would have been difficult
to conceal anything from him: he put into his interro-
gations at the same time so much shrewdness and sim-
plicity! He admired with all his heart when any one
showed him a very nice demonstration! And then, one
was sometimes recompensed for this confidence: he
would suggest an idea to you, and reveal to you a method.
It was he who conceived, by means of the swan's-neck
flasks mentioned in the preceding chapter, the experi-
ment designed to show both that there are germs ar-
rested in the neck, and, by introducing into the neck a
drop from the interior, that the liquid has not lost its
genetic power. We see the drop become clouded and
populated, while the hquid in the flask remains unaltered.
All these experiments on spontaneous generation trans-

108 PASTEUR: THE HISTORY OF A MIND

ported Balard with delight and the laboratory became
animated with his expansive joy as soon as he entered.

Dumas, more majestic, and at this time a power, came
more rarely. He was not desirous of seeing things at
such close range. He judged them from his superior
height and was no less a very good judge; consequently
Pasteur never allowed any of his words to escape him.
It was a little in spite of his advice that Pasteur had
approached this question of spontaneous generations,
and there is no doubt that in giving this advice Dumas
was lacking in perspicacity, so much was this study in
accord with the mind and the works of Pasteur. But
the pupil kept his master in touch with his progress;
and he was never more happy than when he recounted to
the laboratory some word of approbation from Dumas.

Pasteur had need of these encouragements, for, de-
cidedly, he could not make up his mind to take part
in the little war which the partisans of spontaneous
generation were pursuing before the Academy and in the
journals. But this internal ebullition did not prevent
him from being a shrewd manceuverer. Consequently,
he allowed the most hazardous affirmations to be made
without too much protestation, contenting himself with
exposing from time to time the weak points in the ex-
periments which were opposed to his own. He did
not wish to follow his adversaries into their own field,
knowing that this was dangerous, and that thus they
could draw him where they wished: he waited patiently
to see them approach his territory. Thus when they
affirmed, on the day following some experiments made
on the Maladetta, that "wherever they collected a
litre of air, as soon as they put it in contact with a liquid
capable of fermentation, enclosed in a matrass hermeti-
cally sealed, the latter invariably became filled with
living germs," on that day, Pasteur made haste to seize

DISCUSSION WITH POUCHET 109

this affirmation on the wing. The experiments on the
Maladetta, made apparently under the same condi-
tions as his own, contradicted them absolutely. He
demanded that the Academy of Sciences name a com-
mission before which each of the adversaries should re-
peat his experiments, that commission to say on which
side was the truth.

This was in truth a curious episode, and a very in-
structive one, as we shall see. Requested to repeat
their experiment immediately, MM. Pouchet, Joly and
Musset, began by demanding postponement until warm
weather. The demand was singular: the heat of the
thermostat is a perfect substitute for the heat of the
sun, and if the doctrine of spontaneous generation is
true in July, it ought to be true in December. The
commission succeeded, nevertheless, in bringing before
it in June all the adversaries in question. We had come
from the laboratory of the normal school with every-
thing that was needed to repeat the experiment in dis-
pute: Pouchet, Joly and Musset had come alone and
unarmed. It was soon evident that they had no desire
to fight. Having tried various dilatory methods, but
being brought back incessantly to the question in point
by the severe tone of Dumas, and by the slightly mocking
pleasantry of Balard— they ended by declaring that they
made default and retired.

The battle was won, for Pasteur was sure of his ex-
periments which succeeded once more in the hands of
the Commission as an incisive report by M. Balard,
inserted in the Comptes rendus de VAcademie des Sciences,
testified. Had any one told us then that this brilliant
victory amounted to nothing he would have surprised us
very much. Nevertheless, such was the case. Pasteur
was right; but Pouchet, Joly and Musset, were right
also, and if, instead of withdrawing, they had repeated

110 PASTEUR: THE HISTORY OF A MIND

their experiments, they would have embarrassed the
Commission very much, and Pasteur would not then
have known how to reply to them.

It is in reality quite true that if one opens, at any
point whatsoever on the globe, flasks filled with a decoc-
tion of hay, as Pouchet, Joly and Musset did, it often
happens that all the flasks become clouded and filled
with living organisms. In other words, with this in-
fusion the experiments of Pasteur with the water of
yeast do not succeed, and one is led to admit that the
air which enters into all the flasks carries germs into
them.

Let us say immediately that the germs of this air
are a negligible quantity, and that any one would ob-
tain the same result by fiUing the flasks with air sterilized
by heat. The fact is that the germs already exist in
the infusion. They have resisted boiling, as is the case
with a great number of micro-organisms. They have
remained inert as long as the flask, sealed during the
boiling, remains devoid of air. They develop when
the air enters, thanks to its oxygen. But Pasteur did
not yet know this fact. Pouchet, Musset and Joly
were not any more aware of it, but if they were ignorant
of the explanation, they had observed the fact, and if
they had been better experimenters, more men of the
laboratory, if they had studied more thoroughly the
conditions of their success, they would have accepted
the challenge, and would have won the battle, or at
least each of the adversaries would have retained his
own position.

Perhaps it would have been better had things taken
this turn, and the Academic commission been obliged
to determine that all of the adversaries were right,
instead of i)utting an end to its labors by a bulletin
announcing the victory of one of them. Pasteur would

DISCUSSION WITH FREMY 111

have found that he had been deceived in some particu-
lars, but he was not a man to sulk before the truth,
and some ideas which did not enter into science until
ten years later, would have found their place there
at once to the great advantage of all. We were, in reality,
obliged to wait until the contest with Dr. Bastian in
1876 to rediscover them. But the episode is not less
curious, when we consider that the passing error of
Pasteur had also its good side and its advantages. This
is a good illustration of what a series of judgments,
revised without ceasing, goes to make up the incon-
testable progress of science. We must believe in this
progress but we must never accord more than a limited
amount of confidence to the forms in which it is suc-
cessively vested. One sometimes reaches the truth by
error, and sometimes error by the truth.

VIII
DISCUSSION WITH FREMY

Like the preceding, the discussion which opened im-
mediately between Pasteur and Fremy has no interest,
even when studied in the light of to-day. I venture to
say that it never had any, even when it caused heated
discussions in the seances of the Academy of Sciences,
it was so incoherent in its diverse phases. When Fremy
undertook these studies, he had arrived at an age when
the mind does not adapt itself easily to new habits.
He had never been good at unravelling problems, and
this one demanded much ingenuity and penetration.
He had never been familiar with the microscope, nor with
the world of infinitely small organisms. One asks then
what he thought to accomplish and why he embarked

112 PASTEUR: THE HISTORY OF A MIND

on this galley. Perhaps he wished only to parade there,
for she manoeuvered in full sight of the shore. With
all his qualities as a man and a savant, Fremy was, in
reality, from many points of view still a child. Perhaps
he had, notwithstanding, the intention of bringing the
ship to harbour, but what an illusion regarding his quali-
fications for that task! He saw indistinctly and reasoned
awry. In order to explain, for example, why Pasteur's
flasks with the swan's neck did not become clouded, he
conceived the idea that it was due to the vitiation of the
air, resulting from the absorption of the oxygen by the
liquid in the flasks. This was forgetting the experiments
of Schultze, of Schwann, of Schroeder, even those of
Pasteur. But this also was nothing. In order to prove
this vitiation of the air, which, according to him, would
prevent, and consequently would precede, the invasion
of the microbes, he cited some air analyses made on flasks
already invaded, and where the aerobic organisms had
naturally absorbed all or a part of the oxygen. This is
unbelievable, and the excellent man truly did not merit,
he was so unsophisticated, the bit of harsh treatment
which he reaped from his polemic. Pasteur did not
treat him as a serious opponent. He was amused at
seeing him rush on the sword of his adversary, and the
tone which he assumed towards him is well illustrated
by the following phrase, written apropos of an Academic
discussion in which Fremy, made angry and "driven to
the wall" by an experiment of his adversary, had, in
order to explain it, and relieve his own embarrassment,
conceived the idea forthwith, of saying that "small
quantities of grape-must do not ferment," and that there
must be a large amount of it for fermentation to take
])lace. Thereupon, Pasteur parried: "In the seance
which followed that in which M. Fremy made this decla-
ration in regard to small quantities which do not ferment, I

DISCUSSION WITH FREMY 113

gave myself the malicious pleasure of bringing a large
number of very small closed flasks, into each of which I
had aspirated a drop of must from bits of crushed grapes.
I broke the tapered point of many of them before the
Academy, and in all by a sharp hissing, which was heard
at a distance, the fermentation of the drop of liquid
within was made evident. jM. Fremy was present and
kept silent." ^

It must be said in commendation of Fremy that he
did not cherish any ill will because of these thumps,
feeling, confusedly at first but more and more clearly
later, that his opponent was right. He loved the truth,
although he w^as not always very prompt to recognize it,
and when it was necessary to have a treatise written on
the ferments and fermentations for the Encyclopedia,
the publication of which he directed some years later, he
went for this purpose not to one of his own pupils, but
to one of Pasteur's.'- No one could terminate a polemic
more gallantly!

This discussion, nevertheless, did not remain sterile.
There were no sterile discussions with Pasteur, because
he always resorted to experiment to combat the argu-
ments opposed to him. He thus found himself drawn
into diverse fields, which he would never have approached
of his own accord, and, as he had perspicacity, he did not
fail .to make discoveries therein. Thus it is that he de-
rived from his controversy with Fremy a multitude of
curious ideas on the distribution of germs in the air,
and germs of yeast on the skins of the grape — ideas
which he utilized much later, and which we shall en-
counter again.

1 Etudes sur le vin, p. 5S.

- To Emile Duclaux, author of this book. Fremy's Encyclopedie
Chimique, Tome ix, 1'" Section, Chimie Biologique Par M. Duclaux.
8vo, p. vii, 908. Dunod, Editeur, Paris, 1883. Trs.

114 PASTEUR: THE HISTORY OF A MIND

IX

DISCUSSION WITH BASTIAN

The only discussion which produced fruit in the field
in which it arose was that raised by Dr. Bastian. Like
Fremy, Bastian had taken up the question a little
thoughtlessly, without being very familiar with it, and
without any idea of its difficulties. His first experiments
were not of any great value; but he had tenacity, fertility
of mind, the love of the experimental method, if not an
understanding of it, and he has given us ideas, or rather
let us say he forced Pasteur to gain ideas, the absence
of which had hindered the progress of science. All our
present technicjue has arisen from the objections made
by Bastian to the w^ork of Pasteur on spontaneous genera-
tions. It was Bastian who made us see that this work
which had been so vaunted, abounded in false interpre-
tations, which, he said, invalidated its conclusions. It
was Pasteur and his pupils, Joubert and Chamberland,
who showed that even if the interpretation had some-
times been inexact the conclusions w^ere none the less well
founded.

Bastian's first attack was a blow straight from the
shoulder. ''You maintain," he said, "that urine boiled
and preserved in the presence of superheated air, remains
clear and sterile because you have allowed no germ
to penetrate there. I say, on the contrary, that the
germs have nothing to do with it, and that the sterility
of the liquid is due only to the fact that, in spite of all
your care and your dexterity, you have not known how
to reunite in it the physical and chemical conditions
necessary for spontaneous generation. The proof of it
is this: if I saturate this urine with a little potash boiled
and freed from germs, so as to render the urine neutral.

DISCUSSION WITH BASTIAN 115

or a little alkaline, and if I put it, furthermore, not in
one of your ovens where it is not sufficiently hot, but at
50° C, this same flask of urine which remains sterile in
your hands, becomes clouded at the end of 9 or 10 hours
and swarms with bacteria. From whence can they come,
if not from a spontaneous generation?"

Repeated immediately in the laboiatory of Pasteur,
the experiment was successful. It is, in reality, very
exact, but what must we conclude from it? Pasteur
could not interpret it as Bastian did. He acknowledged
that the germs were there: but whence did they come?
In this investigation, Pasteur beat about the bush for a
long time, and during this time his ideas, like his discus-
sion with Bastian, were rather confused. I will simplify
my exposition considerably by saying that these germs
for which Pasteur demanded an explanation from ex-
perimentation, could be derived from three sources,
unsuspected up to that time: first from the solution of
potash ; second from the boiled urine ; and third from the
walls of the flask. It was, we see, the introduction of
solids and liquids, as conveyors of germs, into a question
where up to that time, the air, chiefly, had been incrimi-
nated. Let us examine separately the three sources
which we have just enumerated.

The solution of boiled potash may contain germs, and
yet that seems surprising when one thinks that this solu-
tion is made with a piece of fused potash which, in a
solid state, actively attacks animal membranes and
destroys everything living. Therefore, it is not this
which can carry the germs, and, in reality, if we repeat
the experiment of Bastian, replacing the solution of boiled
potash with an equivalent fragment of fused potash, the
experiment does not succeed, and the urine continues to
be sterile. Then it is the water that conveys the germs,
and in studying this subject Pasteur and Joubert were

116 PASTEUR : THE HISTORY OF A MIND

in reality convinced that there are germs in all water,
even in that which has been carefully distilled, when it
is collected in receptacles which have been washed with
water containing germs. This fact had already been
established by Burdon Sanderson, but the French sa-
vants expanded it to a remarkable degree, and stated
it more precisely. They also recognized that only the
waters from deep sources, those which had undergone
in the soil a slow and long filtration through capillary
spaces, reached the surface without bringing back the
germs which they contained in abundance when they
penetrated the soil. They were filtered. We find
there all the ideas which have been so useful to us later
on the subject of the distribution of germs in water,
and out of which was evolved for purposes of steriliza-
tion, the Chamberland filter, which has been of such
great hygienic value.

Nevertheless, this explanation did not explain every-
thing, and it happened sometimes that when the potash
solution had been thoroughly sterilized, or even replaced
by an equivalent fragment of potash heated to redness,
nevertheless the urine, sterile up to that time, became
populated. It is then the urine which supplies the
germs: they had not been destroyed by the boiling to
which it had been subjected, and thus was introduced
into science this very fertile idea that germs could exist
in a living state in a nutrient liquid and not develop.
Behold the contribution of Bastian! Where Pasteur
saw nothing develop, he said: "There is nothing;"
Bastian entered the field and said: ''Without your
knowing it, there is something of which you prevent the
evolution." Pasteur retraced his steps and admitted:
it is true! but this something is a germ, and if it remains
inert, it is because in all living species the first steps in
life are the most difficult to make.

DISCUSSION WITH BASTIAN 117

At this time, fortunately, Pasteur had already con-
ceived the idea of the spore, the egg of the Infusorian,
which demands other conditions for its existence than
those with which the Infusorian itself is content. The
conditions of this revivification are in general limited,
and each species has its own. Because of this fact, and
because sometimes these conditions are very delicate,
it is possible occasionally for two scientific men who
work on the same species to find that they are in disagree-
ment, because of an insignificant difference in their
method of work. Because of the fact that the condi-
tions vary with the species, it is clear that these savants
will be still more likely to contradict each other if they
work, as is almost always the case, on different species,
and behold herein a hitherto scarcely dreamed-of ex-
planation of a multitude of contradictions in the experi-
mental study of spontaneous generations.

This element of mystery, now revealed, was calculated
to arouse zeal in the laboratory of Pasteur. It was soon
recognized there that two conditions govern the re-
juvenescence of the germ, the reaction of the liquid
and the presence of air. This was especially the work of
Chamberland. In a liquid which is too acid, germs
heated to 100° C. remain alive, but inert. Diminishing
or neutralizing the acidity opens the field for them.
This is what Bastian did, and his experiment contained
nothing contradictory to the germ theory. It is true
that, by way of retaliation, he ought to have recognized
the existence of living germs in the flasks which Pasteur
regarded as sterile, and from which he deduced evidence
against spontaneous generation. But the evidence re-
mained good, although the witness was untrustworthy:
heating to 115° or 120° C. the liquids which Pasteur had
been content to heat to the boiling point, sufficed to
destroy everything that was living therein, and to give

118 PASTEUR: THE HISTORY OF A MIND

to the experiment entire security, and consequently all
its significance. The practice of heating to 120° C. all
liquids which are to be sterilized dates from this time.
It was the advent of the autoclave into the laboratory.

Air is often another important factor in the revivi-
fication of germs, and here it is that we find again the
experiment, cited above, of Pouchet, Joly, and Musset.
They worked, as I have said, with a hay infusion, ob-
tained by macerating hay in tepid or hot water, which
was then filtered and boiled. But this hay contains
ordinarily, as Cohn has since shown, an elongated ba-
cillus forming a pellicle on the surface of the infusion
when it develops in it, and changing into very resistant
spores. It is the famous Bacillus subtilis which is every-
where widespread, and owes its ubiquity solely to the
fact that it is admirably equipped for the strife, being
one of the most resistant of known organisms. Its
spores, particularly, can withstand several hours of
boiling without being killed, but they are the more
difficult to rejuvenate the more maltreated they are.
If we seal, in a flame, the neck of a flask which contains
them, at the time, when the liquid in which they are
submerged is boiling, they are not killed, but they do
not develop in the liquid when it has been cooled and put
in a thermostat, because air is lacking. If we allow
air to enter, the infusion becomes populated and this
is also the case if we allow only heated air to enter; for
the air does not act by introducing germs, as Pasteur
believed at the time of the debate before the Academic
commission on spontaneous generations: it is its oxygen
alone which comes into play.

We see here how necessaiy ingenuity and discernment
are in these matters. Here we have an experiment in
which air coming into contact with an infusion brings
to it fertilit}\ This was performed by Gaj^-Lussac with

DISCUSSION WITH BASTIAN 119

the must of grape, by Pouchet with hay-infusion, by
Bastian with urine. Gay-Lussac conckides: it is the
oxygen which has vivified the dead matter; Pouchet and
Bastian say: it is spontaneous generation. Then comes
Pasteur, who first said: "Not at all; it is germs." Then,
when he had been shown that he was deceived: ''It is the
cooperation of the germs and of the oxygen." The germs
always played a part, and in that respect he won his case.

Finally, these germs, so resistant, so widespread,
present in all waters, stick to the walls of the receptacles
washed with these waters, by a mechanism analogous
to that which fixes them in the capillary tubes of a por-
celain filter. There they dry, and once dried, they are
still more resistant. The heating to 120° 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 180° C. Hence
the utihty of flaming all the receptacles used in micro-
biology, 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.

Thus it was that, little by little, knowledge extended
and became more exact, and that all the objections to the
germ-theory ended in giving us more exact ideas on the
subject of the evolution, the distribution, and the char-
acteristics of germs. From this point of view, one may
say that all these discussions have been useful because
they have given rise to new experiments. The contro-
versy with Bastian was the most useful because there
the two adversaries without being of equal force had the
same creed and the same faith. Bastian rendered a
service to science; he lashed it on its weak side, but he
compelled it to advance.

PASTEUR

(Courtesy of Dr. Winford II. Smith, Superintendent, Johns

Hopkins Hospital.)

FOURTH PART
Wines and Vinegars

INDUSTRIAL METHODS IN THE MANUFACTURE OF

VINEGAR

The theory of Liebig in regard to fermentations,
which Pasteur had combatted, was applied also to a
category of phenomena to wliich Liebig had given the
name Eremacausis, or dry rot, and which were especially
phenomena of oxidation in contact with the air. The
type to which he referred them by preference was the
oxidation of alcohol by platinum black, discovered by
Dobereiner. When drops of concentrated alcohol are
allowed to fall on finely divided platinum, the mass be-
comes hot and gives off vapors which have both the
suffocating odor of aldehyde, and the penetrating and
pungent odor of vinegar. The explanation of the phe-
nomenon is very simple. The alcohol is burned at the
expense of oxygen which the platinum holds condensed
in its pores. A partial oxidation gives aldehyde; a more
complete one, acetic acid; an oxidation still more com-
plete would give carbonic acid, as when alcohol burns
with a flame in contact with air. As for the platinum,
it remains unaltered.

Such was the type, purely chemical, to which liebig
referred the oxidizing action of the soil on the organic
substances which it contains, nitrification, the dry rot
of wood, the oxidation of the siccative oils, and, by ex-

121

122 PASTEUR: THE HISTORY OF A MIND

tension, the different processes of vinegar-making by
oxidation of the alcohol in wine or fermented liquors.

Owing to his study of the different processes employed
in his vicinity, since the time of Schutzembach, by the
vinegar manufacturers of Germany, he had some right
to make this comparison. In a pile of casks with the
heads knocked in, and forming a hollow column several
meters in height, are piled loosely shavings of beech,
over which is showered a feebly alcoholic liquid to which
have been added some milligrams of acetic acid and which
contains, furthermore, a little acid beer, sharp wine, or
some other organic matter in process of alteration, neces-
sary, according to the theory of Liebig, to act as a fer-
ment and set in motion the phenomenon. Under these
conditions the shavings play the role of the platinum
black and do it more economically. On coming into
contact with them the alcohol oxidizes, the mass be-
comes heated, and the pile of casks forms a chimney for
a current of air, which, entering below, diffuses through-
out the mass, bringing constantly to all points new oxy-
gen, so that the process of acetification progresses rapidly.
As with platinum black, there are sometimes formed,
in addition to the acetic acid, suffocating products with
the odor of aldehyde. Finally, to complete the resem-
blance, the shavings seem to act only by their presence.
After 10 or 20 years of use in the manufacture of vinegar,
they are intact, being as sound and clean as on the first
day.

We will acknowledge that the comparison was tempt-
ing, and will understand that Liebig could not resist the
temptation. One falls easily on the side toward which
he leans. Pasteur was entitled to look upon the ques-
tion (juite differently. In connection with his studies on
spontaneous generation, he had just determined that all
organic substances oxidize very slowly in contact with

METHODS IN THE MANUFACTURE OF VINEGAR 123

air when microbes do not intervene; but the acetifica-
tion in the German process is very rapid. It is true
that it was not immediately plain just where the micro-
organisms could intervene in this mass of shavings, which
always remain unchanged, but there was something
which resembled it in the factory of Orleans, a village
which, for a long time, has had a merited reputation for
its vinegars.

There they carry on operations in casks lying on end
in piles and filled about two-thirds full of a mixture of
unfermented vinegar and fermented wdne. Now, on the
surface of the liquid, in the casks which behave properly,
there is a fragile pellicle which the vinegar-maker takes
great pains not to disturb and not to submerge, because
he considers it a precious ally. Experience having taught
him that it needs air, he has opened for it a large window
in the top end of the cask, above the surface of the liquid.
He watches this pellicle and cares for it. As long as it
remains spread over the surface of the liquid, all goes
well; if it is broken and falls in fragments, all is lost.
It is then necessary to produce a new one; and some-
times, God knows, with how much trouble, expense and
groping about ! A blast of heat, a blast of cold, may sud-
denly interrupt all manufacture.

What then is this pellicle which is so precious and so
delicate? Pasteur had been asking himself this question
for a long time, but he only felt himself ripe for the study
of this question after he had carried out his studies on
the nutrition of micro-organisms and on the spontaneous
generations which we have reviewed. He was hence-
forth armed and equipped, and less than a year sufficed
him to make on this subject one of those researches a la
Lavoisier, which immediately become classic because of
their fullness, their elegance and their simplicity.

124 PASTEUR: THE HISTORY OF A MIXD

II

THE MYCODERMA OF VINEGAR

As Pasteur had thought it out, all the work of oxidation
was performed by a micro-organism differing from those
with which he had been familiar up to this time, in that
it is an agent for the transmission of the oxygen of the
air to certain substances. These functions make it nec-
essary for it to live in contact with the air on the one
hand, and with the nutrient substance on the other, and
it develops on the surface of the lic}uid in the form of a
delicate veil, smooth and level at first, later in folds,
because, when the organisms become too crowded, it is
necessary for them to pile up on each other. This form
of veil won for this organism the name of Mycoderma
aceti, or the mycoderma of vinegar.

Three things were remarkable about this organism.
In the first place, its marked aerobic character. It was
the exact antipode of the butyric vibrio, previously dis-
covered, and it was to characterize the two so opposite
functions of these two organisms that there were created
with the collaboration of Chassang, professor of Greek
in the Ecole Normale, the two words aerobic and anae-
robic. The acetic ferment was also singularly prolific-
In 24 hours, it would cover the surface of a vat of any
size whatever, with a fine pellicle of cells crowded to-
gether, provided that one sowed here and there some
cells, as seed. These form islands which become joined
in a continuous layer. The cells of the ferment are
almost twice as long as broad (5, Fig. 8). It takes 400
of them placed end to end, or 800 placed side by side, to
make a millimeter. That makes a minimum of 30
millions of cells to the square centimeter, or 300 thou-
sand millions of cells in a vat with a surface of a square

THE MYCODERMA OF VINEGAR 125

meter, covered in 24 hours. The ferment best known up
to that time, the yeast, gave figures much smaller and less
striking.

This is not all, for we are about to see appear a new
conception, which the future will make productive —
the conception of the fermenting poiver. These 300
thousand millions of cells weigh about 1 gram and can
acidify in 4 or 5 days, when the conditions are favorable,
10 kilograms of alcohol. That is to say, each one of
these cells demands per day two thousand times its own
weight in food material. And here there is raised one
of the corners of the veil which for so long a time has
masked from us the grandeur of the role of the infinitely
small organisms. Their power of work is out of all pro-
portion to their weight. With a feeble volume, they can
produce great effects: we understand that they may
occupy a great place in the economy of the globe and yet
pass unperceived.

The oxidation of these 10 kilograms of alcohol requires
the putting into play of more than 6 kilograms of oxygen;
that is to say, more than there is in 15 cubic meters of
air. We explain thus the utility of the current of air
ascending in the column of shavings in the German
method, and of the large open window in the upper end
of the Orleans casks.

This oxygen, which it derives from the air through its

aerial surface, the mycoderma transmits to the alcohol

through its submerged surface. But oxidation does not

always take place in the same way. Sometimes it is

arrested in the aldehyde state and the organism yields

products with a disagreeable and suffocating odor. As

in case of the oxidation due to platinum black, the

process is arrested half way. At such times the organism

lives with difficulty; it suffers. Why should we not

say that it is sick? Disease and death are the natural
11

126 PASTEUR: THE HISTORY OF A MIND

attributes of life, but the idea of disease in a creature so
small, was none the less original. It was the first time
that it had presented itself. Since then, it has been
greatly developed.

On the contrarj^ sometimes this ferment, instead of
being arrested half way, goes beyond the acetic acid
stage, exactly, again, like the platinum black, and instead
of acetic acid, yields water and carbonic acid. Then it
consumes the acetic acid which it has formed, and here
again we have the first example of the ability of a living
organism under certain conditions to destroy a product
which under other conditions it has manufactured. The
organism consumes the acetic acid when there is no alco-
hol at its disposal, that is to say, it consents, when it is
starving, to touch a food which it scorns and rejects in
other circumstances, and which thus has accumulated
in the ambient liquid. But this acetic acid is its second
choice of food, and it abandons it in favor of alcohol as
soon as it has the opportunity.

Curious, is it not, this choice of food in the world of
infinitesimal organisms! What prevents us from seeing
therein an act of volition or of instinct? Observe that it
is an entirely different thing from finding that each organ-
ism has its own food material, that the yeasts, for ex-
ample, can obtain nourishment only from sugar. The
acetic ferment can make a choice, and show preferences:
it has free will. I know well that it is governed by its
needs, but how many acts of volition have as a cause,
though often obscure, only that of satisfying needs?
Let us not insist upon this point, however, but confine
ourselves to noting with what care Pasteur sought by
their study, as soon as micro-organisms had brought
him into contact with life, new light on the physiology
of the higher organisms. He did not fail to compare his
acetic ferment, the agent of oxidation, with the red cor-

THE MYCODERMA OF VINEGAR 127

puscles of the blood, which are also charged with trans-
porting oxygen to the tissues, giving it up to certain sub-
stances in preference to others, thus carrying on the
oxidation that is needed, even if it is not voluntary and
premeditated. He had asked himself what would hap-
pen if the red corpuscles should become diseased in the
same way as the cells of the acetic ferment, arrested in
their development in the aldehyde stage of oxidation.
In short, he penetrated through his micro-organisms, into
the law^s of physiology and pathology.

The practical consequences of his discoveries equalled
their theoretical promise. They restored security to
the Orleans vinegar manufacturers, who were hence-
forth masters of the mycoderma veil in their casks in-
stead of being subject to its demands and caprices;
they made it possible for the boldest of these men to
adopt a new method of manufacture w^hereby, instead of
leaving intact for a long period the pellicle formed on
the surface of the liquid, they resowed it and renewed
it at frequent intervals. Thus not only could one make
more rapid progress, but could regulate the production
to the demand, whereas, by the old Orleans method
production must be going on constantly and the casks
could not lie idle, lest they should become inert.

But is it only in the Orleans process that the microbe
intervenes? Not at all. We find it also in the German
process, but it is less apparent there, because it is formed
in much less quantity. In Orleans, the white wines,
rich in organic matter, are used especially for vinegar-
making, and the layer which develops on the surface of
the liquid in the casks forms thereon sometimes a thick
veil. In Germany, little else is used for vinegar-making
except alcohols diluted with water and mixed with that
small quantity of wine, or sour beer, wdiich Liebig de-
manded. This liquid is not very nourishing and seems

■J
\

128 PASTEUR : THE HISTORY OF A MIND

unsuitable as food for even the least exacting micro-
organism; but it is sufficient, and if one scrapes with the
point of a knife the surface of these beech shavings, which
seem so sound and clean, he finds there a transparent
pellicle formed of cells entirely similar to those in the
Orleans casks. The manufacture of vinegar is then
everj^vhere due to bacterial action.

Ill

DISCUSSION WITH LIEBIG

This conclusion was not calculated to please Liebig,
who was defeated on his own ground, and on a question
where the close analogy between the industrial results
and those furnished by platinum black seemed to rule
out all physiological action. An old champion such as
he could not yield without fighting, and he retaliated
with two memoirs, the one On fermentation and the source
of muscular energy, ''^ read before the Royal Academy of
Sciences of Munich in 1868 and 1869, the other- in-
serted in the Proceedings of the Bavarian Academy in
1869. Both demonstrate how difficult it is for even
the most eminent scientific man to adapt himself in his
old age to new ideas, when they run contrary to the
current of those in which he has passed his life. Experi-
ence and erudition are then a restraint: one must shed
his old skin and abstract himself from all that he has
learned.

As the title of the first of these memoirs indicates,
Liebig enlarged the scope of the debate and returned
to the question of alcoholic fermentation in search of

1 Ann. de ch. et de phj's., t. XXIII, 4', se. p. 5.

2 lb., p. 149.

DISCUSSION WITH LIEBIG 129

light on the physiology of the cell. We shall not follow
the discourse in all its developments, which are some-
times digressions, but shall ask only what it had to reply
to the new doctrine on the fermentations.

On this point his position became more and more
embarrassing. Already, at the time when he had first
developed his theory, he had been obliged to admit that
the yeast was a living organism which renewed and
destroyed itself continually, and it was only the products
of the destruction which made the sugar ferment. That
point had become difficult to maintain and support
after Pasteur had shown fermentation to be a cellular
phenomenon. It is curious to see how Liebig extricates
himself from this difficulty. He considers that life is
accompanied at every instant, in every cell, by a move-
ment of decomposition and reconstruction, and, naturally,
it is to the first that he has recourse. He admits then
the physiological phenomenon but he takes into con-
sideration only a part of it and, once more, the chemical
side, endeavoring "to reduce the chemical decomposition
of the sugar to a simple formula common to all analogous
phenomena."

The attempt is bold, and we recognize in it the general-
izing mind of Liebig. We shall see how he succeeded.
Let us note in the beginning that, from a chemical point
of view, the vital phenomenon of Pasteur does not differ
essentially from the phenomenon of movement of Liebig,
and that it is possible to reconcile them. "I admit,"
says Liebig, "that the yeast consists of vegetable cells
which come into existence and multiply in a liquid con-
taining sugar and an albuminoid substance (it is I who
underscore). The yeast is necessary in order that there
may be formed in its tissues, by means of the albuminoid
substance and the sugar, a certain unstable combination,"
which alone is capable of undergoing dismemberment.

130 PASTEUR: THE HISTORY OF A MIND

When the yeast ceases to grow, "the union between the
constituent parts of its cell-contents is destroyed, and it
is through the movement that goes on there that the
cells of the yeast cause a derangement, or a separation, of
the elements of the sugar, or of other organic molecules."
And behold how, even in the sciences, that is to say
where one is dealing only with facts, one can always
many the Grand Turk and the Republic of Venice.
Liebig made a concession of words on condition that
his opponent would make to him a concession of facts.
"I grant you," he said, "that this is a vital phenomenon
taking place in a living organism, provided you grant
me that it is of a chemical order. If you do not make
this concession, I shall always have the right to say
that you have not looked into the question far enough,
that you have been arrested before a closed door which
I am trying to open." The curious thing is that, fun-
damentally, he was right; that the term vital phenom-
enon which Pasteur resolved upon, was in no sense
more exact than Liebig's phrase molecular disintegration
(d'ebranlement moleculaire) ; that, furthermore, all phe-
nomena of nutrition within the cell are reduced neces-
sarily to chemical phenomena. But the value of a
theory lies not in the words which express it, all of which
are necessarily somewhat vague; otherwise, absolute
truth and clearness would be reached on a question, and
we shall never arrive at that. The value of a theory
depends upon the direction which it gives to research.
If Liebig was perhaps right in affirming that within
the cell, in the deep roots of the vital act, his theory and
that of Pasteur were blended, one is astonished to see
him ignore or forget that they are essentially distinct
from the point of view of research and progress. The
one theory affirms the specificity of the act of fermenta-
tion and incarnates it in a living organism, which can

DISCUSSION WITH LIEBIG 131

be cultivated and transferred from medium to medium
with its specific properties. The other theory denies
this fertile specificity, since it admits again in 1869,
as we have just seen, that the cells of the yeast can
separate "the elements of sugar or of other organic
molecules."

These two memoirs of Liebig were translated and
published in 1871 in the Annates de chimie et de physique.
I cannot surmise what procured for them the honor of
this exhumation. Pasteur was taken by surprise, and
replied in the Comptes-rendus de V Academie. The war
of 1870 had just ended, and his soul was embittered.
He did not consider at all in these memoirs the special
pleading, or dissertation, on origins and causes. He
went straight to the facts. Liebig had had the impru-
dence to gainsay some of those facts which troubled him.
He would not have it, for example, that the yeast could
develop, live and produce fermentation in a medium
containing only sugar, mineral salts and ammonia, as
the exclusive source of nitrogen. The last dress given
to his theory demanded in addition to these, as I have
emphasized above, a previously elaborated albuminous
compound.

In this respect I find it very difficult to come to terms
with Liebig. While he was on the scent of philosophical
explanations, he could just as well have admitted that
the yeast itself manufactured in its own tissues the
albuminoid substance of which it had need. I do not
see wherein this conception stood in the way of the final
development of his theory. But he had his idea, which
the experiments of Pasteur contradicted. He, therefore,
had repeated this experiment of fermentation in a mineral
medium and had not succeeded, because it is difficult,
and had concluded that Pasteur was deceived.

He denied, furthermore, that Mycoderma aceti was the

132 PASTEUR : THE HISTORY OF A MIND

agent of acetification in the German vinegar works;
"for," he said, "on a wood shaving which had been
used for 25 years in a large vinegar factory in Munich,
there was no trace of mjToderma visible, even under the
microscope."

In the presence of these denials, Pasteur had recourse
anew to the tactics which had proved so successful with
Pouchet, Joly and Musset. He demanded that Liebig
present himself, in company with him, before a com-
mission of the Academy of Sciences, which should be
charged with the duty of pronouncing between them, and
in the presence of which Pasteur offered in the first place
to prepare, in an exclusively mineral medium, as much
yeast of beer as Liebig could reasonably demand; in
the second place he promised to show to the commis-
sion, and to Liebig himself, the acetifying mycoderma
on all the beech shavings of the factory in Munich.

The challenge was urgent. Pasteur would not have
been in position to give it at the time of his studies in
1860 on alcoholic fermentation. His cultures of yeast
in a mineral medium were at that time too poor and too
uncertain, but since he had begun his studies on beer,
to which we shall soon refer, and had found yeasts ac-
commodating themselves to these mediocre culture con-
ditions, he was sure of his facts. Liebig did not accept
the challenge. He only remained a little melancholy.

I have as proof of this a letter in which he states the
somewhat fallacious idea, that by going into the subject
thoroughly enough, Pasteur and he would have ended by
discovering and understanding each other. "I have
often thought," he wrote me in 1872, "in my long prac-
tical career and at my age (69 years), how much pains
and how many researches are necessary to probe to the
depths a rather complicated phenomenon. The greatest
difficulty comes from the fact that we are too much ac-

THE DISEASES OF WINE 133

customed to attribute to a single cause that which is the
product of several, and the majority of our controversies
come from that."

"I would be much pained if M. Pasteur took in a dis-
paraging sense the observations in my last work on
fermentation. He appears to have forgotten that I
have only attempted to support with facts a theory
which I evolved more than 30 years ago, and which he
had attacked. I was, I believe, in the right in defending
it. There are very few men whom I esteem more than
M. Pasteur, and he may be assured that I would not
dream of attacking his reputation, which is so great and
has been so justly acquired. I have assigned a chemical
cause to a chemical phenomenon, and that is all I have
attempted to do."

Thus Pasteur and Liebig, two master minds, each
qualified to grasp the view-point of the other, both of
whom loved science above all things, remained divided,
because they could not agree on the role of the yeast in
alcoholic fermentation. Is there not to be derived from
this a great lesson for scientific men, and even for those
who are not?

IV
THE DISEASES OF WINE

We shall perceive at once the advantage of having the
theories of Pasteur replace those of Liebig in science.
Arrived at this stage of advancement, Pasteur had
before him a fertile province which he could conquer by
a wave of the hand, and which would have remained
closed and inaccessible under the old ideas. I will ex-
plain my meaning.

What had Pasteur just found out? That acetilica-

134 PASTEUR: THE HISTORY OF A MIND

tion, that is to say one of the maladies to which wine is
constantly exposed, is exclusively the work of a micro-
organism. But there are many other diseases which
invade wines with more or less rapidity. The wines of
Bordeaux turn, those of Burgundy become hitter, the
wines of Champaigne become ropy. At this time, the
Phylloxera had not yet made its appearance, and many
persons had caves; but there was no cave where a malady
of the wine did not appear from time to time, and did
not cause losses, which were often grievous.

Upon that point, the ideas of Liebig shed no great light.
According to them, the wine was constantly in move-
ment, at work; those wines which preserved themselves
intact, and were called de garde, reached the end of
fermentation with a certain state of equilibrium between
their sugar and their organic matter serving as ferment;
these two elements were equally exhausted. If there
had been too little ferment in the beginning, a portion of
the sugar remained unchanged, and the wine was sweet,
that is to say incomplete. If there had been too little
sugar, on the contrary, some ferment remained which
continued to work upon the substance and to produce
therein vitiations of the taste. This explanation, so
beautifully symmetrical, had seduced people's minds,
and the reader found it paraphrased in all the books on
the subject. As to a remedy, it did not give any, or at
least it had not done so.

For Pasteur, on the contrary, these ideas had no mean-
ing. He was sure that the activity of the yeast was
arrested after having transformed the sugar, and that
it could act neither upon the alcohol which it had
formed, nor upon the other elements of the wine. In
that he was deceived, for we have seen since that the
yeast can destroy in time the glycerin which it has
produced, just as the mycoderma of the vinegar burns the

THE DISEASES OF WINE 135

acetic acid which it has formed. But, as usual, Pasteur
was deceived only half way, and his deduction was exact.
The vitiations in taste which sometimes are observed in
certain wines could not result from any normal physical
or chemical phenomenon, for the wine was preserved
almost everywhere in the same fashion, and these changes
ought to be seen everywhere. There remained then
one plausible explanation, that is that these vitiations
came from special fermentations, produced by special
ferments analogous to the acetic ferment.

Here is the conclusion to which the logic of his mind
and of his acquired knowledge led Pasteur! It remained
to see what experimentation would show. He had at
Arbois, fortunately, some old comrades of his childhood
who owned some caves well stocked for home and market
purposes, and he easily obtained permission to subject
their wines to a microscopic study.

From the first moment, he surmounted the difficulty.
Every time that the tasters pointed out to him a par-
ticular defect in taste, he found so constantly a distinct
microscopic species mixed with the yeast in the bottom
of the cask, that soon he was able to make the test in-
versely, that is to say, to indicate in advance the savor of
the wine by examining its deposit. The normal wines
contained only the yeast.

With a guiding idea, so clear and so well verified by
experiment, he could begin. After some months passed
at Arbois in an improvised laboratory, Pasteur succeeded
in elucidating the question, and, in 1866, he was able to
place in the hands of the Emperor, who had encouraged
him in his researches, a book containing the complete
solution of the problem which he had set himself to solve.

This book is a trilogy, of which all the parts hold to-
gether. In the first part, he shows that all the maladies
enumerated above, the turning, becoming bitter, becom-

136 PASTEUR : THE HISTORY OF A MIND

ing oily, which are not the sole changes which wine can
undergo, but only those best known, are each dependent
upon a special micro-organism which lives at the expense
of one of the elements of the wine, and imprints on this
beverage a characteristic change of composition and of
taste. This is not the place to insist on the morphology
or the properties of these different organisms represented
in Fig. 8, page 70. We will take from the history of the
facts only what is necessary to explain the history of
the ideas.

The solution of this first problem allowed two others to
be approached. What goes on in a wine which becomes
old normally, in the absence of organisms? What is it
necessary to do, in order that wine may always grow old
normally? It is on these last two questions that some
developments are necessary. I would like to show to
what degree the new manner of regarding them and of
treating them rendered them fertile.

ACTION OF OXYGEN ON WINE

In the way in which it was stated, the first question
was evidently one of pure chemistry, and Pasteur found
himself brought back to his first domain. The natural
aging of a wine, when microbes are absent, can only take
place by the play of forces within the liquid, and of
those which may result from its contact with oxygen.
What did science and practice have to say on this subject?

The practical man seemed to be inspired with a terror
of the oxygen of the air. The wine was exposed to the
air only so long as absolutely necessary for the decanting.
It was the custom to sidphtir, that is to say, to fill with

ACTION OF OXYGEN ON WINE 137

sulphurous acid the casks in which it was to be received;
also, in some portions of the country, to fill, that is, to
keep constantly full, the casks in which it was stored.
It was said that it is more exposed to the danger of
spoiling in casks of permeable wood than in glass bottles.
It was well known that it became fiat in contact with the
air, and recently M. Berthelot had quite justly related
this phenomenon to an absorption of oxygen. Bous-
singault had shown, on his part, that the wine of casks
contained only nitrogen and carbonic acid, that is to
say, there is no longer a trace, in the free state, of the
oxygen which it has certainly taken from the air at the
same time as the nitrogen. In short, for science as for
practice, wine seemed to be a substance most oxidizable
and unstable in regard to aeration.

Of that there was no doubt. Pasteur had a great
respect for secular practices and said that science ought
not to condemn them lightly, but that it had always the
right to search for their interpretation. It might be
that the wine was really unable to endure contact with
air, but also it might be that air is necessary to the
microbes which menace the wine, and that to deprive
it of the air would, in a measure, guarantee it against
disease.

Pasteur had already arrived at a stage where he could
accept only the second of these two interpretations. He
knew from his experiments on spontaneous generations,
how little organic substances are oxidizable without the
intervention of microbes, and on the other hand, he had
just seen that the acetic ferment which constantly
threatens wines with acetification has great need of oxy-
gen. Furthermore, while he was studying this myco-
derma of vinegar he had also studied another superficial
pellicle, that which forms so easily on the surface of
wine left behind in filling the bottles and which resem-

138 PASTEUR: THE HISTORY OF A MIND

bles the preceding in its need of oxygen — the mycoderma
of wine.

The latter, although it is more frequent than the
mycoderma of vinegar, nevertheless has less grievous
effects, because, not stopping half way, it pushes quite
to term the oxidation of the alcohol, and makes out of
it immediately water and carbonic acid. This carbonic
acid replaces the oxygen absorbed from the air, and by
reestablishing the pressure, prevents a new influx of air
and of oxygen. Thus the development of the myco-
derma of the wine, which takes place on the surface of
all the casks which are not full, ordinarily passes unper-
ceived, although sometimes the layer which covers the
liquid may be thick. When it has exhausted all the
oxygen which exists above it in the closed cask, it renews
its supply only slowly; and when this happens it con-
sumes it entirely and leaves no trace of it, in a free state,
in the liquid below. It is an impenetrable filter for the
oxygen, as impenetrable as a wall of glass.

That granted, did the practices employed in wine-
making favor the wine or its parasites? In examining
the question from this entirely new point of view, Pasteur
was not slow in recognizing that, far from being formidable
to the wine, it is the oxygen which makes it, which takes
away the acid and rough taste of new wine, and which
makes it more and more fit to drink. It is also the
oxygen which divests it little by little of its coloring
matter, yellows what is left, and gives to it gradually
that onion-skin tint, with which our ancestors were
familiar, and of which we are ignorant, because they
knew the worth of life, and we know only its cost. Fi-
nally, as its action increases, the oxygen, after having
given to the wine the taste of old wine, ends by consum-
ing it and spoiling it. When he had studied a subject
Pasteur loved to sum up the ideas which he had ac-

ACTION OF OXYGEN ON WINE

139

quired in the form of some startling experiments which
at the same time furnished a verification of his ideas,
and constituted a classical demonstration. Here are
some which were used to illustrate this subject.

Suppose at the end of the fermentation, at the time

Fig. 13. — Mycodernui of wine.
Submerged. In the state of flowers of wine.

when the wine, already clear, is still saturated with
carbonic acid, we fill a bottle full in such a way that at
no time during the process does the wine come into con-
tact with the air. This operation ended, the bottle is
hermetically sealed by melting wax over the stopper.
The wine thus treated remains indefinitely as it was at

140 PASTEUR: THE HISTORY OF A MIXD

the moment of drawing off; it preserves its color; its
savor does not change to any appreciable degree ; it takes
on no particular bouquet ; it is always neiy i(;me. During
this time, the rest of the same wine, preserved in a cask
and subject to the ordinary manipulations, becomes old
in the complex sense which one ordinarily gives to this
word. What differences are there then between the two
wines? One only: under its envelope of glass the former
has not been subject to the action of the oxygen of the
air which filters constantly and slowly through the
barrel staves, and which, combining with the wine,
determines its ripening.

Without taking any particular precautions to avoid
excess of air, let us repeat the experiment which I have
just described, leaving the bottle half empty and closed
with its stopper. While the wine in the previous ex-
periment remained young, that in the new bottle clouds
and gives an amorphous deposit which increases little
by little and finally adheres to the walls. It is the red
coloring matter which has separated from the wine.
At the same time, the oxygen left in the bottle dis-
appears, and the wine changes, loses its original savor,
becomes old, and takes on in a high degree the taste of
rancio,^ if it is red, of viadeira if it is white. It may
even fade away and disappear altogether, if there is
too little of it in proportion to the oxygen.

The essential act in the aging of wine is, therefore, its
slow combination with oxygen. When the absorption
of oxygen is too rapid, the wine becomes vapid, but this
is a passing phenomenon, and it is often sufficient to
let the wine alone for this taste to disappear, as soon
as the oxygen absorbed in a gaseous state has served
in the wine for the oxidations which have consumed it.

1 Old wine which has acquired the taste of Spanish wines, "^rs.

I

TASTEUR

(Courtesy of Dr. ^^'illf()rcl H. Smith, Superintendent, Jolms

Hopkins Hospital.)

THE HEATING OF WINES 141

VI

THE HEATING OF WINES

These facts being formulated and established in the
first two parts of the Etudes sur les Vins, the third part
appears as a denouement. The diseases of wine are
correlative with the development of parasitic vegeta-
tions; it is the fear of these parasites which burdens
all the practices of wine-making and the preservation of
wine, and forbids the employment of other methods
more favorable to the aging. If we can succeed in elimi-
nating these dangerous ferments, or in destroying them
when they are present, we shall have overcome this
antinomy and have solved the problem.

It is here that Pasteur found once more the advantage
of his earHer studies, for it is remarkable that, save from
himself, he borrowed almost never. We have seen this
in what precedes. It will be still more apparent as we
advance.

The problem was to prevent or to arrest the develop-
ment of the parasites without in any way changing
the constitution of the wine. For this purpose he had
at his disposition the action of antiseptics or that of
heat. He tried antiseptics first, especially the hypo-
phosphites and the bisulphites of the alkalin metals,
which are without decided odor and taste when they
are in dilute solution, and which become inoffensive
phosphates or sulphates after having absorbed oxygen.
The results were mediocre or negative. It was then that
he thought of the action of heat.

We understand his hesitations in having recourse

to this agent. By means of it he was sure of killing the

microbes 'without even heating to the boiling pointy

for wine is an acid liquid, and the acidity helps on the
12

142 PASTEUR: THE HISTORY OF A MIND

action of heat, as we have seen when considering spon-
taneous generations. Moreover, there was a chance,
and Pasteur had not failed to perceive this possibihty,
that it might not be necessary to kill the ferments
which, considering the slowness with which they or-
dinarily develop, are under unfavorable conditions in the
wine. To weaken them by the heating so that they could
not multiply would perhaps be sufficient. All this was
encouraging. But, on the other hand, the employment
of even a minimum quantity of heat appeared to have
its grave dangers. Everybody has drunk warm wine
and knows that it is no longer wine. Those ancestors
whom we invoked a short while back recommended
one to drink cooled wine. Only Bordeaux wine, they
added, is improved by conveying it into the dining room
four hours in advance of the guests.

Yes, Pasteur might have replied to these objections:
but all those wdnes which one hesitates to heat are wines
recently drawn off and aerated. Would it be the same
for the bottles which would be heated only after having
allowed their contents time to transform into combined
oxygen the gaseous oxygen absorbed during the racking?
No one could reason more correctly, and it is thus that
Pasteur, at the first step, and almost without groping,
by proceeding always in the direct light of his former
experiments, reached that procedure of heating to 55°
C. for which such a noble future seemed reserved when
it first appeared.

At this time, in 1867, the prosperity of viticulture
was great; France reckoned more than 2 million hectares
planted in vines and her wines, the dissemination of
which was favored by commercial treaties, seemed
destined to reach all the markets of the world. To give
to an industry operating upon 50 million hectolitres,
and worth 500 million francs, the means of avoiding

THE HEATING OF WINES 143

the deterioration of its merchandise and of increasing
more rapidly its commercial value, was a public benefit.

Unfortunately, two years previous, on the plateau of
Pujaut in Gard, there had appeared the Phylloxera which
has since caused so much devastation, and the following-
year the insect had disseminated its colonies over a
large portion of the departments of Vaucluse and Bouches-
du-Rhone. Another microbial power had taken a hand,
against which science and agriculture were at this time
unarmed. Consequently, for some years Pasteur's
method was ruined. No one need consider how to keep
grains in a time of famine, and the heating of wines
was little practised except for those which must be
shipped under bad conditions as to keeping, for example,
in the commissariat of the Navy.

But now they return to it gradually in the wine indus-
try, and for some years it has been employed regularly in
the beer traffic, with the best results. It has done more,
it has entered into the language, and the word pasteur-
ize signifies, even outside of France, to protect against
microbes by the action of heat. We pasteurize wine,
milk, and beer, and are right in performing the operation,
and in so calling it.

I would be through with the subject if it were not for
saying a word or two on the claims of priority raised
against Pasteur, and on the somewhat bitter polemic
which resulted. It is always wrong to confide one's
rancors and jealousies to the public. We do not recollect
sufficiently that this public has its own affairs, is only
moderately interested in the fundamentals of the debate,
and contents itself with being amused at the blows.
Pasteur had the best side here and should have been
content with shrugging his shoulders. He was accused
of having re-invented the process of Appert, as if there
could be the least parity between the empiricism of the

144 PASTEUR : THE HISTORY OF A MIND

one and the experimental logic of the other. Appert
had taught us only one thing, viz., that sometimes wine
could be warmed without changing the taste, or becom-
ing heated wine. If Pasteur had known of this experi-
ment, he would have hesitated less than he did in having
recourse to the action of heat, but his work would have
remained the same. Besides, he made haste, as soon as
he knew of them, to render to Appert's experiments the
credit they deserved.

It was also said to him, in all manner of ways, that the
heating of wines had been known and esteemed for a
long time at Aleze, in the department of Herault, near
Cette. "So be it," answered Pasteur, who had gone to
see, "they do warm the wine at Meze, but it is to age it
more speedily. For this purpose they warm it in con-
tact with the air, for a long time, so as to bring about
changes in taste, which sometimes exceed the limit, and
which it is then necessary to correct; these gropings
about in the dark show that the wine merchants of Meze
do not have any clear idea of what they are about, and
have not read my book. It would be to their interest to
do so, for I give the theory of their practice. Aleair
while, what has this long and dangerous warming in
contact with the air in common with that rapid heating
to 50° C, protected from the air, which I recommend?"

There remains finally the laggard claim of M. de Ver-
gnette-Lamotte, but this is so strange and shows such
ignorance of the subject, that it is better not to speak of
it. It resulted in some bitter-sweet notes which may be
read in the Comptes rendus de V Academic des Sciences and
in the Moniteur scientifique de Quesnehille. All profound
faith is necessarily a little intolerant, and Pasteur had
that faith.

PASTEUR
(From a woodcut in "Jour. d'Agric. pratique," 1895.)

FIFTH PART

Studies on the Diseases of Silkworms

I

ORIENTATION TOWARDS PATHOLOGY

I still recall the day when Pasteur, returning „to the
laboratory, said to me with some emotion in his voice:
"Do you know what M. Dumas has just asked me to do?
He wants me to go into the South and study the disease
of silkworms." I do not recall my reply; probably it
was that which he had made himself to his illustrious
master: 'Ts there then a disease of silkworms? and
are there countries ruined by it?" This took place so
far from Paris! and then, also, we were so far from Paris,
in the laboratory!

However that may be, Pasteur had reached one of the
turning points of his life. For a long time he had had a
presentiment that all the new ideas he had introduced
into science might be of importance for the physiology
and pathology of the higher animals. For a long time
the two notions of fermentation and disease had been
connected, as we have seen during our consideration of
spontaneous generations. But this relation had become
closer since it had been known that it was living cells
which presided over the processes of fermentation.
However, let us keep from believing that the logic of
the ideas of Pasteur led him, at this time, to the spot
where we see him so naturally to-day, namely to the con-
clusion that disease could result from the development,
in the normal tissues, of a living microscopic organism,

145

146 PASTEUR: THE HISTORY OF A MIND

the cause of the disease. That is the idea divested of all
its trappings — an idea reached ordinarily only after
one has made the tour of ideas much more complicated.
In fact, as we shall see, Pasteur reached this conclusion
only, so to speak, in spite of himself, and after two years
of study.

He was, it seems, more disposed to believe at this
moment that the disease, whatever it might be, could
by modifying the fluids of the body prepare the soil
for this or that microbe, which was then according to the
case, either the result of the disease, or the visible evi-
dence of it, or the beginning of a new disease. We shall
see later that these notions are not as exclusive of the
other idea as one might at first sight beheve them to be.
In all cases, they ended with a repercussion of the microbe
on its host, and it was for this reason that Pasteur main-
tained for so long a time the relations between the phy-
siology of the ferments and that of the higher animals.
Thus we have seen him liken the red blood-corpuscle
to the acetic ferment which, like the latter, can take
the oxygen from the air and carry it, endowed with a more
powerful activity, to the combustible substance.

But when there was raised the question of going farther
and of actually coming into contact with the higher
animals, Pasteur hesitated. He was not a physiologist.
To no purpose did we go to hear the course of Claude
Bernard, where he took notes feverishly. It would have
been necessary for him to become a new soul, and he had
neither the time for it nor the patience. The insist-
ance of Dumas had just placed him face to face with
an experience which he both desired and dreaded, and
if his self-distrust had made him hesitate, at the first
encounter, in reality, the attraction for the unknown and
a certain interior voice urged him to accept.

Consequently, his decision was soon made. After

ORIENTATION TOWARDS PATHOLOGY 147

having acquired a fragmentary knowledge of the general
structure of the larvse of insects by causing to be dissected
in his presence a white worm [larva of the May beetle]
or a larva of Orydes nasicornis, after having assisted at
some sittings of an Imperial Commission on Silk Culture
from which he came away more discouraged than en-
lightened, after having skimmed the last published books
on the subject, he set out for the South. It was at the
beginning of June: the cultures of the silkworms were
almost completed. From this fact he might have plead
for more time and the putting ofT of his investigations
until the following year, but his master, M. Dumas, had
spoken : he was also more eager than he himself suspected
to enter into this new world, and he desired to begin the
work at once.

To it he devoted six years, which it will not be unprof-
itable to describe in detail, and that for two reasons.
The first is that nothing can be more curious than to see
Pasteur at close quarters with a bristling, complicated
question, beginning by being deceived about it, by seeing
things the wrong side to, but led back continuously to
the truth by experiment, and ending by unravelling all
the obscurities. I do not know a more beautiful example
of scientific investigation. The second reason is that it
is the first camp on a route wherein he found immor-
tality. The other discoveries had given him only glory.
Finally, I would like to add, as a third reason, that this
period of his life is that of which it is easiest to write
the history, both because of the impressions it has left
on those who helped him in his labors, and because of
the documents he has himself published.

In this part of his researches he had not the right to
keep the Olympian silence with which he loved to sur-
round himself until the day in which his work seemed to
him ripe for publicity. He said not a word about it, even

148 PASTEUR: THE HISTORY OF A MIND

in the laboratory, where his assistants saw only the ex-
terior and the skeleton of his experiments, without any
of the life which animated them. Here, on the contrary,
he was under obligation as soon as he had found out
something to speak and to excite the public judgment
and that of industrial practice on all his laboratory
discoveries.

A hard necessity, that of laboring thus under the public
eye, with an official connection, in the presence of a men-
acing danger which one has been commissioned to exor-
cise! To be sent to combat a conflagration, and not to
know where the fire is, and not to have any pumps! One
must be a Pasteur to accept such a responsibility and
carry it off successfully. In any event, we owe to this
condition of things a multiplicity of documents: reports
to the Academy of Sciences, to the Minister of Agri-
culture, letters to M. Dumas, communications to the
journals of silk culture, and we can make use of all these
signed writings of Pasteur to reconstruct the history of
his thought. He has himself authorized us to consult
them by inserting them at the end of the second volume
of his Etudes sur la rnaladie des vers a sole. "I might
have dispensed with reproducing in toto these pub-
lications," he says, "since the first volume contains the
definite expression of my actual ideas; but I have thought
that they might be of some historical interest and serve
as an example in a difficult and long-winded subject
of the progressive march of ideas in proportion as the
observer multiplies his experiments.

"'Let us gather together some facts in order to have
some ideas' said Buffon. It is not without utility to
show to the man of the world or to the practical man
at what cost science conquers principles the simplest and
most modest in appearance."^

^ Etude sur la maladie des vers a soir, t. II, p. 1.55.

THE CORPUSCULAR DISEASE [pEBRINE] 149

We shall see that Pasteur has nothing to lose from this
attentive study of the progress of his mind. He some-
times wandered in his research, as we have said, allowing
himself to be deceived by false gleams, but he always re-
turned to the right path, and it is just this struggle with
error, always imminent, that makes the interest of this
study.

II
THE CORPUSCULAR DISEASE [PfiBRINE]

Some preliminary notions and details are necessary
to understand thoroughly the moving vicissitudes of
this struggle against a scourge as redoubtable as was
the disease of silkworms at this time. Everybody knows,
at least in a general way, the principal phenomena of the
life of the silkworm: its birth from an egg, whose re-
semblance to certain vegetable seeds has led to its being
given the name of graine; and its four molts or changes
of skin, during which the worm ceases to eat, remains
motionless, seems to sleep upon its litter [feeding place],
and clothes itself, under its old skin, with a new supple
and elastic skin, which allows to it a new development.
The fourth of these molts is followed after two or three
days by a period of extreme voracity during which the
worm increases in volume rapidly and acquires its maxi-
mum size: it is the big gorge. This period terminated,
the worm eats no more, moves about uneasily, and if
sprigs of heather on which it can ascend are offered, it
hastens to choose thereon a suitable place to spin its
cocoon, a kind of silky prison which permits it to undergo
in peace its transformation first into a chrysalis, and
then into a moth. In this cocoon, the body of the worm,
emptied of all the silky matter, contracts and covers

150 PASTEUR : THE HISTORY OF A MIND

itself with a resistant tunic, in the interior of which all
the tissues seem to fuse into a pulp of homogeneous ap-
pearance. It is in the midst of this magma that, little
by little, the tissues of the moth are formed and become
differentiated.

The moth has only a rudimentary digestive canal,
for it no longer has any need of eating: the worm has
eaten for it. It has wings, but, in our domestic races, it
makes no use of them. It is destined only for the re-
production of the species, and the sex-union takes place
as soon as it comes out of the cocoon. The female then
lays a very considerable number of eggs, which may
reach 600 or 800 and in the races that we call annual,
which are the most sought after, this "graine" does
not hatch the same year as its production. It is de-
layed till the reawakening of vegetation the spring of
the following year.

It is only when the grower wishes to have ''graine" or
to induce the laying of eggs {faire grainer) that he awaits
this coming forth from the cocoon, in which the trans-
formation of the worm into a moth requires about 15
days. By adding thereto the 35 or 40 days required
for the culture of the worm, and the time necessary for
the laying of the eggs, we see that the complete evolution
of the silkworm, from the egg around to the egg is about
two months. The period of industrial life is sensibly
shorter. When the grower wishes to use only the cocoons,
he must not wait till the moth, in coming forth, has
opened them and thereby rendered them unfit for spin-
ning. They are smothered 5 or 6 days after they have
climbed the heather twigs. That is to say, the cocoons
are put into a vapor bath in which the chrysalids are
killed by the heat. For the silk grower, in this case,
scarcely six weeks separate the time of egg-hatching
from the time when he carries his cocoons to market —

THE CORPUSCULAR DISEASE [pEBRINE] 151

the time when he sows from the time when he reaps.
As formerly the harvest was ahnost certain and quite
lucrative, the time of the silkworm was a time of festival
and of joy, in spite of the fatigues which it imposed, and
in gratitude the mulberry tree had received the name of
arbor (Tor from the populations who lived upon it.

Unfortunately, silk culture had been attacked for 20
5'ears by a cruel, inexplicable disease, which owing to
its singular behavior and multiple and changing mani-
festations, disconcerted the reason and baffled the efforts
best calculated, in appearance, to overcome it. If, for
example, a culture of worms had succeeded very well
so as to excite the admiration of all the surrounding
country: instead of smothering it to wind the cocoons
for silk, it was saved for the egg-laying in a very natural
hope of obtaining therefrom excellent "graine." But
alas! It happened that almost always this hope was
deceived and that the following year the worms derived
from these eggs, instead of growing rapidly like their
ancestors, and preserving to the end a perfect uniformity,
acquired slowly the most diverse sizes. Many died in the
first stages, and those which had passed the fourth molt
successfully seemed but little able to pass beyond it;
they became smaller, seemed to melt away, little by
little, and ended by disappearing almost altogether,
giving only a negative or insignificant yield. The im-
possibility of obtaining good eggs which was soon demon-
strated by similar failures with our fine French races, had
led numerous silk growers to travel seeking healthier eggs
at a distance; but the disease seemed to have made the
tour of the world along with them, and their exotic
"graines," after having succeeded one or two years in
France, were struck with sterility both in our own country
and in the lands where they originated.

On account of its occurrence in cultures which it ap-

152 PASTEUR: THE HISTORY OF A MIND

peared should be the most robust, the disease seemed
to be epidemic, and on account of its slow and regular
progress, from our country toward the most distant
regions of Europe and Asia, it seemed to present in
the highest degree the contagious character: and yet
other facts, not less numerous, and not less convincing
in appearance, bore witness that it was neither epidemic
nor contagious. I will cite only one of them, which
Pasteur had learned at the beginning of his studies,
and which had troubled him somewhat. In the culture
of a mixture of two ''graines," the one giving white
cocoons and the other yellow ones, it had been observed
that the first died almost completely, while the other
gave a very satisfactory harvest.

The uncertainty was not less great if one sought to
study the disease by itself, without being preoccupied
any more with its nosological character. Thus, de
Quatrefages, after having made a careful study, believed
himself able to characterize it by the existence in the
interior and especially upon the skin of the worm, of very
small spots resembling grains of black pepper, and for this
reason had been led to name it pebrine. But experiment
showed that the worms could be spotted without being
sick, and on the other hand that worms which were
not spotted did not necessarily give good eggs. If one
wished to enter further into the study of the disease,
he found himself in the presence of contradictory results
obtained by various physiologists. For example, Lebert
and Frey had established that in the interior of all the
diseased worms and all the diseased moths there existed
in abundance a peculiar parasite, the corpuscle, visible
only under the microscope, observed for the first time
by Guerin-Meneville, and the importance of which
from the pathological point of view had been caught sight
of by Cornalia. But if one believed Philippi, another

THE CORPUSCULAR DISEASE [pEBRINE] 153

scientific man, these corpuscles existed normally in all
the moths.

A real progress had, however, been realized the day
that Osimo had discovered the corpuscles in the eggs
of silkworms, and the day Vittadini, after having rec-
ognized that their number increased in a laying of
eggs in proportion as they approached the period of
hatching, had based a method of distinguishing the
good from the bad upon a microscopic examination of the
eggs. The corpuscle is, indeed, actually, as we shall
see, the cause of the disease, and an egg which contains
it can never give cocoons; but these two facts not being
demonstrated, uncertainty existed as to the theoretic
value of the procedure. As to the practice, it often
gave out detestable eggs for good ones, and when it
condemned the eggs it was in the name of principles so
uncertain that the silk grower could not be held culpable
for having no confidence in the advice of science.

The same Osimo, in 1859, had endeavored to push
science and practice in another direction. He had ad-
vised examination not only of the eggs but also of the
chrysalids, and rejection of the layings of those stocks
which were found too corpuscular. This time it would
have been to approximate correct procedure, as we shall
see immediately, but this advice, given offhand, and
without experimental support, had been followed and
tested, offhand also, by Cantoni, who, after having
cultivated the eggs coming from non-corpuscular moths,
had seen the worms become corpuscular during the
culture, which proved, he had concluded, that "the
microscopic examination of moths was also unfortunately
as worthless" as the other remedies.

By good fortune, of all this past history, of all this
mixture of truth and falsehood, Pasteur knew nothing
at the beginning of his studies. To his complaint of

154 PASTEUR : THE HISTORY OF A MIND

not being familiar with the subject, Dumas had replied
one day: "So much the better! For ideas, you will
have only those which shall come to you as a result of
your own observations!" Such a reply is not always
a paradox, but one must be careful to whom he makes it.

Ill
STUDIES OF 1865

The first act of Pasteur on reaching the South was to
seek this famous corpuscle, which he had never seen.
He had no trouble in finding it. In the neighborhood of
the little city of Alais, in which he had installed himself,
all of the cultures, already near their end, were infected.
Sick worms and moths showed the corpuscles by thou-
sands. Some rare worms of healthy appearance did not
show any. What seemed especially to result from this
first rapid examination was the exactitude of the relation
pointed out by de Quatrefages between the existence of
the corpuscles and the presence on the surface of the skin
of the black spots of the pebrine. All the worms hav-
ing pebrine showed corpuscles in enormous numbers.
But this fact, even though it might have been more
thoroughly settled than it was really, did not signify
very much. In continuing his researches, a little at
random, Pasteur one day encountered one of those
unexpected facts which it is so useful and so dangerous
to find on our pathway, when we begin any research
whatsoever. They have a sphinx-like physiognomy, and,
in fact, they put the riddle clearly: "Guess or be de-
voured." Pasteur did not guess and was not devoured-
Therein lies the interest of this history.

Near the silk nursery in which he had installed himself,

STUDIES OF 1865 155

there were two cultures of silkworms, two broods (deux
chambrees) : the one finished and ascended to the
heather, the other coming out of the fourth molt. The
first had gone along admirably. The worms had climbed
up all at one time, and appeared so vigorous that they
were preparing to make use of all the cocoons for the
egg-laying. The second had dragged along, and presented
a bad appearance; the worms were languishing, ate little,
and did not grow. The sequel proved that this appear-
ance was not deceptive: the harvest of cocoons was
almost a failure.

Now, on examining with the microscope the chrysalids
and the moths of the culture which had succeeded ivell,
corpuscles w^ere found everjovhere in them, while there
were corpuscles only exceptionally in the worms of the
bad brood. And this was not an exceptional fact, for,
by searching in the neighborhood, Pasteur found a mul-
tiplicity of similar cases.

What did this mean? The corpuscles and the disease
of silkworms were, therefore, two distinct things. Could
worms be very healthy and behave properly, like the
worms of the first culture, and nevertheless give cor-
puscular chrysalids? Could they be sick, like the worms
of the second, and not contain corpuscles? To-day we
know that if Pasteur did not find out this it was because
he investigated badly, confounding in his inexperience
two diseases. There is one in which the corpuscle plays
a role, another in which it does not. But Pasteur did
not know this, having only discovered it later. And, in
the meantime, the disturbing and imperious question
confronted him: what conclusion is to be drawn from the
preceding observation?

In order to decide, it was prudent to wait and see what
would become of the cocoons of the bad brood. In fact,
in studying them day by day, as they developed, Pasteur

156 PASTEUR: THE HISTORY OF A MIND

saw that the number of those containing corpuscles
increased more and more. Among the worms, the cor-
puscles were rare. In the chrysahds, especially in the
older ones, the corpuscles were frequent. Finally, not a
single one of the moths was free from them, and they
were there in profusion.

The question seemed, therefore, to be cleared up, for
how could one interpret this double observation other-
wise than by saying: there is a disease which can weaken
the worm in the absence of the corpuscle, but of which
the corpuscle is the tardy evidence. The two broods
have suffered from this disease but the first has been
attacked only when the w^orms were near the cocoon
stage, and this brood has succeeded well although it
has been a little diseased. In the second, the disease
has attacked the worms more severely, and it is for this
reason that this brood has been languishing and has
almost miscarried.

This interpretation, we know to-day, is inexact, and,
consequently, it was perilous. Its danger was that it
led to a practical conclusion which Pasteur did not hesi-
tate to draw. From the moment that the corpuscle
appeared thus as the evidence of an advanced disease,
it is clear that it would be more advantageous to obtain
eggs from the non-corpuscular moths rather than from
the corpuscular moths. The first might be diseased, but
they would have been so for a shorter period and prob-
ably less seriously. "To say that the disease should
be regarded as affecting by preference the chrysalid and
the moth is only to say that at this age it manifests itself
more apparently and also without doubt more danger-
ously for its posterity." It is thus that Pasteur, starting
from a false idea, immediately put the capstone upon a
method of egg-selection which became theoretically and
practically, still better when the false idea which had

STUDIES OF 1865 157

inspired it was replaced by a true idea. For the cor-
puscle becoming, as it is really, the sole cause and not
simply the effect, or the witness, of the disease, its elimi-
nation was all the more profitable, and it is thus that
error sometimes leads to the truth. But let us not trust
too much to this example.

However this may be, Pasteur found himself led by
his manner of seeing things, to the same method of
egg-selection as Osimo, and it is curious to note with
what firmness, after 15 days only of sojourn in the places,
he indicates to the Agricultural Committee of Alais,^
the 26th of June, 1865, and repeats the 25th of September
following, before the Academy, the conditions of a good
method of egg-selection. "This means will consist in
isolating, at the moment of egg-laying, each couple,
male and female. 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 both from male and female, he will
number this laying which shall be preserved as eggs
absolutely pure, and bred the following year with par-
ticular care. There will be eggs diseased in various
degrees according to the greater or less abundance of
the corpuscles in the male and female individuals which
have furnished them."-

It is, on the whole, a return to the procedure of Osimo,
tried and judged worthless by Cantoni, as we have just
said. Why had it miscarried when it ought to have
succeeded? Perhaps because it had not been tried with
confidence, with the necessary faith, perhaps because
Cantoni had not sufficiently protected his worms from a
new contagion, the effects of which he had confounded
with those of heredity. When one follows an idea in

1 Etudes sur la maladie des vers a soie, t. II. p. 159.
^ Comptes rendus de I'Academie des Sciences, t. LXI, 25 Sept. 1S65.
13

158 PASTEUR: THE HISTORY OF A MIND

the air he must indeed go haphazard, and the least
check discourages. The idea of Pasteur had, on the
contrary, an experimental foundation, and any one
could trust him when he followed an idea proceeding
from experiment. Ordinarily he distinguished very
quickly whether a thing was true or false.

IV
STUDIES OF 1866

However, in the subject under consideration, Pasteur
continued to deceive himself during the whole of the
year 1866, in consequence of a defect of technique which
we must notice. He had had at heart to apply himself
his method of egg-selection in order to procure mate-
rials for study the following year. He had, therefore,
sought in the vicinity of Alais chrysalids and moths
as healthy as possible. But the country was thoroughly
infected; moreover, the cultures were far advanced in
that place, and for the greater part had been used for
the spinning. It was with great difficulty that he could
procure a few cocoons derived from a culture in appear-
ance quite healthy and successfully completed. He
brought them to Paris to obtain their eggs.

In the passage which I have just transcribed, Pas-
teur says that one opens the male and female to seek
therein the corpuscles. They proceeded at that time by
removing with scissors a part of the skin of the abdomen:
they spread out this shred upon a glass slide, scraped off
a little of the adipose cellular tissue which was brought
away with it, and examined this fragment after having
compressed it under a cover-glass. It was only later
that the moth was ground up in a mortar to study a
drop of the pap under the microscope. This slight

STUDIES OF 1866' 159

detail has a very great significance. The second process
is the only reasonably safe one.

On the contrary, the first method is liable frequently
to overlook the presence of the corpuscles, and we shall
see here how things go on in a research. The method
then adopted by Pasteur was the result of his false
idea. If Pasteur had considered these corpuscles as
parasites, he surely would have concluded that they
might be in one place and not in another, and that it
would be necessary to seek them in various places. But
he was convinced that the corpuscle, being a tardy sign
of the pre-existing disease, was a product of transforma-
tion, or, to employ a medical expression, a product of
retrogression of the cells of the tissues. Now, following
this hypothesis, it should occur everywhere in the body.

The method of research, imperfect because it had been
born of a false idea, deceived Pasteur and plunged him
deeper into his idea. In the eight couples brought
from Alais and which he had studied in Paris, he be-
lieved he had found one in which the male presented a
few corpuscles, and the female not any. As a matter of
fact, she also contained them, as shown by the result of
the cultures in which a few corpuscles appeared, not in
the worms and the chrysalids coming from these eggs
but in the moths. This phenomenon, spontaneous in
appearance, of corpuscles in a culture which it seemed
ought to be exempt, naturally confirmed Pasteur in his
belief in the internal origin of the corpuscle. It is thus
that a mode of examination inspired by a false idea leads
sometimes to the confirmation of this false idea, and it is
thus moreover that, during the whole of the campaign
of 1866, Pasteur persisted in likening the corpuscle to
pus-globules and even to red blood-globules. He came
back definitely to the idea of parasitism only after an
experiment of Gernez which we shall find in its place.

160 PASTEUR: THE HISTORY OF A MIND

On the whole, at this time, any one who judged super-
ficially would have concluded that Pasteur brought for-
ward nothing new. He shared the error of Philippi,
of Vittadini, and of Cornalia, upon the origin of the cor-
puscle: his method of egg-selection, proposed by Osimo,
and then by Cornalia, had miscarried in the hands of
Cantoni and of Bellotti. It is necessary to look at the
subject closely to see that Pasteur brought into this
study another idea than his predecessors. This idea
was that of undertaking comparative cultural experi-
ments upon healthy eggs and diseased eggs. The
method of egg-selection which he recommended, how-
ever mediocre it might be from the theoretical point of
view, hoAvever bad it might be from the industrial
point of view, judging from the results of Cantoni, was,
however, sufficient to maintain those original differences
between the eggs, the influence of which it was important
to examine. "The process of selection to which my
first researches had led me seemed to me," says Pasteur,^
"to have an importance more scientific than industrial."
It turned out that this process contained the industrial
solution of the problem, but if it had not contained it,
it would have led to it, for Pasteur introduced experi-
ment into a question where there had been hitherto
only empiricism.

His plan of campaign for the cultures of 1866 was,
therefore, already outlined. After having obtained the
eggs from his different pairs of moths which were more
or less corpuscular, he would first try these out ahead
of the main brood, which is done in March and April in
small lots upon leaves of the mulberry cultivated in
hothouses, then in the big cultures of May and June.
Made with the same precautions and under the same
conditions, the culture of these eggs of different origin

1 Etudes sur la inaladie des vers ii soic, t. I, p. 55.

STUDIES OF 1866 161

ought to give, as regards the influence of the corpuscles
of the father and of the mother upon the result of the
industrial culture, or of the culture for eggs, information
which could not fail to be very important, whatever
might be the true significance of the corpuscle itself.
In fact, advancing with this light, Pasteur perceived
immediately a certain number of facts of the greatest
importance.

The first fact was that on a large scale in the industrial
culture the batches of eggs behaved worse and worse,
that is gave less and less cocoons, in proportion as the
parents were more and more occupied by corpuscles.
This sufficed to establish between the existence or the
number of the corpuscles and the presence of the disease,
the bond of union which was the first need of the new
method.

The second fact was that eggs laid by corpuscular
moths were not, jmr se, destined to miscarry, and might
develop good cocoons giving acceptable yields. Such
was, for example, the case of the eggs received from
Japan, which, although corpuscular, were nevertheless
much sought after by silk-growers. This robust race
seemed better to resist the prevalent disease. Such was
also the case for several cultures of French races. But
none of these cultures, even those which had yielded the
greatest number of cocoons, could give good eggs,
because all the moths were strongly corpuscular. This
explained why one sometimes miscarried in selecting
eggs derived from a successful culture. The success
of this culture proved nothing as to the egg. In addition,
control by means of the microscope was necessary.
And so one came back to the method of egg-selection,
authoritatively recommended by Pasteur, this being
brought forward once more, singularly strengthened
by its first trial.

162 PASTEUR: THE HISTORY OF A MIND

Finally, another prime fact was that even in the most
corpuscular broods, where the mortality of the worms
or of the chrysalids had been the greatest, one always
found some non-corpuscular moths that would give better
eggs than those from which they themselves had come.
From a practical standpoint this was of the highest
importance. Among the objections made to Pasteur,
from the beginning, the following had actually figured:
If the disease is indeed characterized by the presence
of an abundance of the corpuscles, as you say it is, and
as you prove it to be, it is then widespread, universal,
and, this being so, how shall we proceed to find the neces-
sary eggs, we do not say for the regeneration, but for
the simple conservation of the French and Italian racesj
very superior from the point of view of yield and of the
quality of the silk to the Japanese races, which are
replacing them little by little in all the silk-growing
lands. To this Pasteur could reply: But here are co-
coons of a French race which I have just brought from
one of the most infected districts! Look at them, study
them under the microscope, and you will see that they
promise results still more beautiful for next year. Do,
therefore, as I do: let each one procure eggs for himself,
as I do for myself. If you tell me that the microscope
frightens you, and that its manipulation seems to you
not easy, I reply that there is in my laboratory a little
girl eight years old who knows how to do it very well.

V

IS THE CORPUSCLE THE CAUSE OF THE DISEASE?

But this apparent disappearance of corpuscles in some
of the moths descended from a corpuscular pair had theo-
letical consequences more far-reaching than its practical

IS THE CORPUSCLE THE CAUSE OF THE DISEASE? 1G3

consequences. A\Tiat signified these healthy individuals
in a progeny strongly infected from both parents, and
evidently attacked by a hereditary taint? "Can it be
that among the eggs of a laying, derived from a male
and a female badly diseased, there are some healthy
eggs? Or will some eggs slightly diseased give worms
which recover health during the culture? I do not
know which of these two interpretations is the better,
and both are perhaps correct."^ The phrase is curious,
and bears witness that Pasteur began to doubt in 1866
concerning the interpretation of the phenomena which
he had accepted hitherto. The idea of a constitutional
disease of which corpuscles were only the external and
later sign did not harmonize very well with this presence
of a few healthy eggs in the midst of their diseased
neighbors. Excluding parasitism, one does not com-
prehend this immunity of some individuals in the midst
of others entirely alike in that they are the descend-
ants of the same organism. But this idea of
parasitism, which was blended with the idea of the cor-
puscle as a cause of the disease, was repulsed by Pasteur
at this moment with a kind of obstinacy, and with such
a singular mixture of true and false arguments that it is
useful to pass them in review. To do so will be to study
him in a vital point of his career, that in which he aban-
dons tradition and launches out into new ways.

He enumerated these arguments himself the following
year, for his scruples were of long duration. "Is the
disease parasitical?"- he asks himself in the note pre-
sented to the Imperial Commission of Silk Culture, in its
sitting of January 12, 1867, and he rejects this opinion
for the following reasons:

1. "Because the disease is certainly constitutional in

1 Etudes sur la maladie des vers a sole, t. II, p. 165.
* Etudes sur la maladie des vers k sole, t. II, p. 181.

1C4 PASTEUR: THE HISTORY OF A MIND

a great number of circumstances, and precedes the ap-
pearance of the corpuscles." We recognize there the
influence already noted by us of that preliminarj^ ob-
servation on a culture which behaved badly although
the worms did not contain corpuscles. We know to-day
that Pasteur had fallen by chance upon a culture at-
tacked by another disease than pebrine, the disease of
morts-flats} Pasteur, who, at this moment, spoke only
of the disease of silkworms, had confounded everything
and could believe in a disease of corpuscles without
corpuscles;

2, "Because the feeding of corpuscular substances
often kills the worms without giving them corpuscles."
Here again, there was an error of interpretation, due to
the same reasons as the above. Pasteur had very clearly
perceived that the criterion of the corpuscle as cause,
and of the corpuscle as effect and evidence of the disease,
was an inoculation experiment. If it had been possible
to give the corpuscular disease to healthy worms by
causing them to feed upon corpuscles derived from a
preceding silkworm culture, one would have singularly
enlightened not only the etiology of the disease, but also
the causes of its vitality and of its propagation, of its
endemic and epidemic character. With Pasteur the ex-
ecution followed close upon the idea, and the experiment
was made. He had taken, in 1866, as infectious matter,
very corpuscular dirt scraped up in a culture chamber,
and the mashed substance of a very corpuscular moth
or worm. The worms to which he had fed the leaves
of the mulberrj^, thus infected, had showed at the end
of some days a considerable mortality which Pasteur
had the right to attribute to the infected food and to
the prevailing disease: in reality it again resulted from
the intervention of the disease of the morts-flats. But

' Flacherie. Trs.

IS THE CORPUSCLE THE CAUSE OF THE DISEASE? 165

seeing worms inoculated with corpuscular materials die
rapidly and yet not contain corpuscles, we still under-
stand how Pasteur may have been able to believe that
the corpuscles not only were not the cause of the disease,
but were not even the constant sign of the disease, and
could be absent when the disease was in too rapid evolu-
tion, for example, when the substance relied upon to pro-
duce it had too active toxic qualities and killed the
worm too quickly, as was apparently the case in these
two experiments;

3. ''I have not been able," continues Pasteur, "to
discover up to the present time a mode of reproduction
of the corpuscle, and its manner of appearance makes
it resemble a product of the transformation of the tis-
sues." Here Pasteur paid the penalty of his inexperi-
ence in the world -of beings to which the corpuscle be-
longs, a world where the forms of reproduction are quite
other than in the world of microbes, which he knew the
best. Without entering into details, we must know that
the corpuscle, instead of increasing by segmentation or
by budding as do the bacilli or the yeasts, can, under
certain circumstances, swell up into a voluminous proto-
plasmic mass with almost invisible contours. This in-
sinuates itself into the tissues, penetrates them with an
almost invisible network in which then only begins the
process of delimitation which divides it into distinct
and sharply contoured corpuscles. From the initial cor-
puscle we have come to some thousands of identical
corpuscles, children of the same father. Pasteur had
indeed seen this phenomenon of the organization of a
sort of amorphous matrix. He described it with a
marvelous precision because he was a master observer.
He pointed it out to his draftsman, Lackerbauer, who
strove to represent it in two plates (pp. 28 and 64). But
he does not know how to interpret it, and, as he sees

166 PASTEUR : THE HISTORY OF A MIND

the corpuscle appear in the midst of all the tissues of the
diseased worm, he is confirmed naturally in his idea
that the disease is constitutional and that the corpuscle
indicates only one of the stages of it, that in which it
becomes apparent under the microscope.

It is a singular thing, that while his spirit marched in
these pathways and would not be turned aside, his
assistants (preparateurs), to whom he said nothing of
what he thought, were persuaded that he was firmly
attached to the idea of the corpuscle as a cause. They
were astonished that he did not make the crucial experi-
ment, and endeavor to give to healthy worms by means
of corpuscular food, not the disease with a rapid evolution
of which we have just spoken and which did not re-
semble the corpuscular disease, but that same disease
with its slow evolution and concomitant development of
the parasites. Relying on the interpretation he had
given to his first experiment, Pasteur did not hasten to
begin a second. When that appeared useful to him it
was too late. He was in Paris. His associate, M.
Peligot, could, nevertheless, give him some worms of a
culture which was delayed. With these the inoculation
gave results quite other than at Alais; the worms had not,
apparently, suffered from the contaminated food, and
Pasteur was very much embarrassed until he learned
that Gernez had at Valenciennes semi-annual Japanese
"graine," that is to say, eggs which would hatch the same
year they were laid, and give a second culture of worms.
Moreover, these eggs were healthy, the parents not being
corpuscular. He, therefore, asked Gernez to do over the
experiment which had been made at Alais with worms ob-
tained from Peligot, and observe whether the difference
in results obtained in Gard and in Paris was not related to
the age at which the worms had been subjected to the
contagion of the disease. For him it was always the

IS THE CORPUSCLE THE CAUSE OF THE DISEASE? 167

question of seeking the relation which existed between
the time of the corpuscular feeding and the development
of the disease with or without corpuscles. For Gernez,
who believed Pasteur converted to the idea of the cor-
puscle as cause, the question was simpler: the only
question was to know whether the inoculated worms
would have corpuscles, and the healthy worms would not
have them. From this point of view, his experiment was
particularly convincing. Of four lots of 40 worms each:

The first, fed with, ordinary leaves, gave 27 healthy
cocoons;

The second, fed with leaves moistened with ordinary
water, gave 19 cocoons of which not one was corpuscular;

The third, fed after the third molting with leaves
moistened with water containing the debris of corpuscu-
lar moths, gave only four cocoons which were very
corpuscular.

The fourth lot, in which the feeding of corpuscular
leaves had commenced only after the fourth molt, gave
22 cocoons, all or almost all corpuscular.

Here we behold a spectacle rare in the life of Pasteur:
an experiment the full and complete meaning of which
he does not immediately comprehend. This experiment
was highly pertinent. It realized as in a synthesis the
principal aspects of the disease. The third lot was an
example of those silkworm cultures which, after having
begun well, perish by the way and do not reach the cocoon
stage. The fourth lot was an example of those cultures
which succeed well but are incapable of furnishing good
eggs. The first and the second lot bore witness to the
worth, when it is not infected, of a "graine" resulting
from egg-selection under the microscope, made upon a
diseased culture. All that spoke at the same time in
favor of Pasteur's method and of the corpuscle as a
cause, but Gernez, who believed his master converted

168 PASTEUR : THE HISTORY OF A MIND

to this doctrine, was somewhat astonished that Pasteur
saw in his experiment only the practical side and did
not flash everywhere the light which shone out of it.
In reality, Pasteur had not seen it. The proof is that
this experiment was announced to the Academy by him
the 26th day of November, 1866, and that in January,
1867, he was still asking himself whether the disease
was parasitic, and was still advancing against this idea
the arguments which we have just examined. He
changed his opinion on this subject only during the
course of the year 1867, and this change of front has
made that the decisive year. He had until then marched
directly toward the promised land, but he had marched
backwards. As soon as he turned about, the whole of
his conquest appeared to him at once.

VI
STUDIES OF 18G7

He began in fact the early experiments of 1867 with
clarified ideas, and also, which was not less important,
with means for work and experiment. The eggs which
he had prepared in 1865 and which had served for his
experiments of 1866 were not, as we have seen, wholly
freed from corpuscles. By raising them under special
conditions of cleanliness, by giving to his worms space
so that they would not infect each other, by isolating the
divers lots in separate baskets, by shiftings, that is to
say by removing the broods into the open air, all prac-
tices which, in his mind, were so many hygienic measures
as well as precautions against contagion, he had suc-
ceeded in having in 1866 a great number at least, if
not whole lots, of moths which were non-corpuscular.

STUDIES OF 1867 169

giving with certainty eggs that Pasteur was content
to call healthy, but which to-day we would say were free
from parasites. It was with these eggs, the hereditary
conditions of which he knew, that he began the tentative
experiments and the large cultures of 1867.

The first thing which he had to ask himself, since he
had not yet renounced the idea of a constitutional
disease existing before the appearance of the corpuscles,
was whether the districts of silk husbandry truly consti-
tuted, as was said over and over, a deleterious center,
an infected district, in which the disease and the cor-
puscle would appear inevitably, carried by the ambi-
ent air into the healthiest broods. This doctrine spoke
too much in favor of inaction and indolence, not to have
many partisans.

To this objection Pasteur was able to respond at the
end of his preliminary experiments by showing some
lots of worms, offspring of non-corpuscular parents that
had passed through the entire metamorphosis without
being attacked, and had produced eggs which in turn
were free from coipuscles, and this too, although they
were raised not only in an infected district, but in a
silkworm nursery where by the side of them, other lots
died from the disease. Not only did the sound worms
remain sound, but their general health seemed to be
improved, and from 1865 to 1866, from 1866 to 1867,
one saw the broods improve just in proportion to the
original purity of the eggs.

Assured now of not seeing the corpuscles appear in these
sound lots, one could perform experiments on corpuscular
contagion, beginning it at different ages, could repeat
on a large scale the experiment of Gernez, and could
synthesize the results. This synthesis is most clear,
and we may summarize it very simply.

If we take sound worms and make them swallow or

170 PASTEUR: THE HISTORY OF A MIND

by puncture inoculate them with fresh corpuscles taken
either from a diseased worm, or from its excretions,
the worms thus treated are sure to be attacked with a
disease which, in its external characters, recalls com-
pletely pebrine, and correlatively, the corpuscles thus
introduced into their organism, develop there until they
have invaded it throughout. The corpuscle is, therefore,
the cause of the disease, and pebrine is due, and due
solely, to the abnormal development of these little
organisms. All uncertainty has disappeared, and Pas-
teur adopts anew the doctrine of the corpuscle as cause,
and the parasitic theory.

Foitunately, the progress of the disease is not as rapid
as it is certain. It is nearly 30 days after infection be-
fore the animal is sufficiently invaded by the parasite
to be truly sick, and to be able no longer, for example,
to spin its cocoon. As its life in the larval state is only
about 35 days long, every worm which comes from a
sound egg, that is to say which does not contain at
the moment of its birth corpuscles in process of devel-
opment, will almost surely produce its cocoon. In order
that it should be otherwise the larva must become dis-
eased in the first days of its existence, at a time when
the malady is still, so to speak, latent in its neighbors,
even in the most infected ones, and when there are a
thousand chances that it will not come into contact
with any mature corpuscles which it could swallow or
with which it could be infected through wounds.
Therefore, if an egg is sound, that is to say, free from
corpuscles, the offspring cannot die from pebrine. Here
evidently we have a fact of capital importance, and
it is not the only one of this order.

There results, in reality, from this long period of
incubation of the disease, another consequence: that is
that the silkworm, passing from 15 to 20 days in its

STUDIES OF 1867 171

cocoon, if it is ever so little diseased at the beginning of
this period, and it may be so slightly as to appear per-
fectly sound even under the microscope, becomes more
and more diseased, the few corpuscles which it contains
multiplying little by little within it. They invade all
the tissues of the chrysalis and especially those in the
midst of which the eggs are formed. Consequently,
the latter may include some of these corpuscles in their
interior, and the worms which are hatched from them,
corpuscular from their birth, cannot as we have seen,
reach the cocoon stage. The grower will obtain then
a commercial harvest from an egg only when it is pure,
and there is no certainty of its being pure unless it comes
from moths free from corpuscles.

We are, therefore, now authorized to say that the disease
is contagious and hereditary, but we must give to these
two words, heredity and contagion, a well-defined sense,
for they both represent the introduction, either into a
sound worm from its diseased neighbors, or into an egg
from a corpuscular female, of one sole element, the cor-
puscle in process of development. Pasteur has even gone
farther, and by showing that at the beginning of a
silkworm season there are no living corpuscles except
those which are contained in diseased eggs he has
connected these two questions of contagion and heredity.
All other corpuscles, all, for example, which are present in
such great abundance in the dust of the hatcheries, are
dead and incapable of reproduction. It is, therefore, the
hereditary corpuscles alone which permit the malady
to assume each year its contagious character, and it will
disappear forever on the day when, throughout the
entire world, silkgrowers raise only sound eggs.

Such are the theoxetical conclusions of the experiments
of 1867. The practical conclusions are not less clear
cut. "Do you wish to know," said Pasteur to the

172 Pasteur: the history of a mind

silk-growers, "whether a lot of cocoons will give you sound
eggs? Take a portion of them and heat them so as to
hasten four or five days the hatching of the moths, and
see whether the latter are corpuscular. The micro-
scopical examination of the moths is easier and more
certain than that of the eggs because in them the cor-
puscles are many times more abundant. If the moths
are bad, send the cocoons to the spinning mills. On
the contrary, if you find that only a very limited number
of individuals are diseased, allow them to develop:
the eggs will be good and the brood which you mil have
from them the next year will be a successful one. Only,
this brood will be unfit for breeding because of the initial
presence and multiplication in it of the corpuscles.
But do you wish the brood to be sound up to the very end
and give you perfect eggs? Then take absolutely sound
eggs, coming from absolutely pure parents, and hatch
them in conditions of cleanliness and isolation, such
that infection cannot spread there. But if, unfortu-
nately, the disease should appear I still give you the
means of making a selection, and of separating rigorously
the sound eggs from the corpuscular ones."

The problem was, therefore, solved, and the victory
could be considered complete. Let us hasten to say that
no part of it is more widely discussed at the present time.
The examination of eggs with the aid of the microscope
which had been judged impossible has become a custom.
The growers of silkworms have made it encircle the globe
as they once did the disease itself, and pcbrine has
ceased to haunt the mind of those engaged in the silk-
worm industry. On one point only were the expecta-
tions of Pasteur unfulfilled. He hoped that it would be
possible to make the disease disappear. This was a
noble ambition and would have been a great example.
Experience has shown that it was impossible. This is

THE DISEASE OF THE MORTS-FLATS [fLACHERIe] 173

because the silkworm is not the sole host of the corpuscle,
and do what you will to make this source of contag;ion dis-
appear, there are others open. In vain M. Susani, for
example, eliminated for many kilometers around his
immense establishment of Rancate in the Brianza every
corpuscular egg : he still had corpuscular moths, and he was
obliged all his life to defend himself every year against
the contagion of the disease which he had tried in vain
to extirpate. Man cannot suppress an epidemic disease,
but he can keep it within bounds, and render it almost
inoffensive. A great lesson, which, from the silkworm
industry, has passed into pathology, and which we shall
recall later when we see Pasteur grappling with human
diseases !

VII
THE DISEASE OF THE MORTS-FLATS [FLACHERIE]^

In what precedes, I have left out of consideration all
the propaganda which Pasteur undertook in order to
inspire and hasten confidence in his methods: visits,
correspondence, letters to the journals, he neglected
nothing; he distributed healthy eggs and diseased eggs,
sought public judgments on the results of the silkworm
cultures, prognosticated them so as to attract attention
and stir up curiosity, and every morning there was a
great mass of letters which he opened with emotion,
smiling at the good news, attentive to the bad.

In 1867, Pasteur had distributed in small lots his
healthy eggs prepared in 1866, and the success, we knew,
had been general. However, as the letters came in
announcing the result of the cultures, we found our

1 There are no English equivalents. Both words refer to the gaseous
condition of the feces, and mean death or disease due to flatulence. Trs.
14

174 PASTEUR: THE HISTORY OF A MIND

master more and more anxious. He kept us so remote
from his thought that we could not explain his uneasiness
till that day when he appeared before us almost in tears,
and, dropping discouraged into a chair said: "Nothing
is accomplished; there are two diseases!"

He had in mind this disease of the morts-flats, con-
cerning which I have already made brief mention.
He had known it for a long time, indeed since his
first sojourn in the South in 1865, where one of the two
cultures of silkworms which served for the beginning
of his deductions was attacked by this disease at the
same time as by that of the corpuscles. But the cases
of association were so frequent, precisely because the
disease of the corpuscles was widespread, that Pasteur
had considered the two affections as intimately con-
nected and likely to disappear together.

During the silkworm cultures of 186G, the two diseases
were somewhat separated both in fact and in his mind.
He had sometimes seen the second appear in cultures
hereditarily exempt from the first, and he had asked
himself whether they were not independent. His pub-
lications at this time bear the trace of these preoccupa-
tions, which had not yet become a source of uneasiness.
The cases of morts-flats had been rare, and had besides
appeared here and there, without visible preference,
like cultural accidents attributable to the growers.

It was in 1867, in the preliminary trials, and especially
in the large cultures, that the gravity of the danger first
appeared. Almost entire lots of eggs free from cor-
puscles and bred by various growers had perished
everywhere of the disease known as morts-flats, what-
ever might be the circumstances of place, time, climate
and culture. It could not be any longer a question of
accidents: it was the manifestation of an inherited dis-
position, and on seeing these mishaps renewed, on finding

THE DISEASE OF THE MORTS-FLATS [fLACHERIe] 175

behind the disease which he thought he had conquered,
another redoubtable disease, and one about which he
as yet knew nothing, we can understand why Pasteur
experienced and exhibited a moment of despair. The
pubHc, to which one shows only the finished work, is
ignorant of the painful hours with which the scientific
man, the artist, or the writer has paid in advance for
the joy of his success.

Naturally, we strove as best we could to comfort the
discouraged master. Since all was not finished, it was
not necessary to conclude that nothing was accomplished,
but only to begin over again if necessary. We were
young and we had confidence, not in ourselves, but in
him. Well employed were those hours in which we saw
him struggling with these difficult questions, ceaselessly
on the hunt, sometimes deceived in his previsions and
hesitating, sometimes triumphant and marching with
great strides. We did not always know whither he was
bent, for he said little; but we tried to guess, judging
from the circumstances, and rectifying our ideas by
what we were allowed to perceive of his own.

This differentiation between the two diseases, which
had now become evident, was a first step, and one of the
most important, in the study of the second disease.
Henceforth only what belonged to each disease need be
credited to it. At the beginning of his researches, as we
have seen, Pasteur had credited to the corpuscular
disease results due to the other disease. Now, the light
having penetrated into obscure corners, many difficulties
and apparent contradictions were explained and even
by going over recollections and records of experiments,
and removing therefrom all that related to the disease of
the morts-flats, a very considerable volume of data
bearing upon it, was obtained.

The most striking feature in its history was its mani-

176 PASTEUR: THE HISTORY OF A MIND

festly hereditary character. As we have said, it ravaged
certain lots of eggs, which were sometimes distributed
among a number of silk-growers, and bred, owing to
this fact, under the most varied conditions, and which,
nevertheless, were attacked at the same period, in the
same age of the worm, as if they had all brought with
them a germ of destruction. Most frequently after the
fourth molt, during the period of voracity called the "big
gorge," when the healthy worms greedily devour the
foliage given them, the diseased worms were seen to be
indifferent to the provender, crawling over the leaf
without attacking it, even avoiding it, and having the
appearance of seeking a tranquil corner in which to die.
When dead, the worm sometimes softened and rotted,
but sometimes remained firm and hard, so that one must
touch it to be certain it was dead. At other times, when
the disease attacked the worm more slowly, it climbed
the heather, but with difficulty, slowly spun its cocoon,
sometimes did not finish it but left it in the condition of
skin, and died without changing into a chrysalis or a
moth.

In recalling the conditions under which the production
of the eggs showing this hereditary predisposition to the
disease of the morts-flats had taken place, Pasteur
remembered suddenly that one of the cultures had not
been entirely satisfactory at the time the worms climbed
up to undergo their transformation. The worms had
climbed up soft, had dragged thernselves at this time.
Here Pasteur reaped the advantage of that constant and
penetrating supervision which he exercised over every-
thing. In a year, he had become an excellent breeder
of silkworms. If he observed well, he knew also how to
draw conclusions, and immediately he reflected that the
eggs subject to this hereditary sensitiveness to the morts-
flats must have come from those apparently successful

THE DISEASE OF THE MORTS-FLATS [fLACHERIe] 177

cultures, which he had used for the production of eggs
because the worms did not contain corpuscles, ))ut which
showed, on climbing up the heather for their transforma-
tion, that peculiar sluggishness which he had sometimes
observed. As in the corpuscular disease, the malady
had not killed the progenitors, but was not the less
menacing to their descendants.

Forgetting his discouragement, he set to work im-
mediately upon this idea. There were still in the
neighborhood some silkworm cultures attacked by the
disease of the morts-flats. He took the cocoons they
had yielded, satisfied himself of the absence of corpus-
cles, and obtained eggs from them. These eggs were
used for the preliminary cultures of the following year,
and as early as the 20th of March, 1868, he was able to
announce to Dumas that, out of the seven lots thus
selected from seven distinct cultures, six had miscarried
at various ages, especially in the fourth molt, with the
disease of the morts-flats.

''Consequently, there is no more doubt," he added, ^
"that the disease of the morts-flats can be hereditary
and attack a brood, independently of all conditions as to
mode of hatching of the eggs, ventilation of the brood,
excessive heat or cold to which the worms are exposed,
conditions which without doubt may occasionally pro-
voke this same disease. Hence, the imperious necessity
of never using for the egg-laying, whatever may be the
external appearance or the results of the microscopic
examination of the moths, broods which have shown
from the fourth molt to the cocoon, any languishing
worms, or which have experienced a noticeable mortality
at this period of the culture, due to the disease of the
morts-flats. I insist again on this advice, and with
more force than last year."

^ Etudes sur la maladie des vers a soie, t. II, p. 232.

178 PASTEUR: THE HISTORY OF A MIND

He felt, however, that this prescription was a httle
uncertain. What is a languishing worm? One must
be a good grower of silkworms to see it, and there were
no longer any such. Several years of successive dis-
asters had overthrown practices, experiences, and
traditions. He must find for the disease a more palpable
sign, and, for that purpose, must study it in its origins,
in its etiology.

vni

STUDIES OF 1868, 1869, 1870

The etiology of this disease was the work of the
years 1868, 1809 and 1870, an intermittent labor,
interrupted as it was by other occupations. The
recommendation Pasteur had made to eliminate from
the egg-laying everything that had the appearance of
flacherie suppressed for the time being all grave fears
on the subject of this disease, leaving the corpuscular
disease alone in the foreground. It was urgent to prove
to all the worth and the eminently practical character
of the new method of silkworm breeding.

In this work Pasteur showed qualities not among
those of which I have undertaken the history, because
they do not form a part of his greatness, and because
he could well have done without them. But I must
mention them because they complete his physiognomy.
These were the masterful qualities of a chief of industry
who watches everything, lets no detail escape him,
wishes to know everything, to have a hand in everything,
and who, at the same time, puts himself in ])ersonal
relation with all his clientele, asking both those
who are content and those who are not the reasons
for their opinions.

STUDIES OF 1868, 1869, 1870 179

He knew well that a process of silkworm breeding
which clashed with interests, which transformed com-
mercial or industrial practices, could not make its way
without arousing anger, without stirring up criticisms,
the more bitter because they were not disinterested.
He showed himself less and less sensitive to these attacks
the surer he became of his facts, and no contradiction,
even though it came from the Silk Commission of Lyons
ever stirred him as much as those which he was obliged
to encounter later in connection with his studies on
fermentation or researches on anthrax and human rabies.
Yet, as the diffusion of the method had become a practical
question, he did not disdain to become a silkworm
breeder, and he went voluntarily to preside at the in-
stallation of his process in the nurseries of the growers in
the lower Alps or the Eastern Pyrenees, who invoked
his aid.

It was in the intervals of this practical apostolate
that he returned to his investigations on the malady
of the rnorts-flats, which, as he studied it, showed itself
to be more complicated than the corpuscular disease
and more nearly related to human diseases. This re-
lation was at the time still very vague in the mind of
Pasteur, who had not studied medicine, and who had,
furthermore, the faculty almost necessary, it seems, to
men of his temper, of isolating themselves in what they
do, and of working so much the better the less they look
out of the window. But as these studies of Pasteur
had brought him into the domain of pathology, had
led him to examine a host of new problems, and had had
clearly a reflex action on his later discoveries, perhaps
it is well to state the point which he had reached in 1878,
after 10 years of study, which was intermittent and
interrupted by other pieces of work. It was just before,
or at the beginning of his researches on anthrax, and the

180 PASTEUR : THE HISTORY OF A MIND

subject had not ceased to haunt his mind. In this
year, 1878, there was held in Paris a Congress on
silk husbandry, where the subject of flacherie was much
discussed, and where Pasteur often found himself moved
to speak. From his discourses and conversations we
gather the following resume of his ideas on a question
to which he never again returned.

We have described the external signs of the disease
and we know also that the mortality may be considerable
within a few days, which gives it a distinctly epidemic
character. One might call it the cholera or the typhoid
of the silkworm. But these are only words; let us
endeavor to get at the facts, and at the causes.

The simplest examination shows that, as in the case
oi typhoid or of cholera, it is the digestive organs which
are diseased. Sometimes their contents are all foamy,
and in full process of fermentation. Sometimes, on the
contrary, the fecal substances are in compact masses,
hard, and of the same aspect from one end to the other
of the intestinal tract, which seems to hava become an
inert receptacle. In all cases there is nothing resembling
regular, normal digestion, the solid product of which
is molded and separated into bits by the muscles of the
anus, with the regularity of a machine for making Italian
pastes.

On examining microscopically these normal excre-
ments, we find therein debris of leaves but no microbes,
or almost none. There is not, so to speak, any place for
them in the powerful mechanism of the nutritive system
in this animal, which seems made only to eat. It is
(juite otherwise in the diseased worms. Their digestive
tract is full of microbes; these are bacilli, more or less
plump, some of them spore-bearing, and micrococci in
pairs and in chains.

This being the state of affairs, the question arises at

STUDIES OF 18G8, 1869, 1870 181

once: Is the disease contagious? Can it be carried
from a diseased worm to a sound worm, its neighbor?
It happens exactly in this disease that the excrements are
ordinarily viscid and smear the leaves which the worms
eat in common. If we imitate this natural contagion by
making worms eat leaves smeared with the excrement of
a diseased worm, we shall see them become sick in their
turn, as in the case of the corpuscular disease. The
flacherie is therefore contagious, like the pebrine.

But here is a difference: all the worms which had
eaten the fresh corpuscles became sick at nearly the same
time. The ingested corpuscle undergoes a regular evolu-
tion, and it is not in the digestive tract that it develops.
It is not the same with the flacherie. Its stronghold is
in the intestine, and the time which separates the moment
of contagion from that of death may vary from 12 hours
to 3 weeks, and even more, for invariably some of
the worms escape death. Therefore, worms which re-
semble each other in regard to the corpuscle, no longer
do so when exposed to the germs of flacherie. Thus it is
that Pasteur encountered for the first time this question,
then so new, of receptivity to germs, differing in different
individuals of the same species.

He discovered a second question just as new to him,
although it was a little less so to science, when he sought
to learn whether the germs of flacherie from different
sources were equivalent from the point of view of the
production of the disease. So^ie bacilli taken from an
artificial fermentation of mulberry leaves, for example,
caused death in from 8 to 15 days. If we inoculate
fresh worms with the substance taken from the digestive
tract of the former, death follows in from 6 to 8 days.
The virus is, therefore, augmented in intensity as the
result of its passage through the organism.

Finally, the influence of the port of entry, which

182 PASTEUR: THE HISTORY OF A MIND

Davaine was at this moment occupied in studying in
anthrax, was also apparent to Pasteur through the com-
parison which he had made of the results of inoculation
by pricks and by contamination of the digestive tract.
We see what an excellent preparation these studies on
flacherie gave him, and with what good reason he ad-
vised young medical students, who later learned the
path to his laboratory, to read these two volumes onj the
disease of silkworms: the great teachings of microbial
pathology are already found there.

This is not all. We have seen that the germ of the
corpuscle is not common, and must be acquired from a
li\dng worm, or from one just dead, in order to preserve
its vitality. Pasteur even believed, as we have seen,
that it had no other habitat than the silkworm, and
that man could make pebrine disappear by making the
production of sound eggs universal. On the contrary,
the appearance of flacherie is sometimes spontaneous,
and my result from an accident or from some error
during the breeding. Whence, then, come the germs?
The germ is common, replies Pasteur. It suffices to
leave in a flask, at summer temperature, a bit of bruised
mulberry-leaf, in order to see appear in the maceration
microscopic organisms in every way similar to those
which one encounters in the digestive tract of the
flatulent worms, a canal which, in fact, seems to have
become an inert receptacle. In a healthy worm the
tract arrests or prevents all development of microbes;
in a flatulent worm, it opens the way for the germs which
the leaf introduces, and, with approximately the same
virulence, the germs of the flasks and the germs of the in-
testinal tract behave the same. That explains to us how
the disease can appear sometimes without having been
introduced from a distance, a thing which did not happen,
at least so Pasteur thought, in the corpuscular disease.

STUDIES OF 1868, 1869, 1870 183

The discovery of the common character of the germs
of flacherie obhges us now to turn back and ask our-
selves a question. Why, if this germ is everywhere,
does it not develop always and everywhere? This is
clearly a general question, like those which precede,
and may be asked regarding a multitude of human
diseases. The germ of tuberculosis is widely dissemi-
nated, we could say to-day. There is not one of us
who has not inhaled it. We are exposed to it every
day and everysvhere! Why are not all of us tuberculous?
To this question, not yet solved, Pasteur had made,
concerning flacherie, a double response.

This intermittent and localized development of germs
universally distributed can take place, he said, whenever
external conditions, of which the grower is not always
the master, favor the multiplication of the microbes, or
enfeeble the digestive power of the worm. The animal
is constantly taking in, with the leaves which it eats,
germs which would develop in a flask and which do not
develop in its digestive tract, arrested as they are by
physiological influences. But imagine that they are more
numerous for some reason, that the leaf is heated by
fermentation before being served to the worm; or
again that the number of germs remains the same, but
that the worms have been weakened by a stormy period
or by a stifling heat when no air is in circulation, or by
the fact that the worm-nursery is too warm or poorly
ventilated, or by the result of some other accident, and
then the germs take advantage of the lowered resistance
to multiply and the malady breaks out!

Finally, to this idea add the fact that the weakening
of the digestive tract may be constitutional, organic,
may result from the fact that the worms which were the
larval ancestors of these eggs, were themselves sick at
the time of their pupation or before, with the disease of

184 PASTEUR: THE HISTORY OF A MIND

the morts-flats, and we have united by a common bond
all the modes of appearance of the disease, both that
which is encountered in the sporadic state on sound eggs
exempt from all hereditary predisposition, and that
which rages among the descendants of a brood where
the morts-flats has been.

The disease of the morts-flats is then, like that of the
corpuscles, a contagious disease, but sometimes be-
cause its germ is so common, it may become a disease
which appears to be spontaneous, sporadic or epidemic,
benign or disastrous, and the origin of which a super-
ficial observer might, with reason, attribute to the com-
mon conditions of cold, heat, humidity, electricity, so
often invoked by ancient medicine. More enlightened
now, we can say: No, these common influences neither
are the disease nor make the disease; they open the door
for it and give it scope. In this case, and in all the cases
where one is led to lay on them the blame, we find on
close investigation a germ, more or less widespread,
ordinarily kept within bounds by natural laws, but able
when conditions change, when its virulence is exalted,
when its host is enfeebled, to invade the territory which
was barred to it up to that time. The bacillus of flach-
erie is always present, but the sound worm is able to
defend itself on the side where it is threatened. It will
not, perhaps, resist a wound — an unusual way for con-
tagion; it will better resist an introduction into the di-
gestive tract, but still there must not be too many ba-
cilli, nor too virulent ones.

For the same reasons the hereditary })redisposition
no longer makes for the same certainty of action as it
does in pebrine. There it resulted from the deposition
in the egg of a germ the development of which was as-
sured; here there is no transmission of the germ. We
find, it is true, in the stomach of the chrysalis (a stomach

STUDIES OF 1868, 1809, 1870 185

atrophied because it has become useless) the still recog-
nizable forms of organisms which were present in the
stomach of the worm, especially of those organisms
which have been so Httle active as to permit the worm
to continue its development in spite of the weakening
which they have caused. Among these is a small fer-
ment in chains, analogous to the organism figured in the
fourth section of Fig. 8, page 70. When one finds this
in the stomach of a chrysalis or of a moth he may
rest assured that the disease of the jnorts-flats was
present at the end of the metamorphosis, and that the
egg is suspicious. We may tiy to find in this direc-
tion a criterion of purity which the egg itself is in-
capable of furnishing, since the egg contains nothing.
The heredity which is transmitted is not the inheritance
of a germ; it is the inheritance of a function, a reversed
vaccination, favoring the invasion of the common germ
of the malady, as ordinary vaccination prevents the
invasion of the specific germ. Such is, we might say
to-day, the inheritance of tuberculosis. If the tubercle
organism is not common, if it is incapable of developing
outside of the body, a fact of which we are not yet very
certain, it is at least widely di'^tributed, and has no
need, as we see in case of flacherie, of being transmitted
through the parents by heredity in order to attack the
offspring. All that is necessary is a hereditary feebleness
in the functioning of the lungs. The soil prepared, the
seed always ready, the disease will always find the
occasion to implant itself.

On the contrary, as in flacherie, there will be always
some hereditary predispositions which will be effaced
owing to favorable conditions.

In conclusion, at the end of his Etudes, Pasteur found
not only that he had solved the problem which he had
undertaken on the regeneration of sericiculture, but

186 PASTEUR : THE HISTORY OF A MIND

had placed on an experimental basis the great questions
of contagion and of heredity which dominate all path-
ology. He was ripe to attack them, and to solve them
wherever he should meet them, for his mind was molded
upon them. But he was much less advanced in the
matter of his technique. He was, in 1870, in a posi-
tion to grasp the most delicate features of the patholog-
ical history of the anthrax of animals but not in a posi-
tion to approach the question experimentally. It was
necessary for him first to perfect his equipment, and his
methods of research. The guardian spirit which seemed
to have undertaken the direction of his destiny fur-
nished him the opportunity by forcing him into a prob-
lem apparently entirely different, the study of beers.

m

PASTEUR
(From a steel engraving by Manesse, Minerva, \\)\. Ill, 1894.)

SIXTH PART
Studies on Beer

STUDIES ON BREWING

These studies were begun in 1871, in my laboratory
in the Faculty of Sciences of Clermont-Ferrand, and in
the chemical laboratory of the School of Medicine of the
same town. They were undertaken without any definite
aim, simply to occupy the enforced leisure which the
Commune and the Siege of Paris gave to Pasteur. He
had at once set himself to work to contribute his knowl-
edge which was already great, as his share in the rehabili-
tation of his humiliated country. He already dreamed
of a Pasteur Institute where he would be surrounded
by all of his assistants and where he would lead them
on to new victories. "I have a head full of the most
beautiful projects for work," he wrote me March 29,
1871. ''The war has forced my brain to lie fallow.
I am ready for new productions. Alas! Perhaps
I am laboring under an illusion. In any case I shall
make the attempt. Oh! why am I not rich? A
millionaire! I would say to you, to Raulin, to Gernez,
to Van Tieghem, etc., Come! We will transform the world
by our discoveries! How fortunate you are to be young
and to have good health! O, that I could begin a new
life of study and work! Poor France, dear land of our
fathers! Why can I not help to lift you up once more
from your disasters?"

While waiting to engage in the great schemes, the

187

188 PASTEUR: THE HISTORY OF A MIXD

thought of which already haunted him, he allowed him-
self to be seduced by the idea of studying the manufac-
ture of beer. Was it not possible to make it in France
as well as in Germany, and to free us through science
from paying tribute to the breweries across the Rhine?
Such was the ambition that took possession of him little
by little as he penetrated more and more into this diffi-
cult subject. To-day we may say that this ambition
has been realized as much b}^ the efforts of Pasteur as
by the intelligent activity displayed by the French
brewers. At the present time, the best French beers
are equal to the best German or Austrian beers, and for
this progress the French brewers, in the Congress of
1889, gave the honor and credit to the labors and to the
book of Pasteur on beer.

This book is not an ordinary book, not a kind of
theoretical treatise on brewing. It reflects so clearly
the varied preoccupations of Pasteur at this stage of his
existence, that I am obliged to draw attention to its
somewhat eccentric composition. Of brewing there is
very little said. The first chapter shows that the dis-
eases of beer are always due to the development of
microscopic organisms foreign to a good fermentation,
not at this time a new idea. The last chapter gives the
means of making pure and unalterable beers. And it
seems, in reality, that this is sufficient, and that one
might be content with saying to the brewers: This is
why your beers are bad, and here is the means of making
good ones !

It was, in fact, in these relatively simi)le terms that
Pasteur stated the problem in the beginning. But he
was not slow to see that the question was much more
complicated. An egg of a silkworm developed accord-
ing to a scientific formula is surely a good egg. A beer
protected from pathogenic ferments during its manufac-

STUDIES ON BREWING 189

ture is not necessarily a good beer. Questions of taste
enter into the judgment of beer, that is to say, the least
scientific thing in the world, the most variable, and the
most difficult to grasp. This complex taste, to which
each brewery accustoms its patrons, depends at the
same time on the original material used, on the yeast,
on the water emploj^ed in the brewing, and, in a much
greater measure than one would believe, on all the varied
processes of the manufacture. So that the problem
was not that of making a good beer* but of making
many good beers, differing each from the other, and re-
producing for each brewery the type to which its patrons
had become accustomed.

Now, for this work of adaptation and detail Pasteur
lacked a very necessary qualification. He did not like
beer, and although, as the result of exercise and volition,
he finally succeeded in developing a taste for it and a
sufficiently trained palate, he remained insensible to
differences which the brewers extolled, and which he
was sometimes stupefied to see exquisitely appreciated
also by his friend, Bertin, who was his neighbor in the
Normal School, and who was frequently invited to the
laboratory for the tasting seances. At the joyous
railleries with which his friend sometimes plied him,
Pasteur was disconcerted, knowing that they were carrj^-
ing him into regions which he did not desire to enter,
and he might have renounced immediately this labor of
Sisyphus, if he had not had the imprudence to solicit
the pecuniary aid of a brewing school which was very
large and generous, but with which he had contracted
the moral obligation of succeeding in his enterprise.

It is not simply a bad play on words to say that he

has never become master of his subject, because he has

never been possessed by it. There was no longer that

profound absorption in his work so evident in his study
15

190 PASTEUR: THE HISTORY OF A MIND

on crystals, on spontaneous generation, and on silk-
worms. At every instant his thoughts and his actions
got away from him without his being conscious of it,
attracted by some question which seemed to him more
important than the influence of the degree of aeration
of the must on the quality of the beer, and it is this
which we see in his book, where he attacks and solves a
multitude of questions which have only a remote con-
nection with the brewery. The studies on the trans-
formation of species, one into another, on the first origin
of the yeasts of the vintage, on the general theory of
alcoholic fermentation, fill three-fourths of the book.
His obviously desultory style renders its analysis difficult.
We shall consider it, en bloc, only as a document which
is of great value for the history of the scientific man who
composed it.

There is another way of tracing the preoccupations
of Pasteur at this time; that is to examine the Comptes
rendus de VAcademie des Sciences. The Academy served
him both as a tribune from which to reply to his oppo-
nents without, and as a field of combat for the discus-
sions, sometimes picturesque, into which he entered with
some of his confreres. All this part of his Kfe forms an
animated picture. Let us endeavor to trace the prin-
cipal facts without following strictly the chronological
order.

II

TRANSFORMATION OF ONE SPECIES INTO

ANOTHER

There is in the beginning one part with which we are
already familiar, through having encountered it in its
proper place. That is the whole discussion with Bastian
on spontaneous generations, and with Liebig on the role

TRANSFORMATION OF ONE SPECIES INTO ANOTHER 191

of ferments in fermentation. We have seen that Pasteur
had come to know that the air was not that receptacle
for germs, that redoubtable enemy which he had hitherto
supposed it to be, and had convinced himself that,
provided the liquids were well sterilized in the auto-
clave and the flasks in an oven, it was possible to work
with some security in contact with air, and not have to
fear too much the entrance of germs from this source.
All our present technique has come from these ideas.
Personally Pasteur was indifferent to perfection of
technique; the complexity of his apparatuses was of
little importance to him. He only required that they
should be reliable, and answer the questions he asked
without ambiguity. But accuracy and facility or
rapidity of question and answer may go hand in hand.
This is the role of a good technique. That which has
come out of the laboratory of Pasteur was the offspring of
the ideas and discoveries of the master; but it is only just
to say that it was created by the three collaborators
whom Pasteur had the good fortune to encounter at
this time — Joubert, Chamberland and Roux.

Pasteur needed another thing for approach to the
domain of pathology, which every circumstance invited
him to enter. He saw the germ theory inspire the works
of Davaine on the anthrax bacteridium, the startling
experiment of M. Chauveau on castration by sub-
cutaneous torsion (bistournage) , Alphonse Guerin's new
method of dressing wounds, the researches of M. Guyon
on antiseptic washings of the bladder and of the urethra.
He had applauded in 1871 Dr. Declat's successful
experiments in the antiseptic dressing of wounds; he
did not yet know the work of Lister in antiseptic surgery,
which has opened a new era, but he was not slow in
finding it out and admiring it. But in order to approach
the promised land of which he dreamed, and especially

192 PASTEUR: THE HISTORY OF A MIND

to do SO with security, he had need of an equipment of
facts and ideas which he did not yet possess, and which
his opponents forced him to accjuire.

The most remarkable example I can cite in support of
what I wish to say comes from the discussion with
Trecul, who, renewing an opinion introduced into science
by Turpin and later supported by Bail, Berkeley,
Hoffmann, Hallier, admitted the transformation of
microscopic species, one into another. This was denying
the specificity of the germ established by the first
labors of Pasteur on fermentations, and Pasteur had
combatted this opinion, beginning in 1861 in the Bulletin
de la Societe 'philomaihique. To comprehend what
obscurities this theory would have introduced into
microbian pathology, it is sufficient to recall that a
denial of the specificity of the germ would have contro-
verted the present day belief in the specificity of disease.
It was, therefore, important that it should be rooted out
of all minds.

Unquestionably, it was not the demonstrations of
Bail, of Hoffmann, or even those of Trecul which could
give credit to this theory. All these eminent botanists
were poor experimenters, going out to meet sources of
error, not to bar the way, so to speak, but to open it up to
them. But favoring this idea of the mutability of
species was the doctrine of spontaneous generation,
which found in this mutability one of its arguments.
There were the new ideas introduced by Darwin and the
school of evolutionists. Finally, and this was more
grave, Pasteur himself, the greatest authorized exponent
of the opposite school, or rather of the experimental
method, rejected, in the name of experimentation,
the transformation of yeast into Penicillium glaucum,
but accepted that of the Mycoderma lini, or flowers of
wine, into an alcoholic ferment under certain conditions.

TRANSFORMATION OF ONE SPECIES INTO ANOTHER 193

On sweetened wine or must of beer, exposed in a
shallow porcelain basin, he sowed some mycoderma which
formed a pellicle on the surface. He then submerged
this pellicle, thoroughly shaking the liquid in order to
dislocate and moisten all parts of it. Then he introduced
the whole into a flask which he filled completely full and
which he closed with a stopper to which was attached a
tube, the opposite end of which opened under water
so as to allow no contact of air with the liquid. In this
closed flask he saw a true fermentation take place, which
he attributed to the transformation of the mycoderma
cells into yeast.

At Clermont, where Pasteur did me the honor of
working in my laboratory, we repeated this experiment
several times, and as I was naturally more intransigent
than he, being his pupil, I refused to yield to this proof,
and I objected to the possible presence of globules
of yeast derived from the air, from the water, or from
the flasks before or after the filling, in spite of the pre-
cautions taken to avoid it. Pasteur resisted because,
in his mind, this fact was related to other ideas which
we shall encounter soon, and which are relative to the
general theory of fermentation. The experiment, further-
more, sometimes succeeded with a clearness which made
it convincing and closed my mouth. In short, Pastuer
had reported his conviction in Paris, and it reappears
several times in his Notes of 1872 and 1873 before the
Academy of Sciences.

If I recall this fact, it is because Pasteur loved to cite
it himself as an example of the ease with which the
least preconceived idea leads even the most alert observer
into error. Thus it is that he has taken pains to re-
count how he discovered his self-deception. It is in-
teresting to see his mind at work in one of the thousand
details of his scientific life.

194 PASTEUR: THE HISTORY OF A MIND

"In the experiments conducted as I have just de-
scribed, the yeast which comes into existence, and which
very promptly causes an active alcoholic fermentation,
is introduced originall}^ by the atmospheric air, which
allows the germs to fall either upon the mycoderma
pellicle or the objects which are used during the succes-
sion of manipulations. Two circumstances of these
experiments gave me warning of the existence of this
cause of error. It sometimes happened that I found
among the cells of the mycoderma in the bottom of
the flasks where I had submerged the flowers of wine,
some large spherical cells of Mucor mucedo or racemosus,
yeastlike cells with which we shall soon become familiar
in studying this curious mold. Since there is present
Mucor mucedo or 7'acemosus, although I had sown only
Mycoderma vini, it must be, I said to myself, that one
or several spores of this Mucor have been introduced
by the ambient air. Now, if the air brings the spores
of Mucor into my operations, why would it not bring the
cells ot yeast, especially in my laboratory? Further,
more, it happened that in a number of the experiments
which I repeated many times, under the pressure of my
doubts, and in which I did not grow weary of searching
for this desirable transformation which accorded so well
with the physiological theory of fermentation to which
I had been led, some had a negative result, that is to say
the transformation of the mycoderma into yeast did
not occur, although the conditions were as similar as
one could wish to those of the experiments in which I
saw it take place. Why, thought I, this inactivity
in the cells of the mycoderma? Even in the most
favorable cases of the supposed transformation it hap-
pened without doubt that a multitude of cells of Mi/co-
derma vini did not become yeast cells, but how admit
that among the billions of submerged cells all were

TRANSFORMATION OF ONE SPECIES INTO ANOTHER 195

unfitted for transformation, if this transformation were
really possible?

"It was, then, to avoid this embarrassment, that I
resolved to modify entirely the conditions of the ex-
periment, and to apply to the research which I had in
view a culture method which would suppress completely,

Fig. 14.

-Flask used by Pasteur in his study of the transformation of

species.

or at least very nearly, the sole cause of error which I
had encountered, that is the possible falling of germs or-
of yeast cells from the air during the manipulation."'^

To carry out this idea, Pasteur added to the flask
with the curved neck which he had used in his studies on
spontaneous generations, a second tulxilure (Fig. 14)

1 Etudes sur la biere, p. 118.

196

PASTEUR : THE HISTORY OF A MIND

peimitting the inoculation of the hqiiid by removing
the glass stopper which closed the rubber tube attached
to the straight tubulure. In this flask the culture is in
contact with air. When there is need of provoking a
fermentation in. the absence of air, the straight tubulure
is connected by means of its rubber tube with a matrass
sufficiently small for the liquid to fill it completely.
In order to make with this apparatus a study of the
transformation of the mycoderma into yeast, it is

Fig. 15. — Apparatus used by Pasteur in his study of alcoholic and other

fermentations.

sufficient to sow with the flowers of wine an alcoholic
licjuid, or a sugar solution placed in Z), and to pour it
immediately, when the pellicle has formed, into the
matrass BC, where it finds the conditions of great depth
and of small free suiface existing in the flask of the first
experiment (Fig. 15). The details of the manipulation
necessary to realize this transfer in the absence of all
exterior germs are of little moment. The apparatus is
furthermore, complicated and has been advantageously
replaced since. It suffices, however, to attain the

TRANSFORMATION OF ONE SPECIES INTO ANOTHER 197

desired end, which is the comparative study of the same
mycoderma on the surface and in the depths.

''Never again," continues Pasteur, "did I see the
yeast or an active alcoholic fermentation, following the
submersion of the flowers, either in the flasks or in the
matrasses connected with these flasks. . . . At a time
when ideas on the transformation of species are so
easily adopTed, perhaps because they dispense with
rigorous experimentation, it is not without interest to
consider that in the course of my researches on the culture
of microscopic plants in the pure state, I have once had
occasion to believe in the transformation of one organism
into another, in the transformation of the Mycoderma virii
or cerevisine into yeast, and that, this time, I was in
error. I did not know how to avoid the cause of error
which my justified confidence in the germ theory
had led me to discover so often in the observations of
others."

The same flask with two tubulures served Pasteur to
show that the alcoholic yeast is not transformed into a
lactic ferment, as J. Duval said, nor into Penicillium or
Aspergillus, as HofTmann maintained; that this yeast,
itself, did not come from the transformation of the
spores of Penicillium, as Trecul said; nor furthermore
did the Mycoderma aceti yield the bacteria which
Bechamp believed he saw derived from it. In short,
the idea of species was saved for the time being from the
attack which was directed against it, and it has not
been contested seriously since that time, at least on this
ground.

198 PASTEUR: THE HISTORY OF A MIXD

III

ANAEROBIC LIFE OF AEROBIC SPECIES

In exchange, Pasteur had the sorrow of seeing ruined
one of the arguments most favorable to his physiological
theory of fermentation. But he ought not to have been
slow to congratulate himself upon this slight check,
because behind the fallen argument there arose another
still more convincing, which the first had masked. It
sufficed him, in order to find it, to repeat with Mucor
mucedo the preceding experiments.

Bail had announced in 1857 that this mucor which
lives the life of an aerobic plant, when in contact with
air, can, when submerged in the absence of air, produce
a very active alcoholic fermentation.

There are found then in the liquid, instead of more or
less septate mycelial filaments which serve to some
extent as roots for this plant, chains of round or oblong
cells, which Bail had taken for the cells of yeast of beer.
Repeating these experiments under the pure-culture
conditions which we have described, Pasteur determined
that these affirmations were exactly true. Submerged
and in the absence of air, the mycelium of the fungus
becomes very much septate, being transformed into a
chain of cells; simultaneously bubbles of carbonic acid
are given off, and alcohol is present in the liquid. What
is the explanation of this? Is this mucor then an ex-
ception? Can it undergo transformation into yeast?
This was the opinion of Bail; but we shall soon see
how much was gained by going l)elow the surface of
this question. From this apparently insignificant fact,
Pasteur has evolved a whole theory of fermentation.

In order to place these phenomena in their proper
light we shall suppose that Pasteur treated them as

PASTEUR
(From a common photo.)

ANAEROBIC LIFE OF AEROBIC SPECIES 199

was his ordinary custom, that is, that immediately
following their discovery, he combined them in a syn-
thetic experiment. If he had wished to pursue that
course in this case, the following undoubtedly would
have been his method of procedure.

Into a series of flasks with two tubulures like those
we have just described, each one-third filled with steril-
ized must of beer, he would have introduced, by remov-
ing for an instant the glass stopper closing the rubber
tube, a small platinum wire which had been flamed and
passed over a spore-bearing culture of the mucor. He
would then have flamed the stopper and replaced it.

Let us take for example the three Mucedinese studied
by Pasteur, Penicillium glaucum, Aspergillus niger,
and the Mucor mucedo. That makes three flasks. At
the end of 24 or 48 hours, the spores introduced by the
platinum wire will have produced a branching mycelium,
which if well aerated produces aerial branches sur-
mounted by tufts of young spores; but at the bottom
of these flasks, which communicate with the exterior
only by means of a long capillary neck, our mycelia
have only an insufficient quantity of air and the}^ fruit
little or not at all, but nevertheless in time they oxidize
completely the sugar on which they live.

Before the sugar has disappeared let us connect as
before the straight tubulures of each of the flasks with
a smaller matrass which the liquid will fill up to the
neck, and let us pour the liquid into it. In its new
receptacle, this must of beer will be less exposed to air
than before. We might even say that it has no air at
all at its disposal, for the mycelium has caused all that
which was in the solution to disappear, and has replaced
it by the carbonic acid which, being given off from the
surface of the latter, prevents the arrival of new oxygen.
Under these conditions, we find that the mycelium of

200

PASTEUR: THE HISTORY OF A MIND

Penicillium rapidly suspends its action and becomes inert ;
the mjTelium of Aspergillus continues a little longer to
consume the sugar, but its growth is also soon arrested.
Only the mycelium of Mucor endures for several hours
this deprivation of air. It becomes foamy as the result
of an ebullition, abundant at first then more slow, of
bubbles of carbonic acid; and we find in the liquid very
perceptible quantities of alcohol. In short, to the com-
plete combustion which the mucor gives in contact with

Fig. 16. — Yeast-like forms assumed by Mucor mucedo in the absence

of air.

air, there succeeds, without transition and without ap-
parent difficulty, at least in the beginning, a partial
combustion in the form of an alcoholic fermentation.

Singularly, the mycelium of the plant becomes modi-
fied under these new conditions of existence; that of the
Penicillium remains almost as it was; that of the Asper-
gillus segments and in place of the branching filaments
has chains of cells. It is in the mycelium of the jVIucor
that the changes are the most marked. As long as the
fungus is living as a mold in free contact with air, its

ANAEROBIC LIFE OF AEROBIC SPECIES 201

mycelial filaments are slender, branching, and inter-
twined, but when it becomes a ferment as the result of
an insufficient supply of air, the hyphae segment, sepa-
rate, enlarge, and finally are transformed into chains
of large, round, or slightly oval cells (Fig. 16) which,
in reality, resemble large cells of yeast. Bail had be-
lieved in their transformation, but Pasteur shows that
when these supposed yeasts are introduced into aerated
must of beer they do not produce alcoholic fermenta-
tion: they reproduce the Mucor. There has not, there-
fore, been any transformation of species; there has
been only an adaptation to a new life, with a change of
form corresponding to change of functions.

When he had reached this point, Pasteur might recall
that there are analogous changes in the mycoderma of
wine when submerged in a sugar solution. The cell
becomes more turgescent, its protoplasm less granular
(Fig. 13). The mucor and the mycoderma, so different
in form, resemble each other, therefore, in their nature.
In the case of both, and of a certain number of other
lower species, the fermenting property, that is to say
the ability to break up sugar into alcohol and carbonic
acid, appears to us, therefore, not as a specific property
but as a transitory faculty related to the conditions of
existence, and we may briefly sum up the foregoing by
saying that fermentation is life witJiout air.

When Pasteur gave utterance to these facts before
the Academy of Sciences, he was not understood at
first, and his opponents shouted cries of victory. This
modification of form accompanying a modification of
properties was transformation, as much as that of
Hoffmann, or Turpin, or that of Darwin. No, Pasteur
unceasingly repeated, it is not a question of a trans-
formation of species but of a general physiological law
which is applicable alike to all living species and respects

202 PASTEUR : THE HISTORY OF A MIND

their individuality. It is a question of a functional
elasticity of the cell, permitting it to adapt itself without
changing its nature, to he and to become according to
varied conditions of existence. We see to what heights
he had raised the debate: by changing the mode of
interpretation of facts alreadj^ known, he caused them to
give birth to a new theory.

IV

AEROBIC LIFE OF ANAEROBIC SPECIES

The preceding facts had in reality a bold counter-
part. We have just seen that some species, aerobic
under ordinary conditions, can lead an anaerobic life
for a greater or less length of time. In like manner
we ought to be able to acclimate a species which is
ordinarily anaerobic to an aerobic life.

Such is the yeast of beer. Let us try first to ascertain
just how far it can go in its anaerobic life by sowing it
in a nutrient solution which we have completely de-
prived of oxj^gen, it matters not how. In this dis-
aerated medium the yeast lives, but feebly; its develop-
ment is slow, and the fermentation takes a long time.
But it comes to an end, and if, when it has terminated,
we investigate the relation between the weight of the
sugar transformed and the weight of yeast present we
find a very high figure, of 150 to 200. If, for example,
we work with 100 grams of sugar, we shall see that from
5 to 7 decigrams of yeast have been sufficient to trans-
form it into alcohol and carbonic acid.

Let us now give to the yeast a little more air. Let us
sow it in a fermental)le aerated liquid, contained in a
flask which we shall not fill completely, so that the yeast

AEROBIC LIFE OF ANAEROBIC SPECIES 203

has at its disposal for its needs the oxygen dissolved
in the liquid, and a little free oxygen in the air of the
flask. This time life is more active, fermentation more
rapid, reproduction of the yeast more abundant, and
for 100 grams of sugar transformed we have about
1.5 grams of yeast produced.

Fig. 17. — Left side: disjointed cells of old yeast. Right side: Their re-
juvenation in a sugared must.

Let us go a step further in the process of aeration.
Let us spread out our sugar solution over a broad
surface or shake it in contact with air, so that each
yeast cell finds itself constantly in contact with the
free oxygen of which it has need. This time, the sugar
disappears rapidly; it no longer gives alcohol, or at

204 PASTEUR: THE HISTORY OF A MIND

least gives very little; it is a complete combustion which
has followed the incomplete combustion of the preced-
ing experiment in the same way as an incomplete com-
bustion followed a complete one in the case of the
mucor when deprived of air. Finally, a last analogy:
the yeast, like the mucor, multiplies and increases mark-
edly in weight in contact with air, so that, this time,
for 100 grams of sugar used, we find 20 to 25 grams of
yeast produced.

Some modifications of form accompany here also these
changes of function. The yeast in contact with air is
less full of cavities, has a much finer content, and is
younger in aspect, as the comparison of the two halves
of Fig. 17 shows.

In this very aerobic existence, the yeast, therefore,
approaches the Mucedinese. It differs from them
in that it can lead the anaerobic life, to which it is adapted
for a very much longer time, than even the IMucor.
But here also, the appearance of the ferment-character
accompanies life without air.

So that in the presence of the general character of
these facts, Pasteur had been led to ask himself the
following question: Can we admit that the yeast and the
other plants capable of becoming alcoholic ferments
which absorb and consume oxygen so actively when
they have it at their disposal, cease to have need of it
when it is refused them, and in this case change com-
pletely their mode of existence? If we repl}', ''Yes,"
to this ciuestion, then there is no relation between
aerobic and anaerobic life. These are two different
living organisms which succeed each other in the same
protoplasm and within the same cell-wall. If we admit,
on the contrary, as it is evidently more natural to do,
that the needs of the cell in its two modes of existence
remain the same, and that only the means of satisfying

AEROBIC LIFE OF ANAEROBIC SPECIES 205

them change, then the appearance of the ferment-
character is connected with the absence of oxygen, and
we are led to think that if the yeast and the analogous
plants can act thus on sugar during their anaerobic life,
it is because they have the ability to obtain from it the
oxygen which they need, the oxygen which serves, fur-
thermore, for their respiration, and which is given off
at once, more or less completely, in the form of carbonic
acid.

According to this conception, everj' living cell having
need of oxygen, if deprived of this gas in a free state, and
if able to obtain it from substances which contain it in
a combined state, would be b. ferment for these substances.
Here is a theory of fermentation very directly related to
the facts, as we have come to see, and, furthermore, very
suggestive, for, if it notably enlarges the field of cellular
ferments, it at the same time restricts the field of fer-
mentable substances by showing that only those sub-
stances can be fermented which are capable of furnishing
to their ferment the oxygen which the latter uses by
burning a part of it. Every fermentable substance is
capable, consequently, of undergoing an internal com-
bustion, giving off heat thereby, for since there is a life
to maintain, it is necessary that there be somewhere a
source of energy. The living organism does not pro-
duce it; it consumes it in order to build up its tissues,
in order to make them live. So that a fermentable
substance, before producing heat by undergoing an
internal combustion, becomes, in a certain measure,
comparable to an explosive body, gun-cotton or nitro-
glycerin, which burns little by little in the labora-
tory of the yeast cell. Here is the very simple con-
ception which Pasteur called the physiological theory of
fermentation.

We are forced to believe that it was not clear, since,

16

206 PASTEUR: THE HISTORY OF A MIND

leaving aside the Dii mmores, such men as CI. Bernard
and Berthelot did not succeed in comprehending it.
It is true that only with difficulty do great minds under-
stand one another. We have seen Liebig remain deaf to
the arguments of Pasteur and blind to his demonstra-
tions; we are going to see the same struggle in the dark
follow between Bernard, Berthelot and Pasteur.

IDEAS OF CLAUDE BERNARD ON FERMENTATION

The history of the discussion with Bernard is curious
in that Bernard took no part in it, and that Pasteur,
was obliged to debate with a shade. This was very
painful to him. Bernard had been while he lived, I will
not say a confidant, but a friend with whom he loved
to chat during the seances of the Academy of Sciences.
These seances are of value only because of these chats,
and it would be beneficial to allow them to go on fieely
in the salon, while the Bureau proceeded, in another
part of the building, with the official reception of notes
and memoirs. We may well believe that between Bernard
and Pasteur, who occupied neighboring arm chairs, there
w^as no question of religion, politics or scandal. They
spoke of science to the great benefit of themselves and
of others. Theirs were two powerful minds, concentrated
in their work, the more capable, consequently, of a mutual
appreciation and understanding, but gaining by an
exchange of blows and a sharpening of wits one against
the other.

Bernard, toward the end of his life, had been led to a
conception of the phenomena of life which seemed then
and still seems a little strange. He conceived that there

IDEAS OF CLAUDE BERNARD ON FERMENTATION 207

were in the living organism two kinds of phenomena:
the phenomena of construction or synthesis, which alone
he considered as truly vital, and the phenomena of or-
ganic destruction, which he considered to be of a physico-
chemical order. In a word, it was life alone which was
constructive, leaving to the forces of death the work of
destruction. These phenomena, different in origin, were,
nevertheless, not separated in space and time. Bernard
admitted that there were phenomena of destruction in
the living cell, and that whenever a muscle contracts,
a gland secretes or the mind works, there is a portion of
the tissue, muscular, glandular or cerebral, which is
destroyed. But although simultaneous and correla-
tive to a certain degree, these phenomena of synthesis
and decomposition were none the less of different essence,
and not obedient to the same mechanism.

Pasteur, in his refutation of these ideas, does not seem
to me to have perfectly understood them. Bernard
does not believe at all as Pasteur thought,^ ''in a forced
opposition between the phenomena of life and synthe-
sis and the phenomena of death and destruction, be-
tween life, properly speaking, and fermentation." At
least he nowhere says so. On the contrary they were,
according to his conception, two machines which con-
curred in the same work, propelled b}^ two different
motive forces. When death occurs and the life-motor
ceases to act, the second motor which is fed by com-
bustions and fermentations, remains in action, and it is
that which, in ways purely physical or chemical, having
no longer anything vital, presides at the return of dead
matter to the ambient nature.

This conception did not contravene, as one might
believe at first, the demonstrations of Pasteur on the

1 Examen critique d'un ecrit posthume de M. Bernard sur la fermenta-
.tion. p. 47.

208 PASTEUR : THE HISTORY OF A MIND

subject of the non-existence of spontaneous genera-
tions, and on the subject of the role and muUiphca-
tion of the ferment in fermentations. Bernard was very
respectful when face to face with facts, but when he
reflected on them he gave himself, as he had every right
to do, a great liberty of interpretation. Not because
one salutes another is he obliged to think well of him.
Now, on reflection, Bernard came to approach, little by
little, the stand taken by Liebig, and asked himself,
for it was still only the period of hypotheses and of brain-
work which preceded that of laboratory work in his case,
asked himself, I say, whether, perchance, it was not
in virtue of the second mechanism which he predicated,
that is to say by disassociation and destruction, that the
microbes caused the destruction of organic matter.

Unquestionably a mind like his had the right to put
these questions since it was in his power to solve them.
If he could show that the best-known phenomena of
organic destruction, the transformation of sugar into
alcohol and carbonic acid, could be produced entirely
without the intervention of yeast or even of living cells,
by the natural play of forces exterior to the cell, and
subject only to the laws of physics and chemistry, what a
precious confirmation of his preconceived ideas! These
physico-chemical forces could not, it is true, be common
forces taken by chance from the ambient nature. Pas-
teur had shown too clearly, apropos of spontaneous
generations, that, reduced to these forces alone, the trans-
formation of dead matter was a very slow process. But
if living cells are needed to accelerate this transformation
w^hy should these cells not act by manufacturing and
secreting, on the vital side of their organization, sub-
stances capable then of acting outside of the cell, and in
a physico-chemical way? The yeast secretes a diastase
which, outside the cell, can invert cane-sugar. A\Tiy

IDEAS OF CLAUDE BERNARD ON FERMENTATION 209

should it not secrete another diastase capable of trans-
forming sugar into alcohol and carbonic acid? ^

Such was, at least as far as we can see, the cycle of
ideas which Bernard made a beginning of submitting
to experimental verification at his country house at
Saint- Julien, at the time of the vintages of 1877, some
months before his death. Without saying anything
about it to any one, he had written down, a little care-
lessly, his first results and his new projects for experi-
ments in the loose leaves of a manuscript which was
found after his death, and which his friends believed
worthy of publication. It is always necessary to dis-
trust one's friends, especially when one is no longer there
to watch them. Posthumous writings have never aug-
mented the glory of any one, and the publication of these
few pages of notes, w^hich Bernard had very wisely con-
cealed at the bottom of a drawer, had not, in my opinion,
any pretext or excuse. The kind of general ideas in the
light of which they had been conceived and written was
sufficiently well-known by the recent publication of the
work Sur les phenomenes de la vie cormnuns aux animaux
et aux vegetaux, the proof of which Bernard had carefully
corrected at Saint-Julien in 1877. If the ideas of the
master had undergone a little change since then, it is
not to be observed in the sybilline phrases of the manu-
script. In running through them to-day, it seems evi-
dent that Bernard could not have considered his work
as anything more than a blow given with a mattock
in order to test the soil before beginning his labors.

^ We now know that it does do this, but that this enzyme (called Zy-
mase) can be obtained for study only by crushing the yeast under high
pressure. Trs.

210 PASTEUR: THE HISTORY OF A MIND

VI
DISCUSSION OF THE IDEAS OF CLAUDE BERNARD

Assuredly, in the presence of these confused experi-
ments, published without the consent of the one who
made them, Pasteur might have replied only with
that Olympian silence which Bernard would certainly
have maintained in like circumstances. He preferred
rather to do what he had always done, to go straight
to his adversary at the risk, he said, of encountering
M. Berthelot behind the manuscript of Bernard. To
the latter he T-eplied first: "Your diastase which makes
alcohol? Do not think that that embarrasses me. I
shall be happy to salute it, but I should like to see it first.
I have searched for it and never found it. In some
recent experiments which took place under your eyes,
at the Academy, and which met with your approval,
I put some cells of the grape, taken from the interior of
the fruit, into a sugar solution in contact with pure air
and I have found neither diastase nor alcohol there.
How is it that you, to whom I have so often spoken of it,
have forgotten or been unmindful of these experiments?

To which the shade of Bernard might have replied:
'■Reassure yourself, my friend, I am not unmindful nor
do I forget anything! But because you have not seen
a thing, does not prove that this thing is impossible.
In order to demonstrate the existence of this diastase
I make other conditions than yours. I take grapes
which are beginning to decay, because for me the decay
is a maturity, not advanced, as you make me say with-
out, in your turn, at all understanding my point of view,
but anticipatory, that is to say, premature. A decayed
grape is one which is mature before the others, and in
which are beginning the phenomena which only mani-

DISCUSSION OF THE IDEAS OF CLAUDE BERNARD 211

fest themseh'es later in its sound neighbors. In these
decayed grapes I find alcohol. I find it also, at least
so I believe, in the dry grapes, and I see there no cells of
yeast. Thence, the idea of my diastase. It may very
well be that this secretion of diastase takes place only
once, and that I came at a fortunate moment, while
you were too early or too late, but that will not hinder
us from remaining good friends.

"Note furthermore," Bernard might have continued
if he had been able to plead his own cause, or if he
had had an advocate, ''that my conception is in accord
with some of the experiments which you cite in support
of yours. MM. Lechartier and Bellamy before you
have seen fruits, put in closed flasks in the presence of
air, begin by absorbing oxygen, then give off carbonic
acid, and, furthermore, produce alcohol by an interior
fermentation accomplished without the aid of any yeast
cell. It is one of the experiments which you cite in
support of your ideas of life without air. I consider
it as a score for me, and I say that the results of MM.
Lechartier and Bellamy have to do only with the decay
of fruits in confined atmospheres. But if they were
rotted in contact with the air it would be the same, as
my results with grapes testify, and as, I hope, the
experiments which I intend to make on apples will
also testify."

"But," responded Pasteur, "you who have such a
good memory for the results of MM. Lechartier and
Bellamy who, moreover, are in accord with me, how is it
that you have forgotten my experiments in which,
instead of waiting until they shall have consumed the
oxygen of the air with which they are in contact, I
plunge the fruits immediately into carbonic acid, and
see the formation of alcohol begin there immediately.
Can it be a question of decay in this quick experiment

212 PASTEUR : THE HISTORY OF A MIND

when the fruits come out of their matrass healthy,
of good flavor and sometimes, as in the case of prunes,
more firm than when they entered? Do you not know,
furthermore, that AI. Miintz has made the same ex-
periment on entire Uving plants, which produce alcohol
when made to live for some time in carbonic acid, and
which resume their ordinary existence, when restored
to the air, with as much facility as a traveller who comes
out of a tunnel and finds once more the air and sunshine?"
And thus the discussion, which I have made a dialogue,
and which was a monologue, might have been continued
a long time without bringing forth any new arguments
or elements of conviction, for the experiments of Bernard
were too vague to signify anything, and Pasteur has
not added anything new to this point of the discussion
which has remained sterile.

It was the same with a lively and somewhat passionate
dialogue which took place between Pasteur and Bert helot
on the work of Bernard. This, however, does not lack
interest. There is always interest in a strife between
men of this stamp. There is always profit in hearing
them develop their arguments and discuss the ideas
of their adversary. But here the opponents were not
equal. One of them led into a field which was not his
own, fenced a little at random, and sometimes laid
himself open to a thrust. As soon as he left the least
spot unguarded, the blow of the button came straight,
promptly, irresistibly. It was truly a curious passage
at arms, but as it did not bring forth any new facts, its
interest has disappeared. Pasteur came out of it more
fixed in his ideas, and Berthelot, apparently, without
having yielded any of his. This should lead us to
distrust all discussions, even scientific ones.

It is a common belief that a scientific discussion has
a greater chance of coming to something than any other,

DISCUSSION OF THE IDEAS OP CLAUDE BERNARD 213

because it takes place in the domain of facts. But a
fact, even of the physical order, is nothing by itself.
It becomes something only when it passes into the state
of an intellectual fact, by traversing an intelligence the
imprint of which it receives. It is then related to another
fact, sometimes this and sometimes that, and thus are
born a certain number of conceptions or of theories,
which make more or less proselytes. There are certain
facts, or certain groups of facts, on which tradition,
habits of education and the general debility of intel-
hgences have set everyone in accord, and which are
considered as verities, as belonging to the foundations
of science, until the day when an investigator more bold
than others thinks of taking a look at them, and con-
tradicts them. Then they disappear, or are interpreted
differently, which overthrows the accepted theories.

If the verities of the rear-guard are so subject to
caution, what must be the case with those of the advance
guard, those which are the recent conquests? For
these there is no rule and tradition; every person can
interpret them according to his liking. Thus, in a
discussion with Pasteur, Fremy had had on this subject
an idea of astonishing candor. He proposed to his
adversary that he would accept all his, Pasteur's, facts,
provided Pasteur would accept all his, Fremy's, inter-
pretations. This was to demand everything, for we do
not discuss facts, but their interpretations. Whence
it results that even a serious discussion between two good
minds has no chance of leading to anything, so long as it
remains in the domain of facts already acquired. It
is useful only when it leads the adversaries to investigate
and produce something new. If they both succeed,
they are both light, even when they are not in agree-
ment. If they do not venture, or if neither one reaches
any results, the discussion may amuse the gallery,

214 PASTEUR: THE HISTORY OF A MIND

instruct it, perhaps even give rise to some new ideas
there, but it is sterile for those who have taken part in it.
A savant is not the routine man of the study; he is the
man of the laboratory.

VII
ORIGIN OF THE YEASTS OF WINE

Pasteur had entered into his own domain in the dis-
cussion of a part of the posthumous work of Bernard.
He wished to elucidate a question which he had had
at heart since the beginning of his studies on alcoholic
fermentation, to which he has returned many times,
but which he has not completely solved, because it is
difficult. That is the question of the origin of yeasts.

In his Etudes sur la Mere, he had very much enlarged
the conclusions of his first memoir of 1862, published
in the Bulletin de la societe chimique, and had shown
that there existed a great number of yeasts, different
not only in form, but also in their physiological prop-
erties and in the various tastes which they communicate
to the liquids which they ferment. But whence come
these numerous yeasts? Are they special vegetative
forms of a microscopic plant other than the yeast, and
known under another name? And if so, what is this
plant? or rather, what are the different plants which
give birth to the different yeasts? If, on the contrary
these yeasts have no other form of reproduction than
that with which we are familiar, how, in nature, do they
pass the winter and the periods during which there are
no sugary solutions to ferment? Experiment teaches,
as a matter of fact, that, when dried and exposed to the
air, the various yeasts rapidly lose their vitality.

ORIGIN OF THE YEASTS OF WIXE 215

The question does not arise regarding the cultivated
yeasts, those for example which the brewer transfers
from vat to vat in all seasons, as has been the custom
for centuries, but applies onl}' to the wild yeasts, which
reappear at the appointed place every j'ear, to ferment
the grape crop. For the wine-manufacturer does not

Fig. is. — Top yeast of the brewery.
Old. Rejuvenated.

add yeast to his casks, and yet the ordinary fermentation
begins freely and actively, sometimes in 24 hours. At
what moment do the stems of the cluster and the newly
formed fruits become charged with these germs?

Experiment has shown that this occurs late in the
season. As long as the grape is in the stage of verjuice

216 PASTEUR: THE HISTORY OF A MIND

which, in the Jura, is toward the end of July, we can
introduce into a fermentable juice bits of the fruit and
fragments of the stem of the cluster without any fermen-
tation of this juice, provided we work carefully and
avoid every chance of the introduction of germs other
than those which we wish to study. But, as the grape
ripens and the day of the harvest approaches, there is
an increase in the number of grapes and fragments of
the stem which carry the yeasts with them into the juice
in which they are sown. The wood of the cluster is at
this time more charged with germs than the fruit, which
is, itself, more richly supplied than the wood of the
branch or the twigs of the \dne. Even at the moment
of the harvest, not all the grapes are carriers of germs
capable of fermenting them, and one may crush them
individually and even by twos in sterile flasks, that is
to say, place their superficial pellicle in contact with
their juice without seeing the latter ferment. Then,
after the harvest, when we have made it by collecting
only the grapes, leaving behind the stem of the cluster,
the germs of yeast upon the latter gradually become fewer
and fewer, so that by December and throughout the
winter there are none at all. There remain on it only the
germs of molds.

This first question when solved gave rise to another.
In what state, on the surface of the berry and on the wood
of the stem, do we find these germs of yeast, the existence
of which we have just demonstrated? Washing these
surfaces with a clean badger's-hair brush, we obtain a
clouded drop which, under the microscope, shows nothing
resembling yeast. We see the^'e only numbers of
corpuscles (A, B, P'ig, 19) of a more or less deep brown
color or reddish yellow color, with thick and opaque
walls, and other more translucent cells, none of which
give the idea or present the aspect of the familiar yeasts.

ORIGIN OF THE YEASTS OF WINE

217

But let us leave this dust, evidently living, in a thin
layer of sugar solution exposed to the air under the micro-
scope, and we shall see come forth in profusion from
certain groups of the brown corpuscles, cells (Ai, Ao,
Bi, Bo, Fig. 19) or branching filaments which at once
bud and segment into cells. Now these cells are yeast
cells, for, once rejuvenated in contact with air and sown
in a sweet must, they produce in some hours an active
alcoholic fermentation.

Pasteur must have felt a profound joj^ in discovering

#

O

B

Fig. 19. — Thick-walled brown cells that give rise to wine yeasts.

these facts, for, with his usual perspicacity, he must
have seen immediately the solution of a problem which
had been in his mind for a long time, and of which
he had many times tried in vain to find the solution.
The origin of this difficulty was the experiment of Gay-
Lussac which we have described, and in which this scien-
tist had seen some bubbles of oxygen produce fermen-
tation in the juice of grapes crushed in a test-tube under
mercury and remaining inert up to that time.

It is here that we can find a proof of the truth of that

218 PASTEUR: THE HISTORY OF A MIND

which I have affirmed above. Here is a fact: fermen-
tation takes place. All the world accepts it, but how
interpret it? The proof that this is not easy, is the fact
that it has received four different interpretations, namely,
one by Gay-Lussac, one by Liebig and two by Pasteur.

Gay-Lussac was content to say: ''It is the oxygen
which sets the fermentation going." Liebig, after him,
had searched more profoundly and said: ''It is the albu-
minoid matter of the must which needs oxygen in order
to enter into decomposition and to acquire the proper-
ties of a ferment." For 30 years this interpretation
had enjoyed the honors and credit of a demonstrated
truth. Pasteur arrives on the scene and says: "The
albuminoid matter has nothing to do with the phenom-
enon. The ferment is a living organism which comes
from a germ, and if the air has conveyed into our test-
tube a cause of fermentation, it is because it has
brought a germ there."

It was surely not without some regret that he came
to this conclusion, because this view fm-nished a weapon
to the partisans of spontaneous generation, and per-
mitted them to say: "How is this? Do you admit the
germ of a ferment in each bubble of air? Then what
becomes of your conclusions relative to the rarity of
germs in the atmosphere?" This objection embarrassed
him only a little; but if he had had a discussion to support
on this subject he would only have been able to multiply
words upon it. He must have uttered a cry of joy when
he was led by experiment to a fourth interpretation:
The germs of the yeast are carried by the grape-berry;
they are inert as long as they are depri\'ed of oxygen
and it is the introduction of the bubble of gas which
gives the whipstroke of departure for existence in a state
of fermentation.

It is a singular thing that all these results, so curious

ORIGIN OF THE YEASTS OF WINE 219

and so new, known for a year through the pubhcation
of the Etudes sur la biere, had been forgotten in 1877 by
Claude Bernard. One of his principal experiments at
St. Julien, which he had repeated at various times
because he had never been content with the results, had
consisted in crushing ripe grapes, sound or decayed, to
express and filter therefrom the juice until it was per-
fectly clear, then to compare in an approximate manner
the quantity of alcohol in the liquids after their filtration,
and in the same liquids after standing about 48 hours,
Bernard found that in this interval the amount of alcohol
increased, although the liquid remained clear, and he did
not hesitate to draw from this fact conclusions favorable
to the existence of the diastase of which we have al-
ready spoken.

The experiment of Bernard allowed various sources
of error which Pasteur pointed out in the discussion
which he made of it. He cites in opposition the results
described in the Etudes sur la Mere, but he goes farther:
he proposes to repeat the same experiments on a much
larger scale, in such a way as not to allow any of those
conditions of time and place of the experiments of Ber-
nard, which one could invoke in their favor, to come
into play. Here, we can let him speak, for he has him-
self given an account quite at length of this episode,
wherein he has painted a very exact portrait of himself,
with his ardor in returning to already conquered posi-
tions when they were menaced, and that suddenness
which he always brought into his decisions when a
great question was under consideration.

The day following the posthumous publication of the
manuscript of Bernard, Pasteur's plan and program were
made: "Without too much care for expense,"^ he said, 'T

1 Examen critique d'un ecrit posthume de CI. Bernard sur la fermenta-
tion, p. 66.

220 PASTEUR: THE HISTORY OF A MIND

ordered in all haste several hothouses with the intention
of transporting them into the Jura, where I possess a
vineyard some dozens of square meters in size. There
was not a moment to lose. And this is why!

''I have shown, in a chapter of my Etudes sw^ la biere,
that germs of yeast are not yet present on the grape
berry in the state of verjuice, which, in the Jura, is at
the end of July. We are, I said to myself, at a time of
year when, thanks to a delay in growth due to a cold
rainy season, the grapes are just in this state of verjuice
in the canton of Arbois. By taking this moment to
cover some vines with hothouses almost hermetically
closed, I would have in October during the grape har-
vest, vines bearing ripe grapes without any yeasts of
wine on the surface. These grapes, being crushed with
the precautions necessary not to introduce germs of
yeast, will be able neither to ferment nor to make wine.
I shall give myself the pleasure of taking them to Paris,
of presenting them to the Academy, and of offering some
clusters to those of my confreres who may still believe
in the spontaneous generation of yeast.

''The fourth of August, 1878, my hothouses were
finished and ready to be put up. The work of setting up
and of putting in the glass was finished in a few days.

''During and after the installation of the hothouses,
I searched with care to see if the germs of yeast were
really absent from the clusters in the state of verjuice,
as I had found hitherto to be the case. The result was
what I expected; in a great number of experiments I
determined that the verjuices of the vines in the canton
of Arbois and notably those of the vines covered by the
hothouses, bore no trace of germs of yeast at the beginning
of the month of August, 1878."

"In the fear that an insufficient sealing of the hot-
houses would allow the germs to reach the clusters, I

ORIGIN OF THE YEASTS OF WINE 221

took the precaution, while leaving some of the clusters
free, to cover a certain number on each vine with cot-
ton which had been brought to a temperature of about
150°C."

'*. . . Toward the tenth of October, the grapes in the
hothouses were ripe; through the skin of the berry, one
could clearly distinguish the seeds, and in taste they were
as sweet as the majority of the grapes grown outside;
only, under the cotton, the grapes, naturally black, were
scarcely colored, rather violaceous than black, and the
white grapes had not the golden yellow tint of white
grapes exposed to the sun. Nevertheless, I repeat, the
maturity of both left nothing to be desired.

"On the tenth of October, I made my first experiment
on the grapes of the uncovered clusters and on those
covered with the cotton, comparing them with some which
had grown outside. The result I may say surpassed
my expectation. . . . To-day, after a multitude of trials,
I am just where I started, that is to say, it has been
impossible for me to obtain a single time the alcoholic
yeast fermentation from clusters covered with cotton,
and as for the uncovered clusters of the same vines I
have had only a single case of fermentation, by a yeast
which I described a long time ago in the Bulletin de la
Societe chimique, and which has since received from Dr.
Reess the name of Levure apiculee.

"A comparative experiment naturally suggested it-
self. When the hothouses were set up we were in the first
period, that in which the germs are absent from the
stem and the clusters. At the time when the experiments
which I have just described took place, from the 10th to
the 31st of October, we were, on the contrary, in the
period when the germs were present. It was then pre-
sumable that if I detached hothouse clusters covered

with cotton and exposed them, after removing the cot-
17

222 PASTEUR: THE HISTORY OF A MIND

ton, on the branches of vines in the open, these clusters
which up to this time could not enter into fermentation
after the crushing of their berries, would ferment under
the influence of the germs which they could not fail to
receive in their new position. This was precisely het
result which I obtained."

It is clear that in the presence of these results, nothing
was left of the mediocre experiments of Bernard. It
was certain that the germs of the yeast were brought
periodically to the vine by an external plant, on the nature
of which Pasteur could make only some plausible hy-
potheses, and furthermore, on which we are not yet exactly
informed. If I have dwelt so long on this last demon-
stration of Pasteur, it is not simply to consolidate an
already established proof, but to show, by an example
which seems to me typical, how Pasteur was able to
broaden the problems which he approached.

The problem which he had placed before himself in
the preceding experiments was apparently very limited:
it was the origin of yeasts. Behold how he enlarged it :

"May I be permitted," he continued immediately
after having written the lines which precede, "to enter
here into an experimental digression, very worthy of
interest? I have said that the clusters of ripe grapes
carry on their surface the germs of ferments which pro-
duce the wine in the vat and in the casks of the vine
grower. Consequently, is it not probable that at the
time of the harvest the rains may collect many of these
germs and spread them over the soil of the vineyard?
Experiment confirms these suppositions. Having de-
posited very small quantities of earth from a vineyard
in a series of tubes which contain the must of grapes
sterilized by a preliminary boiling, I have seen this must
undergo alcoholic fermentation in many of the tubes
of each series. Without injuring the success of the

ORIGIN OF THE YEASTS OF WINE 223

experiment we may take these samples of earth at a
considerable distance from the surface, even from a depth
of 10 to 15 centimeters. Still more frequent in this
kind of experiment, is the alcoholic fermentation by
yeasts of the genus Mucor, so abundant in cultivated
soil are the spores of these little plants.

''I have had the curiosity to compare the soil of the
vineyard and that covered by my hothouses with
regard to the presence of the spores of grape yeasts and
the spores of Mucor. But, although the experiment
has been made a great number of times, I have never
seen produced in my tubes with the soil from my hot-
houses, the alcoholic fermentation due to the alcoholic
yeasts of the grape; very frequently there appears,
on the contrary, the fermentation due to the yeast of the
Mucor.

"How many reflections these results lead to! Can we
fail to observe that the further we penetrate into the
experimental study of germs, the more we see therein
unexpected lights and just ideas leading to knowledge
of the causes of contagious diseases! Is it not worthy
of attention that in this vineyard of Arbois, and this
would be true of the millions of hectares of vineyards
all over the world, there was not, at the time when I
made these experiments which I have just described,
a particle of soil, so to speak, which was not capable
of provoking the vinous fermentation, and that, on the
contrary, the soil of the hothouses of which I have spoken
was unable to do this. And why? Because, at a defi-
nite moment, I covered this soil with some glass. The
death, if I dare to speak thus, of a grape berrj- which
has been thrown on the ground of any vineyard, will
be, somehow or other, infa^llibly accomplished by the
yeast parasites of which I speak; but this kind of death
will be impossible, on the contrary, in the little corner

224 PASTEUR: THE HISTORY OF A MIND

of soil which my hothouses cover. These few cubic
meters of air, these few square meters of the surface
of the soil weie there in the midst of a possibly universal
contagion, and they withstood it for a period of many
months. But of what service would the shelter of the
hothouses be in the case of disease and death caused by
the Mucor parasites? Not the least! Since the para-
sites of the saccharomyces reach the surface of the grapes
at a definite period of the year, a shelter, put on in time,
■was able to keep them free from these germs, as Europe
is protected from the cholera and the plague by quaran-
tines. The Mucor parasites, on the contrary, being
present during the whole year in the soil of our fields
and our vineyards, were necessarily under the hothouses
when they were put up, like, in some respects, the germs
of our common contagious diseases, against which the
quarantines opposed to cholera, yellow fever, or the
plague are ineffectual.

"Must we not believe, by analogy, that a day will
come when preventive measures, of easy application,
will arrest these plagues which at one blow desolate
and terrify whole populations, as did the yellow fever
in its recent invasion of the Senegal and the valley of
the Mississippi, or the bubonic plague which has raged
on the shores of the Volga."

These few lines form the introduction to a new life.
They show the preoccupations which had just taken
possession of Pasteur's mind and which already com-
pletely filled it. They were written in 1S79, when the
studies of anthrax and of chicken cholera were already
begun. They form the connecting link between the
old labors and the new, and it is for this reason that I
have transcribed them. I .should be very much aston-
ished if the reader has not noted their resolute manner
of expression and their i)rophetic tone.

PASTEUR

(From an engraving by Noj'es.)
(Courtesy of the J.ibrary of the Surgeon General.)

SEVENTH PART
Studies on the Etiology of Microbial Diseases

I
THE IDEAS ON CONTAGION PRIOR TO 1866

We have reached the period when Pasteur, who had
his eyes fixed for a long time upon the promised land
of pathology, was going finally to be able to enter it. He
was ripe for this work, and provided with the necessary
technical outfit to undertake it. His laboratory was
at that time the only one in which it was possible to
properly handle bacteria and be certain of the purity
of a sowing carried through an indefinite series of suc-
cessive cultures. While elsewhere every one was strug-
gling with nutrient liquids of mediocre composition
such as those mineral solutions of Pasteur or of Cohri,
which have played so many tricks with Klebs and those
who made use of them, Pasteur had discarded them for
a long time, and had adopted the fertile principle of
giving to each bacterium the kind of medium adapted
to it.

It was following the beautiful researches of Raulin
that he had understood the importance of this question.
He had reflected for a long time and he called the atten-
tion of his pupils frequently to the fact that when cul-
tivated upon its favorite medium, the discovery of
which had given Raulin so much trouble, Aspergillus
7iiger defends itself unaided and successfully against the
intervention of every parasite. While one is obliged
to operate protected from the germs of the air and in

226 PASTEUR : THE HISTORY OF A MIND

flamed flasks, when he wishes to cultivate and keep pure
a species the condition for the development of which
he knows only imperfectly, Aspergillus niger gi\-es
admirable cultures, flourishing and pure, in contact with
the air, and in liquids and flasks which one has not taken
the trouble to sterilize. Consequently, in the presence of
every new species, his first care was to try several culture
media so as to find that which suited it the best.

Having this principle of culture in the most favorable
medium, Pasteur was also the only one who had the
ability to add a proper technique. This was due especially,
as we have seen, to the efforts of his assistants: Joubert,
Chamberland and Roux.

Finally, as a last advantage, Pasteur had that of being
20 years old in the study of microbes and of having more
complete notions about them, their need?, their physi-
ology and their morphology, than any of the scientific
men of his time. It was because of this that he was
able so quickly to catch up with and soon to distance
those who had entered before him on this pathway,
for at the time when he first took up the study of anthrax
in 1876, there had been already several pathogenic mi-
crobes discovered, and Koch had just published his
famous work on the spore of the anthrax bacteridium.

To appreciate thoroughly the role and the part of
Pasteur in this great question of pathology, one must
know the general state of science and of the scientific
mind in 1876.^ That is not as easy as one might believe
it to be, considering that we have to go back only a few
years. The ideas which had currency in 1840 and even
in 1860 on the subject of contagious diseases are so far
removed from our own that they have almost the dis-

1 One may obtain a verj'^ good idea of what it was in Germany by
reading Niigeli's Die niederen Pilze in ihren lk>ziehungen zu den Infec-
tionskrankheiten und der CJe.sundhcitspflege, Munich, 1S77. J";-*-.

THE IDEAS ON CONTAGION PRIOR TO 1866 227

tance of centuries. One finds the same trouble in assim-
ilating them that he would if they were some philo-
sophical work of the middle ages, and therein we see very
well what a chimera is the history of scientific ideas.
In order to understand the past state of a question, it
is necessary to assume an artificial state of mind, to pass
the sponge over certain ideas which we believe to be
true, putting in their place others which we know to be
false, in brief, to change the state of one's brain, and
that is impossible.

I know very well that there remain in the books of
the period words which are supposed to be the clothing
of ideas, and through which one may try to see what
they covered. The partisans of the history of science
tell us, when it is a question of mathematics or physics
or of natural history, that these words have a more
precise meaning than when it is a question of philosophy,
and they are right. But if they conclude therefrom that
the history of science is easy to write, or even possible,
they are wrong, for, even in science homonyms are not
synonyms 30 years apart. The same tinsels cover very
different small rough models. We have just here a
striking example of this fact.

For example, the words contagium vivum or animatum
have been current in science for a long time. They
have been found in Varro and Columella. Acknowl-
edging that they may still serve to express the ideas of
to-day, one has sometimes concluded that these ideas
are very old, that only knowledge of the mode of con-
tagion has been perfected with progress of time, and
that Pasteur is only the last one come, and the most
powerful, of a series of investigators who have labored
with the same directive idea.

I have no need to go back very far to demonstrate the
inexactness of this point of view. I will confine myself

228 PASTEUR: THE HISTORY OF A MIND

to the scientific man whom one most willingly cites as
the immediate precursor of Pasteur, to Henle who,
about 1840, published a sort of theory of disease, the
developments of which seem in fact in harmony with
our present ideas. For Henle, the evolution of a disease
is in all respects comparable to that of a living being.
The quantity of morbid matter which may produce it in
a healthy individual, like the seed of the plant or animal,
is out of all weighable proportion to the quantity of effect
produced, and to the quantity of morbid matter which
the diseased individual produces in his turn. An acorn
produces an oak, which jdelds in its turn a multitude
of acorns.

So much for a first point of view. Here is a second:
Between the time when the morbid matter enters into
the body, and that in which it is translated into dis-
orders preceding disease, a period intervenes which is
well known under the name of period of incubation, which
is nearly constant for each disease, and differs from one
disease to another. How is it possible not to connect
it with the duration necessary for the development of
the germ and the infection of the tissues? How explain
it otherwise than by the doctrine of parasitism? !-^o
long as the disease lasts, he who has it must be a source
of contagium. When it has ceased, all danger of conta-
gion ceases. This means that the germ is dead and can
no longer injure. The same for epidemics. In their
appearance, their extension over a territory more or less
great, their lingering termination, do they not resemble
absolutely the beginning, the middle and the end of a veg-
etation, and is it not remarkable also that many disin-
fectants and even remedies should be at the same time
active agents of destruction of vegetable or animal life?

Behold, it has been said, an unlettered print of the
system of Pasteur, and that which makes still further

THE IDEAS ON CONTAGION PRIOR TO 186G 229

for the perspicacity of Henle is that he pointed out the
bacteria as among the beings capable of giving infectious
germs, and that he thus foresaw and ahnost enunciated
our present day ideas. I reply, you forget a detail
which is far from being insignificant. For Henle, the
germ of the disease was not something superposed upon
the sick person and independent of him, it was something
belonging to him, borrowing from him a sort of patho-
logical vitahty, and able to transport it elsewhere.
The system of Henle is much more in consonance with
what one then knew of viruses, of the transmission of
smallpox, of vaccine, than with what one had recently
learned of the transmission of itch or of muscardine, and
we find therein nothing of the new idea brought by
Pasteur concerning the living virus, which can be
cultivated and modified outside of the organism.

A physician of La Teste. J. Hameau, had entered upon
a better pathway in a paper which, written in 1836,
was unfortunately not published until 1847, a long time
after the work of Henle. Hameau, contrary to Henle,
had taken the itch especially as the point of departure
for his deductions and for his system, and all that which
is in accord with this premise is correct for he had truly
method and logic in his mind. On the contrary he wan-
ders when he takes up the question of miasms, to which
he attaches dysentery, erysipelas, and hospital gangrene.
For him, there was not in these cases any contagium
vivum, while there was such for Henle, and that shows us
how necessary it is to distrust words, and how much one
would have disturbed both Henle and Hameau by placing
them in the same camp, under the pretext that they had
the same words inscribed upon their banner.

It is not these philosophical speculations which cause
science to advance. We must be grateful to all of those
from Columella and Varro, by way of Paracelsus, Fra-

230 PASTEUR : THE HISTORY OF A MIND

castoro and Linnaeus, who have outstripped their epoch
by showing with more and more precision the evident
analogies between the phenomena of fermentation and
of diseases, and who have more or less suspected living
organisms in diseases in proportion as they appeared in
fermentations. But it is not in these multicolored
big lanterns moving about in the night that we are to
see the dawn of our present ideas.

II

CAUSES OF THE STERILITY OF THE IDEAS UPON

CONTAGION

Such being the case, what one has the right to ask is
why these ideas did not attract the attention of con-
temporaries to a greater extent. Why have systems as
suggestive as those of Henle, of Hameau, remained
unknown or disdained? We shall here find the secret
of their weakness. It is because they were works of
the closet and because not being developed from experi-
ment, they did not end in experiment. Systematic
and brilliant minds have never been wanting in medi-
cine. When Hameau was writing, Broussais was still
alive: the cloud of dust which he had raised, and in the
midst of which his disciples were felicitating themselves,
was too thick for the vague light of the little physician
of La Teste, who explained very well certain known
facts, but did not point out new pathways.

In 1840, at the moment of the appearance of the mem-
oir of Henle, the German physicians had, on their side,
better excuses than those of to-day for not paying atten-
tion to these new ideas. They were too nmch in oppo-
sition to the strong and fertile conceptions that Mr-
chow was introducing at this time into the science.

THE STERILITY OF THE IDEAS UPON CONTAGION 231

Without doubt it must be admitted that certain skin
diseases like favus, herpes tonsurans, thrush, and itch
could be produced by animals or vegetables. But of
what importance were these maladies when placed by
the side of the infectious diseases in which one found
nothing comparable? Now cellular pathology explained
the latter by the famous principles of heterotopy and
heterochronia. Every pathological modification was for
it only a physiological transformation displaced in time
or place, developing itself in an organ which could not
endure it, or at a time when it was abnormal. The
secret of the disease was, therefore, in the anatomy of
the tissues, which, under this powerful impulse, multi-
plied its discoveries and took in all, from tumors to
viruses, from exostoses to exanthemata, and to the pus-
tules of smallpox or of vaccine.

The idea that there could be in the tissues organisms
come from the exterior which, by penetrating and de-
veloping there, impressed upon them specific modifi-
cations, was in disagreement with the general current
of anatomical ideas; and yet more with physiological
views. At this moment in fact, a pleiad of illustrious
scientific men, Helmholtz, Du Bois Reymond, Ludwig
and Briicke, began to oppose the ancient conception of
the vital force, and to explain all physiological phenom-
ena of the living being by forces of the physico-chem-
ical order. It was the same idea that Liebig followed,
as we have seen, in the study of fermentations. Into
a coterie shining with such names, it is plain with what
welcome the idea would be received of the interven-
tion under the form of living and pai'asitic organisms
of this proscribed and everywhere driven out vital force.

And this is precisely why Pastern* who had overthrown
the ideas of Liebig respecting fermentations, found it
in continuing his work necessary to meet and o\erthi()w

232 PASTEUR: THE HISTORY OF A MIND

the ideas of Virchow in pathology. If Fate had willed
that he should not finish his task, that he should suc-
cumb to the hemiplegia which attacked him at the time
of his studies on silkworms, some other scientific man
would have come, a Koch for example, for whom Pasteur
would have been a precursor because he would have
pointed out the way and left behind him the means of
following it. His pathological work was the develop-
ment and the compliment of his work upon the fermen-
tations. But Pasteur had no precursor in the proper
sense of this word, that is to say, he did not develop
and extend the ideas of anyone else. He remains the
equal of many when he demonstrates the bacterial origin
of anthrax or of other diseases. Where he is without
equal is when he discovers the attenuation of viruses,
and when he introduces into science that fertile no-
tion which allows us to act upon a disease by acting,
not upon the sick person, as up to that time one had
been in the habit of doing, but upon the pathological
bacterium.

What renders his history particularly interesting at
this period, is that we can follow the stages of his
progress. As we have seen, he had had for a long time
the desire to enter into pathology. He was led to it
by that secret force of things the elements of which we
have just analyzed. He showed himself an eager student
of medical works and after having borrowed from them
certain words, as we have seen, at the beginning of his
studies upon the disease of silkworms, he began to pene-
trate into things. From this stage his choice was nar-
rowly restricted. He had read and meditated on the
works of Jenner upon vaccine, those which Coze
and Feltz had just published. But what interested him
most of all were the studies which Davaine was pursuing
at this time upon the anthrax bacteridium.

anthrax: pollender, brauell, delafond 233

III
ANTHRAX: POLLENDER, BRAUELL, DELAFOND

The history of this bacteridium was already quite
ancient; it began in 1850. It was at this time that
Rayer, studying at Chartres the anthrax of horned
cattle with the aid of Davaine, had seen it in the form
of little rods in the blood of dead animals (Fig. 20),
but without comprehending its importance. In 1855,
Pollender had seen it again, had noted, like Rayer, the
agglutinated condition of the red blood-corpuscles in
the anthrax blood, and the considerable number of
leucocytes which were observed along with it. In addi-
tion, by reactions under the microscope, he had estab-
lished that the little rods found in this blood were not
filaments of fibrin, but behaved on the contrary like
vegetation. The principal interest of his communi-
cation respecting them centers in the fact that he asked
what they signified. Are they the infectious matter
itself? Are they only the carriers of this matter? Or,
have they nothing to do with it? We should say to-day:
Are they the infectious agent, do they convey this agent,
or is it necessary to seek it elsewhere? This is the
question that Pollender asked himself with much per-
spicacity, and which it required 30 years to settle.

Science is like a train in the hands of a crew, which,
after having gone forward, sometimes goes backward.
Scarcely had Pollender well set forth the question than
Brauell befogged it by confusing the bacteridia of an-
thrax, considered up to this moment as sufficiently spe-
cific, with the harmless bacteria of putrefaction, which
led him quite naturally to discover them in various
diseases, and consequently to sever them from anthrax.
At most he admits that, in this disease, the harmless

234

PASTEUR : THE HISTORY OF A MIND

bacteria appear in tlie blood, before death instead of
after death as in other diseases.

The following year he took a new step in the wrong
direction. He stated that inoculation with the blood
of a horse having anthrax had caused a deadly anthrax
in the inoculated animal, although this blood did not

Fi<;. "JU. — Jiactcndium of antlirax.
Ill artificial cultures. In the blood of a diseased animal.

contain bacteridia. Evidently, therefore, these little
rods were neither the contagion nor the carrier of the
contagion nor even, one might add, the necessary com-
panions of it. Brauell, therefore, undid what Pollender
had done. Henceforth the little rods retained only a
diagnostic or a prognostic value in certain cases, that is to

anthrax: pollender, brauell, delafond 235

say, the animals which showed them in their blood
during life had anthrax without question, and were
certain to die in the near future, but they might also
die of anthrax without containing the bacteridia.

The reaction against these retrograde ideas was set
on foot by Delafond, who pointed out the confusion
made by Brauell and even by Pollender between the
bacteridia of anthrax and the harmless bacteria of putre-
faction: because in proportion as the second develop,
the first disappear.

Delafond goes further. He seeks to prove the vege-
table nature of the anthrax bacteridia by subjecting
them to culture experiments. He exposed the anthrax
blood in open flasks to the air at a suitable temperature.
After 4 or 5 days, the short rods in the blood had in-
creased and doubled or tripled their length, and they
quadrupled or quintupled it after 8 or 10 days. This
well demonstrated that the bacilli were living. Delafond
even tried to push the growth to its completion to see
it arrive, as he says, at the spore or seed. These words
spore and seed had evidently for him not the precise
meaning which they have since acquired, but they do
honor to his perspicacity, and it is curious to see them
appear in connection with bacteridia, in a memoir of 1860.

To sum up then, for those who kept au courant with
the question, a connection between the bacteridia of
Rayer and the development of the disease of anthrax or
sang de rate, although still obscure, was probable from
the proofs and the culture experiments of Delafond.
But it is not with such a feeble array of facts that an
idea can enter into the domain of science, especially
when it finds therein minds prejudiced against it.
"What is it worth to us," one might have said at this
epoch, "this new etiological doctrine? Is there not
something strange about it? Can one imagine the

236 PASTEUR: THE HISTORY OF A MIND

powerful and colossal life which animates a horse or
an ox, threatened and destroyed by this miserable httle
rod which we can see only under a microscope? This rod
appears, moreover, only some hours before death, and
when the animal is already very ill. Where is it and
what has it been doing earlier? You tell us, you who
believe in it, that it does not long survive the animal
which it has killed, and dies when the tissues decay.
But all animals dead of anthrax decay, for we bury
them quickly without making any use of them. And.
therefore, how do you explain that there are epidemics of
anthrax every year, epideixiics which appear in the summer
after having disappeared from the country all winter?
How do you explain, also, that there are in Beauce
cursed fields, in Auvergne dangerous mountains, where
animals from the farm can neither be pastured nor
driven, without paying a tribute, more or less great,
to the disease? From this is it not evident that the
disease is attached to the soil, to the vegetation, and to
certain climatic conditions, which have nothing to do
with this bacteridium in the blood of diseased animals?
"All that we are able to grant you," the skeptics
might have added, "in the presence of your proofs and
of your experiments, is that this bacteridium is an
epiphenomeno7i. It sometimes accompanies the virus,
or follows it, but it is not the virus itself. The virus
of anthrax, like that of smallpox, or of sheeppox, is
something which one can handle without seeing it and
recognizing it. It exists, since the disease is inoculable,
but we do not see it outside of the animal. It is not
something independent of the animal but a modality of
its being. It is living, it may be granted you, but it
borrows its life from the being which carries it, it is
nothing outside of the animal, and we recognize it only
in transit through living beings."

DAVAIXE 237

All these objections are not wanting in force, and as
they favored idleness of mind and invited intellectual
repose, they were very much in vogue. To Davaine
belongs the honor of beginning again the struggle against
them.

IV
DAVAINE

After the discovery of the bacteridium, which Davaine
had made in 1850, with Rayer, he had paused for reflec-
tion. His was a very keen and discriminating mind.
He regarded science from the point of view of medicine.
The brief note by Pasteur in 1861 on the butyric ferment,
of which we have spoken, had revealed to him the exist-
ence of very active microscopic organisms morpholog-
ically similar to the anthrax bacillus and capable, by
means of their power of fermentation, of producing
effects out of proportion to their weight and volume.
Consequently, despite its small size, the anthrax bacil-
lus might easily cause the death of a large animal and
be guilty of all that was attributed to it. A singular
thing which we have difficulty in explaining to-day,
is the fact that while no one then refused to admit that
a thing as imperceptible as the virus of smallpox could
convey the disease and bring death to the individual
inoculated with it, because this virus seemed to derive
its energy from the creature into which it penetrated,
and to change only the modality of its life, all refused
to understand that the bacillus, an independent living
organism, could by its own activity, triumph over the
animal which it invaded.

To Davaine belongs the credit of having seen farther
along this line than the men of his generation and of

18

238 PASTEUR : THE HISTORY OF A MIND

applying himself to the demonstration of the fact that
the bacteridium was the sole cause of anthrax. Without
entering into the details or the chronology of his mem-
oirs on this subject, it will suffice here to point out the
status to which he had brought the question at -the time
when Pasteur attacked it in so masterly a manner.

It can be said that Davaine had perfectly demon-
strated the coexistence of the bacteridium and of the
anthrax. This fact of coexistence which is not, how-
ever, necessarily to be considered a relation of cause
and effect, became known as the result of a long series
of observ^ations made on cases of malignant pustule,
which is the most common form of anthrax in man, as
well as on animals killed by anthrax either naturally, or
as a result of artificial infection. This coexistence had
been disputed. After Brauell, Signol, Leplat and Jail-
lard, Bouley and Sanson had pubhshed observations
or experiments in which anthrax seemed to be present
and the bacteridium absent. But Davaine had replied
to this by showing that these scientists either had failed
to recognize the bacteridium or else had called something
anthrax which was not anthrax.

Leplat and Jaillard, for example, imparted a deadly
malady to rabbits by inoculating them with i)utrid
blood from an anthrax victim, or in default of that, with
bacteria of putrefaction, and did not find bacteridia
in the blood of the dead animals. "Nothing is less
astonishing," replied Davaine, "your malady, and also
that of Signol, is not anthrax. It differs from the latter
in its shorter incubation period, because it is accom-
panied neither by the agglutination of the blood-cor-
puscles nor the congestion of the spleen, the most con-
stant and characteristic symptoms of anthrax, and
because it kills birds, on which the bacteridium has no
effect. Do not be surprised, therefore, that in this new

DAVAINE 239

malady there are no bacteridia in the blood." The
argument was solid, well supported by facts and en-
tirely worthy of the one who produced it.

"This is not all," continued Davaine, "the bacterid-
ium is not simply the inseparable companion of the
disease. It is the cause of it, and the only cause. The
proof is this: As long as the bacteridium is not present
in the blood, the latter is not infectious, and it becomes
so when the organism enters it. If from the sick animal,
some hours before its death, you take blood with which
you inoculate another animal you will not impart to
the latter the disease. If you inoculate it with blood
as soon as the microscope shows bacteridia in it, the
inoculated animal will die. If you wait to make the
inoculation until the bacteridia have disappeared under
the influence of putrefaction, you would then possibly
obtain the malady of Leplat and Jaillard but not anthrax.

''You may say, it is true, that in this experiment,
the blood before, during, and after the appearance of
the bacteridium is not the same blood, or at least may
differ in other ways than that which the microscope
reveals in the presence or absence of bacteridia. But
here is another argument. Take a pregnant animal,
give it anthrax and when it is dead make inoculations
with the blood; it is infectious; at the same time make
inoculations with the blood of the foetus; it is not
infectious. This blood is, nevertheless, the direct
emanation from the blood of the mother from which it
receives through the placenta all the soluble elements.
The placenta, acting as a filter, keeps out only the bac-
teridia and because of their absence the blood of the
foetus is incapable of transmitting anthrax.

"Does not that seem to you proof? Here is another
experiment : Filter blood from an anthrax victim through
a porous earthen filter, as Klebs and Tiegel have done.

240 PASTEUR: THE HISTORY OF A MIND

No solids pass through the filter. The serum passes
through and it is not infectious. The cause of the mal-
ady is, therefore, not soluble in the serum. It remains
on the surface of the filter where there are only red
corpuscles, white corpuscles and bacteridia. Choose
the cause among these three, but choose!"

Davaine was not only ambitious to demonstrate that
the bacteridium was the cause and the only cause of
the development of anthrax: he wished also to explain
by its aid the etiology of the disease, that is to say, the
different conditions governing its natural appearance
and its endemic or epidemic character. In this direc-
tion he was less successful. He had observed, as we
have just said, that putrefaction rendered the blood
incapable of transmitting anthrax. He was obliged,
therefore, to give up seeing in the blood and tissues of
an animal buried as a victim of anthrax the cause of the
revival of the disease from one year to another, in the
same region or pasture. He observed, nevertheless, that
blood rapidly dried preserved its virulence for a
long time. Now, said he, this rapid desiccation must
often occur in countries where anthrax is prevalent;
when animals are slaughtered for the sake of the skins,
pools or drops of blood remain on the ground, on the litter,
on the walls, and these dry rapidly and preserve their
germs. As for the infection of other animals, Davaine at-
tributed it to flies some of which by sucking, and others
simply by means of their feet, are the agents of infection
among animals in stables or the open field, and he sup-
ported all these opinions by well carried out experiments.

There were grave objections to this etiology. If
it is the fly which disseminates the virus, it was said,
why does it sometimes respect so carefully the bound-
aries of a field or an estate? There are in Beauce and
in Auvergne dangerous fields or meadows; the adjoining

KOCH : THE SPORE OF ANTHRAX 241

meadows are not so; why do not the flies pass from one
to the other? And furthermore, if they are the agents
of transmission all the cases of anthrax in animals ought
to begin with a subcutaneous tumor or a lesion of the
mucous membrane, similar to the malignant pustule in
man, the origin of which is always external.

But these cases of external anthrax are very rare
among the domestic animals. It was necessary, there-
fore, to search for some other explanation. But what?
No one knew. In the meantime, as long as the bac-
teridium did not explain or explained so badly the eti-
ology of the disease, the partisans of the theory of spon-
taneous anthrax had a good chance, and the opinion
of the investigators was still wavering when the work
of Koch appeared. This dissipated many of the obscur-
ities and silenced some of the objections.

V

KOCH: THE SPORE OF ANTHRAX

It was in reality this work which introduced into the
question a very important idea, that of the spore, which
plays so great a role in our ideas of to-day, but which
at that time, was unknown or at least abandoned.
Pasteur had observed, in 1863, the formation of spores
in the butj^ic vibrios. But he had not foreseen their
role nor did he know their exact significance. In 1869
he had found them in the vibrios of the flacherie of the
silkworm and, this time, he had proved that these spores,
these cysts, as he called them, had a resistance greater
than that of the rods, and could endure a long drying.
By means of these cysts he had explained the persist-
ence of the epidemics of flacherie in different regions.

242 PASTEUR : THE HISTORY OF A MIND

After Pasteur, Cohn had studied the mode of formation
and the resistance of these spores in Bacillus subiilis, and
had put forth the hypothesis that the bacteria of an-
thrax possibly behaved hke this baciUus. But none
of these precedents detract in the least from the merit
of Koch: it was he who showed the role of the spore in
the etiology of anthrax, and he did it in a way trulj^ mar-
vellous for its simphcity.

If one places in the thermostat or even leaves exposed
to summer heat a drop of fresh beef-blood serum or of
the aqueous humor of the eye, sown with a very small
fragment of fresh spleen from a mouse affected with
anthrax, a microscopical examination at the end of
15 to 18 hours shows the following appearances: in the
center of the slide which covers the preparation, where
the air cannot penetrate easily, the bacilli are in their
original state and have not elongated. Half way, from
the edges of the cover-glass the bacilli are longer, twisted
and bent and so much the more elongated as they are
nearer the margin. Certain ones, those which are most
in contact with the outer air, contain typical spores,
sometimes arranged regularly in the filament like beads
(Fig. 20, left side). Ultimately these free themselves
from the envelope in which they are formed. They
are then disseminated through the liquid like an amor-
phous powder. But this dust is living, for, if transferred
to a new drop of serum, these spores produce at the end
of 3 or 4 hours new bacilli, capable, like the first, of
causing the death of the animal inoculated with them.
There is then no diminution of virulence in passing
through the spore state.

We see that Koch, passing over and beyond Davaine,
who had not thought of it, was not satisfied to repeat
Delafond's cultural experiments. He succeeded in the
first attempt in doing that which Delafond had tried

KOCH : THE SPORE OF ANTHRAX 243

to do in vain — in forcing the rods of the anthrax to
produce spores. Furthermore he gave to this spore an
important place, which it has not since lost, in the eti-
ology of the disease. He did this by showing that it
always forms in the blood and tissues of an animal dead
of anthrax, if the temperature is suitable and there is
sufficient oxygen.

These two conditions are necessary. Below 18°C,
spores are not formed; at 30°C. they occur at the end of
30 hours; at 35°C., in 20 hours. The rapidity with which
spores are formed is, therefore, directly proportional to
the amount of heat. Oxygen is also indispensable.
Anthrax blood, if deprived of this gas, ceased to be vir-
ulent in 24 hours without putrefaction. When the
blood is allowed to putrefy, the virulence also disap-
pears if putrefaction exhausts the oxygen quickly
enough so that the spores have not time to form at the
temperature to which they are exposed. If the spores
have already formed, putrefaction does not kill them
or prevent them from developing ultimately on the same
field or in the same region if circumstances are favor-
able. All the contradictory results of previous investi-
gators on the duration of the virulence of the blood
or of diseased organs, some saying that it could persist,
others that it was lost immediately, were at once
explained. The persistence of the disease and its
return in an infected country was also explained,
and in an entirely natural way. It was the spore which
was the agent of preservation, which persisted where
the conditions of temperature and of aeration had per-
mitted it to form, and where it always held itself in
readiness to make new victims.

Koch was not satisfied in thus broadly explaining
the etiology of the disease. He studied the mode of
transmission, proved that the symptoms of natural

244 PASTEUR: THE HISTORY OF A MIXD

infection revealed infection through the food, and
actually demonstrated that the small animals of the
laboratory could contract anthrax when the anthrax
bacilli or the spores were mixed with their food. For
want of resources he could not make the same experi-
ments on the large domestic animals, and regarding
them he left the question an open one. He also left
undecided the problem of infection by respiration and
through the lungs. But science had nevertheless made
a great stride when, with the discovery of the spore
and its power of resistance, there disappeared one of the
great objections which the etiological conception of
Davaine had raised.

Nevertheless, the victory still remained indecisive,
for a new adversary had arisen. To the affirmation
of Koch, P. Bert had replied in 1887 by an experiment
in which by exposing anthrax blood to the action of
compressed oxygen, he killed or at least believed he
killed the bacteridia. Inoculation of this blood thus
robbed of the parasite produced the disease and death,
without the reappearance of the bacteridia. Therefore,
he concluded, the bacteridia are neither the cause nor
the necessary effect of the anthrax disease. It was
reverting, with new arguments, to the idea of Brauell
which we discussed in the beginning of this short history.

OBJECTIONS TO THE NEW DOCTRINE

From what standpoint could a man, as unfamiliar
with this class of studies as Pasteur, regard the facts
which precede, studying them with his characteristic
vigor? From what standpoint also ought the medical

OBJECTIONS TO THE NEW DOCTRINE 245

men of the time to have regarded these new ideas, ob-
hged as they were to reconcile their desire for the prog-
ress of science with scholastic traditions and the hatred
of innovation, so native to the practitioner. Objec-
tions occurred naturally. These remained vague to
medical men because for the most part they did not
have the laboratory spirit, but they were formulated
^ore clearly in the mind of Pasteur, and behold the
result !

In the first place anthrax appeared clearly to be a
contagious, inoculable disease due to something which
taken in an infinitesimal quantity from a diseased
animal could produce the disease or kill a sound animal
after a period of incubation which was evidently a period
of development and of invasion of the organism. But
what was this something? Was it the anthrax bac-
teridium, as Delafond, Davaine and Koch said? Was
it a virus, as tradition would have it — the tradition
created by what was known of smallpox, vaccine, and
sheeppox, and even by what was supposed to be known
about glanders?

The question does not seem very important to us,
who have made a choice, and who, furthermore, with
our knowledge, and without being misunderstood, are
able to give the name of virus to the anthrax bacteridium
itself. But 20 years ago the domain of viruses and
that of parasites remained separate. M. Chauveau, who
was one of the first to make a remarkable study along
this line, defined virulent diseases as contagious diseases
which were neither caused nor transmitted by a parasite.

This distinction not only seemed well founded, but
determined the direction which research was to take.
A virus could be cultivated only within the animal or-
ganism adapted to it. It could enter it in various ways
and produce in it different manifestations according

246 PASTEUR: THE HISTORY OF A MIND

to the point of entry, but it did not on that account
change its nature, and its entity, its fundamental unity
in the midst of the different phases of the disease which
it produced, was the foundation of the doctrine. With-
out doubt variations in strength, in virulence, had been
observed when a virus was transmitted from one spe-
cies to another, but this had been observed also and even
to a greater degree in the same species; epidemics of
smallpox were more or less benign; smallpox produced
by inoculation was ordinarily less dangerous than that
which had furnished the material for the inoculation.
All of these variations in the severity of the disease or
of the epidemic seemed beyond the reach of experimen-
tation and were attributed to external factors, cold,
heat, or meteorological conditions. Such is the state
to which one was reduced by the impossibility of ob-
serving the virus outside of a living creature.

If, on the contrary, the bacteridium is a ferment, a
parasite, the aspect of the question is changed. We
can cultivate the bacillus outside of the organism, study
its properties, learn its physiology, and compare its
physiological with its pathological role to discover what
effect its normal functions have on the normal functions
of the animal it invades. Disease resulting thus from the
physiological conflict between two organisms which can
be studied separately, its study took a new direc-
tion. It is very clear that Pasteur was not thinking at
this time of variations in virulence among bacteria, nor
of vaccinations. But his was an intellect so keen that
I would not aflSrm that this idea was not in the back-
ground of his mind and I could cite as an argument the
eagerness with which he fell upon the first explicable fact
in this class of ideas. We shall see him at this presently.
In the first place, the important question to be solved
seemed to him to be this: is the essential agent of anthrax

OBJECTIONS TO THE NEW DOCTRINE 247

the bacteridium, or the virus which accompanies this
bacteridium?

Viewed from this standpoint the results of Davaine
and even those of Koch left room for hesitation and
doubt. When one made inoculations, as Davaine did,
with anthrax blood, he inoculated along with the bac-
teridia all the substances accompanying them in the
blood, and among these there might be a substance
in the nature of a virus, developing along with the bac-
teridia in the inoculated animal and escaping observa-
tion because one could not distinguish the virus micro-
scopically from granulations of the organic liquids.
The bacteridium, which can be seen and distinguished,
seems, therefore, to develop alone and to be the exclusive
cause of the malady, when it is possible, that it is only
an epiphenomenon as they say in the medical school

The experiments dealing with the natural filtration
of the blood through the placenta and of artificial filtra-
tion through a porous wall, which Davaine presented
as arguments in favor of the role of causal agent be-
longing exclusively to the bacteridium, demonstrated
only that this active role was not vested in the soluble
elements. We know, since Chauveau's time, that a
virus is a solid organized body which cannot pass
through the placenta or porous plates and which, re-
maining on the surface of the filter with the bacteridium,
may be inoculated with it.

Koch had made more convincing experiments along
this line. He sowed in a drop of serum a tiny drop of
blood or bit of tissue from an anthrax victim, and left
the culture to grow. Then, from this first culture, he
had inoculated a new drop and thus made 8 successive
cultures, the last of which was capable of producing an-
thrax in a healthy animal. But there again, there was
room for a doubt. There was no certainty that the

248 PASTEUR: THE HISTORY OF A MIND

virus was not carried by the blood into the first drop,
thence transferred diluted to the second, third, etc.,
and was still present in sufficient quantity in the last drop
to produce the effect attributed to the bacteridium.
Chauveau's experiments had just shown that viruses
could undergo great dilution, as much as 1/150 for the
vaccine, 1/500 for glanders, which was ranked then,
as we have said, with smallpox and cowpox. These
cultures of Koch's were neither numerous enough nor
made in sufficiently large volumes of liquid to eliminate
the influence of the virus from the dilution. Add to
that the results of P. Bert, which were still perplexing
to the partisans of the new doctrines.

All these objections appear to us to-day as mere hair-
splitting. It is certain that if any one should bring
to us now, for any disease whatsoever, such a collection
of proofs as those which Davaine and Koch furnished
for anthrax, no one would have the least doubt of their
significance. Why? Because the ideas of men of
research and of the public have orientated in this direc-
tion. The weather-vane has turned; but this vane
turned only with much difficulty and much squeaking.
Davaine and Koch had blown at it in vain with all the
power of their lungs, they had succeeded in stirring it but
not in changing its position. It was Pasteur who over-
came all resistance by putting to rout everything which
served as a pretext for immobility and inaction.

This definite orientation of mind and effort was the
more urgent because for 10 years science had struggled
with the difficulties and obscurities of the subject and
multiplied its labors and discoveries without seeing
light burst forth from any side. The ideas of Pasteur
on fermentation did not create a stir solely in the
study of anthrax; the preoccupation with the role of
bacteria in pathology was general. Klebs had found

OBJECTIONS TO THE NEW DOCTRINE 249

organisms in purulent nephritis in 1865; Rindfleisch in
pyemia in 18(36; von Recklinghausen and Waldej^er
in metastatic abscesses in 1865. In 1872 Klebs had
shown how, starting from a wound, bacteria could pene-
trate the lymphatics or the veins by means of the in-
terstices of the connective tissue, and from there infect
the thrombi of the blood vessels or produce abscesses.
Then came the discovery of bacteria in erysipelas,
hospital gangrene, puerperal fever, diphtheria and other
diseases.

But on all these points there was still more legitimate
cause for doubt than in the case of anthrax, and far
from corroborating each other these different discov-
eries succeeded in being almost contradictory. Instead
of bringing order, they seemed to produce confusion. For
example, contrary to what appeared logical, pus of the
same nature and origin contained very different organ-
isms and, on the contrary, forms almost indistinguishable
occurred in very distinct diseases such as smallpox,
diphtheria and cholera. In a general way the organ-
isms discovered in these diseases bore a striking resem-
blance to each other and could scarcely be said to have
any special physiognomy, except the anthrax bacter-
idium, on account of its size and because it was found
in the blood, and the spirillum of recurrent fever, dis-
covered in 1873 by Obermeier, which also passes into
the blood when the fever is at its height, and the spiral
form of which serves to distinguish it. All the other
organisms were alike in form, size and properties, and
this formed an argument of which those who resisted
the contagion of the new ideas were not slow to avail
themselves.

Finally, to complete the perplexity of investigators,
bacteria were not found in some diseases which were
clearly of a contagious nature. After having set up

250 PASTEUR: THE HISTORY OF A MIND

the virus in opposition to the microbe these persons now
asked: Why are not bacteria present in all virulent diseases?
However, an answer to this question was just beginning
to be found in a simple perfection of technique which had
demonstrated the presence of organisms where their ex-
istence was suspected, but where they had not been seen.

Their discovery was easy in anthrax, where they pass
into the blood, even before death. It is more difficult,
even in anthrax, to trace them in the organs of the body.
There were only very imperfect methods for doing that:
the treatment of the tissue with potash, as Davaine
advised, or with acetic acid, as in von Recklinghausen's
method. We cannot be too grateful to C. Weigert for
the great service he rendered in 1875 by teaching us
how to stain bacteria with basic anilin colors, and
thus to make them visible in the tissues. Two years
later, Koch achieved a new advance in technique
by teaching us to study unstained structures micro-
scopically with a very subdued light and stained objects
with a flood of light [structure-picture vs. color-picture].

We see, from this brief exposition, that the science was
mature, and that, moreover, it was thoroughly equipped
for new discoveries. What did it lack? Faith, the
conviction that it would not be deceived on entering
these new paths, and that there were genuine bacterial
diseases. It is this demonstration that Pasteur gave.

YII

PASTEUR: THE BACTERIDIUM IS THE SOLE CAUSE

OF ANTHRAX

To this question : Is it a virus? Is it a microbe? Pas-
teur was happily in a better position to reply than any
one would have been in 1877. From his Etudes sur

THE BACTERIDIUM IS THE SOLE CAUSE OF ANTHRAX 251

la Mere, and his contests with his opponents, he came
out well equipped, with a perfected technique, and a
knowledge both of bacterial species and of how to grow
them. To solve all these problems he could draw only
from his own depths, and this he showed at once.

Old observations and experiments had taught him
that the blood of a sound animal, taken as it circulates
in the veins and exposed to air which is free from germs,
does not putrefy at the highest temperatures, nor give
birth to any organism. It seemed to him probable,
therefore, for he knew nothing then of the cultural ex-
periments of Delafond and of Koch, that the blood of
an animal infected with anthrax, if sown in a suitable
medium, would stock it solely with anthrax bacilli which
he could then keep pure for an indefinite time in suc-
cessive cultures, as he had done with yeast and other
ferments.

Experiment proved it to be so, and showed that this
bacteridium multiplies abundantly in urine made neu-
tral or slightly alkaline. Fron that time, the problem
was solved. Let us take a series of cultures of this
bacteridium transferring each time one drop from the
preceding culture into 50 cc. of fresh urine. The first
dilution is 1/1000, the second 1/1,000,000, the third
1/1,000,000,000, etc. After ten cultures it falls to
such a figure that the original drop of blood which
furnished the first sowing, has been, so to speak, drowned
in an ocean. Everything that it carried with it, to
which we might be tempted to attribute a role in the
production of anthrax — red corpuscles, white corpuscles,
granules of all sorts — are either destroyed by the change of
medium or are widely disseminated in this ocean and are
lost there. Only the bacteridium has escaped the dilution
because it has multiplied in each of the cultures.
But a drop from the last culture kills a rabbit or guinea

252 PASTEUR: THE HISTORY OF A MIND

pig as surelj^ as a drop of anthrax blood. It is, there-
fore, to the bacteridium that the virulence belongs.
Behold a conclusion of the first rank firmly established,
avoiding the objection which could be made to the
corresponding conclusion of Koch, because Pasteur,
at this time, knew how to make with certainty an in-
definite series of cultures, while Koch learned to do
this only later. Such is the advantage of technique.

This first step taken, we can ask ourselves how the
bacteridium acts. Does it secrete a soluble poison
which spreads about it in the liquid, as it undoubtedly
spreads in the tissues of an attacked animal to produce
the disease and kill it? No, for the liquid of the culture,
filtered through a porous membrane and injected in
any desired quantity into a rabbit, barely makes it sick.
This time it was Davaine's experiment but carried on
under convincing conditions because the experiment was
not with a complex liquid like the blood, but with an
artificial culture of the bacteridia.

Finally there remains the hypothesis that the bac-
teridium itself produces a virus in the form of living
granules which it disseminates in the liquid or in the
tissues, and which alone is the active agent. This
hypothesis accepts the bacteridium: its only object is
to connect the bacteria with the virus, whereas the actual
current of events is, on the contrary, to connect the
virus with the bacteria. But it matters not! To this
objection, Pasteur and Joubert responded that nothing
suggestive of virulent granules can be seen in the liquid
of a bacterial culture even when examined with the
highest magnifications. There- are only well-defined
filaments, floating in the midst of a perfectly clear liquid.
We have the right to consider this reply as insufficient,
since nothing is to be seen in the yellow serosity of some
pustules of sheeppox, yet we know that it is virulent.

CONFLICT OF THE MICROBE WITH THE ORGANISM 253

Strictly speaking, it is entirely possible that a virus
should exist in the sense formerly attributed to this
word, produced by the bacteridium and accompanying
it in all its cultures. But this is the essential thing,
that it is not produced independently of the organism,
and that, consequently, whatever the mechanism of
its action, the bacteridium is the sole cause of anthrax.

This is the demonstration which the note of April
30, 1877,^ gave with a clearness and conciseness truly
marvelous. It was said at the time and has been
repeated since, that it was unnecessary, and that the
proof which it set forth had already been made and
accepted by many scientific men. Yes, but it was not
accepted by all, and those who did accept it were in-
capable of convincing others. Some of us had faith,
nobody had assurance or certainty. Henceforth, there
was a sure beginning of things, and a method of work:
one could go ahead, and Pasteur made haste to reach
the goal before the others.

VIII

CONFLICT OF THE MICROBE WITH THE ORGANISM

In order to comprehend thoroughly the history of
his efforts from this time on and not to be too much
impressed with their seemingly disconnected character,
we must recall the fact that Pasteur was neither a
physician nor a veterinary surgeon, and that the history
of any disease, as a disease, did not interest him deeply.
That which he studied in the anthrax bacteridium was
not the anthrax, but the mode of reaction of the microbe

^ Pasteur et Joubert, Charbon et septioemie, Comptes rendus de
I'Academie des Sciences, 1877.
19

254 PASTEUR : THE HISTORY OF A MIND

toward the organism in which it developed. Every
bacterial cell able to become pathogenic in any way or
by any means whatsoever, and thus to throw light on
the mechanism of the struggle with the cells of the host
organism, was welcome in his laboratory.

It was for this reason that he sometimes passed so easily
and so rapidly from one organism to another. It was also
the reason why he was so indifferent to their morphology.
A clever and positive micrographer who came to him
one day and told him in very cautious language that
a certain microbe which he had taken for a coccus was
in reality a very small bacillus, was very much aston-
ished to hear him reply: "If you only knew how little
difference that makes to me." Perhaps he carried this
disregard of anatomical detail a little too far. But
his rule was to attack at once the most important things
and to neglect trifles.

With his prodigious insight, he had divined at once
that, for the solving of these problems, he had a weapon
which none of his predecessors had possessed. He was
able, as we have said, to study, in pure culture, the
physiological properties of the bacteridium, or of any
other microbe, and to compare them in their pathological
reaction. In other words, he could estabhsh the eti-
ology of the disease, not only by estabhshing more firmly
than had hitherto been done a relation of cause and
effect between the microbe and the disease, but by
connecting each one of the symptoms of the disease
with the reaction of the physiology of the micro-organ-
ism on that of the tissues. This was the new program,
which he pursued instinctively, perhaps without delib-
erate intention, but led by his habits of mind and the
trend of affairs in his laboratory. At once, he reaped
a harvest of discoveries.

For example, the anthrax bacteridium is aerobic,

CONFLICT OF THE AIICROBE WITH THE ORGANISM 255

as Koch had seen, and must have contact with oxygen
in order to live. Therefore, as soon as the bacteria
reach the blood they struggle with the red corpuscles
for the possession of this gas, and, consequently, the
latter are asphyxiated. Thus, clearly, originates the
black color of the blood and viscera at the moment
of death, which is one of the most marked character-
istics of anthrax.

These corpuscles of anthrax blood are, furthermore,
agglutinated and massed together. Why? Because
of a secretion of the bacteria. Anthrax serum filtered
and mixed with fresh normal blood agglutinates the
corpuscles as much and even more than occurs natu-
rally in the disease, due, without doubt, to a diastase
which the bacteria have secreted in the culture medium.
Here we have the first example introduced into science
of a bacterial secretion producing one of the symptoms
of a disease.

The second, still more striking, was taken some months
later from the history of chicken cholera. One of the
most curious symptoms of this disease is the uncon-
querable somnolency which overtakes the diseased
fowls. But one can produce a somnolence entirely
similar though less profound by inoculating a healthy
animal with a filtered culture of the microbe of chicken
cholera. The filtered liquid is free from the microbe
but contains substances secreted by it, which we call
to-day its toxines, and this word alone is sufficient to
recall all that has sprung with time from this fundamen-
tal observation of Pasteur concerning which we have
just spoken.

We are not yet done with this note of the 16th of July,
1877, from which we have derived the preceding facts.
There are some species of animals which are refractory to
anthrax. Such are the birds. Nevertheless the blood

256 PASTEUR: THE HISTORY OF A MIND

of a bird, drawn from the animal, is an excellent culture
medium for the bacteridium. Why does it resist in-
fection in the animal? Because "the living blood in
full circulation is filled with an infinite number of cor-
puscles which in order to live and perform their physio-
logical function, need free oxygen: it might be said that
the blood corpuscles are obligate aerobes. When, there-
fore, the anthrax bacteridium, enters normal blood,
it meets there an enormous number of organic indi-
vidualities ready, figuratively speaking, for what one
sometimes calls the struggle for existence, ready, in
other words, to seize for their own use the oxygen nec-
essary for the existence of the bacteridium."^

We see developed here the formula and the ideas of
Darwin, but in a singularly precise form. What could
be more vague than the phrase ''struggle for existence?"
But "struggle for oxygen," that opens the way to ex-
perimentation, and Pasteur begins at once.

Some common bacteria sown wdth the anthrax bacter-
idium, in neutral or alkaline urine, prevent its developing
because they take possession of the ground more rapidly
and exhaust the oxygen. They can, in the same way,
arrest its development in an animal. "It is possible
to inject great quantities of the anthrax bacteridium
into an animal without its contracting the disease, if
some of these common bacteria have been present in
the culture used." Here we have the first example of
baderiotherapy , to which Cantani returned later, and
which has not spoken its last word.

The interpretation of these facts has changed, and
we know now that it is less simple [than it seemed at that
time] but the idea of the struggle for existence was never-
theless then introduced into patholog}^, in the domain
of cellular antagonism: and it has remained there.

' Comptes rendus do I'Academie des Sciences, 16 juillet, 1877.

THE SEPTIC VIBRIO 257

IX

THE SEPTIC VIBRIO

This idea also shed a light over the past. We have
seen that MM. Leplat and Jaillard had contested the
interpretations of Davaine by showing that an animal
inoculated with putrid anthrax blood died quickly with
symptoms analogous to those of anthrax, but without
having bacteridia in the blood, a proof to them that the
presence of the bacteridium in anthrax was only an
epiphenomenon. To that, Davaine had replied that
the disease produced by Leplat and Jaillard was not
anthrax, but differed from it in the length of the incu-
bation period and in many other ways. He was right,
but exacting minds, and it is always necessary that there
should be such in science, were justified in finding his
reasons insufficient. It might be, after all, that the
disease produced by Leplat and Jaillard was the true
anthrax and Davaine's was an anthrax modified by
the presence of the bacteridium. The intervention of
this microbe might well change the symptoms, modify
the evolution of the disease, and permit it to attack
other species of animals.

How was one to meet this objection, which was like
viewing the same facts through opposite ends of the
lorgnette? There would have been one way, viz., to dis-
cover the cause of Leplat and Jaillard's disease. But
in his attempt to do this Davaine was shipwrecked, in
spite of his efforts. He had found the anthrax bacillus
in the blood: it was in the blood that he searched ob-
stinately for the second disease but he found nothing
there. If it had occurred to him to examine the tissues
he might have found myriads of the organisms which he
sought. The abdominal serosity in particular is full

258 PASTEUR: THE HISTORY OF A MIND

of them, it is almost a pure culture of the microbe (Fig.
21), while in the blood the rods are rare, more elongated
and difficult to find in the midst of the corpuscles; fur-
thermore, they enter the blood late in the course of
the disease and Davaine had not seen them there. Thus

Fig. 21. — The septic vibrio in the alxloininal serosity and in the blood.
In the serosity the forms are variable. In the blood they are long filaments,
infrequent and hard to see in the midst of the corpuscles.

it is that one can just fail of making the most beau-
tiful discovery.

Pasteur, for whom everything was a pretext for micro-
scopical study, did not allow this opportunity to escape,
and threw himself with his customary ardour into the
study of this new microbe. There also, a harvest of
facts awaited him.

THE SEPTIC VIBRIO 259

This one, immediately: This organism is a common
one. The disease which it causes is identical with
that which Signol had produced, two years before, by
inoculating with blood taken from the deep-lying veins
of a healthy animal, asphyxiated 15 or 20 hours. In
this case the bacteria reach the blood by way of the
intestinal canal which often contains millions of them,
but where they are harmless. Only after death do they
pass the barrier which this canal opposes to them, and
reach the organs and the blood.

It was the same bacterium that was present in Leplat
and Jaillard's putrid anthrax blood: as the disease which
it causes develops more rapidly than anthrax, it gets
the better of the latter in the animals which have been
inoculated with this blood and we see it alone. Davaine,
therefore, was right. The animals which Leplat and
Jaillard inoculated did not die of anthrax, and it was
left for Pasteur to tell what killed them.

Finally, it was probably this same organism which
caused the illusion of P. Bert. The blood in which he
beheved that he had killed the bacteridia with oxygen,
and which gave anthrax without microbes when inocu-
lated, very probably contained Signol's organism pro-
tected by its spore stage against the action of oxygen,
and bringing to the inoculated animal the disease of
which it is the agent. ^

Thus disappeared with one wave of the wand the
greatest of the objections to the new etiology of anthrax.
But this was not all. Pasteur made haste to subject
the new bacterium, which he has made famous under
the name of septic vibrio, to that physiological study

1 This disease, common to man and various domestic animals, is known
variously to-day as gangrenous septicemia, malignant oedema, traumatic
gangrene, gaseous gangrene, etc. It is believed to be due to various
distinct anaerobes called Vibrion sepiique, Bacillus osdematicus, Bacillus
welchii, Bacillus egens, etc. Trs.

260 PASTEUR: THE HISTORY OF A MIND

which had been so successful with the anthrax bac-
teridium. He saw at once that he could cultivate
it only in the absence of air, as it was an obligate an-
aerobe.

Therefore, he concluded, with the assurance that long
practice had given to him, it is a ferment, and, in fact,
in culture media it liberates gas, forms carbonic acid,
hydrogen and a small amount of hydrogen sulphide
which imparts an odor to the mixture. How is it that
this fact was not deduced at once from that other fact,
namely that when a post-mortem is made on an animal
which has died of septicemia, we find tympanites, gas
pockets in the cellular tissue of the groin or of the axilla,
and frothy bubbles in the serosity which flows from all
points in the body when an opening is made The
animal exhales a characteristic odor toward the end
of its life. Its parasites, driven out it ma}^ be by this
production of hydrogen sulphide, leave the skin to take
refuge at the extremity of its hairs. In short, septicemia
may be termed a putrefaction of the living organism.

When the anaerobic character of the septic vibrio
was once discovered, a series of logical deductions at
once presented themselves.

"When a liquid containing the septic vibrio is ex-
posed to pure air, the bacteria ought to be killed and
all virulence destroyed. That is what happens. When
some drops of septic serosity are spread out in a very
thin layer in a tube placed horizontally, in less than half
a day the liquid becomes absolutely harmless, even
though in the first place it was so virulent that inocu-
lation with the very smallest fraction of a drop would
produce death.

"Furthermore, all the vibrios which occur in profusion
in the hquid in the form of motile filaments, are de-
stroyed and disappear. We find after this exposure

THE SEPTIC VIBRIO 261

to the air only fine amorphous granules, which cannot
be cultivated and which will not communicate any
disease whatsoever. One might say that the air burns
up the vibrios.

"If it is terrifying to think that hfe is at the mercy
of the multiplication of these infinitely small organisms,
it is, on the other hand, consoling to hope that science
will not always remain powerless before such enemies,
since having barely begun the study of them, she has
taught us, for example, that simple contact with the
air is sometimes sufficient to destroy them.''^

The progress we have just made seems perplexing
in the light of what we already know. How can sep-
ticemia exist if air destroys the vibrios? How can the
blood, kept in contact with the air, become or remain
septic? How did Leplat and Jaillard, who had no idea
of anaerobic life and its demands, obtain, almost at
once, septicemia in the animals they inoculated? The
reason for this is that all we have said is true for vibrios
in course of development but it does not hold good for
the spores. The latter do not form in contact with air.
They are not produced in the serosity spread out in a
thin layer such as that just described. But place the
same quantity of serosity in a tube of small diameter
which we keep upright, and allow the oxygen to act on
it in the same way and all will be changed. The vibrios
on the surface die by absorbing oxygen and thus protect
those in the depths, which have time to form spores.
The latter, once formed, have nothing to fear from the
air, and the liquid which the oxygen had rendered harm-
less in the first instance, here remains virulent, because
instead of being in a horizontal tube it is in a vertical
one.

1 La Theorie des germes et ses applications a la Medecine et a la
Chirurgie. Lecture faite a I'Acad. de Medecine, le 28 avril, 1878.

262 PASTEUR: THE HISTORY OF A MIND

Pasteur who believed he could never accumulate too
much proof in support of his opinion, was here not un-
mindful of the fact that the animate cause of certain
virulent diseases was still contested. He had a beautiful
argument to add to those which he had already given
on anthrax. He made it instantly in the same shrewd
way that he made an ingenious analysis.

"We should search," he says, "for proof that apart
from our vibrio there is no independent virulence pecu-
liar to liquids or solids, that, in short, the vibrio is not
simply an epiphenomenon of the disease of which it
is the obligate associate" (l. c). Here are two liquids
which are identical in the beginning, exposed to air for
the same length of time. One remains virulent, the
other does not.

They continued originally and both still contain two
kinds of substances — solids and fluids. To which does
the virulence belong? It is evident that the substances
in solution have remained the same in both cases. It
is not possible to imagine any action produced on them
by the air which would not be alike in both tubes. Only
the solids, and there are none except the vibrios, have
undergone a change, being converted into resistant spores
in one case, and harmless granules in the other. It
is, therefore, to these alone that the virulence must be
attributed.

We have not finished. We have just demonstrated
that the spore is the resistant aerobic form of the anae-
robic vibrio. How does it return to the vibrio stage?
This is equivalent to asking, since the spore-form occurs
everywhere, under what circumstances does it again
become dangerous? We shall soon see with what bril-
liancy Pasteur answers this question.

A COMMON MICROBE MAY BE PATHOGENIC 263

m

X

A COMMON MICROBE MAY BE PATHOGENIC

The septic vibrio, we have said, occurs everywhere.
Ahnost always there are bilUons of them in the intes-
tinal canal of all animals. We invariably find them
in the soil, and, from studies on the etiology of anthrax,
which we shall meet again shortly, Pasteur was con-
vinced that the chances were very great that a guinea
pig or a rabbit inoculated with drainage water from
any soil whatsoever would die of septicemia.^

Here, therefore, we have a very common organism,
which we discover to be very dangerous and capal)le
of causing a deadly malady when it enters the tissues
through a wound. Why this penetration of the tissues
does not occur more often and why the malady induced
thereby is not inscribed on the list of prevalent diseases
was an embarrassing question, and one with which the
partisans of the theory of the spontaneous generation
of disease should have triumphed. ''You see clearly,"
they might have said, ''that something more than the
microbe is needed to make us ill, since in this case we
so often find the organism and so rarely the disease."
Pasteur knew well that he laid himself open to attack,
since this theory would not be easily accepted, that a
common organism could become pathogenic under cer-
tain conditions and at certain times, and it was for
this reason that at the end of his Note to the Academy
of Medicine he gathered together examples and proofs
of this fact. This Note, which seems a little disconnected,
is unified only when it is regarded in this light.

1 Examinations made during the late German war, in which gas gan-
grene very commonly followed neglected wounds, indicate that this
organism or one acting like it occurs in practically every gram of soil in
Northern Fraace and Belgium. Trs.

264 PASTEUR : THE HISTORY OF A MIXD

His method was as follows: to demonstrate for the
septic vibrio that the return of the spore to activity
and to virulence does not depend on the obscure questions
of vital force or vital resistance, which medicine invokes
so readily, but that it is simply a question of the pres-
ence or absence of oxygen; then, when he had thus
smoothed the way, to marshal together and launch,
somewhat pell-mell, other analogous facts regarding
the ability of water- and soil microbes to become patho-
genic. Now that we know his plan of campaign let
us see how he carried it out.

In the first place let us ask if "the germ corpuscles
of the septic vibrio, although formed in a vacuum or
in pure carbonic acid gas, would not need, in order to
become active, a small quantity of oxygen. Physiology
does not know to-day of any case in which germination
is possible in the absence of air.^ So be it! nevertheless,
experiment has shown that the germs of the sepic vibrio
are absolutely inactive in contact with oxygen, whatever
may be the proportion of this gas; but this is always
on condition that there is a certain relation between the
volume of air and the number of germs, for the first
germinations, using up the air which is in solution, may
serve as a protection for the remaining germs, and it is
thus that, actually, the septic vibrio may propagate itself
even in the presence of small quantities of air, but not
if much air is present."

That is, if, in addition to the septic vibrio, there are
present common aerobic bacteria, the latter by de-
veloping, prepare the way for the former. Thus it is
that the vibrio develops in the intestinal canal, which is
ordinarily destitute of oxygen, and Pasteur here recog-
nized once more the role played by associations of bac-

1 Rice and some otlier seeds are now known to germinate in this way.
See paper by Takahashi. Bull. Imp. Agr. Col., Tokyo, 1905. Vol. G,
p. 439, Trs.

A COMMON MICROBE MAY BE PATHOGENIC 265

teria which we have dwelt upon throughout this book
and which he understood so well.

Preoccupied as he was with the application of these
facts to medicine, he could not fail to write, at this stage,
the following lines, the advantage of which we shall
find once more at the end of this chapter.

"A curious therapeutic observation presents itself.
Let us suppose a wound exposed to the air and under
putrefying conditions leading to the accident of simple
septicemia in the patient, I mean without other compli-
cations than would result from the development of the
septic vibrio. Theoretically, at least, the best means of
preventing death would be to wash the wound unceas-
ingly with common aerated water, or to fiood the sur-
face with atmospheric air. The adult septic vibrios,
about to divide by fission, would die in contact with
the air; as to their germs, they would not grow.
Furthermore, one might expose the surface of the wound
to air heavily charged with the germs of the septic
vibrio, or wash it with water holding in suspension billions
of these germs without producing the least septicemia
in the patient. But under similar conditions let a single
clot of blood, or a single fragment of dead flesh, lodge
in a corner of the wound sheltered from the oxygen of
the air, where it remains surrounded by carbonic acid
gas, even though it might be over a very small area,
and beginning at once the septic germs will give rise?
in less than 24 hours, to an infinite number of vibrios
multiplying by fission and capable of causing in a very
short time a mortal septicemia."

And immediately, through the door he has opened,
he passes a whole series of similar cases. There is,
for example, in common waters from the most varied
sources, another vibrio both aerobic like the bacter-
idium of anthrax and anaerobic like the septic vibrio.

266 PASTEUR: THE HISTORY OF A MIND

inoculation of which into a guinea pig produces pus
collections or abscesses, that is to say, a pathological
condition very different from that produced by either
the anthrax bacillus or the septic vibrio. Its power of
producing pus is so great that it still does so even though
the inoculation is made after the vibrio has been killed
by the action of heat and thus it behaves like an inert
body. This should interest you, you medical men,
we seem to hear Pasteur saying, for, with this organism
one can obtain those celebrated metastatic abscesses
which have puzzled you so much from the time of
Hippocrates. When it is inoculated, living or dead,
into the veins so that the circulation will distribute
it throughout the tissues, we see the lungs, the liver
and other organs filled within 24 hours with an infinite
number of metastatic abscesses in all stages of develop-
ment. Why should it be astonishing that a diseased
organ can do the same thing in a living being, if it emp-
ties its parasites into a blood vessel?

Here again, as is always the case in ordinary water
and in the air, there are other anaerobic vibrios which,
when introduced into the tissues, do not develop there
for various reasons: in one case, because the normal
temperature of the body is too high; in another case,
because the healthy tissues are too well supplied with
oxygen. But diminish in any way whatsoever this
vital resistance, which, mark my words, has no abstract
significance in my discourse, and always represents a
concrete force, and you will see these microbes hitherto
dormant, take possession of the organism and combine
their actions and efforts to produce purulent septi-
cemias or purulent septic infections. These are the
enemies with which we are threatened on all sides in
ordinary life, and to which we are still further exposed
when the surgeon intervenes and causes or repairs lesions

A COMMON MICROBE MAY BE PATHOGENIC 267

in the tissues. "This water, this sponge, this hnt with
which you wash or cover a wound, deposit germs there
which, as you see, have an extreme facility for multiplying
within the tissues and which would infallibly cause the
death of the patient in a very short time, if the body
by its vital processes did not check the multiplication
of these germs. But alas, how many times this vital
resistance is impotent, how often the constitution of
the wounded man, his weakness, his morale, and bad
dressing of the wound oppose only an insufficient barrier
to the invasion of these infinitely small organisms with
which, unwittingly, you have entirely covered him in the
injured part. If I had the honor to be a surgeon,
impressed as I am with the dangers to which the patient
is exposed by the germs of microbes scattered over the
surface of all objects, particularly in hospitals, not only
would I use none but perfectly clean instruments, but
after having cleansed my hands with the greatest care
and subjected them to a rapid flaming, which would ex-
pose them to no more inconvenience than that felt by a
smoker who passes a glowing coal from one hand to
the other, I would use only lint, bandages and sponges
previously exposed to air of a temperature of 130° to
150° C; I would never use any water which had not been
subjected to a temperature of 110° to 120° C. All this
is very practical. In this way, I would only have to fear
the germs in suspension in the air around the bed of the
patient; but observation shows us daily that the num-
ber of these germs is, so to speak, insignificant in com-
parison with those distributed in the dust on the surface
of objects, or in the clearest ordinary water. And, fur-
thermore, nothing should prevent the use of antiseptic
methods in dressing wounds, but, joined with the pre-
cautions I have indicated, these methods of procedure
could be very greatly simplified. A weak phenic acid.

268 PASTEUR: THE HISTORY OF A MIND

which consequently does not affect the hands of the
operator, or cause him trouble in breathing, could be
advantageously substituted for a caustic phenic acid."

it was in this way, scarcely raising the tone of his
voice, and without any high sounding phrases but
merely by following rigorously and patiently the thread
of his thought that Pasteur compelled surgeons to per-
fect the methods for dressing wounds which had been
employed by Lister, and which had themselves been
such a great discovery. These methods had been in-
spired by an inexact idea as to the true state of affairs,
an idea which Pasteur had shared, as we have seen, but
from which he detached himself, more and more.
This idea was that the air, especially, was to be feared
as the conveyor of germs. In this memorable note,
we have Pasteur laying the blame upon the sponges,
the lint, and, without wishing to put it into so many
words, upon the surgeon himself.

To make this idea acceptable to the illustrious prac-
titioners, his colleagues in the Academy of Medicine,
that they were responsible for the accidents which oc-
curred to their patients, and that when there was a
case of death by purulent infection in their service, or
even merely a case of operative fever it was their fault,
was a task that Pasteur had not ventured to assume,
and yet one which he accomplished; because the new was
certain to destroy the old, because it was only necessary
to leave to itself the idea lodged in this Note in order
to see it invade and overthrow everything. Modern
surgery has arisen full fledged from this Note of 1878,
the general outlines of which we have just traced.

"Some weeks ago," said Pasteur in conclusion, "one
of the members of the Section of Medicine and Surgery
of the Academy of Sciences, M. Sedillot, after long
meditation on the things he had learned in the course

NEW EXAMPLES OF PHYSIOLOGICAL CONFLICTS 269

of a brilliant career, did not hesitate to declare that
success and failure in surgery found a rational explana-
tion in the principles on which rests the so-called theory
of germs, and that this would give rise to a new surgery,
that already inaugurated by a celebrated English surgeon,
Dr. Lister, who was one of the first to understand its
fecundity. Without any professional competence, but
with the conviction of a qualified experimenter, I ven-
ture to repeat here the words of our eminent confrere."

XI
NEW EXAMPLES OF PHYSIOLOGICAL CONFLICTS

In this rapid review of the etiological work of Pasteur
I have naturally omitted some details which seem to
me secondary, and some ideas which would have con-
stituted merely replicas of ideas already well-known.
Pasteur studied, or caused to be studied under his eyes,
all the bacteria which he could find, however little patho-
genic they were or appeared to be. As I have said,
that which interested him was the pathological conflict
between the physiological properties of the micro-
organism and of the cells of the tissues, and for examples
of this conflict he searched everywhere.

As the laboratory was not a hospital we scarcely saw
diseases there; he was obliged to profit by the indisposi-
tions of the personnel. I was, just at this moment,
beset by a series of boils and the first thing that Pasteur
did when I showed him one of them was to prick it,
or rather have it pricked, for he was not fond of operating
himself, and to take therefrom a drop of blood in order
to make a culture, in which undertaking he was success-
ful. A second boil gave the same result, and thus the
staphylococcus was discovered which since that time

20

270 PASTEUR: THE HISTORY OF A AIIND

has been so well known. He found the same microbe,
made up of little agglomerated granules, in the pus of
an infectious osteomyelitis which AI. Lannelongue had
submitted to him for examination, and we see liim,
declaring immediately with a fine audacity that the
osteomj-elitis and the boil are two forms of one and the
same disease, and that the osteomyehtis, which is a
suppuration of the marrow, is the boil of the bone.
What could be worse than to liken a grave malady
taking place in the depths of the tissues to a superficial
malady, which is generally trifling! To confound
internal and external pathology! When he launched
this opinion before the Academy of Medicine, I picture to
myself the physicians and surgeons present at the meet-
ing staring at him over their spectacles with surprise
and uneasiness. Nevertheless, he was right, and this
assertion, daring at the time, was a first victory of the
laboratory over the clinic.

A second followed straightway: "In the puerperal
infections, the pus of the uterus, that of the peritoneum,
and the blood-clots in the veins contain a microbe
occurring in the form of rounded granules arranged in
chains. This chaplet-like aspect is especially apparent
in the cultures. Pasteur does not hesitate to declare
that this microscopic organism is the most frequent
cause of infections among women in confinement. One
day, in a discussion on puerperal fever at the Academy
of Medicine, one of the most renowned of his colleagues
made an eloquent dissertation on the causes of epidemics
in the maternity hospitals. Pasteur from his place
in the audience interrupted him: 'The cause of the
epidemic is nothing of the kind! It is the doctor and
his staff who carry the microbe from a sick woman
to a healthy woman!' And when the orator replied
that he was convinced that no one would ever find this

I

NEW EXAMPLES OF PHYSIOLOGICAL CONFLICTS 271

microbe, Pasteur darted to the blackboard and drew
the organism with its chaplets, saying: 'There! There
is its picture!' His conviction was so strong that he
could not refrain from expressing it forcibly. One
can scarcely understand to-day the surprise, and the
stupefaction, even, of the medical men and their students
when at the hospital, with a simplicity and an assurance
which seemed presumptuous in a man who was entering
a lying-in hospital for the first time, Pasteur criticised
the methods of dressing wounds, and declared that all
bandages should be placed in a sterilizing oven. Further-
more, he maintained that he could tell by examination
of the lochia, which women would have an attack of
puerperal fever, and he assured them that in a woman
who was very badly infected he could demonstrate
the microbe in the blood of the finger. And he was as
good as his word. In spite of the tyranny exercised by
the medical education which weighed heavily at that time
on the minds of the students, some of them were capti-
vated and came to the laboratory to observe at closer
range those methods which afforded diagnoses so exact
and prognoses so sure."^

I will cite only one more fact, which in some degree
forms a connection with what is to follow. In the course
of this search for microbes which has been so fruitful,
Pasteur encounters a bacterium which cannot develop
under the skin because the temperature of the human
body is a little too high for it. Immediately his thought
reverts to the anthrax bacteridium which is unable to
develop in birds, and he asks himself if this does not
result from the high temperature of these animals,
which is always in the neighborhood of 42° C. What
would happen if one could lower the temperature of

1 L'ffiuvre medicale de Pasteur, par le Dr. E. Roux, Agenda du chim-
jste, 1S9G.

272 PASTEUR: THE HISTORY OF A MIND

an inoculated chicken some degrees? The success of
the experiment was immediate. A chicken, the feet
and hind quarters of which were plunged into water at
25° C, so that the temperature of its whole body was
lowered to 37-38"^ C, which is the temperature of animals
susceptible to anthrax, died of this disease, although
resistant to it under normal conditions. If the chicken
is taken from the water and heated at the time when
the first symptoms of invasion of the tissues appear,
it triumphs over all the parasites and recovers. Later
Gibier made the reverse experiment, giving anthrax
to frogs which are not susceptible to this disease because
they are cold-blooded animals, the body temperature
being too low. To accustom them little by little to
living in warm water, suffices to render them capable
of succumbing to anthrax when their body temperature
has been thus raised. The interpretation of these two
facts is less simple then Pasteur supposed it to be and
we shall meet them again very soon in connection with
variations in virulence. I cite them only as further
evidence of his tendency to relegate everything as much
as possible to the domain of physics and chemistry,
to study, in the light of these two sciences, the physio-
logical properties of the microbe and to oppose these
properties to those of the tissues.

However broad-minded one may be, he is always
to some extent the slave of his education and of his past.
It is clear that Pasteur inclined naturally to the side
of chemistry, and there were not lacking men to reproach
him for this. To this chiding he always disdained to
respond. Doubtless he thought it was not worth while,
and that he must be content to pity those who believed it
possible for a vital problem to be something other than a
problem of physics and chemistry. This will be still more
evident in the study which we shall make of virulence.

PASTEUR

(Int. Med. Congress at Copenhagen, 1884.)

(Courtesy of Capt. .1. C. Pryor, Naval Med. School, Washington,

D. C.)

EIGHTH PART
The Study of Viruses and Vaccines

]\nCROBIAL DISEASES AND VIRUS DISEASES

What idea could one have, about 1880, of virulence
as we understand it to-day? The answer is easy if one
is willing to regard it from the point of view of our
actual knowledge. Considerable variation in virulence
had been determined in various microbial diseases,
but it was not known whether they had the character
of the virus diseases, that is, would not recur in the same
individual. For the true virus diseases, such as small-
pox and cowpox, the established variations in virulence
were feeble, and supposed to be dependent, as we have
seen, on external conditions, which amounts to saying
that they were unexplained.

This point of view shows us clearly the difficulties
of the question, but it is not from this standpoint that
out observations should be made. What could one
think at that time concerning the relation between
microbial diseases and the virus diseases, is what
we must ask ourselves. Strange to say, one thought
nothing! These were two territories separated by an
arm of the sea over which there was no bridge. From
one of the continents a person might indeed from time
to time glimpse the other and observe its outlines,
but both seemed isolated and equally impenetrable.

For Pasteur alone, the man of the large horizons,
they were in some places in contact. The careful

273

274 PASTEUR: THE HISTORY OF A MIND

reading of the works of Jenner and his followers had
left a profound impression on the mind of the master,
and by correlating incessantly in his thoughts the
teachings of the books and those of the laboratorj', he
had formed a general impression which I desire to
summarize, relying not simply on my own recollections,
but also on that of his collaborators at this memorable
time.

On the subject of variation in power of microbes to
attack there existed only the curious results obtained by
Coze and Feltz in 1869, confirmed since then by Davaine
for the anthrax bacteridium, and especially for the dis-
ease of Leplat and Jaillard. The virus increased in
strength by passage through the organism. The blood
of the first animal inoculated was fatal to a second only
in a dose, let us say, of one-tenth of a drop. The fatal
dose decreased little by little with successive animal
passages to that of a hundredth, a thousandth, a millionth
of a drop. This fact was the only one of its kind. It
was eminently curious and suggestive. It would have
been more so if there had not been needed, in
order to realize it, the cooperation of the organism,
at cross purposes with which everything becomes ob-
scure. Men so little dreamed of ascribing the increased
virulence to its true origin, the microbe itself, that when
Pasteur, in his study of the septic vibrio, finds cultures
which prove to be unequally active in animals, his first
thought is that he has two or several septic vibrios of
unequal virulence, which the cultures have separated
more or less completely. Under this impression he
carried on investigations for a long time without result.
It was only when he discovered that a simple change
in culture method, namely, the substitution of a blood
serum slightly charged with coagulated fibrine for Liebig's
bouillon, suddenly increased the virulence of a vibrio

MICROBIAL DISEASE AND VIRUS DISEASES 275

which for 20 or 30 generations had shown itself to be
attenuated, that he accepted the idea that these varia-
tions depended on one single vibrio and its culture
medium.

It was a great step indeed; but beyond this there was
nothing, and in order to see farther it was necessary
to consider the virus diseases. The latter presented
facts analogous to those of Coze and Feltz, and Davaine.
It was known that there w^ere benign epidemics of small-
pox and others that were deadly, that the severity was
variable in the course of the same epidemic, and generally
diminished as it drew to a close. It was also known from
the practise of smallpox inoculation, resorted to before the
time of Jenner, that inoculation from a benign case of
smallpox ordinarily produced a smallpox still more
benign, but this was not always true, for sometimes
the inoculated patient died.

The vaccine introduced by Jenner had been a wonder-
ful discovery, but it had made the veil still thicker
behind which the virus diseases lay concealed. With
it variations in virulence were scarcely to be feared.
After being very clearly diminished in passing from
the cow to the man, the virulence of the vaccine was
maintained very constantly from arm to arm, for a
long series of generations. But if there was something
immutable in the severity of the disease or in its period
of evolution, there was, on the contrary, great variation
in the duration of the immunity which it produced.
So that, to sum up, the ideas which seem to us to-day
the most closely related, the most coherent, were at
that time scattered and contradictory, and no one
attempted to correlate them.

It is here that Pasteur experienced the benefit of
his former studies and of facts which he alone knew,
since he had published them only in part, and in that

276 PASTEUR : THE HISTORY OF A MIND

somewhat dogmatic style, general and without details,
which he still affected at this time. I speak of his
study of chicken cholera, concerning which I have as
yet said only a word, and which I have reserved for
the following chapter, because it is a disease which has
the closest analogies with the virus diseases. We shall
see, in reality, that this cholera, like smallpox, is some-
times epidemic and deadly; sometimes chronic and
harmless; that transferred from the chicken to the
guinea-pig, hke the cowpox transferred from the cow
to the man, it may become an artificial and fixed dis-
ease, preserving its character indefinitely.

II

CHICKEN CHOLERA

"Sometimes there breaks out in the poultry-yard a
disastrous disease, commonly known as chicken cholera.
The animal which is a prey to this infection is without
strength, trembles and has drooping wings. The feath-
ers of the body are ruffled giving it the form of a ball;
an unconquerable drowsiness overpowers it; if forced
to open its eyes it appears to waken from profound
slumber; soon the eyes close again, and in most cases,
the animal does not change its position until death comes,
after a dumb agony. At most it sometimes shakes its
wings for a few seconds."^

These singular symptoms are due to the development
of a microbe which can be isolated in cultures in neutral-
ized chicken bouillon. Sowing in this liquid a drop
of the blood of a chicken which had died of the cholera,

' Sur le chol(5ra des poules. Comptes rondus de I'Academie des
Sciences, 1880.

CHICKEN CHOLERA

277

and working as he had done with anthrax blood, Pasteur
saw develop everywhere small non-motile segments of an
extreme tenuity, slightly constricted in the middle (Fig.
22), and clearly approaching, much more than the anthrax
bacteridium and the other bacilli, those microscopic
granules to which Chauveau had attributed the active
role in the virulent humors of cowpox, smallpox, and
sheeppox.

Fig. 22. — Microbe of chicken cholera.
Young. Old.

This organism is so tenuous that the precipitate which
it forms at the bottom of the flask is sometimes
almost invisible; it appears scarcely to touch the nutri-
tive substances placed at its disposal, and one might
ask himself the question whether it changes in any
respect the culture fluid. ''Let us try," said Pasteur
to himself; and he tried, and saw with surprise that if
this bouillon culture was filtered by passing through
a porous wall in order to remove from it all the parasites,
and then re-inoculated, no growth took place. The

278 PASTEUR : THE HISTORY OF A MIND

first culture has rendered the medium unsuitable for
a second, as the first attack of a virus disease protects
against all new attacks. Thus was sown in the mind
of Pasteur, a seed which fell on good ground and could
not fail to be productive.

Inoculation with this organism is usually fatal but
it sometimes happens that the chicken, after having
been sick, seems to recover. Nevertheless it eats little,
its comb loses color, it grows thin, and finally it succumbs
after weeks or months of languor. Is it always the
same disease? Yes, for the organism which we find
in the tissues, if isolated, kills the chickens into which
it is inoculated. \Miy, then, did it not cause the death
of the chicken which carried it? \Mience comes this
relative immunity? Pasteur was not yet able to
answer this question, but he already had the right to
put it to himself. While waiting to find the solution,
he pointed out the analogy between these larval forms
of the cholera, and the grave and often incurable forms
of certain virus diseases, such as measles, scarlatina,
and typhoid fever.

Many ideas are already knocking at the portals of
his mind: and this is not the end. The chicken is not
the only domestic animal capable of offering a habitat
to the microbe. The dog, the horse, and many animals
of the barnyard are also inoculable. The rabbit is
particularly susceptible, and Pasteur discovered later
that the contagion could be propagated in terriers.
The guinea-pig, on the contrary, is quite resistant.
It succumbs to inoculations in the veins, but those
under the skin produce scarcely more than a slight abscess,
which bursts spontaneously and heals without making
the animal which bears it appear sick. This abscess
is a kind of pure culture of the microbe, and if we inocu-
late a little of its contents into chickens, 'Hhese chickens

CHICKEN CHOLERA 279

die quickly, while the guinea-pig which furnished the
virus, recovers without the least suffering. We are
present here, then, at a restricted evolution of a micro-
scopic organism which causes the formation of pus and
a closed abscess without bringing about any internal
disturbance or the death of the animal on which it
occurs, and, nevertheless, one which is always ready to
convey death to other species into which it is inoculated,
ready even to kill the animal on which it occurs in the
form of an abscess, if more or less fortuitous circum-
stances enable it to pass into the blood or into the
splanchnic organs.

''Chickens or rabbits which live in the company of
guinea-pigs bearing such abscesses may suddenly become
sick and die without the health of the guinea-pigs appear-
ing to be in the least impaired. For this to occur, it
is only necessary that the abscesses of the guinea-pigs
should rupture, scattering a little of their contents on
the food of the chickens and the rabbits. An observ-
ing person, seeing these facts and ignorant of the rela-
tion of which I am speaking, would be astonished to see
chickens and rabbits destroyed without any apparent
cause, and would believe that the disease was sponta-
neous, for he would be far from supposing that it had
originated in the guinea-pigs, all in good health, especially
if he knew that the latter are also subject to the same
disease. How many mysteries in the history of conta-
gions will some day receive solutions still more simple
than that of which I have just been speaking! Let
us reject theories which we can contradict by convincing
facts, but not on the vain pretext that certain of
their applications escape us. The combinations of
nature are at the same time more simple and more
varied than those of our imagination!"

For anyone who pondered over Jenner's work, what was

280 PASTEUR: THE HISTORY OF A MIND

more analogous than these facts with what was known on
the subject of those apparently spontaneous sudden
appearances on the horse, on the cow, on the hands of the
milkers, that is, those eruptions of horsepox, of cowpox,
and of vaccinia? What more natural than to see in
smallpox and vaccinia different manifestations of the
presence of the same microbe, or at least of two closely
related microbes? In all these cases, the ideas regarding
microbial diseases and those concerning virus diseases
are more and more bound together. Pasteur has just
spoken of the imagination. He had much of it, and he
allowed it to have full play on this subject. He did
not even scorn the dream. "I take the liberty" he
said one day, "of recalUng to my confrere, M. Blanchard,
that the illusions of an experimenter form a great part
of his power. These are the preconceived ideas which
serve to guide him. Many of them vanish in the long
path which he must travel, but one fine day he discovers
and proves that some of them are adequate to the truth.
Then he finds himself master of facts and of new prin-
ciples, the apphcations of which, sooner or later, bestow
their benefits."^

The hour had come for him to enter the enchanted
grotto full of treasures.

Ill
DISCOVERY OF VACCINES

The first experiments on chicken cholera date from
1879. Interrupted by vacations, they had been resumed,
but were upset at once by an unforeseen obstacle. Al-
most all the cultures left in the laboratory had become
sterile.

' Comptes rendus de rAcademie des Sciences, !"■ sem., 1880.

DISCOVERY OF VACCINES 281

As all these belonged to the experiments under way,
an attempt was made to revive them, and with that
end in view, transfers were made from them either into
chicken bouillon or into chickens. Many of these made
no growth, and also spared and left unimpaired the
animals into which they were inoculated, and we were
about to throw them away, in order to begin anew, when
it occurred to Pasteur to inoculate a fresh young culture
into these chickens which, at least in appearance, had
so well resisted the inoculations with the cultures
made the preceding summer.

To the surprise of all, perhaps even of Pasteur him-
self, who did not expect such a success, almost all of these
chickens resisted, whereas new chickens, just brought
from the market, succumbed in the ordinary length of
time, thus showing that the culture used for the inocu-
lation was very active. With one blow, chicken cholera
passed to the list of virus diseases and vaccination was
discovered! What secret instinct, what spirit of divin-
ation impelled Pasteur to knock at this door, which
was only waiting to be opened? Here we see clearly
the part played by his readings and his former studies,
by the incessant ponderings which had been going on
in his mind, and by the intervention, in the midst of
these obscurities, of this faculty of imagination to which
he has referred in the lines that precede, lines written
just at the time when he was setting forth, a conqueror,
in the realm of his dream.

He had, in reality, just established between certain
microbial diseases and the virus diseases a definite
connection which it was to be the task of the future
to enlarge and consolidate. There were, then, microbial
diseases which did not recur! One could, therefore,
prepare vaccines insuring protection against a viru-
lent inoculation! Prudently, Pasteur refrained from

282 PASTEUR : THE HISTORY OF A MIND

sayijig how he obtained this vaccine. He preferred to
insert in the Note in which he announced the preceding
fact, another fact not less astonishing, to wit, that this
vaccine, once developed, could be reproduced indefinitely
by cultures, with all its vaccinal properties, or with what
has since been called its degree of attenuation.

If one can say, strictly speaking, that Pasteur had
had a presentiment of the first of these facts, the latter
at least was entirely unforeseen. It is, or seems to us
at least, entirely independent of the other, and it is
possible that vaccination would still be in force even
if the latter did not exist. But it was none the less
valuable in practice, and Pasteur in running across it
must have recalled the history of Jenner, and even
have re-lived it. And here is my reason!

It is well known that Jenner, after having discovered
that inoculation with cowpox gave protection against
smallpox and became a vaccine, had had some anxiety
regarding it. He feared, in the first place, being obhged to
return to the cow and to the cowpox to obtain his vaccine,
and this prospect was scarcely calculated to please
him. According to his idea, cowpox was inoculated
into the cow by a milker affected with smallpox, was
found only in the female and at the points touched by
the milker, that is on the udder, and represented con-
sequently the bovine form of human smallpox. If this
were so, there must be smallpox in order to produce
cowpox, and as, theoretically, the vaccine suppressed
the smallpox, here was a vicious circle. Jenner sought,
therefore, with an emotion of which we find traces in
his memoirs, to obtain from man the material for inocu-
lation, the vaccine, to vaccinate from arm to arm, and
he succeeded. It was his chief discovery, and one which
makes for his eternal glory. But the same history
repeated itself in Pasteur nearly a century later and

DISCOVERY OF VACCINES 283

there was this further resemblance that the absolute
conservation of the virulence was realized neither by the
vaccine transferred from arm to arm, as Jenner believed,
nor by the chicken cholera vaccine, transferred from
culture to culture, as Pasteur believed. In both cases,
there is a deterioration, but a very slow, one, which it
has required years to perceive.

In any event, a new world was opened to him, and
he must push on into it eagerly. This is what Pasteur
did with the incomparable authority of a master, con-
stantly guided, it is true, by the then prevaihng notions
regarding virus diseases, but having as a means of illumi-
nating his every step those methods for cultivating
the virus which were entirely his own. I have no inten-
tion of following up his study of chicken cholera; I
should hke, merely, to point out the principal facts,
those which should not be forgotten because they tell
us, in a particularly simple case and one which has been
well worked out, what a virus disease really is.

If we inject a few drops of a young culture of the
microbe of chicken cholera into one of the large pectoral
muscles of a chicken, or inject them into its blood, or
still better, put them on the food, on the bread or 'the
meat, we shall see, after a time varying with the path
of entrance, the symptoms of the disease appear in this
fowl. The animal loses its appetite, becomes drowsy,
ruffles itself into a ball and dies sometimes in 24 hours,'
entirely invaded by the microbe, which is found in its
blood and in all its organs.

Instead of using a young culture for inoculation, let
us repeat the experiment with a culture several weeks
old. We shall still have a disease marked by loss of
appetite, drowsiness, and ruffled feathers, but the chicken
does not die. After some days of more or less severe
illness, it apparently fully recovers. There has been,

284 PASTEUR : THE HISTORY OF A MIND

however, a development of the microbe, since there
has been disease, and, in reahty, when this disease is
in progress, the organism can be found at the point of
inoculation and in all the tissues, but this time it has
not caused death. The chicken has repelled the attack.

Has, then, this benign cholera played in the chicken
the role of the benign smallpox or vaccine in man? Yes,
for this chicken is henceforth immune to inoculation with
the youngest and most virulent culture of the micrococcus.
It has been vaccinated against the cholera.

Let us continue this study which has already proved
so fruitful. Since the power of action on the organism
diminishes with the age of the culture, let us make
our inoculation from a very old culture, one which is
near the point of death. The microbe, still alive, can
still cloud the bouillon into which it is sown. It does
this slowly, but life and virulence are not synony-
mous in this case, for the organism is absolutely incapable
of developing in the body of a chicken, or communi-
cating to it even the slightest disease. Here it is the
chicken which overcomes and kills the inoculated microbe
straightway. The latter, in spite of its specific origin,
entirely resembles, therefore, those thousands of spe-
cies of micrococcus which are met with everywhere on
the surface of the body, which fill the intestinal canal,
and which are always harmless. It is, nevertheless,
that same microbe which some weeks before killed ten
chickens out of ten. A virus, then, is not that entity,
not that unity, which it was considered to be by the
old physicians. It is in a state of perpetual evolution,
of continuous variation, due to wholly natural causes.

Let us take, now, this last chicken which suffered no
inconvenience from the inoculation with our dying
virus, and let us try to inoculate it with the virulent
virus; it behaves toward this exactly as a new chicken

DISCOVERY OF VACCINES 285

would; it dies, or at least is veiy sick, the extent of the
disease and the danger of death being in inverse ratio
to the amount it had suffered in the previous inocula-
tion, for the slightest disease produced by inoculation
serves as some protection.

Instead of making the three experiments which pre-
cede, we might, clearly, arrange a greater number
extending over the period of hfe of the virus, six, ten,
etc., in other words, interpose between the most sensi-
tive animal and the most resistant, a whole series of
animals differing in degree of immunity, each one of
which will acquire a degree of immunity corresponding
to the amount of vaccine which it can endure without
dying. The more severe the disease the greater the
protection the disease will afford it.

All these animals, identical in appearance, different
in reahty, clearly behave in a very different manner
toward the same microbe of virulent cholera. Some,
vaccinated, resist it without any trouble. Others, httle
vaccinated or only recently, will become sick or die.
Furthermore, an animal, vaccinated or not, behaves
very differently toward microbes of unequal attenua-
tion. It is the variable result in this conflict which
makes the variety of pathological cases, and there are
not on the palette of any painter colors enough to des-
ignate the innumerable differences in receptivity which
we find in the virulent diseases.

IV

ANTHRAX IS ALSO A VIRUS DISEASE

As the study of chicken cholera progressed Pasteur
devoted much thought to anthrax on which he was work-
ing at the same time. He wished to study its etiology, to

286 PASTEUR : THE HISTORY OF A MIND

determine precisely the means by which the bacteri-
dium passes from one animal to another, to discover
how the disease can be at the same time endemic and
epidemic, can have more or less periodic awakenings,
or lie dormant for long years. Koch had already out-
lined this subject, and Pasteur had to content himself
with adding the finishing touches, but these touches
are the work of a master. We shall be thoroughly con-
vinced of that when we note the principal facts.

Koch had shown how the spores are formed when an
animal, dead of anthrax, is buried, but he had never
found them in the earth, nor did he know how long
they lived there. Pasteur succeeded at the outset in
isolating the bacteridium of anthrax from the myriads
of germs which accompany it in the soil, always employ-
ing for this purpose the same method: that of pure
cultures in the medium best fitted to the physiological
needs of the anthrax bacillus. These experiments
date from 1881. The method of making cultures on
sohd media, conceived by Koch, was not yet known in
the laboratory, having been published only that year. It
would certainly have simplified the problem and facil-
itated the researches, but we see, as has since been
admitted, that it was not indispensable for studies of
this kind, and that Pasteur extricated himself from
his difficulties without it. It is true that another would
probably have failed.

Thanks to this method, Pasteur discovers that the
anthrax spores can persist a long time in the vicinity
of the place of burial, and that they can be found there
after a period of 12 years, as vinilent as on the first day.
This gave birth to a new problem. How can these
spores on the soil of the burial pit resist the rain which
engulfs them, the wind which sweeps them away, and,
we should add, to-day, the light of th(^ sun, which is more

ANTHRAX IS ALSO A VIRUS DISEASE 287

active on them than its heat. This might be conceived
as due to intermittent cultures which renew and multiply
the spores, but there is no probability in such an
explanation, the soil, rich in vegetable matter, being
full of organisms which are much better prepared
than the anthrax bacteridium to profit by the slightest
condition favorable to bacterial growth. Pasteur was
seeking an explanation in some other direction, but he
knew not where. The solution came to him by intuition
one day, in the course of a walk. "It was after the
harvest; there remained only the stubble. The atten-
tion of Pasteur was drawn to a portion of the field be-
cause of the difference in the color of the soil. The
owner explained that some sheep which had died of
anthrax had been buried there the preceding year.
Pasteur, who always investigated things very closely,
observed on the surface of the soil a multitude of the
tiny castings of earthworms. The idea occurred to
him then that in their continual journeys from the
depths to the surface, the worms brought with them soil
rich in the humus which surrounds the carcass of the
animal, and with it the anthrax spores which it contains.
. . . Pasteur never stopped with theories; he imme-
diately proceeded to experimental work. The latter
justified his suppositions, the earth from one of the
worms when inoculated into guinea-pigs gave them
anthrax."^

These spores, brought to the surface of the soil in
this way, contaminate vegetation and reach by way of
food and drink the digestive canal of the fann animals.
Sheep which are kept over the spot where a victim of
anthrax is buried, easily contract anthrax, especially if
their food contains chaff, stubble, awns, or small prickly

lon.^'^"''"^ medicale de Pasteur, par le Dr. E. Roux, Agenda du ckindste,
1896.

288 PASTEUR : THE HISTORY OF A MIND

or sharp substances, capable of injuring in places the
epidermis of the intestinal canal, and of thus breaking
the natural barrier opposed to the invasion of the germs.
The symptoms of the disease thus provoked are those
of the disease as it occurs naturally, so that, as Koch
had conjectured, it is especially through the food that
contagion takes place. And it is thus that the disease
may be at the same time endemic and epidemic, and
may render certain regions and certain fields dangerous,
without causing any trouble in their vicinity.

All these researches, as the reader divines, had been
carried on for the sake of establishing a prophylaxis
for anthrax, and already a certain number of practical
conclusions could be drawn regarding precautions to
be taken in burying an animal affected with anthrax.
These were abruptly broken off as soon as there ap-
peared the first intimations of the possibility of a vaccina-
tion for anthrax. Was, then, anthrax also a virus
disease, not prone to recur?

This question was solved for Pasteur as soon as it
was stated. Furthermore, his solution was published
without anyone's having observed it in the Note in
which it was inserted. In this Note of July 12, 1880,^
devoted to the etiology of anthrax, Pasteur had in
reality introduced, almost in parenthesis, and without
explaining at all its place in this question, a phrase in
which he had incidentally pointed out this fact: When
8 sheep, which had been subjected to a prolonged so-
journ on a spot where an anthrax victim had been buried
and had proved resistant, were inoculated at the close
of the experiment with a culture of virulent anthrax,
several of them survived, whereas fresh sheep of the same
race succumbed almost without exception to the same in-

' Sur rotiologie du charbon (en collaboration avec MM. Chamberland
et Roux). Comptes rcndus de I'Ac. des Sciences, t. XCI, 1880, p. SG.

ANTHRAX IS ALSO A VIRUS DISEASE 289

oculation. This fact had remained in the mind of Pasteur
as a question, and he had beheved that he could solve it.
Afterwards, calling to mind that chickens, fed upon food
contaminated by the cholera organism, do not always die
and are sometimes found to be vaccinated when they
survive, he had asked himself if the sheep in the preceding
experiment had not acquired their immunity through a
former contagion caused by food. But then, according
to this hypothesis, anthrax was a disease which would
not recur.

Later something else occurred to confirm him in this
idea. In a series of experiments made with Chamber-
land in the Jura,^ in order to test the value of a cure
for anthrax, he had had the opportunity of seeing two
cows become very sick as the result of a trial inoculation,
but, having resisted, endure without any apparent
difficulty a virulent inoculation which made very ill
or even killed fresh animals not previously prepared.

All this proved to Pasteur that anthrax was a virus
disease, and now the only question was how to find its
vaccine. Naturally, he turned first to the method
which had been successful with chicken cholera, and
tried to let the bacillus become old in its culture me-
dium. But immediately a difficulty arose, that is, the
anthrax bacillus very quickly transformed itself into
spores, and the spore does not grow old; the spore is a
"seed," and for a seed, time is almost suspended.' It was,

^Sur la non recidive de I'affection charbonneuse (en collaboration
avec M. Chamberland). Co. rend, de I'Ac. des Sci., t. XCI, 1880, p. 533.

- It IS not known how long seeds or spores will live under favorable
conditions. Dr. W. J. Beal buried 25 varieties of weed-seeds in sandy
soil in bottles of earth, mouth down, and found some individuals of
11 varieties alive after 25 years, but they germinated very irregularly.
The senior writer put spores of the hay-bacillus into concentrated
glycerin, exposed to the air in a cotton-plugged test tube, 10 years ago
and a very few are still living. Trs.

290 PASTEUR: THE HISTORY OF A MIND

therefore, necessary to prevent spores from forming,
at the same time keeping the bacillus alive. This can
be accompHshed in different ways, the first successful
method being the use of antiseptics. That did not
satisfy Pasteur. He wished a second edition of the
chicken cholera. He searched in another direction
and finally discovered that it sufficed to keep the culture
in a shallow layer of neutral chicken bouillon at 42-43'^ C.

We then see reproduced the same phenomena as in
chicken cholera. After a month passed under these
conditions, a little extreme as to temperature, the bac-
teridium is dead, that is to say, the best culture medium
inoculated with it remains steiile. After 8 days, cultures
are still made from it readily and give abundant growth,
but the organism is harmless to the guinea-pig, the
rabbit, and the sheep, three species most susceptible
to anthrax. Before the virulence is lost, it passes in
the course of about a week through all degrees of atten-
uation, and, as in the case of the chicken cholera organ-
ism, each of these grades of attenuated virulence may be
indefinitely preserved through cultures. Thus vaccines
were created. Nothing is easier than to find in these
graded viruses the means of giving to sheep, cows, and
horses a benign fever, capable of preserving them after-
wards from the fatal disease.

These vaccines had in this respect a practical impor-
tance very much greater than those of chicken cholera.
The victims of anthrax were counted by thousands in
France alone, and the losses were reckoned in millions.
Anthrax vaccination could remedy all this but before
bringing about its acceptance, what trouble, what time,
what efforts to convince the pubhc, the veterinarians
and the farmers! Here it is that we shall find again
Pasteur the apostle, whom we have seen in action
after his studies on the silkworm, the Pasteur who

ANTHRAX IS ALSO A VIRUS DISEASE 291

would have wished to be everywhere, to see every-
thing, and to rely on no one. He had opened the cam-
paign in an almost startling manner with that famous
experiment at Pouilly-le-Fort, which so impressed every-
body. I shall borrow the account from M. Roux, who
saw it and collaborated in it.

^'The Society of Agriculture of Melun had proposed
to Pasteur a public trial of the new method. The pro-
gram was arranged for the 28th of April, 1881.
Chamberland and I were away on a vacation. Pasteur
wrote to us to return immediately, and when we were
reunited in the laboratory he told us what had been
agreed upon. Twenty-five sheep were to be vaccinated,
and then inoculated with anthrax; at the same time 25
other sheep would be inoculated as checks; the first
would resist; the second would die of anthrax. The
terms were exact; no allowance was made for contin-
gencies. When we remarked that the program was
severe, but that there was nothing to do except carry
it out since he had agreed to it, Pasteur replied:
'What succeeded with 14 sheep in the laboratory will
succeed with 50 in Melun.'

"The animals were collected at Pouilly-le-Fort, near
Melun, on the property of M. Rossignol, a veterinarian
who originated the idea of the experiment and who was
to watch it. 'Be sure not to make a mistake in the
bottles,' said Pasteur gaily, when on the fifth of May,
we were leaving the laboratory in order to make the
first inoculations with the vaccine.

"A second vaccination was made on the 17th of May,
and every day Chamberland and I would go to visit
the animals. On these repeated journeys from Melun
to Pouilly-le-Fort, many comments were overheard,
which showed that belief in our success was not universal.
Farmers, veterinarians, doctors, followed the experi-

292 PASTEUR: THE HISTORY OF A MIND

merit with active interest, some even with passion.
In 1881 the science of microbes had scarcely any parti-
sans; many thought that the new doctrines were baleful,
and regarded it as an unexpected piece of good fortune
that had drawn Pasteur and his staff out of the labora-
tory to be confounded in the broad daylight of a public
experiment. They were going then with one blow
to put an end to these innovations, so compromising to
medicine, and to find again security in the same tradi-
tions and ancient practices, for a moment threatened!

''In spite of all the excitement aroused by it, the
experiment followed its course; the trial inoculations
were made the 31st of May, and the rendezvous was
appointed for the second of June to determine the result.
Twenty-four hours before the time decided upon, Pasteur,
who had rushed into the public experiment with such per-
fect confidence, began to regret his audacity. For some
moments his faith was shaken, as though he feared the
experimental method might betray him. A mental ten-
sion too long continued had brought about this reaction,
which, however, did not last long. The next day, more
assured than ever, Pasteur went to verify the brilliant
success which he had predicted. In the multitude which
thronged that day at Pouilly-le-Fort, there were no
longer any who were incredulous; only admirers."

This fine success^ did not immediately bring convic-
tion. He had to repeat the experiment in different
places in France and abroad, in order to convince those
who wished to touch and to see before believing. Noth-
ing can give an idea of the activity of Pasteur at this
time. To the life within the laboratory, which continued

1 Fourteen days after the second vaccination the 50 animals were in-
oculated, all in the same way from the same virulent culture, and 2 days
later, as Pasteur had predicted, the 25 vaccinated animals were unharmed
and the 25 unvaccinated animals were dead. Trs.

ANTHRAX IS ALSO A VIRUS DISEASE 293

at full flood, and where studies on rabies had already
commenced, was now added a public life not less active.
He must superintend the manufacture and the sending
out of the vaccine wherever public or private experiments
were made, must inquire into the results, details of
which were never given in sufficient number or pre-
cisely enough, must reply to the demands for information,
to the fears which preceded an experiment, to the com-
plaints which sometimes followed it. Pasteur carried
on almost all this correspondence himself. He must
also reply to criticisms and to sly attacks as well as
to those of open war. Nor were his adversaries confined
to France. Koch and his pupil, Loffler, for example,
had published against the theory and practice of vaccina-
tion some awkward and fruitless criticisms, which they
must regret to-day. In this continual strife, Bouley
made himself the champion of Pasteur and devoted
his whole spirit to the task.

Thanks to these prodigious efforts, thanks to the
precision of the results, the practice of vaccination
quickly became the custom, and when publishing, in
1894, in the Annates de VInstitut Pasteur, the statistics
on anthrax vaccination on sheep and cattle, M. Chamber-
land was able to state, that in the case of the former
a total of 3,400,000 animals had been vaccinated in
10 years with a mortahty of less than 1 per cent; in the
case of the second, a total of 438,000 had been vacci-
nated with a mortality of about 3 per thousand. Finally,
he estimated the beneficial results for French agriculture
from the use of vaccines at 5,000,000 francs for sheep,
and 2,000,000 francs for cattle. It is evident that if
the laboratory had been laboriously painstaking, it was
not labor lost. It is anthrax vaccination that first
spread through the public mind faith in the science of
microbes.

294 PASTEUR: THE HISTORY OF A MIND

STUDIES ON RABIES

Although it was these experiments at Pouilly-le-
Fort and the anthrax vaccinations which first overcame
the general scepticism regarding the new doctrines,
it was the prophylaxis for rabies which gave them the
great place in pubUc confidence which they now enjoy.
We cannot fail to recognize that, from this point of view,
this disease was well chosen. It has, fundamentally,
no importance. The mortality which it causes is slight.
Man can protect himself from it without any scientific
apparatus, simply by police measures, as is done in
Germany, and that country may w^ell scoff at us, since
without any Institute for fighting rabies, she had less
deaths from it throughout the whole empire than we
have in Paris. But rabies has a hold on the pubHc
imagination; it evokes legendary visions of raging
victims, inspiring terror in all those in their vicinity,
bound and howling, or asphjTdated between two
mattresses.

The reaUty is much more simple and calm, and few
deaths are more peaceful than certain deaths from
rabies, but it was easy to foresee that a victory over this
disease would be reckoned none the less as a great one.
Only it did not seem easy. In the first place, while rabies
might pass with the public for a virus disease, it had not
that character for the physician or the surgeon, because
every man and every animal that contracted it died
from it, and it was consequently impossible to know
whether it would recur in the same individual. In the
second place, the only means of transmitting it was by
having a mad animal bite another animal, or by in-
oculating it with saliva from a rabid animal, but this

PASTET'R STT'DYING RABIES
(From the painting by Edelfolt.)

STUDIES ON RABIES 295

method of transmission was most micertain. The
incubation period for rabies is extremely variable;
it may be some days or it may be several months.
Nothing is more unendurable for an experimenter than
these long and uncertain delays between an experi-
ment and its results. Moreover, sometimes it happens
that the bitten or inoculated animal does not die, and
everything has to be done over again. Finally, as a
last obstacle, numerous attempts carried on for a long
time in the laboratory of Pasteur, and elsewhere, had
shown that it was impossible to discover in the saliva
of rabid animals any organism having an assured etio-
logical relation to the disease. Pasteur, after having
believed that he had discovered it, had renounced this
idea, which he had had the prudence not to pubhsh,
so that he attacked the question without knowing
whether the disease was a virus disease, without knowing
or being able to cultivate the microbe, and even without
having a certain and quick method of inoculation. It
is here that we shall soon see the power of the experi-
mental method when it is handled at the same time
with prudence and audacity. It is a marvelous tool,
having an extraordinary power of penetration, being
able, provided it is handled by one who thoroughly
understands it, to work even in obscurity, like those
drills which attack and pulverize everything that is
presented to them in the depths of a black pit, provided
that they are entirely in the grasp of the man who di-
rects them.

The general symptoms of rabies bore witness that it was
especially the nerve centers which were attacked. Dr.
Duboue, of Pau, had already observed this and concluded
that not simply the saliva of a mad animal but also its
nerve-substance should be virulent. Experiment has
demonstrated the justice of this conclusion. Nerve tissue,

296 PASTEUR : THE HISTORY OF A MIND

inserted under the skin of an animal, can give it rabies.
But this method of transmission is quite as uncertain and
capricious as transmission through the saUva. Rabies
does not always appear, and it sometimes does so only after
a prolonged incubation of months. Inoculation under
the skin, therefore, is an uncertain method. But, said
some one in the laboratory of Pasteur, why not try to
deposit the virus in the nerve centers, since it is there
that it grows and reproduces itself.

For that purpose it was not necessary to know the
microbe, nor even to be sure that there was one; the proof
of its presence and its development would not be micro-
scopical examination, but the appearance of rabies in
the animal inoculated. As a culture medium the nerve
tissue offers, moreover, guarantees which one does not
find either in the saliva or even in the blood, both of
w^hich are much more accessible to contamination from
the exterior. Furthermore, it seemed to be a chosen
medium for the virus of rabies, and to fulfil naturally
for it that condition which was the foundation of the
culture method, and which was realized only after much
labor in the artificial culture media for the anthrax
bacteridium and the microbe of chicken cholera. The
main thing was to gain access to it properly and to make
an antiseptic inoculation there. The surest way was
to attempt to inoculate a dog under the dura mater,
by trepanning. "Ordinarily an experiment once con-
ceived and talked over was put under way without delay,"
says Dr. Roux. "This one, on which we were counting
so much, was not begun immediately. Pasteur, who
had been obliged to sacrifice so many animals in the
course of his beneficent studies, felt a veritable repug-
nance toward vivisection. He was present without
too much squeamishness at simple operations, such as
a subcutaneous inoculation, and yet, if the animal cried

STUDIES ON RABIES 297

a little, Pasteur immediately felt pity and lavished on
the victim consolation and encouragement which would
have been comical if it had not been touching. The
thought that the skull of a dog was to be perforated
was disagreeable to him; he desired intensely that the
experiment should be made, but he dreaded to see it
undertaken. I performed it one day in his absence;
the next day, when I told him that the intracranial
inoculation presented no difficulty, he was moved with
pity for the dog: 'Poor beast! His brain is without doubt
wounded. He must be paralyzed.' Without replying,
I went below to look for the animal and had him brought
into the laboratory. Pasteur did not love dogs; but
when he saw this one full of life, ferreting curiously
about everywhere, he showed the greatest satisfaction
and straightway lavished upon him the kindest
words. He felt an infinite liking for this dog which
had so well endured trepanning, and thus had put
to flight for the future all his scruples against it."^

The method was in reahty discovered. It was that
of making pure cultures in the organism. The dog
thus trepanned developed rabies in fourteen days,
and all the dogs treated in the same fashion behaved
similarly. It was now possible to make progress, and
from that moment everything went on as in the case
of chicken cholera and of anthrax.^

For these latter maladies the virulence can be varied
by changing the culture medium. Pasteur had hkewise
discovered, for chicken cholera as well as for anthrax
that the virulence varied with the transfer of the microbe
from one animal species to another, and we shall soon

1 L'ffiuvre medicale de Pasteur, par M. le Dr. Roux, Agenda du chim-
iste, 1896.

2 All the studies on rabies are summarized in Comptes rendus de 1' Acad-
emic des Sciences, beginning with ISSl. They were done in collaboration
with MM. Chamberland, Roux et Thuillier.

298 PASTEUR: THE HISTORY OF A MIND

re-survey these results and the conclusions which can be
drawn from them. In the case of rabies, where cultures
could be made only on the living creature, this method
was obligatory. He tried, theref<{re, the inoculation
of a rabbit by trepanning and saw that the virus, when
thus passed from rabbit to rabbit, was strengthened,
and that the duration of the incubation in the end was
no more than six days. In the monkey, on the contrary,
the virus becomes attenuated. This confirmed the
analogies between rabies and the virus diseases.

But if the spinal cord of an animal that has died of
rabies can be considered as a pure culture of the virus,
why not try to attenuate the virus by allowing a portion
of this cord to become old in contact with pure air, as the
virus of anthrax is attenuated by exposing a pure culture
to pure air. Thus occurred wholly naturally this great
discovery that the spinal cord from a rabid animal,
exposed to the action of air, in an atmosphere free from
humidity, loses its activity on drying. After 14 days,
the virus is harmless in the strongest doses; between the
fresh cord and that 14 days old, there is a whole series of
degrees of attenuation. "A dog that receives this
rabic spinal cord 14 days old, then the following day
that 13 days old, then that 12 days old, and so on until
the fresh cord is used, does not contract rabies and has
become immune to it. Inoculated in the eye or the
brain with the strongest virus, it remains healthy. It
is, therefore, possible in 15 days to give to an animal
immunity against rabies. Now men, bitten by mad
dogs, ordinarily do not contract the disease until a month
or even more after the bite, and this period of incuba-
tion can be utilized for rendering the bitten person
immune.

''Experiments made on dogs bitten and inoculated
were successful beyond all hope. One recalls how, with

THE PROBLEM OF IMMUNITY 299

the aid of MM. Vulpian and Grancher, the experi-
ments were extended to man. To-day almost 20,000
persons have undergone this antirabic treatment and the
mortality occurring among these treated persons has
been less than 5 per thousand.

''The discovery of the prophylaxis for rabies aroused
everywhere great enthusiasm. It increased the popu-
larity of Pasteur more than all his former works. In
return for such a benefaction, the great public desired
to manifest its gratitude in a manner worthy of itself
and of the man it wished to honor. It was then that
the subscription was started which has made possible
the founding of the Pasteur Institute."^

Once again the method had brought forth fruit. We
could further cite, as proof of its value, the vaccination
for erysipelas of swine, preeminent among the workers
on which was the regretted Thuillier. But we should
find therein only what we already know. We are not
writing the history of the work of Pasteur, but that of
his mind, and it is better to take up an aspect of the
question of viruses which we have not yet considered.

VI

THE PROBLEM OF IMMUNITY

The theoretical importance of all these facts was
superior even to their practical importance. This
method of the physiological study of microbes in pure
cultures which had at first given the etiology of the
different diseases studied, which later had furnished
all the ideas which we have just summed up on varia-
tions in virulence, was about to exhibit a new fecundity
by opening up the problem of immunity, on which

1 Roux, 1. c, p. 543.

300 Pasteur: the history of a mind

scientists are still working, and on which the last word
has not been said.

On what depends that immunity which vaccinated
animals possess, which is also possessed by animals nat-
urally resistant to certain diseases fatal to other species?
Why does the cow contract anthrax less easily than the
sheep of Beauce, and the sheep of Algiers less easily
still than the cow? Why is man not attacked by certain
diseases of the domestic animals, and inversely? Here
were questions which, yesterday premature and auda-
cious, could now be stated and become the object of an
experimental study. In a word, it was not alone the
mechanism of the disease which ought to be the subject
matter for experiment, but also the mechanism of health,
that is to say, the entire physiology of the living creature,
and already one could foresee that Pasteur and Claude
Bernard were about to join hands to contribute to a
deeper conception of the life of the cell.

The new idea which Pasteur brought into this study
was the idea of strife between two cells or two groups
of cells, and here I seem to be advancing a daring prop-
osition, to such a degree does the idea of strife form a
part of the old conception of disease and even, gener-
ally, of the appearance of the sick person. During the
metaphysical period of pathology, when the direction
of life was attributed to a vital force superposed on all
the organs, one had been led to imagine the disease as
a distinct entity, entering into combat with the vital
force in the organism.^ When, through the progress
of physiology, the vital force was, so to speak, reduced
to an infinite number of cellular lives, each having its

1 This is the theory of homeopathy. If the proper drup; is administered,
that is, one having a greater affinity for the entity of the disease than the
latter has for the body, then the drug-spirit and tlie cUsease-spirit will
combine and the patient will return to his normal condition. Vide
Hempel's Materia IMedica. 7'rs.

THE PROBLEM OF IMMUNITY 301

modality and its direction, it was necessary that the
idea of disease also be changed, and we have already
seen the efforts made to ascribe physico-chemical origins
to pathology. In this conception the old idea of strife
had entirely disappeared, and although, for Virchow,
a tumor was a physiological development misplaced in
time and space, that is to say, produced where it ought not
be, and at a time which was not its own, it was difficult
to see therein anything which resembled the conception
that made the disease something at war with the vital
force.

It is for this reason that the physiologists were so
opposed to the microbian doctrines. The microbe,
producing a chemical phenomenon or causing a disease,
was the sudden reappearance of the vital force in regions
from which it was desired to eliminate it. The idea of
the microbe brought back in the clearest manner the
idea of conflict, of strife for the necessities of life, of the
struggle for existence. Such is the idea which Pasteur,
more than any one else, was instrumental in introduc-
ing into science and into pathology.

This idea in its turn underwent some transformations
in his mind. At the time of the publication of his
Etudes sur la maladie des vers a soie, the microbe was for
him a pathogenic cause external to the organism, func-
tioning simply and in some measure irresistibly. In
order to be rid of the disease, the parasite must be cUs-
posed of. This is what Pasteur had done for the corpus-
cle of the pebrine. It was what had been done before
him for the muscardine fungus and the itch mite.

This rather absurd conception of bacterial diseases
was for Pasteur in perfect accord with what he then knew
of microbes. He believed that the bacterial species
were nearly constant in form and possessed immutable
properties. Transferred from medium to medium they

22

302 PASTEUR: THE HISTORY OF A MIND

would always cause the same reaction, which was a
surer means of recognition than their microscopical
appearance. Transferred in the same way to a living
creature they would produce a definite disease, that is,
one which was always the same when the avenue of
entrance was the same, and which became thereby a sort
of morbid entity: thus bringing us back, in the experi-
mental field, to the oldest conceptions of medicine.
Studies on the flacherie scarcely modified this point
of view. They had shown merely that the microbe,
in order to become active, sometimes needed to be aided
by external conditions. But when it did act, it always
produced the same results.

In short, when nearly 60 years of age, Pasteur dis-
covers facts which are not in accord with this old concep-
tion. These relate to the attenuation of virus. One
and the same microbial species can invest itself, accord-
ing to the culture conditions, with characters which
render it unrecognizable to one who has not followed
it closely through all of its transitions. I have stated
above how Pasteur had endeavored to convince himself
that there were in his cultures of the septic vibrio two
species of unequal virulence, which the culture conditions
enabled him to separate. He refused to admit that these
culture conditions could produce them. The same may
be said of the chicken cholera. It was the struggle be-
tween the old spirit and the new, and one must admire
the readiness with which Pasteur abandoned his first
conceptions when experiment had taught him that they
were not in accord with the facts.

It was with ardor and without regret that he threw
himself into this new path, divining the resources which
he would find there for attacking the greatest and most
delicate problems of pathology. He could henceforth
take up again his old idea of conflict, no longer that

THE PROBLEM OF IMMUNITY 303

brutal strife where the only possible means of interven-
tion consisted in the suppression of one of the adversaries,
but a gentle strife which one might attempt to direct by
augmenting or diminishing the forces of one of the con-
testants. It was only a question of finding the ground
and the object of the strife, and, for that purpose, he had
the experimental method: it was possible, working with
a single species subject to anthrax, to study bacteridia
of different degrees of virulence; it was possible, with
the same bacteridium, to study different species, or
animals of the same species unequally vaccinated, which
made them, to a certain degree, different animals. We
see what a field of labor opened before him. It is
characteristic of certain discoveries that they suddenly
reveal vast horizons. Pasteur had climbed little by
little to one of those mountain heights from which
a whole new country is visible. He plunges into
it with delight. Let us accompany him. We can
no longer follow him closely and must abandon the his-
torical order. In the first place, we have reached the
latter part of his life and his later conceptions. In the
second place, what interests us is the plan of the edifice,
and not the order in which its different parts have been
erected. If we wish to know which part belongs to
Pasteur himself, which part he has built, we must take
it in the condition in which Pasteur left it, with its
finished parts, with its stones yet unplaced, and with a
brief indication of what the progress of science has
contributed to it.

304 PASTEUR : THE HISTORY OF A MIND

VII

VIRULENCE AND ATTENUATION

Attenuation is a general phenomenon. After having
determined its occurrence in chicken cholera, the
anthrax bacteridium, rabies, and the organism of
erj'^sipelas of the pig,^ Pasteur found it in a microbe occur-
ring in horses which had died from typhoid fever, and
in another organism derived from the saliva of a child
attacked by hydrophobia, which last mentioned or-
ganism was found later to be the pneumococcus of
Talamon-Fraenkel. All these bacilli became attenuated
when they were allowed to grow old in the fluid culture
medium.

But what do we mean by this expression "grow old"?
Age is a result, and cannot be an active cause. It ac-
companies attenuation, it does not produce it; or, rather,
the same cause which produces one, at the same time
produces the other. When we search for some physico-
chemical influence which might come into play, we think
at once of oxygen.

The micrococcus of chicken cholera is, for example,
an aerobe in the culture flask and in the organism.
When it ceases to multi]:)h' in the culture medium, it
continues to respire there, to give off carbonic acid
by consuming its own tissues. It contracts and shrinks
visibly (Fig. 22). Its attenuation, which is a proof of
its debility, is probably due to this internal process, and
in reality experiment teaches that when the supplj' of
oxygen is limited by sealing the tubes, allowing only a
small amount of this gas to be present, the virulence is
maintained much longer. It is the same in all cases,
and always the oxygen, regarded as the agent of com-

• Fr. Rougct de pore; Gtr. Schweinerothlauf. Trs.

VIRULENCE AND ATTENUATION 305

bustion of the tissues in the absence of food, and conse-
quently as the agent of enervation, is, at the same time,
an agent of attenuation. Attenuation and weakening
are synonymous, and we have here a conception which
harmonizes well with our idea of strife in the microbial
diseases. That which is harmful to the microbe is of
value to its host.

We are then justified in asking ourselves if all these
causes of weakening on the part of the microbe, all these
factors which contribute more or less quickly to its
death, do not first cause it to pass through a series of suc-
cessive attenuations, that is, transform it into vaccines.
To this new question, experiment replies without hesi-
tation, "Yes." In a general way, attenuation is one of
the forms of the gradual weakening of a microbial cell
which is on its way to death, and every action harmful
to the microbe begins by diminishing its virulence.
Such, for example, is heat, too high a degree of which
kills the microbe, as we know. Between the optimum
temperature for culture and the death point exists a
zone of attenuation, observed by M. Toussaint and
carefully studied by M. Chauveau, for the anthrax
bacteridium. The duration of the heating should be in
inverse ratio to the elevation of the temperature and, for
a given temperature, directly proportional to the degree
of attenuation to be obtained.

Next to the action of heat naturally comes that of the
light of the sun. It kills the microbe after a certain
length of exposure to it, but before killing, it causes
attenuation. This is the conclusion from my experi-
ments, followed by those of M. .Aj'loing.

So much for the physical agents. Now for the
chemical ones. Oxygen is a physiological factor of
the greatest importance, and we have already examined
its role in this relation. But it plays also a role more

306 PASTEUR : THE HISTORY OF A MIND

exclusively chemical, a toxic role, demonstrated l^y
P. Bert. All microbes require a small amount of oxj^gen
and are injured by an excess of it. The anaerobes must
have traces of it but die in ordinary air. The aerobes
live in ordinary air but die in compressed oxygen. Be-
tween the physiological hmits and the toxic hmits there
is, moreover, a zone of attenuation, studied by M.
Chauveau for the anthrax bacteridium.

After oxygen, come naturally the antiseptics which,
likewise, when present in very small proportions, are
harmless or even beneficial to the microbes, but if
present in larger quantities kill them. MM. Chamber-
land and Roux have studied the action of phenic acid,
of bichromate of potash and of sulphuric acid on the
anthrax bacteridium and have discovered in this way
some curious facts to which we shall soon return.

In short, there are several means of producing from the
same virulent race a whole series of races more and more
attenuated. Up to this time we have studied them only
as vaccines. In order fully to investigate their role from
this new point of view, it is necessary to study them in
themselves.

How do bacteridia which are not equally attenuated
differ physiologically? They are very much alike in
bouillon cultures. When attenuated they produce rods
which separate easily and diffuse through the culture
medium, clouding it, while the virulent bacteridia
adhere in flakes, which float in the midst of a clear liquid.
But their ijliysiological needs are the same, and it is
almost impossible to differentiate them by means of the
microscope. For that purpose they must be inoculated
into living creatures.

Let us study them in animals. In proportion as the
bacteridium becomes attenuated, we find that it ceases,
first, to become virulent for cattle, but that it is still

VIRULENCE AND ATTENUATION 307

capable, at this time, of killing sheep; attenuated a httle
more it ceases to be fatal to sheep, but still kills rabbits
and guinea-pigs. When it no longer kills adult guinea-
pigs, it still kills young guinea-pigs or young mice. This
is also true for other microbes.

Virulence appears to us, therefore, to be an intrinsic
quality of which the microbe will be divested more and
more until it becomes harmless. But here is a fact
which proves that things are not as simple as they seem.
If virulence were only this, the different methods of
attenuation would destroy it in the same fashion, and
the order in which the different species of animals are
attacked would be always the same. But experiment
shows that this order varies according to the method of
attenuation. The anthrax bacteridium attenuated, for
example, with bichromate of potash, in the experiments
of M]\I. Chamberland and Roux, as we shall see at once,
may still kill the sheep or at least make them very ill,
leaving them in the latter case vaccinated, while it
produces no effect whatever on rabbits or guinea-pigs,
and does not even vaccinate them. It is exactly the
reverse of the behavior of the anthrax bacteridium
attenuated by growth at 42° to 43° C, which kills guinea-
pigs and rabbits at a stage when it is harmless for the
sheep, and does not even vaccinate them. We obtain
the same results with sjwres of the anthrax bacteridium
attenuated by the action of a temperature of 35° C, in a
liquid containing 2 per cent sulphuric acid.

Thus virulence is not, as we might suppose, an absolute
ciuality, diminishing little by little after the fashion
of reserve food; it is a relative quality, in the estimation
of which not only conditions pertaining especially to the
microbe must be taken into account, but also those
pertaining to the nature, age, and as we shall soon see, the
individuahty of the animal on which it is studied.

308 PASTEUR: THE HISTORY OF A MIND

According to our way of looking at things, nothing is less
surprising. The word ''virulence" sums up the result
of the conflict between two organisms. It is necessary,
therefore, to take into account the qualities of the two
adversaries.

VIII
RETURN TO VIRULENCE

We shall reach the same conclusion by an inverse
method, that is, by examining the conditions determin-
ing the return of virulence in a microbe which has lost it.
We know that these positive and negative variations of
virulence may be produced by simple changes in the
culture medium, but, from this standpoint, they are of
little interest. These variations become interesting only
as they manifest themselves in living creatures. Let us
see, therefore, if we cannot revive virulence by passage
through different species of animals unequally sensitive.

We have obtained, it will be remembered, a strain of
the anthrax bacteridium absolutely harmless, then one
very much weakened, still able to kill guinea-pigs a day
old, but not to kill older guinea-pigs nor other species of
animals, then, starting from this one, a whole series of
microbes more and more virulent. Can one bring back
the most attenuated strains to a state of the highest
virulence? Experience replies, "No," in the case of a
completely non-virulent anthrax bacteridium, for it
escapes our experimentation by refusing to grow in any
living organism; it is henceforth fixed, and if it ever
returns to virulence, it will be by passing through a new
species of animal different from those which hitherto
have been shown to be capable of contracting anthrax.

But the case is different for those strains which still

RETURN TO VIRULENCE 309

preserve an action on a living species. Let us take for
example the most attenuated, that which is barely able
to kill a guinea-pig a day old: if we inoculate its blood
into a guinea-pig of the same age, that of the second
animal into a third, and so on, we shall shortly see the
virulence of the bacteridium return little by little.
Soon we shall be able to kill with it guinea-pigs three or
four days old, a week, a month old, and finally sheep.
By successive cultures in living media, the bacteridium
has been restored to its original virulence.

It is justifiable to form out of these facts a general rule,
in accordance with our theory. A microbe introduced
into the body of an animal is not living under the same
conditions as one sown in an inert vessel; it is subjected
to the pressing alternative of living or dying, of being
victorious or vanquished. Vanquished, its history is
soon written; victorious, it will come out of the struggle
strengthened, that is to say, having complied with the
conditions of its new medium, it is better prepared to
accommodate itself therein anew. If it is transferred
several times from individual to individual of the same
race, without having been influenced by external con-
ditions in the interim between two passages, we may
expect to see its virulence augmented and in some degree
fixed for the race and for the customary mode of trans-
mission in this race. Thus the bacteridium of sheep an-
thrax, for example, living for a long time on our soil, is
acchmated to some degree in the race which shelters it,
and its virulence varies little from one subject to another,
and from one year to another for the same country.
The same thing is true, to a certain extent, for Jenner's
vaccine, if it is transferred directly from arm to arm on
unvaccinated healthy individuals, and if it is carefully
preserved between the two operations. The same thing
is also true for the virus of rabies administered by tre-

310 PASTEUR: THE HISTORY OF A MIND

panning, after a certain number of passages through
individuals of the same species.

Having once attained this stability, which is not its
maximum virulence for the race, as we shall see later,
the virus preserves this degree of virulence practically
unchanged, if the paths of penetration do not vary.
This increased virulence may permit it to invade another
race or another species. Thus our anthrax bacteridium,
invigorated by a passage through the guinea-pig, can
infect the sheep. But there may also be produced cases
analogous to those in the experiments of MM. Chamber-
land and Roux, in which the virulence augmented for
one species will be diminished for another, or inversely,
and we reach a third possible case, that of the diminution
of virulence for one species bj^ passages through another
species.

We shall find an example of this fact, so clear that it is
almost diagrammatic, in the work of Pasteur and Thuil-
lier, on the erysipelas of the pig. This disease is due to
the development in the tissues of the animal of a very
short and slender rod. It goes through its stages of
evolution very rapidly, and may cause death in some
hours.

It is not confined to swine, but may also be communi-
cated to the pigeon and the rabbit. If there is injected
into the pectoral muscles of a pigeon the microbe of the
erysipelas taken from a diseased pig, or from a culture in
veal bouillon, the pigeon dies in from 6 to 8 days,
after having shown the external symptoms and the som-
nolence of chicken cholera. We might believe that the
two diseases are identical if the organism of the erysipelas
were not absolutely harmless to the chicken, which is so
sensitive to the action of the cholera microbe.

If the blood of the first pigeon is injected into a second,
the blood of the second into a third, and so on, the malady

RETURN TO VIRULENCE 311

becomes acclimated in the pigeon, makes it sick and
somnolent more quickly, kills it sooner, and the blood
of the last pigeon injected into the pig, manifests there
a virulence superior to that of the most infectious mate-
rial from a pig which has died of erysipelas, even if the
pig was naturally infected. Here we have then aug-
mentation of virulence for the pig by passing the or-
ganism through the pigeon. The maximum to which a
virus can attain by passage through a race is, therefore,
not always, the maximum for that race.

There we have a case of augmentation, here is a case of
attenuation to which I wish especially to call attention.
Let us substitute the rabbit for the pigeon in this series
of experiments. The microbe becomes accustomed to
the rabbit; all the animals die, but if we inoculate pigs
with the blood of the last rabbits for comparison with
that taken from the first rabbits in the series, we find a
progressive diminution of virulence. Soon the blood
of rabbits, inoculated into pigs, no longer kills them;
it only makes them sick and leaves them vaccinated
against the fatal erysipelas. Entirely parallel facts
have been worked out with other microbes. They
furnish a method of attenuation of viruses by passages
through living species, and increase our means of action
in a field of studies the future of which will show its
astonishing fruitfulness.^

We have now come back, apparently, to a conclusion
already stated: Virulence is a state of perpetual becoming.
But how much we have developed this idea, and what
precision the new facts have given to it, and to the bond
of theory which has enabled us to unite them I In the

1 This prediction has been more than fulfilled. Since this book was
written very wonderful advances have been made in bacterio-therapy,
the most striking of which have been the control of diphtheria and the
prevention of typhoid fever and of tetanus. Trs.

312 PASTEUR: THE HISTORY OF A MIND

beginning we ascribed variations in virulence to the
microbe itself and there was there a vast field for evolu-
tions, but it did not embrace all the possible ones. We
have been obliged to add to it those which come from
the variation of the living organisms in which the mi-
crobes establish themselves, and the virulence which we
see results from an infinite number of combinations of
these two causes of variation.

IX

CHEMICAL AND HUMORAL THEORIES OF

IMMUNITY

From what we have just said it follows that the word
virulence has no meaning either in relation to the microbe
or to the host. It signifies little more than the relation
between strength and resistance, without telling us
anything about the absolute value of these two forces.
A microbe which does not kill a given animal or does not
make it ill is devoid of virulence with respect to that
animal, and one might believe from this statement that
all the truths which we have discovered are naivetes, or
mere definitions of words; that would be making a great
mistake. What we have discovered, in reality, is a new
field of study. With respect to this or that animal, such
or such a microbe may remain harmless for many
reasons. It cannot develop in its tissues, or, if it does
develop, deposits there no injurious substances, or even,
perhaps, produces beneficial effects, leading to increased
resistance. The field of hypotheses is unlimited. Let
us see what experience offers, and let us observe how
much the field of experiment has been extended, thanks
to Pasteur.

Here are normal sheep inoculated, some with the

CHEMICAL AND HUMORAL THEORIES OF IMMUNITY 313

virulent bacteridium, others with the attenuated bacteri-
dium. The first develops and kills the sheep. The
second, after a period of growth made with more or less
difficulty and causing a transitorj^ illness of the sheep,
abandons the struggle and leaves the animal more or
less vaccinated. This is one method of studying the
influence of the bacteridium alone.

Now let us take a normal sheep and a vaccinated
sheep, into which we inoculate a very virulent strain of
the anthrax bacteridium. It kills the first and has no
effect on the second. Here we have a way to study the
influence of immunity acquired by a former vaccination.

Let us take now a French sheep and an Algerian sheep;
let us inoculate both of them with a light dose of a viru-
lent strain of the bacteridium. The first will die, the
second will resist, after an illness in general benign. In
this we have the influence of race or of natural immunity.

The French sheep has a natural immunity for the
attenuated bacteridium; the Algerian sheep, a natural
immunity against the virulent disease; the vaccinated
sheep an acquired immunity, more or less marked; the
dog, a natural and absolute immunity. In all the cases,
the natural or acquired immunity, when it is complete, is
correlative with the non-development of the bacteridium,
which instead of invading the tissues, remains confined
to the point of inoculation or its vicinity, and finally
perishes there.

What is the cause of this non-development of a
living cell which has been sown? This question is what
the inquiry led to! We see that it was precise. It was
already a conquest only to be able to state it thus. Until
that time it had been necessary to bow down without
seeking to penetrate the mystery. What reply, in fact,
can be given to this general question: Why is the sheep
sensitive to anthrax, and the dog not sensitive? Whj^

314 PASTEUR : THE HISTORY OF A MIND

is man alone able to contract syphilis?^ These are
questions which one did not even dream of putting to
himself. But after living viruses were discovered and
their conditions of growth were known, man could ask
himself why they develop here and not there, on the
French sheep and not on the Algerian sheep, both of
which are, however, authentic sheep.

For an answer to this embarrassing question, Pasteur
sought quite naturally, as any man of science would do,
in his experience and memory. They were, it is true, the
experience and the memory of a chemist, and the question
did not remain long in the field where he first placed it.
But all theory is good which foresees new facts, and
however inexact it appears to-day, the explanation of
Pasteur has had that merit.

He knew, through his long experience with fermenta-
tions, that even when one works in vitro the smallest cir-
cumstances suffice to permit or to hinder the development
of a microbe. When he saw certain of them demand veal-
bouillon and certain others fowl-bouillon, it did not sur-
prise him that a particular disease was peculiar to a
particular species, and another disease to another species.
Neither was it astonishing, knowing how hard to please
the microbes are on questions of temperature, that the
chilled fowl should contract anthrax, while at its ordinary
temperature it remained unaffected. Finally, knowing,
as we have said, that the chicken cholera microbe refuses
to develop again in a medium in which it has already
lived, why be astonished that it should refuse to live
again in an organism which it has already invaded?
There was, in these exclusively physical or chemical

' We now know from the studies of Metchnikoff that syphilis is in-
oculable into apes, and from those of Noguchi into rabbits the living
testicles of which are the best culture medium for the propagation of the
Treponema paUidutn — the protozoan cause of syphilis. Trs.

CHEMICAL AND HUMORAL THEORIES OF IMMUNITY 315

facts, a wholly natural explanation of the non-recurrence
of virus diseases.

Let us investigate in this direction. Why does not the
same bouillon culture nourish easily a second time the
species which has already lived in it? The failure might
result from one of two things: either the organism
removed from the bouillon the first time a substance
needed in its development, or else it deposited in it an
injurious substance.

Pasteur and his colleagues inclined toward the first ex-
planation. M. Chauveau, on the contrary, favored the
second and supported it on two arguments of unequal
value. He was of the opinion, for instance, that the
vaccination of the foetus by the mother, that is to say,
the transmission of immunity through the placenta,
which he had often had occasion to verify in anthrax, and
which MM. Arloing, Cornevin and Thomas had just
proved for the symptomatic anthrax, was better ex-
plained by the introduction of an injurious substance
into the blood of the foetus, than by the disappearance of
a needed substance. The two bloods of the mother and
of the foetus being constantly in position to exchange
chemical substances, are likewise in position to lose or
to acquire, and there appear to be no reasons for be-
lieving that preference is given one over the other.
Another argument of M. Chauveau was worth more.
He called attention to the curious influence of the quan-
tity of virus used in inoculation. The Algerian sheep is
immune to doses which kill the French sheep, but, if
we increase the dose, we also kill the Algerian sheep.
If it is much diminished, the French sheep resists in its
turn, experiencing only an illness, from which it emerges
vaccinated. This is not explained by the hypothesis of
Pasteur. If there is lacking in the sheep an element
needful for the multiplication of the bacteridium, we

316 PASTEUR: THE HISTORY OF A MIND

do not understand why its absence no longer interferes
with growth when the number of microbes increase
which have need of it for their development. On the
contrary, it is much more comprehensible why the
presence of an injurious substance can stop a small
detachment of the enemy, and not a large troop.

It is useless to dwell upon the discussion of these ex-
planations of immunity, both of which may indeed have
their part in the phenomenon, but cannot play a stellar
role. Strictly speaking, they are sufficient to explain
the immunity produced by vaccination, but they weaken
when it is a question of explaining the duration of immu-
nity. How can we admit the persistence for years of
this injurious element, or the absence of the necessary
element, when nutrition and destructive metabo-
lism bring and remove such varied elements. The
element duration is represented in the tissues, not by
the chemical substances which compose them, but by
their permanent form — by the cell.

The tw^o explanations which we have just considered
are not the only ones which have been proposed. There
have been successively attributed to the humors, and
to the liquids of the animal economy, a destructive
power for microbes, an attenuating power, an anti-
toxic power, all these powers depending solely on con-
ditions of the physico-chemical order. Without entering
into a detail which however important it is, would be
out of place here, it can be said that all these theories
have shown themselves to be powerless to explain the
great fact of the creation and the persistence of inmiunity.
As to the creation of this property in the individual,
either it has been found that the liquids in circulation
or the humors that occur in the interior of the body,
did not have the destructive, attenuating, or antitoxic
power which we find in them outside of the organism,

CELLULAR THEORY OF IMMUNITY 317

or else if they did have these powers, they were without
apparent relation to the resistant or vaccinated state
of the animal. For the conservation of immunity, the
same criticisms apply as to the theories of Pasteur and
Chauveau. A chemical action, whatever it may be,
cannot be lasting in an organism in which all the chemi-
cal elements are constantly being renewed. There is
only the cell which lasts, because it lives. It is more
likely that the explanation of immunity lies in the
cellular theories than in the humoral theories which we
have just briefly reviewed.

X

CELLULAR THEORY OF IMMUNITY

Pasteur, who in his heart was indifferent to theories
and asked of them only that they suggest experiments
to him, held for a long time a purely cellular conception
of microbial disease. It was by a struggle between the
red blood corpuscles and the bacteridium that he ex-
plained in 1878 the resistance of the living fowl to anthrax,
and we see him at every instant, in that period, having
recourse to vital resistance, and saying: "Among the
lower forms of life, still more than in the higher species
of plants and animals, life prevents life." Again, it was
this same sentiment which guided him in the experiments
which we have seen him making, to prevent the develop-
ment of the anthrax bacteridium by inoculating at the
same time with some common bacteria. Pasteur, how-
ever, was conscious of not having laid hold of the vital
point of the mechanism of the resistance of the organism,
and it is perhaps for that reason that when he heard of
the researches of Metchnikoff on phagocytosis, he gave

23

318 PASTEUR: THE HISTORY OF A MIND

immediate attention to them. It is his letter, inserted
in the first number of the Annates de VInsiitut Pasteur,
which first pointed out to the French public the re-
searches of M. Metchnikoff.

The simplicity of this conception was striking. These
white corpuscles of the blood and of the tissues, playing
the role of gendarmes in the organism, constantly in
circulation, always ready to throw themselves on every-
thing foreign appearing there, and consequently upon
enemies living or dead, surrounding by virtue of this
general property the cells of the microbes, digesting
them and making them disappear — all that could not
fail to captivate him! The idea was the idea of a biolo-
gist and of a naturahst; it had not occurred to Pasteur,
but that did not prevent him from welcoming it with
deference. As long as he lived, he wished to keep in
touch with its progress.

It pleased him so much the more that after remaining
for some time in the field of anatomy and natural history,
the problem was not long in returning to the field of
chemistry, to which all our conceptions, whatever may
be their objects, provided they are deep, are not slow
in returning, because, at bottom, it is chemical mutations
which govern everything.

The theory of Metchnikoff had, moreover, for his
mind, this satisfying side that it equalized the competi-
tive forces. There is something disproportionate in a
bacteridium which kills an ox. One understands better
a localized struggle between the leucocytes of the ox
and the invading microbes, which perish if they are
too feeble, or too few in number, but which take posses-
sion of everything if they are the stronger, because they
have the power of multiplication in their favor.

Nevertheless, thus limited and defined, the conditions
of the struggle remained hazj'' and somewhat mysterious.

CELLULAR THEORY OF IMMUNITY 319

One might have understood a conflict between the
microbe and the cells directly reached by the inoculation
or located in its neighborhood; but obedient to what
mysterious call do the white cells come from all parts of
the organism, filtering through vessels, and penetrating
to the region where they will be useful? The living cells
have no emotion, not even that of well-being, they have
only needs, and obey only physical or chemical actions.

The discovery of chemiotaxis, and the extension to the
leucocytes of ideas introduced into science by Pfeiffer
has taken away from the theory of M. MetchnikofT a
little of its mysterious aspect, and with the same stroke
has brought back to the field of chemistry the question
which had been referred to the cellular field. It dem-
onstrates the existence in the leucocyte of a sort of
far-away scent, which indicates to it the directions in
which it will find substances suited to its taste, or from
which it can derive benefit. These substances are se-
creted by the microbes used for inoculation, or intro-
duced with them in the bouillon cultures. Immediately,
they challenge the enemy and the struggle begins. It
can happen, and in fact does happen sometimes that the
secretions of the bacillus are not inciting, and even that
they are repellent. Then the bacillus protects itself
against the leucocytes, and can develop at its ease, if the
host does not put into play secondary causes of resistance.

As to the struggle, when once begun, its issue always
rests undecided a priori. Sometimes the leucocyte,
surrounds the microbe and digests it. It becomes a
phagocyte. Sometimes also the ingested microbe suc-
ceeds in remaining alive, continues to secrete injurious
substances, a toxine, and it is the leucocyte which suc-
cumbs. In cases in which disease follows the inocula-
tion, the victory remains undecided for some time, then
results in favor of one of the adversaries.

320 PASTEUR: THE HISTORY OF A MIND

When it is the host which succumbs, the microbe seems
to emerge more inured to the struggle, capable of secret-
ing in greater abundance the products which have ren-
dered it victorious. We explain this fact by saying that it
has become more virulent, and a good way of increasing
its virulence is to make it pass through species, which
without being absolutely immune, can resist it a long
time and enable it to acquire a new vigor. That is what
we did when we rendered the anthrax bacteridium more
virulent by making it pass through species more and more
resistant to its action.

On the other hand, when it is the microbe which suc-
cumbs in the struggle, the leucocytes in their turn issue
from the conflict stronger, more sensitive to the chem-
iotaxis of the microbes which they have killed, and more
accustomed to their toxines, and the animal consequently
has a power of resistance, an immunity, which it did not
formerly possess.

It is not necessary to enter into details to see that we
have here a conception which lends itself in a remarkable
manner to the interpretation of all the very curious facts
discovered by Pasteur. I add that this interpretation
is not purely theoretical. It is sufficient to read, in the
Annales de VInstitut Pasteur, the numerous works ac-
cumulated on this subject by M. Metchnikoff and his
pupils, to be convinced that we are face to face not only
with a captivating theory, but with a theory true to its
smallest details, and in all respects fruitful.

In resume, the resistance of each living being with
respect to a microbial inoculation is at the same time
a question of species, a question of individuals, a question
of place and of time, a question of quantity of inoculating
material, and also a question of temperature, for a low-
ering of temperature can diminish the activity of the
leucocytes and increase that of the bacillus, as in case

CELLULAR THEORY OF IMMUNITY 321

of the chicken which, when chilled, contracted anthrax.
A microbe may be harmless for the species which carries
it, and may not be so for others, the resistance of which
is not organized in the same fashion. It will be under-
stood that it may be fatal to the young animal, whose
phagocytes are not inured, that it may develop where
the phagocytes are not numerous, and not where it
finds them in great numbers and better trained, etc.
And all this happens through the intermediary of cel-
lular secretions, that is to say through physico-chemical
agencies. It is evident that Claude Bernard and the
physiologists who feared to see Pasteur re-introduce into
science the idea of life as a hidden cause had in him
not an enemy of their doctrines, but a powerful ally.
We see also that the physicians were right in treating
him as a chemist. They were wrong only in pronouncing
this name with a disdainful air. With Pasteur chemistry
took possession of medicine and we can foresee that it
will not relinquish its hold.

I'AS'I'IUR

(Photo. l)y the writer, from a bronze plaque l^}' G. Prud'homme.)

(Courtesy of ("ol. .1. F. Silcr, Office of the Surgeon General,

Washington, 1). 0.)

ANNOTATED LIST OF PERSONS MENTIONED IN THIS BOOK

[The following statements have been derived principally from French,
Italian, and German sources. In a few instances I have taken dates
from Garrison's "History of Medicine" (W. B. Saunders Co., 2d edition,
1917). This book contains an appendix entitled "Medical Chronology,"
very useful to students in fixing dates of various important discoveries
in pathology and bacteriology. It contains also portraits of many of
the persons here mentioned, and to these portraits I have referred as

"Garrison, p. ." The book is very readable and is recommended to all

students, even those not interested in medicine. They cannot read
it without becoming so. The other abbreviated portrait references,
not self-explanatory, are of Pagel's very interesting "Biographisches
Le.xikon hervorragender Arzte des neunzehnten Jahrhunderts," Berlin

and Vienna, 1901, referred to as "Pagel, p. ," Werckmeister's "Das

neunzehnte Jahrhundert in Bildnessen," 5 vols. (1898-1901), Berlin,

Photog. Gesellschaft, referred to as "Werckmeister, p. ," Veit Brecher

Wittrock's Catalogus illustratus iconothecse botanicae horti Bergiani
Stockholmiensis, Pars I and II. Acta Horti Bergiani. Bd. 3. Nos. 2
and 3, Stockholm, 1903 and 1905, referred to as "Wittrock I, or II, Tafl.

" and "Histoire illustree de la Litterature Frangaise Precis Methodi-

que." Par E. Abry, C. Audic, P. Crouzet. 3^ Edition revue et corrige.
Paris. Henri Didier, Editeur. 1916, pp. XII, 664. A copiously illus-
trated, inexpensive and fascinating beginner's book of French literature,
referred to as "Abry p. ."]

Appert, Emile ( ). French mathematician and chemist.

First science teacher of Duclaux.

Appert, Franfois (17 1840). French manufacturer. Brother of the

philanthropist. Invented canning for the preservation of foods.
Received 12,000 francs from the French Government for making
public his discovery. His book (1810) entitled "Le livre de tous
les menages, ou I'art de conserver pendant plusieurs annees toutes
les substances animales et vegetales," passed through five editions.

Arloing, Satumin (1846-1911). French physician and veterinarian.
Professor of experimental medicine at Lyons. Studied sympto-
matic anthrax with Cornevin and Thomas. Investigated peri-
pneumonia, etc. Wrote an "Anatomy of domestic animals"
which f)assed through four editions.

Bacon, Francis Lord Verulam (1561-1623). English judge and natural
philosopher. His 'Novum Organum" was published in London
in 1620.
"The wisest, brightest, meanest of mankind." (Pope.)

323

324 ANNOTATED LIST OF PERSONS

Bail, Karl Adolph Emmo Theodor (1833 ). German mycologist.

Discovered the submerged yeast form of Mucor mucedo.

Balard, Antoine Jerome (1802-1876). French chemist. Born in
Alontpellier. Professor in the Normal School, the College of France
and the Sorbonne. Inspector general of higher education. Member
of the Academy of Sciences. Discovered bromine (1826) and
succeeded in extracting sodium sulphate from sea water.

"Par sa chaleur d'ame, il entrainait tout le monde dans un mouve-
ment gencreux. C'etait un eveilleur d'activites. ... Ce qui me
charmait en lui, c'est qu'il avait le culte de la science pure. Des
qu'un homme de laboratoire mele a ses travaux d'autres preoccupa-
tions, il est arrete dans sa marche." (Pasteur.)

Barbet ( ). Director of the "Maison Barbet," a Parisian

preparatory school. Teacher of Pasteur and of Duclaux.

Bastian, Henry Charlton (1837-1915). English physician, physiologist
and pathologist. Born in Cornwall. Professor in University of
London. Member of the Royal Society. Bastian WTote "The
Modes of Origin of Lowest Organisms" (1871), "The Beginnings of
Life" (1872), and "Studies in Heterogenesis" (1901). Student
of nematodes and of the brain and nervous sj-stem. Adversary
of Pasteur. For portrait see Pop. Sci. Monthly, Nov., 1875.

Beal, William James (1833 ). American botanist. Born in

Michigan. Student of Louis Agassiz and of Asa Gray. For many
years professor in Michigan Agricultural College.

Bechamp, Pierre Jacques Antoine (1816-1908). French physician.
Professor in Faculty of Medicine in Montpellier and afterward in
the Catholic Faculty in Lille. Antagonist of Pasteur. Copious
writer. His chief work is "Les Microzymas dans leurs rapports
avec I'h^tcrogenie, I'histogenie, la physiologic et la pathologic,
examen de la panspermie atmospherique continue ou discontinue,
morbifere ou non morbifere," 8 vo., pp. 992, Paris (1883); see also
"Microzymas et Microbes" (1888).

"As to the nature of the disease [flacherie] and its cause, M. Be-
champ ascribes it to mobile molecules which he calls microzymas
and which he sees swarming everywhere 'on the surface of the
worms, in their fluids, in the eggs, etc' I leave to M. Bechamp
the complete priority of these facts." (Pasteur.)

Becher, Johann Joachim (163.T-1682). German chemist and political
economist. A forerunner of Stahl. Helped to introduce potato-
culture into Germany — a vast undertaking, since there wds a strong
popular prejudice to be overcome.

Beethoven, Ludwig van (1770-1827). Greatest of composers. Son of a
drunkard who was a mediocre musician and of a tuberculous woman
who was the daughter of a cook. Generally reckoned as a German,

ANNOTATED LIST OF PERSONS 325

but his masque shows Slavic features. He was born in Bonn on
the Rhine. His father's father came from the low countries
(Antwerp), and his mother's maiden name was Maria Magdelena
Kewerich. He was an upright, democratic man, passionately fond
of nature and what is best in music, literature and art. He wrote
German badly, but in music he was a god! He spent most of his
mature life in Vienna and died there. For portraits see "Beethoven"
by Vincent d'Indy in "Les Musiciens Celebres" Paris, Renouard,
and "Beethoven, the man and the artist as revealed in his own
words," by Fr. Kerst (Tr. by Krehbiel. N. Y., B. W. Huebsch, but
without the portraits) .

Bellamy,

Bellotti, Cristoforo ( ). Italian student of silk-worm diseases

in the Museo Civico of Milan. Published several papers in Milan
(1863-1879). Wrote also on the fossil fish of Lombardy.

Berkeley, Rev. Miles Joseph (1803-1889). Enghsh microscopist and
crj^ptogamic botanist. Author of "British Fungi," "Decades of
Fungi," "Introduction to Cryptogamic Botany," "Handbook of
British Mosses," etc. Wrote also on diseases of plants for "The
Gardeners' Chronicle." For portraits see Wittrock II, Tafl. 145,
and Whetzel's History of Phytopathology, p. 56.

Bernard, Claude (1813-1878). Distinguished French physiologist.
Magendie's assistant. Professor in Paris. Member of the
Academy of Sciences and of the Academic Fran^aise. Senator.
Discovered action of the pancreas in the digestion of fat, storage of
glycogen in the liver, existence of nervous centers acting independ-
ently of the brain and cord (sympathetic system), and sugar in
the urine as a result of wounding the fourth ventricle of the brain.
Author of many books and papers. His "Legons sur les phenomenes
de la vie commune aux animaux et aux vegetaux" appeared in
Paris in 1879. For portraits see Garrison, p. 576, Pagel, p. 147,
Abry, p. 589 and Pop. Sci. Monthly, Oct. 1878.

Bert, Paul (1833-1886). French politician (Republican) and physi-
ologist. Student of Claude Bernard. Professor in Bordeaux and
in Paris. Received 20,000 francs reward for barometric investiga-
tions in relation to life processes. Member of Gambetta's ministry.
Pasteur's friend. Wrote "Lemons sur la physiologic comparee
de la respiration," 8vo, pp. xxxv, 588. Paris, 1870. Dedicated
to Claude Bernard. For portraits see Harper's Mag., 1882, p. 560,
and Pop. Sci. Monthly, July, 1888. .

Berthelot, Marcelin Pierre Eugene (1827-1907). French chemist.
Senator. Remarkable for his studies of organic substances:
polyatomic alcohols; synthesis of organic substances; thermo-
chemistry; explosives. Assistant of Balard. Professor in School of

326 ANNOTATED LIST OF PERSONS

Pharmacy and College of France. Member of the Institute.
Author of many books and papers. His "La synthese chimique"
passed through eight editions. For portraits see McClure's Maga-
zine, 1894, p. 305, and Pop. Sci. Monthly, May, 1885.

Bertin, Pierre Augustin (1818-1884). French physicist. Student in
the Normal School. Professor in Strassburg. Professor in the
Normal School: master of conferences and sub-director. Friend
of Pasteur. For portrait see "Le Centenaire de I'Ecole normale."
Paris, 1895, p. 400.

Berzelius, John Jacob (1779-1848). Swedish physician and chemist.
Professor in Stockholm. Introduced symbolic notation, determined
atomic weights, developed the doctrine of valency. Studied and
developed electrolysis: in the decomposition of water showed that
hydrogen, metals and alkalies go to the negative pole, and oxygen
and acids to the positive pole of the battery. Discovered selenium
and cerium; showed calcium, barium, strontium, tantalium, silicium
and zirconium to be elements; investigated whole classes of com-
pounds. Author of many papers and books, including an annual
review of the progress of chemistry and mineralogy for 27 years.
One of the fathers of modern chemistry. For portrait see Harper's
Mag., 1897, vol. 95, p. 756.

Biot, Jean-Baptiste (1774-1862). French physicist, mathematician and
astronomer. His chief contributions were in optics. Associate
of Gay-Lussac and Arago. A brave and just man. Very helfjful
to the j'oung Pasteur. For portraits see L'Art, 1876, p. 183, Art
and Letters, 1881, p. 187, and Harper's Mag., 1897, p. 49.

Black, Joseph (1728-1799). Scotch chemist. Professor in Edinburgh.
Foreign member of the French Academy of Sciences. A forerunner
of Cavendish and Priestley. Studied alkalies and alkaline earths.
Discovered latent heat and "fixed air" (carbon dioxide). One
of the creators of modern chemistry. For portrait see Garrison,
p. 323.

Blanchard, Emile (1820-1900). French naturalist. Professor in the
National Agronomic Institute. President of the Academj- of
Sciences in 1881. Wrote a natural history of insects, etc.

Bloch, Gustave (1848 ). French historian. Professor in Besan^on,

Lyons and Paris. Officer of the Legion of Honor. French normal
school graduate. Eulogi.st of Duclaux.

Bomet, Jean Baptiste Edouard (1828-1912). French algologist. Mem-
ber of the Academy of Sciences. Contributed much to our knowl-
edge of red algiB and lichens. Collaborated for many j'ears with
Thuret. For portraits sec Wittrock I, Tafl. 33, and Wittrock II,
Tafl. 83.

ANNOTATED LIST OF PERSONS 327

Bouley, Henri (1S14-1S85). French veterinarian and comparative
pathologist. Member of the Institute. President of the Academy
of Sciences in 1885. Champion of Pasteur. For a portrait see
Rec. Med. Vet., 7 scr., Tome II, No. 23, 15 dec, 1885.

Boullay, Polydore (1806-1835). French chemist. Wrote "Memoire
sur hi formation de I'cther sulfurique" (1827), "Memoire sur les
ethers composes" (1828).

Boussingault, Jean Baptiste Joseph Dieudonne (1802-1887). French
anaeytical and agricultural chemist. Fought under Bolivar in
South America. Climbed Chimborazo (1831). Professor in Lyons
and in Paris. Member of the Academy of Sciences; Member of the
National Assembly (1848). Grand officer of the Legion of Honor.
He showed that ordinary plants cannot assimilate free nitrogen.
One of the founders of the Science of Agronomy (see his "Traite
d'Economie rurale" and his "Agronomie, chimie agricole, et
physiologic"). For portraits see Wittrock II, Tafl. 58, and Pop. Sci.
Monthly, Oct., 1888.

Boutron, Charlard Antoine Francois (1796-1878). French chemist.

Boyle, Robert (1627-1691). English chemist and physicist. Brother
of the statesman. Discovered Boyle's law. Wrote his "Sceptical
chymist" in 1661. Used vegetable colors for determining acidity
and alkalinity of solutions; invented a freezing mixture. Founded
a lectureship on the Evidences of Christianity. For portrait
see Pop. Sci. Monthly, Feb., 1893.

Brauell, J. Fr. ( ). German veterinarian at Dorpat. Brauell's

first communication appears to have been in Virchow's Archiv,
1857. Wrote also on rinderpest (1862).

Bremer, Gustav Jacob Wilhelm (1847-1909). Dutch chemist. Taught
in Rotterdam. Published in Dutch a paper on malic acid (Een
rechtsdraaiend appelzuur) in 1875.

Broussais, Francois Joseph Victor (1772-1838). French physician and
pathologist. Founder of a school of medicine called "the physio-
logical school," which for a time had an enormous following in
France. Broussais was a great believer in the value of starvation
and blood-letting. He would cover a patient with leeches. For
portraits see Garrison, p. 416, and Pagel, p. 29.

Brucke, Ernst Wilhelm Ritter von (1819-1892). German anatomist and
physiologist. Professor in Koenigsberg and Vienna. Author of
numerous papers on physiology of speech, physiology of colors,
etc. For portraits see Garrison, p. 489, and Pagel, p. 259.

Buffon, George Louis Leclerc de (1707-1788). French naturalist.
Celebrated for the style of his books, which were translated into
many languages but are of slight value now. It was he who said:

328 ANNOTATED LIST OF PERSONS

"Le style est rhomme meme." For portraits see Abry, p. 387
and Petit Larousse illustr6, p. 1193.

Burdon-Sanderson, Sir John Scott (1828-1905). English physician
and physiologist. Lecturer at 8t. Mary's Hospital. Professor in
London University and Lmiversity College of London. Member
of the English Rabies Commission (1886).

Cagniard-Latour (or de la Tour) (1777-1859). French physicist.
Invented the siren whistle (1809), called in French cagniartlelle.

Cantani, Arnaldo (1837-1893). Italian physician, clinician and pa-
thologist. Son of a Neapolitan physician. Senator. Professor in
Pavia and then in University of Naples. Author of several books.
Interested especially in infectious diseases. Wrote on cholera.
For portrait see Pagel, p. 303.

Cantoni, Gaetano (1815-1887). Italian student of silkworm diseases.
Professor in the Royal Museum in Turin. Founder and director
of the High School of Agriculture in Milan. Author of many books
and papers on agricultural subjects. Wrote "Trattato complete
teorico-pratico di agricoltura," 3d ed., 2 vols., Milan, 1884-5.

Chamberland, Charles Edouard (1851-1908). French physicist, pa-
thologist and bacteriologist. Normal school graduate. One of
Pasteur's collaborators. Member of the Legion of Honor. Col-
laborated also with Roux, Joubert, Strauss, Fernbach and Jouan.
Elected radical Republican Deputy from the Jura in 1885. Author
of several independent works: "Origin and Development of Micro-
scopic Organisms" (1879), "'Drinking Waters and Epidemic
Diseases." Invented the Chamberland filter (1884). For portrait
see "Ann. d I'lnst. Pasteur," May, 1908.

Chantemesse, Andre (1851 ). French physician. Professor in the

Faculty of Medicine. Officer of the Legion of Honor. Author
of "Mosquitos and Yellow Fever," "Flies and Cholera," "Traits
d'hygiene," etc. Collaborated in anti-rabic inoculations at Pasteur
Institute. One of the Editors of "Ann. de I'lnst. Pasteur."

Charrin, Albert (1857-1907). French physician. One of the discovereis
of the glanders bacillus (Bouchard, Capitan et Charrin, "C. R.
Acad. d. Sci.," Dec. 26, 1882). Collaborated in anti-rabic inocula-
tions at Pasteur Institute. Author of "Les defenses naturelles
de Torganisme" (Paris, 1898).

Chassang, Alexis (1827-1888). French grammarian, lexicographer and
litterateur. Author of many books — grammars, dictionaries,
anthologies.

Chauveau, Jean Baptlste Auguste (1827-1917). Distinguished French
veterinarian, anatomist, physiologist and pathologist. Commander
of the Legion of Honor. Member of the Academy of Sciences and of

ANNOTATED LIST OF PERSONS 329

the Academy of Medicine. Editor of the "Journal de Physiologie
et de Pathologic Generale" and "La Revue de la Tuberculose."
Author of the classical "Traite d'anatomie descriptive des animaux
domestiques." For portraits see "The Veterinary Journal," Lon-
don, vol. 73, No. 2, Feb., 1917. "Journal de Physiol, et de Path.
Generale." Tome XVII, No. 1. Paris, 1917, and "Recueil de
Medecine Veterinaire," Tome XCIII. Nos. 1-2, Paris. 1917.

Cohn, Ferdinand Julius (1828-1898). German botanist. Professor
in Breslau. Studied mostly the morphology and developmental
history of alga>, fungi and bacteria. Born and died in Breslau.
For portrait in age see "Bact. in Rel. to Plant Diseases,"
Carnegie Inst, of Washington, vol. I, (Frontispiece) and at 33,
Wittrock II, Tafl. 84.

Collin,

Columella, Lucius Junius Moderatus. Roman poet of the First Century.
Wrote "De re ru.stica" (12 books in dactylic hexameters).

Comalia, Ser Emilio (1824-1882). Italian zoologist. Student of
silkworm diseases. Wrote a monograph on the Bombyx of the
mulberry (Milan, 1856). Discovered "Cornalia bodies" (Nosema
bombycis Nageli, Panhistophyton ovale Lebert), cause of pebrine.
Wrote also on geology.

Comevin, Charles Ernest (1846-1897). French pathologist. Student
of symptomatic anthrax with Arloing and Thomas. Wrote also
on "rouget," and a book on poisonous plants (Paris, 1893).

Coze, Leon (1817-1896). French pathologist.

Darwin, Charles Robert (1809-1882). English naturalist. A great,
simple-minded, humble and lovable man. Probably the most
influential person in the nineteenth century. His greatest book
"The Origin of Species by Means of Natural Selection" was published
in 1859. For portraits see Wittrock II, Tafl. 65, Garrison, p. 540,
Pagel, p. 33, and Pop. Sci. Monthly, Feb., 1873, and Nov., 1901.

Davaine, Casmir Joseph (1812-1882). Illustrious French physician,
zoologist and pathologist. Student of anthrax. Member of the
Academy of Medicine. Author of a "Traite des entozoaires et des
maladies vermineuses de I'homme et des animaux domestiques"
(2d ed., 8 vo., Paris, 1878). For portrait see "Arch. d. Parasit.,"
T. 7, p. 123.

Dechambre, Amedee (1812-1886). French physician. Member of
the Academy of Medicine. Chevalier of the Legion of Honor.
Wrote on "Diseases of Old Age," etc. His vast "Diet, encycl.
des Sci. Medicales" (1864-90) includes 100 volumes.

Declat, Gilbert (1827-1896). French physician. Following Pasteur's
studies on fermentation he made early use of antiseptics in medicine

330 ANNOTATED LIST OF PERSONS

and surgery. Edited from 1874 a journal for the diffusion of his
ideas called "Medecine des ferments."
Delafond, Onesime (1805-1861). French veterinarian. Professor in
tlio school at Alfort. Member of the Academy of Medicine. Dela-
fond was appointed to study anthrax in sheep in 1841. His "Traite
sur les maladies du sang des betes a laine" was published in Paris
in 1845. His second book "Traite sur [la maladie du sang des
betes bovines" appeared in 1848. Delafond's anthrax paper of
1860 referred to in the text, is in "Recueil de Med. Veter.," 1860,
p. 735.

Delafosse, Gabriel (1796-1878). French mineralogist and crystallog-
rapher. Pupil of Hatiy. Pasteur's teacher in the Normal School.
Member of the Academy of Sciences.
"Un homme qui avait le don de I'enseignement." (Pasteur.)

Descartes, Rene or Renatus Cartesius (1596-1650). Distinguished
French geometer, physicist and philosopher. Created analytic
geometry. Destroyed scholasticism and founded modern psy-
chology. Author of the "Cartesian" system. Cogito, ergo sum was
his foundation stone. From this he derived two other fundamental
ideas, the existence of God and the reality of an external world.
According to his "corpuscular philosophy," all phenomena of
matter depend on the movement of ultimate particles. Beginning
with 1629 he lived 20 years in retirement outside of France working
on his system. Died in Stockholm. For portraits see Garrison, p.
247, Abry, p. 130 and Pop. Sci. Monthly, Oct., 1890.

Desmazieres, Jean Baptiste Henri Joseph (1786-1862). French botanist
and microscopist, especially noted for his "Plantes cryptogames de
France" (182.5-1859). Desmazieres acquired a fortune in business,
which he used for the study of science. For portrait see "Bull,
de la Soc. Mycologique de France." Tome XX. Paris, 1904.

Dessaignes, Victor (1800-1885). French chemist in Vendome. Cor-
responding member of the Academy of Sciences in chemistry.

Deville (See Sainte-Claire-Deville).

Dobereiner, Johann Wolfgang (1780-1849). German chemist. Pro-
fessor in Jena. Friend of Goethe.

Dreyfus, Alfred (1859 ). French Captain of Artillery. A Jew.

Fal.sely accused by military men and anti-Semites of selling or
giving military secrets to Germany. Arrested (1894), condemned,
degraded (1895), and sent for life to Devil's Island in the Atlantic
near French Guiana. The effort on the part of the French liberals
to free him and convict the really guilty parties, who were other
military officers (Major Esterhazy and Colonel Henry), nearly
disrupted the French Government, but was finally successful, and
Col. Henry committed suicide. Zola defended Dreyfus in "L'affaire

• ANNOTATED LIST OF PERSONS 331

Dreyfus." With the exception of the noble and brave Col. Picquart,
the French war department chiefs, almost to a man, insisted on his
guilt, even after his innocence was established, and they were ably sup-
ported in their iniquity by the clergy, religious orders, and all
anti-Jewish influences. The authorities refused to reopen the case;
Col. Picquart was ordered to Tunis and subsequently imprisoned;
Esterhazy, who had been accused by Dreyfus, was tried by court
martial behind closed doors and acquitted; Zola was prosecuted
and convicted, and fled from Paris; and Dreyfus, finally retried by
court martial at Rennes, was again convicted but with "extenuating
circumstances;" Maitre Labori, his leading attorney, was shot
during the trial; the President of France was insulted; and Paul
Deroulede, the poet, urged the military to destroy the republic.
The injustice of the judgment at Rennes was so apparent and so
flagrant that Dreyfus was pardoned (1899), but all France was in a
ferment which did not subside for several years. Dreyfus demanded
another trial which was finally granted in 1905 and this time he
was fully acquitted. Dreyfus and Picquart were then restored
to the army with promotions and when Clemenceau selected his
first cabinet he made General Picquart minister of war. The dis-
establishment of the French church and the abolition of the religious
orders, as dangerous to the republic, was a direct consequence of the
Dreyfus affair.

Du Bois-Reymond, Emile (1818-1896). German physiologist and
philosopher, of Swiss-French extraction. Author of many books.
"Ignorabimus" is his famous word. Born and died in Berlin.
His brother Paul was a mathematician. For portraits see Garrison,
p. 564, Pagel, p. 210, and Pop. Sci. Monthly, July, 1878.

Duboue, ( ). French physician. Early student of

rabies.

Duclaux, Emile (1840-1904). French chemist, bacteriologist, patholo-
gist and rural economist. Director of the Pasteur Institute
from 1895-1904, and closely associated with it from its beginning
in 1888. For a bibliography of Duclaux's writings (220 titles
including 9 books, two of which are on milk) see the appendix
to Dr. Roux's Review of Duclaux's work in "Ann. de I'lnst. Pasteur,"
No. 6, 1904, pp. 354-362.

"Les amis qui ont ete le plus meles a son existence n'ont jamais
surpris en lui la moindre defaillance morale; il reste pour eux le
modole auquel ils voudraient ressembler." (Dr. Roux.)

Duclaux, Madame Mary (1857 ). English literary woman, nee

Agnes Mary Robinson, wife of James Darmesteter, the French
orientalist, then of Emile Duclaux (1901). Poet and prose writer
in English and French. Author of many books.

332 ANNOTATED LIST OF PERSONS

Duclaux, Pierre Justin (1798-1860). Father of Emile Duclaux.

Dujardin, Felix (1801-1860). French zoologist, student of Vermes,
Rhizopods, etc. He left unfinished a "Natural History of
Echinodermes."

Dumas, Jean Baptiste Andre (1800-1884). French chemist. Member
of the Academy of Sciences. Professor in the Sorbonne, Minister
of Agriculture and Commerce. Senator. Succeeded Guizot in
the Academie Fran^aise and was followed by Renan. Determined
the atomic weight of many elements. Studied amyl alcohol;
discovered the law of substitutions, which upset the ideas of Berzelius.
Published a great treatise (in 8 volumes) on applied chemistry.
For portraits see Harper's Mag., 1898, p. 625, and Pop. Sci. Monthly,
1880, p. 145.

"I attend at the Sorbonne the lectures of M. Dumas, a celebrated
chemist. You cannot imagine what a crowd of people come to these
lectures. The room is immense, and always quite full * * *
there are always six or seven hundred people." (Pasteur in 1842.)

"Le premier banc etait reserve aux eleves de I'Ecole normale.
J'ecoutais, j'applaudissais, je sortais de chacune de ces legons
I'esprit tourne vers de vaste projets." (Pasteur in 1895.)

Dusch, Theodor Freiherr von (1824 ). German pathologist.

Student of Henle. Professor in Heidelberg. Wrote on Icterus,
brain sinus thrombosis, and diseases of the heart. Collaborated
. with H. Schroder in the discovery of cotton as a dry (air) filter
for bacteria ("Ueber Filtration der Luft in Beziehung auf Fiiulniss
und Gahrung." Ann. der Ch. u. Pharm., Bd. 89, p. 232, Heidelberg,
1854). For portrait see Pagel, p. 431.

Duval, or Duval- Jouve, Joseph (1810-1883). French botanist. Studied
Equisetums and anatomy of grasses. Father of the anatomist.
For portrait see Wittrock II, Tafl. 138.

Ehrenberg, Christian Gottfried (1795-1876). German medical man,
naturaUst and traveler. Author of many elaborate and important
works on microscopic organisms, partly in Latin, and many of
them magnificently illustrated. Ehrenberg discovered fossil in-
fusoria and laid the foundations of our knowledge of this group of
animals. Traveled with Humboldt in Asia and with Hemprich
in Egyi)t. Opposed to the theory of spontaneous generation.
For portraits see Pop. Sci. Monthly, March, 1879, and Werck-
meister, 1901, 5, pi. 481.

Fabroni, J. Valentin (1752-1822). Italian chemist and engineer.

Farges, Agnes ( ). Mother of Emile Duch\ux.

"Tons les mendiants de la ville connaissaient le chcmin de sa j)ortc."

(Madame Duclaux.)

ANNOTATED LIST OF PERSONS 333

Feltz, Victor Timothee (1835-1893). French pathologist. Associated
with Coze.

Fembach, Ernst ( ). French pathologist at the Pasteur

Institute.

Fracastoro, Girolamo (1483-1553). Italian physician and poet.
Famous for his learning. Born in Verona. Wrote in verse
"Syphilis, sive morbus Gallicus" (1530). This is said to be the
first use of the word syphilis. For portrait see Garrison, p. 219.

Fraenkel, Albert (1848 ). German physician, bacteriologist and

pathologist. Discovered the pneumococcus. For portrait see
Pagel, p. 535.

France, Anatole, pseudonym of Jacques Anatole Thibault (1844 ).

Greatest of living French stylists. Author of many books and
papers, the most interesting of which, perhaps, are certain stories
about children, and four volumes of literary criticism entitled
"La vie litteraire." A master of irony. It was he who said of
Zola's novel "La Reve": "I marvel it can be so heavy, being so
flat!" For portraits see "Les Annales," No. 1729. Aug. 13, 1916.

Fremy, Edmond (1814-1894). French chemist. Member of the
Academy of Sciences. Wrote with Pelouze a "Traite de chimie
generale" (7 vols.). Editor of the "Encyclopedie de Chimie,"
(11 vols.).

Frey, Heinrich (1822-1890). German anatomist and zoologist.
Professor in Zurich. Collaborated with Leuckart. Published a
book on the microscope which passed through many editions, and a
book on the elements of histology which had several editions.

Gay-Lussac, Joseph Louis (1778-1850). French physicist and chemist.
Member of the Academy of Sciences. Peer of France. An elevated,
simple, disinterested, ingenious and philosophic mind. Discovered
the law of expansion of gases known as Gay-Lussac's law, also various
other laws. In 1804 made two balloon ascensions. First prepared
with Thenard the alkali metals, sodium and potassium, in quantity
from their salts. Also with Thenard showed chlorine to be a simple
substance. Developed alkalimetry and acidimetry. A friend and
companion of Humboldt, who styled him (1850): "ce grand et
beau charactere." At 16 he was without knowledge of the sciences.
He learned mathematics without a teacher and tutored his way
through college, studying at night. For portraits see Harper's
Mag., 1897, p. 757, and Werckmeister, 1899, v. 2, pi. 214.

Gemez, Desire Jean Baptiste (1834 ). French chemist. Student

at the Normal School. Assisted Pasteur in the study of wines and
of silkworm diseases. Officer of the Legion of Honor. Member of
the Academy of Sciences. Professor in the Normal School (1898-
1904). Author of "Crystalhzation of supersaturated solutions," etc.
24

334 ANNOTATED LIST OF PERSONS

Gibier, Paul (1851-1900). French pathologist.

Grancher, Jacques Joseph (1843-1907). French physician. Professor
in the Faculty of Medicine. Member of the Academy of Medicine.
Collaborated with Vulpian in vaccinating men for prevention of
rabies. Wrote on rabies, tuberculosis and pneumonia. One of
the Editors of "Ann. de I'lnst. Pasteur."

Guerin, Alphonse Franfois Marie (1817-1895). French surgeon.
Member of the Academy of Medicine and Commander of the Legion
of Honor. An introducer of antiseptic methods into French surgery
(after the war of 1870).

Guerin, Jules Rene (1801-1886). French physician. Editor of the
"Gazette mcdicale de Paris." Founded an orthopaedic institute.
Opponent of the preceding. Challenged Pasteur to a duel as
result of a dispute over vaccines.

Guerin-Meneville, Felix Edouard (1799-1874). French zoologist and
entomologist. Born in Toulon, died in Paris. Wrote a "Guide to
silkworm culture" (1856).

Guyon, Casmir Jean Felix (1831 ). French physician and surgeon.

Following Pasteur, early to apply antiseptics to diseases of the
bladder and urethra. Commander of the Legion of Honor, Pro-
fessor in the Faculty of Medicine. Member of the Academy of
Medicine, etc. Author of an atlas of a hundred plates on urinary
diseases (1881-1885). For portrait see Pagel, p. 667.

Hales, Stephen (1677-1761). English botanist, physicist and inventor.
Wrote "Statical Essays" (1727) and "Ha'mastatics" (1733).
One of the founders of scientific physiologj'. For portraits see
Garrison, p. 317, and Wittrock U, Tafl. 22.

Hallier, Ernst (1831-1904). German botanist. Assistant to Schleiden,
Professor in Jena. Author of many books. Quarreled with De
Bary. Much of his scientific work was vitiated by his ideas on
species transmutation. Unable to reason correctly from premises.
Wrote on philosophy and aesthetics toward the end of his life.

Hameau, Jean (1779-1851). French physician of La Teste, with ideas
somewhat like Henle's. Author of "Etude sur les virus." For por-
trait .see "Arch. d. Parasit.," T. 2, p. 317.

Haiiy, Rene- Just (1743-1822). French mineralogist. Member of the
Institute. Founder of crystallography. His "Essai d'une thc^orie
sur la structure des cristaux" was published in 1784. Brother of
Valentine Haiiy who invented raised characters for the blind.

Helmholtz, Hermann Ludwig Ferdinand von (1821-1894). Cierman
physicist, anatomist and jjliysiologist. Published on conservation
of energy (1847), optics, electricity and acoustics. Professor in
Koenigsberg, Bonn, Heidelberg, and Berlin. President of the

ANNOTATED LIST OF PERSONS 335

Pysikalisch-Technischen Reichsanstalt in Berlin. His chief works
are on optics and acoustics. Invented the ophthalmoscope (1850).
It was he who said: "The only laws I know are the laws of physics."
For portraits see Garrison, p. 562, and Pagel, p. 714.

Helmont, Jean Baptists van (1577-1644). Belgian physician and mystic.
Invented a system of medicine founded on that of Paracelsus.
Discovered the gastric juice, laudanum, carbon dioxide (gas syl-
vestre) and carbonate of ammonia. Introduced the words "gas"
and "ferment" into chemistry. For portrait see Garrison, p.
251.

Henle, Friederich Gustav Jakob (1809-1885). German anatomist,
physiologist and pathologist. Professor in Zurich, Heidelberg and
Gottingen. Published important books and papers on anatomy,
physiology, pathology, zoology and anthropology. His paper
referred to in the text is his "Pathologischen Untersuchungen"
(1840). See also his "Handbuch der rationellen Pathologie"
(1853). For portraits see Garrison, p. 473, and Pagel, p. 718.

Herschel, Sir John Frederick William (1792-1871). English astronomer.
Son of the astronomer Frederick William Herschel. Famous for
his catalogues and measurements of double stars. For portraits
see "Tennyson and his friends" by Cameron, 1893, pi. 10, and
Harper's Mag., 1897, p. 549.

Hippocrates (B. C. 460 — ). Greek physician and surgeon. "The

father of Medicine." . Descended, so said, from Aesculapius.
Born in Cos. Pupil of Democritus. A careful observer and great
clinician. He emancipated medicine from many superstitions and
enjoyed a great reputation as a healer, not only during his life but
for centuries after. For portrait from a bust see Garrison, p. 81.

Hoff (See Van-t-Hoff).

Hoffmann, Hermann ( ). German mycologist. The person

referred to in the text is probably the above, who was professor
in Giessen in 1874.

Hugo, Victor (1802-1885). French poet. Son of Gen. Hugo. Born
at Besangon. Member of the French Academy. Peer of France.
Spent 20 years in exile. Great lyric, epic, and dramatic poet.
Copious writer of romances and various critical and philosophical
essays. Democratic in politics. His published works comprise
eighty-two volumes. For portraits and caricatures see Abry, 497,
500, 502, .536, 540, 543.

Jaillard, Pierre Frangois (1827-1883). French physician. Professor in
Val de Grace. Associated with Leplat in anthrax studies.

Jenner, Edward (1749-1823). English physician. Discovered cowpox
vaccine, a preventive of smallpox. His studies of it were begun
in 1775 and the first human vaccination was in 1796. His first book,

336 ANNOTATED LIST OF PERSONS

with illustrations, "An Inquiry into the Causes and Effects of
Covvpox, or Variola; Vaccinae," was published in London in 1798.
For portraits see Garrison, p. 375, and Pagel, p. 24

Joly, Nicolas (1S12-1885). French physician and zoologist. Professor
of physiology in Toulouse. Member of the Legion of Honor.
Wrote on silkworms and their diseases, milk, yeast of beer, man
before metals, comparative psychology, German grammar simplified,
etc. Antagonist of Pasteur.

Joubert, Jules Franfois (1834 ). French physicist, especially

interested in electricity, on which he published two books. Pro-
fessor at College Rollin. One of Pasteur's collaborators. Officer
of the Legion of Honor. Ex-president, Soc. de Physique, and of
Soc. d'Electriciens.

Klebs, Edwin (1834-1913). German physician and pathologist.
Virchow's assistant. Assistant or professor in various places:
Koenigsberg, Bern, Wiirzburg, Prague, Zurich, Asheville, N. C,
Chicago (Rush Medical College) and elsewhere. For portrait see
Garrison, p. 614.

Koch, Robert (1843-1910). German pathologist and bacteriologist.
Geheimrat Regierungsrat, Med. rat. Born at Klausthal in the
Harz. A great investigator. Studied wound infections and demon-
strated their aetiology (1878). Introduced the poured-plate method
(1881). Discovered the cause of tuberculo.sis (1882) and of cholera
(1884). For the latter discovery he was given 100,000 marks by
the German Government. Introduced tuberculin (1890). In 1891
was made director of the newly founded Institute for Infectious
Diseases in Berlin. In 1896 discovered a remedj- for rinderpest
in South Africa. Studied malaria, sleeping sickness and other
diseases in South Africa, which he visited three times. Also studied
diseases of men and animals in India. Visited the United States
in 1908. For jjort raits see (iarrison, p. 612, Pagel, p. 878, and Pop.
Sci. Monthly, Dec, 1889.

Kiitzing, Friederich Traugott (1807-1893). German algologist. Author
of "Synopsis Diatomearum" (1833); "Tuhuke phycologica^"
(1845-1870, 2 vols., 2,000 colored plates); "Phycologia generalis"
(1843); etc. Distributed exicatti of fresh water alga; (16 parts).
For portrait see Wittrock II, Tafl. 64.

Lackerbauer, P. ( ). Painter and photographer who illus-
trated Pasteur's book on diseases of silkworms.

Lannelongue, Odilon Marc (1840-1911). French surgeon and patholo-
gist. Commander of the Legion of Honor. Professor in University
of Paris. Senator. Wrote various medical paj^ers, also "Travels
Around the World." Friend of Gambetta. His pathological collec-
tions are in the Musce Dupuytren. For portrait see Pagel, p. 959'

ANNOTATED LIST OF PERSONS 337

Lavoisier, Antoine Laurent (1743-1794). French chemist and physicist.
Member of the Academy of Sciences. One of the greatest investi-
gators of the 18th century. Founder in chief of modern chemistry.
He created chemical nomenchiture, determined the composition
of air and water, determined the role of oxygen in respiration
and combustion, and showed that the diamond is a form of carbon,
"Nothing can be destroyed, nothing can be created" was one of his
favorite expressions. He was guillotined during the French Revo-
lution. For portraits see Garrison, p. 325, and Pop. Sci. Monthly,
Aug., 1889.

Le Bel, Joseph Achille (1847 ). French chemist. Wrote on

stereochemistry.

Lebert, Hermann (1813-1878). German physician, pathologist, chemist
and microscopist. Author of numerous memoirs in German and
French. Studied and collected with Robin in France. Professor
in Zurich and Breslau. Wrote on various pathological subjects,
including pebrine and cancer.

Lechartier, Georges Vital (1837 ). French chemist. Normalien.

Student of Sainte-Claire-Deville. Wrote on the soy bean (Ann.
Sci. Agron., Paris, 1903).

Leeuwenhoek, Antony van (1632-1723). Dutch microscopist. Some-
times called "The father of microscopy." Was elected member
of the Royal Society of London and of the Academy of Sciences
of Paris. Discovered infusoria, bacteria, spermatozoa, striped
muscle fibers, the capillary circulation and "globules" in the blood.
He also discovered spiral vessels and pitted vessels in plants and
distinguished between the structure of dicotyledonous and mono-
cotyledonous stems. A man of limited education but great per-
sistency. The first opponent of spontaneous generation. His
progenitors were wealthy brewers. For portraits see Garrison, p.
243, and Pop. Sci. Monthly, April, 1901.

Lefevre, Amedee (1798-1869). French physician and chemist.

Lemery, Louis (1677-1743) French chemist.

Lemery, "The Younger" ( 1721). French chemist. Brother of

above. One of these is probably the person mentioned in the text.

Leplat, F. ( ). French student of anthrax with Jaillaird.

Liebig, Justus von (1803-1873). German organic and agricultural
chemist. An industrious analyst, a copious writer, and a competent
teacher, who attracted students from all parts of Europe. He
organized the first chemical laboratory for students. Studied
with Thenard and Gay-Lussac in Paris. Professor in Giessen
and Munich. Discovered chloroform, chloral, aldehyd, hippuric
acid, tyrosin and many other substances. Introduced a meat

338 ANNOTATED LIST OF PERSONS

extract which bears his name. A friend of Wohler with whom
he edited "Annalen der Chemie und Pharmacie." Nearly all of
his ideas on biological problems have now been set aside. For
portraits see (iarrison, p. 492, and Pop. 8ci. Monthly, June, 1873.

"As to the opinion which explains putrefaction of animal sub-
stances by the presence of microscopic animalcule, it may be
compared to that of a child who would explain the rapidity of the
Rhine by attributing it to the violent movement of the numerous
mill-wheels of Mayence." (Liebig, 1845.)

Linnaeus or Linne, Charles de (1707-1778). Swedish naturalist.
Foreign member of the French Academy of Sciences. Knight of
the Polar Star. Author of the Linnean system of botany, founded
on the reproductive organs. He introduced the binary sj'stem of
nomenclature, and described many genera and species. A copious
writer and diligent collector of plants from many lands. He wTote
among other things: "Flora Suecica," "Hortus Upsaliensis,"
"Systema Naturje," "Fundamenta Botanica," "Genera Plantarum,"
"Bibliotheca Botanica," "Critica Botanica," "Classes Plantarum,"
"Philosophia Botanica," and "Species Plantarum" (1753). For
portraits see Wittrock I, Tafi. 2, 2a, 25, 2c, 3, 3*, 3**, Wittrock II,
Tafl. 25, Garrison, p. 304, and Pop. Sci. Monthly, Oct., 1899.

Lister, Joseph (1827-1912). Distinguished English surgeon. Knighted,
and President of the Royal Society. Son of a distinguished father.
Professor in Edinburgh and King's College in London. The first
to reform surgical operations with reference to bacterial infections.
He treated wounds with concentrated phenol and operated under
a phenol spray. He banished hospital gangrene and from his work
at Glasgow (1860-69) dates the beginning of modern surgery.
Previous to his improvements, which were stimulated by Pasteur's
discoveries, the healing of wounds by first intention was a rare
occurrence and suppuration and septic poisoning raged in the
surgical wards of hospitals like the plague. For portraits see
Minerva XX, Garrison, p. 622, Pagel, p. 1019, and Pop. Sci.
Monthly, March, 1898.

Loffler, Friedrich August Johannes (1852-1915). German physician,
bacteriologist, sanitarian, and pathologist. Son of Gottfried
Friedrich P>anz LofHer, a distinguished army physician. Robert
Koch's pupil. Professor in Greifswald. Member of the Imperial
Board of Health. Discovered with Schlitz (1882) the cause of
glanders; isolated in 1884 the cause of dijjhtheria (Klebs had seen
it in the diphtheritic membranes in 1883); in 1885 stained the organ-
ism causing erysipelas of the pig, and furnished the first full account
of it. (It was discovered by Pasteur and Thuillier.) ^^'ith Frosch
discovered the first filterable virus (Foot and Mouth disease).

ANNOTATED LIST OF PERSONS 339

With Uhlworm and Leuckart founded the "Centralblatt fiir Bakteri-
ologie und Parasitenkunde" (1887). For portrait see Pagel, p.
1034.

Loir, Adrien ( ). Pasteur's nephew. Assistant at the Pasteur

Institute. Director of the Pasteur Institute in Tunis.

Ludwig, Karl Friederich WiUielm (1816-1895). German phj-siologist
of same group us Briicke, Hehnholtz and Du Bois-Reymond. Pro-
fessor in Zurich, Marburg, Vienna and Leipzig. A very genial,
upright, lovable man and a great teacher. About 200 physiologists
studied in his laboratories. Invented the kymograph. For
portraits see Garrison, pp. 589 and 592, and Pagel, p. 1055.

Metchnikoff, tlie (1845-1916). Russian zoologist and pathologist.
Professor in Odessa. Resident many years in Paris. Member of
the French Academy of Medicine and of the Royal Society of
London. Became vice-director of the Pasteur Institute. Dis-
covered phagocytosis. Wrote a book on "Immunity," another
on "Prolongation of Human Life," and a third on "Old Age."
For portraits see Garrison, p. 619, and Critic, 1903, p. 391.

Mill, James (1773-1836). English economist. Father of John Stuart
Mill.

Mitscherlich, Eilhard (1794-1863). German physicist and chemist.
Professor in Berlin. Discovered at 25 the law of isomorphism
(1819), for which he received a gold medal from the Royal Society
of London. Determined dimorphism. Described the paratar-
trates. Discovered benzol, nitrobenzol, etc. Interested also in
geology. For portrait see Werckmeister, 1898, v. 1, pi. 100.

"Un jour, dans la biblotheque de I'Ecole, je lus une note du
celebre chimiste cristallographe Mitscherlich, relative a deux combi-
naisons salines: le tartrate et le paratartrate de sonde et d'ammo-
niaque. Apres en avoir etudic toutes les proprietes, Mitscherlich
concluait ainsi: 'La nature et le nombre des atomes, leur arrange-
ment et leurs distances sont les memes. Cependant le tartrate
de vie Ic plan de la lumiere polarisee et le paratartrate est indifferent.'"

Cette note restait comme un point d'interrogation obstinement
place devant mon esprit. Comment deux substances pouvaient-
elles etre aussi semblables sans etre tout a fait identiques? Des
mois et des mois se passerent. Je fus regu agrcgc des sciences
physiques. Cette note de Mitscherlich me poursuivait toujours.
Par une serie d'expcriences dont il est facile de retrouver les commen-
taires explicatifs dans les comptes rendus de I'Academie des sciences,
j'arrivai a separer le paratartrate de sonde et d'ammoniaque en
deux sels de dissymetrie inverse et d'action inverse sur le plan de
polarisation de la lumiere. Coup sur coup les obscurites de la note
de Mitscherlich se dissiperent; la composition et la nature de I'acide

340 ANNOTATED LIST OF PERSONS

paratartrique furent expliquees; ime grande lueur se projeta sur
la constitution intime des corps, puisque les principes essentiels a
la vie m'apparaissaient comme devant prendre naissance sous
I'influence de forces dissymctriques. Ce premier cliapitre de phy-
sique et de chimie moleculaires devait me conduire a d'autres
chapitres utiles a I'histoire de la science. Quelles joies de travail
j'ai ressenties pendant ces premieres annees de recherches!" (Pasteur
in 1S95.)

Moitrel d'Element (1678-1730). French physicist. Discovered a means
of collecting and studying gases. Lived in great poverty and was
considered "mad" by his contemporaries. Died in America.

Moliere (Stage name of Jean Baptiste Poquelin) (1622-1673). French
actor and dramatist. He often satirized medical men: "lis savent
la plupart de fort belles humanites, savent parler en beau latin;
savent nommer en grec toutes les maladies, les definir et les diviser;
mais pour ce qui est de les gucrir, c'est ce qu'ils ne savent point
du tout." (Le Malade imaginaire.)

"On me vient chercher de tous les cotes; et, si les choses vont tou-
jours de meme, je suis d'avis de m'en tenir toute ma vie a la medicine.
Je trouve que c'est le metier le meilleur de tous; car, spit qu'on
fasse bien, ou soit qu'on fasse mal, on est toujours paye de meme
sort. . . . Un cordonnier, en faisant de souliers, ne sauroit gfiter
un morceau de cuir, qu'il n'en paye les pots casscs; mais ici Ton peut
gdter un homme sans qu'il en cotite rien. . . . c'est toujours la
faute de celui qui meurt." (Le Medecin malgre lui.)

"Moliere is the greatest French poet, he is so sane" (Alfred
Tennyson). For portraits see Petit Larousse, p. 1467, Oeuvres
completes de Moliere, Lahure, Paris, 1858, p. 8, and Abry, p.
231.

Montaigne, Michel Eyquem de (1533-1592). French essayist, philoso-
pher and moralist. Hardheaded, always demanding a reason, satu-
rated with medieval and classical learning which bristles on every
page, yet kindly and interesting beyond most ancient writers, he
fills a place in literature occupied by no other person. For por-
traits see Abry, p. 105, and "Essais de Michel Montaigne avec des
notes de tous les commentateurs. Edition revue sur les textes
originaux." Paris, Firmin Didot Freres, P'ils et Cie, Libraires.
1870.

"So long as an unaffected style and an appearance of the utmost
simplicity and good nature shall charm, so long as the lovers of
desultor}^ and cheerful conversation shall be more numerous than
those who prefer a lecture or a sermon, so long as reading is
sought by the many as an amusement in idleness, or a resource in
pain, so long will Montaigne be among the favorite authors of
mankind." — (Hallam.)

ANNOTATED LIST OF PERSONS 341

"II faisait trop d'histoires, parlait trop de soi. . . . le sot
projet qu'il a de se i)eindre." (Pascal.)

Miintz, Charles Achille (1846-1917). French agronomist. Member
of the Academy of Sciences, Officer of the Legion of Honor. Director
of the Laboratories of the National Agronomic Institute.

Musset, Charles ( ). Student of Joly in Toulouse.

Nageli, Karl Wilhelm von (1817-1891). Brilliant Swiss-German bota-
nist. Born near Zurich. Died in Munich. Studied in Zurich,
Genoa, and Berlin. Professor in Freiburg, Zurich and Munich.
Systematist of higher plants, morphologist, physiologist, algologist,
bacteriologist, student of evolution. His discovery, of wild Hiera-
cium hybrids and of oligodynamic phenomena (effect of very dilute
poisons) in living cells are perhaps his best known work. He had
a habit of tasting his bacteriological cultures which enabled him to
make many fine discriminations but undoubtedly shortened his
life (Oscar Loew). Wrote with Schwendener Das Mikroskop, 2
ed. 1877. For a list of his books see Meyer's "Grosses Konversa-
tions-Lexikon," Leipzig, 1909. For a portrait see Wittrock II,
Tafl. 75.

Needham, John Turberville (1713-1781). English Jesuit, physicist
and microscopist. Member of the Royal Society. Founded the
Academy of Sciences in Brussels and was its director. Wrote
"Microscopical Discoveries" (1745) and "Idee sommaire, ou vue
generale du systeme physique et metaphysique sur la generation"
(1780). Engaged in a dispute with Voltaire on miracles. Wrote
a book to show that the Chinese written characters indicate descent
from the Egyptians. Walter Needham, with whom he is sometimes
confused, as in Garrison, p. 318, died before Spallanzani was born.

Nocard, Edmond Isidore Etienne (1850-1903). French veterinarian.
Professor in Alfort. Member of the Academy of Medicine. Showed
in 1880 that the cause of rabies is a non-filterable (solid) virus.
He used dog saliva and filtered it through plaster of Paris — what
came through was innocuous, what remained on the filter was
infectious. Wrote on tuberculosis, glanders, tetanus, rabies,
peripneumonia, etc. Author with Leclainche of "Les maladies
microbiennes des Animaux" (3d edition, 8vo, 2 volumes. Paris,
1905), an important work on parasitic diseases of domestic animals.
Was on the Egyptian cholera commission (1883). Nocard was son
of a wood merchant. For a portrait see Rec. de mod. vet. 8 ser.
Tome X, No. 15, 15 aout, 1903.

Noguchi, Hideyo (1876 ). Distinguished Japanese pathologist

working in the United States. Obtained Treponema pallidum
in pure culture. Showed connection between syphilis, general
paresis and locomotor ataxia by finding the parasite of syphilis

342 ANNOTATED LIST OF PERSONS

in the brain and cord. Improved syphilitic diagnosis. Cultivated
the rabies parasite. Cultivated the yellow fever parasite {Lepto-
spira ideroides Nog.) and with it produced the disease in guinea
pigs ("Jour. Exp. Med.," vol. 29, No. 6, June 1, 1919).

Obermeier, Otto Hugo Franz (1843-1873). German pathologist.
Studied the spirillum of recurrent fever in Berlin in 1873. His
last paper was "Die ersten Falle und der Charakter der Berliner
Flecktyphusepidemie von 1873 (Berl. klinische Wochenschr., 1873,
X, No. 30). Died of cholera while studying an outbreak of this
disease. To all such be eternal honor!

Osimo, Marco ( ). Italian student of silkworm diseases.

Published in Padua in 1859. Recommended egg-selection as a
remedy for pcbrine.

Paracelsus (1493-1541). German Swiss alchemist and physician.
His real name was Theophrastus Bombast von Hohenheim.
Paracelsus is said to mean superior to Celsus. Learned, original,
obstinate and 'arrogant, opposed to tradition, a great traveler,
a shrewd observer, and a successful healer, he died in poverty,
destroyed by fools. He taught the doctrine of signatures and was
hostile to Galen. He said: "If nature can instruct irrational
animals, can it not much more men?" His works in 10 volumes
were published in Basel in 1589-1591. For portraits see Garrison,
p. 189, and Pagel, p. 13.

Pascal, Blaise (1623-1662). French mathematician, physicist and
philosopher. A profound thinker and great prose writer. In-
vented the omnibus and the calculating machine; made important
observations with the barometer in high places. Wrote "Lettres
6crites a un Provincial par un de ses amis," a covert arraignment
of the Jesuits, in which he is "witty as Moliere and eloquent as
Bossuet" (Voltaire), and "Pensces sur la religion." A deeply
religious Roman Catholic, he abandoned scientific pursuits in 1649
for religious studies and became very ascetic. For portraits see
Lettres Provincial, Paris, Firmin Didot Freres, 1846, and, Abry, pp.
200, 208 (masque).

Pascal, Etienne ( ). French advocate. President of the

Court of Aids. Father of Blaise Pascal.

Pasteur, Louis (1822-1895). French physicist, chemist, microscopist
and pathologist. Son of a tanner whose father and grandfather
were also tanners. A man with an iron will and a great soul,
born for combat and mastery. Professor in Dijon, Strasburg,
Lille and Paris. In 1S74 the French Government granted him a life
annuity of 12,000 francs in consideration of his ])ublic services and
out of the 556 votes there were only 24 dissenting ones. Nine
years later, again through the instrumentality of Paul Bert, this was

ANNOTATED LIST OF PERSONS 343

increased to 25,000 francs. Pasteur succeeded Littre in the
Academic Fran^aise. Monuments have been erected to him in
Melun, Lille, Arbois, Dole, Besan9on and Paris. Both Roty and
Dubois made low relief circular bronze plaques of Pasteur. That
by Dubois, especially the larger one (7 inch), is very desirable.
There is also a fine bust by Dubois in Copenhagen. For a frank
and charming letter at 26, proposing marriage, see "Les Annales,"
Paris, 2 Fevrier, 1919, p. 105, and [for a vivid description of his
personal appearance at the time of his rabies studies, see "Monsieur
Taine and Monsieur Pasteur" by Gabriel Hanotaux of the French
Academy {Ihid., pp. 102-103). For a bibliography of his principal
writings consult "Revue scientifique," 4 se., tome IV, No. 14,
Paris, 1895, pp. 427-431. For portrait as a young man see "Les
Annales," 1. c, p. 105, and when old, Wittrock II, Tafl. 78.

"At the middle of the last century we did not know much more of
the actual causes of the great scourges of the race, the plagues,
the fevers and the pestilences, than did the Greeks. Here comes in
Pasteur's great work. Before him Egyptian darkness; with his
advent a light that brightens more and more as the years give us
ever fuller knowledge. * * * It was a study of the processes of
fermentation that led Pasteur to the sure ground on which we now
stand." (Sir Wm. Osier.)

"Your father is absorbed in his thoughts, talks little, sleeps little,
rises at dawn, and, in one word, continues the life I began with him
this day thirty-five years ago." (Madame Pasteur, 1884.)

Aphorisms and Ideals of Pasteur :

The characteristic of a true theory is its fruitfulness.

Science should not concern itself in any way with the philosophi-
cal consequences of its discoveries.

Hypotheses come into our laboratories in armfuls, they fill our
registers with projected experiments, they stimulate us to research
— and that is all.

The recompense and the ambition of a scientist is to conquer the
approbation of his peers and of the masters whom he venerates.

It would seem to me that I was committing a theft if I were to
let one day go by without doing some work.

If that teaching [the higher education] is but for a small number,
it is with this small number, this elite, that the prosperity, glory and
supremacy of a nation rest.

Whatever career you may embrace, look up to an exalted goal; wor-
ship great men and great things. [To the students at Edinburgh,

Great is the joy of a teacher whose pupils become masters.

A man of science should think of what will be said of him in
the following century, not of the insults or the compliments of one
day.

344 ANNOTATED LIST OF PERSONS

II y a dans la jeunesse de tout homme de science et sans doute de
tout homme de lettres, un jour inoubliable ou il a connu, a plein esprit
et a plein coeur, des emotions si genereuses, oil il s'est senti vivre
avec un tel melange de fierte et de reconnaissance, que le reste de
son existence en est eclaire a jamais. Ce jour-la, c'est le jour ou il
s'approche des maitres, a qui il doit ses premiers enthousiasmes, dont
le nom n'a cesse de lui apparaitre dans un rayonnement de gloire.
Voir enfin ces allumeurs d'ames, les entendre, leur parler, leur vouer
de pres, a cote d'eux, le culte secret que nous leur avions si longtemps
garde dans le silence de notre jeunesse obscure, nous dire leur disciple
et ne pas nous sentir trop indignes de I'etre! Ah! quel est done le
moment, quelle que soit la fortune de notre carriere, qui vaille
ce moment-lii et qui nous laisse des emotions aussi jjrofondes?
Peligot, Eugene Melchoir (1811-1890). French chemist. A student
of silkworms. Pasteur's associate. Wrote "Traite de chimie
analytique appliquee a 1 'agriculture" (1883).

Perdrix, Charles ( ). French pathologist. Normal school

assistant.

Pfeflfer, Wilhelm (1845 ). German plant physiologist. Professor

in University of Leipzig. Author of many papers. Discovered
osmotic pressure in plant cells, chemotaxis of bacteria, etc. His
extensive and important "Physiology of Plants" has been translated
into English by A. J. Ewart (Oxford: Clarendon Press). For por-
trait see Wittrock II, Tafl. 94, and Pop. Sci. Monthly, Jan., 1897.

Pfeiffer, August (1848 ). German physician, bacteriologist and

pathologist. This man, or the next, must be the one named in the
text.

Pfeiffer, Richard (1858 ). German physician, sanitarian and

bacteriologist. Robt. Koch's assistant. Professor in Breslau.
Discoverer of the influenza bacillus. Associated with Carl Frankel.
Wrote on immimity. For portrait see Wittrock II, Tafl. 130.

Philippi. The person referred to in the text under this name is Filippo
de Filippi (1814-1867) commonly known as de Philippi, a distin-
guished naturalist of Turin and IMilan. At one time he was Pro-
fessor of Zoology in the University of Turin. Afterwards he was
Senator. He wrote: Alcune Osservazioni Anatomico-Fisiologiche
sugl'-Insotti in Generale, ed in Particolare sul Bombice del Gelso."
(Annali della Accad. R. d' Agirc. di Turino, \'ol. V., 1851, pp. 1-25,
3 plates.)

Piria, Raffaele (1815-1865). Italian chemist and patriot (Garabaldian) ;
senator. Wrote "Elements of Inorganic Chemistry;" "Lessons
on Fermentation;" "Elements of Organic Chemistry" (2d ed.,
Turin, 1S70), etc.

ANNOTATED LIST OF PERSONS 345

PoUender ( ). German veterinarian. His paper on the

microscopic and microchemical investigation of anthrax blood
was published in 1855 in Vierteljahrschr. f. ger. Med., Bd. 8.

Pouchet, Felix Archimede (1800-1872). French naturalist. Director
of the Museum of Natural History in Rouen. Opponent of Pasteur.
His "Hetcrogenie, ou Traite de la generation spontanee, etc."
was published in Paris in 1859 (pp. 32, 672) and his "L'Origine
de la Vie" (3d ed.) in Paris in 1868. The Maladetta on which
Pouchet opened flasks of hay-infusion, all of which clouded, is a
glaciated mountain in the Alps.

Provostaye, or Herve de la Provostaye, Frederick (1812-1863). French
crystallographer.

Quatrefages de Breau, Jean Louis Armand de (1810-1892). French
anatomist, zoologist and anthropologist. Member of the Royal
Society of London. A clear, forcible, fluent writer. He wTote a
"Histoire generale des races humaines" (1886-1889), and "La
race prussiene" (1871) which led to a polemic with Virchow. For
portrait see Pop. Sci. Monthly, March, 1885.

Quevenne, Theodore Augusta (1805-1855).

Rabenhorst, Ludwig (1806-1881). German botanist. Author of a
cryptogamic Flora of Germany; "Flora Europaja algarum," etc.,
collected and distributed dried cryptogamic plants. Founded
"Hedwigia."

Raulin, Jules ( ). French chemist and physicist. Student

at the Normal School. Pasteur's assistant. Professor in Brest,
Caen and Lyons. His famous paper "Etudes chimiques sur la
vegetation" is in Ann. des Sci. Nat. Bot. V ser. Tome XI, Paris,
1869, pp. 93-299.

Rayer, Roger J. (— ). French physician and pathologist.

Rayer's account of the discover^' of the rods in anthrax blood is in
"C. R. Soc. biol.," 1850, p. 141.

Recklinghausen, Friedrich Daniel von (1833-1910). German patho-
logical anatomist. Virchow's student. Assistant in Berlin.
Professor in Konigsberg, Wiirzburg, and Strassburg. Author of im-
portant papers on inflammation, the lymphatic system, and multiple
fibromas. Discovered the wandering cells of the connective tissue
and the ameboid movements of living pus cells. His paper on
Erysipelas is in Virchow's Archiv, Bd. 60, 1874. For portrait see
Pagel, p. 1351.

Redi, Francesco (1626-1698). Italian physician and naturalist. Born
in Arezzo, practiced in Florence. Discovered the itch mite. Ap-
plied the experimental method in natural science. He was also
a poet. For portrait see Garrison, p. 245.

346 ANNOTATED LIST OF PERSONS

Reess, Max Ferdinand Friedrich (1845-1901). German mycologist.
Professor in Erlangen and director of the botanic garden.
Produced the first lichen synthesis. Published "Rust fungi of Ger-
man Conifers" (1869); "Alcoholic fermentation fungi" (1870);
"Nature of Lichens" (1879), etc. For portrait see Wittrock II,
Tafl. 125.

Renan, Ernest (1823-1892). French Semitic scholar. Born in Brittany.
Member of the French Academy. Director of the College of France.
One of the most engaging and delightful writers of modern France.
Author of "Histoire des origines du Christianisme" (8 vols.);
"Histoire du peuple d'lsrael" (5 vols.), "Ma Soeur Henriette,"
"Souvenirs d'enfance et de jeunesse," and many other books. For
portraits see Pop. Sci. Monthly, April, 1893, "Souvenirs d'enfance
etc." (Nelson ed.) and Abry, p. 630.

Rindfleisch, Georg Eduard (1836-1908). German pathological anato-
mist. Assistant to Heidenhain. Professor in Ziirich, Bonn and
Wiirzburg. Author of a handbook of pathological anatomy
which passed through many editions. For portrait see Pagel, p.
1391.

Rossignol, H. ( ). French veterinary surgeon of Melun.

It was he who collected by subscription money for the famous
anthrax experiments at Pouilly-le-Fort.

Roux, Pierre Paul Emile (1853 ). French physician, bacteri-
ologist and pathologist. Pupil of Duclaux. Normal School as-
sistant. Collaborated with Pasteur, Chamberland, etc. Present
director of the Pasteur Institute. Dr. Roux has made important
contributions on rabies, diphtheria, tetanus and other diseases.
His studies of diphtheria with Yersin preceded and laid the foundation
for those of Behring and Kitasato. Diphtheritic antitoxin (serum)
obtained from vaccinated horses was used by Roux in 1894 in a
Paris hospital on hundreds of children with marvellous results.
For portraits see "Bacteria in Relation to Plant Diseases," vol.
I. Frontispiece. Carnegie Institution of Washington, and Mc-
Clure's Mag., 1893, p. 338.

Saint-Simon, Louis de Rouvray, due de (1675-1755). Brilliant, biting,
picturesque French diarist, especially of the Court of Louis XIV.
A great painter of manners. His "Memoirs" in 20 volumes is a
vast historical storehouse. For portraits see Abrj', p. 296, and
Saint-Simon "Mdmoires sur le Sifecle de Louis XIV, et la Rogence."
Iiii)liotheque Laroussc, Paris, 1911 — a good 4 vol. abridgement.

"Nul ecrivain democratique n'a portc comme lui le fcr rouge
dans les ulcores de la noblesse." (Larousse: Grand Diet, universel
du XIXe Siecle.)

ANNOTATED LIST OF PERSONS 347

Sainte-Claire-Deville, Henri Etienne (1818-1881). French chemist.
Brother of the geologist. Both were Students at College Rollin.
Professor in the Normal School and in the Sorbonne. Member of
the Academy of Sciences. Discovered high temperature disasso-
ciation. Studied the silicates. Improved methods of working
platinum, aluminium, sodium and magnesium. Discovered nitric
anhydride (1849). Obtained in masses, melted and pure, the re-
fractory metals, manganese, chromium, nickel and cobalt; with
Caron succeeded in producing, artificially, rubies, sapphires, and ori-
ental emeralds. Induced the Metric Commission to use an alloy
of platinum-iridium for its standards and during the last ten years
of his life was engaged with his illustrious friend Stas of Belgium in
preparing sets of these measures, which were not permitted to vary
more than one thousandth of a millimeter. Friend of Pasteur.
Collaborated with Wohler, Caron, and Debray. For portraits
see "Le Centenaire de I'Ecole normale" (1895), p. 407, and Pop.
Sci. Monthly, Feb., 1882.

For a splendid appreciation of Sainte-Claire-Deville by Desire
Gernez see "Le Centenaire de I'Ecole normale." Paris, 1895,
pp. 407-425.

"II est impossible de decider lequel des deux fut le plus grand
en lui, de I'homme de science ou de I'homme de bien."

"Puisse son example developper, chez les jeunes gens qui s'en-
gagent dans la carriere scientifique, le devouement a la Science,
I'une des formes les plus elevees, les moins bruyantes et les plus
pures de 1' amour de la Patrie!" (Gernez.)

Sanson, ( ). French pathologist.

Schroder, H. ( :). German chemist. Collaborated with Th.

von Dusch on fermentation and also published independently.
Wrote many papers on "Volumconstitution fester Korper."

Schwann, Theodore (1810-1882). German physician and naturalist.
Professor in Louvain and Liege. Discovered pepsin in gastric
juice. Following Robert Brown's discovery of the nucleus in plant
cells (1831) and Schleiden's studies, he discovered the nucleus in
animal cells, and showed (1839) that animals and plants are
composed of the same (cellular) elements ("Mikroskopische Unter-
suchungen liber die Uebereinstimmung in der Structur und dem
Wachsthum der Thiere und Pflapzen," Berlin, 1839). Schwann's
observations referred to in the text were published in 1837 in Pogg.
Ann. der Physik und Chemie, Bd. XLI, p. 184 ("Vorlaufige
Mittheilung, betreffend Versuche iiber die Weingiihrung und
Faulniss").

Schulze, Franz ( ). German chemist in Berlin. His lucid paper

"Vorlaufige Mittheilung der Resultate einer experimentellen

348 ANNOTATED LIST OF PERSONS

Beohachtung iibcr Generatio aequivoca," is in Pogg. Annalen
dor Physik u. Chemie, Bd. 39, Leipzig, 1836, pp. 487-489.
Schutzembach, ( ). German chemist.

Sedillot, Charles Emmanuel (1804-1883). French surgeon. Born in
Alsace. Served in the war of 1870 as surgeon. Introduced the
word microbe (C. R. de I'Acad. des Sci., March 11, 1879). The
following is one of his aphorisms: "Le succes des operations depend
de I'habilete du chirurgien. Le revers accusent notre ignorance
ou nos fautes, et la perfection est le but de I'art."

Sevigne, Madame Marquise de, nee Marie de Rabutin-Chantal (1626-
1696). Parisian of the time of Louis XIV. Greatest, with perhaps
the exception of Voltaire, of all French letter writers. For a por-
trait see Abry, p. 189.

"Sa correspondence est un tableau fidele de la societe et des moeurs
du XVIIe siecle ; c'est un journal des faits les plus interessant des
quarante plus belles annees du Siecle de Louis XIV. C'est surtout
un des monuments de la literature frangaise." — (Larousse: Grand
Diet, universel du XIXe Siecle.)

Signol, Jean Jules (1841-1904). French veterinarian. Signol's
confusing discovery in relation to anthra.x was announced in 1875.

Spallanzani, Lazzaro (1729-1799). Italian phj-siologist, naturalist, abbe,
and traveler. Educated at Bologna. Professor of logic, meta-
physics and Greek in Reggio ; then of natural history, first in Univer-
sity of Modena (1760-1769), afterward in University of Pavia.
One of the most perspicacious minds of the 18th century. It is
said that we owe to him our first exact notions of circulation of the
blood, digestion, respiration and generation in plants and animals.
In 1785 he fertilized eggs by means of spermatozoa. For
portrait see Iconogr. di uomini sommi nelle scienze e nelle arti
italiane. Napoh, Soc. Editrice (1854) pi. 69.

Stahl, George Ernst (1660-1734). German chemist and physician.
Opposed Hoffmann and developed a doctrine of psychic influence
known as animism. Professor in Halle. Physician to the Iving
of Prussia. His "Zymotechnica fundamentalis seu fermentationis
theoria generalis" was published at Halle in 1697. For portrait
see Pagel, p. 18.

Strauss, Isidor (1845 ). French physician and pathologist. Pro-
fessor of comparative and experimental pathology in Paris. Co-
operated with Chamberland in studies on transmission of anthrax,
and with Roux, Nocard and Thuillicr on cholera in Egypt. Wrote
on cholera in Toulon (1884), etc. For portrait see Pagel, p. 1670.

Susani, Guide ( ). Italian silkworm proprietor. Published

several papers on silkworms in Milan, 1870-72. Entertained
Pasteur.

ANNOTATED LIST OF PERSONS 349

Talamon, Charles (1850 ). French physician and pathologist.

Student of pneumococcus. Discovered it independently of Frankel.

Tennyson, Alfred (1809-1892). English poet. Laureate and knighted
baronet. Son of a clergyman, brother of two other poets, Charles
and Frederick T. Born at Somersby, in Lincolnshire, educated
at Trinity College, Cambridge. Author of charming lyrics, elegies,
odes, epical verse, and dramas. The most distinguished and finished
English poet of the 19th century and the one who best expressed the
prevalent sentiment of scientific and social unrest, with which he
mingled a deep religious strain. He lived a very retired life.
"Smokes infinite tobacco" (Carlyle). For portraits see Alfred
Lord Tennyson, A memoir by his son (the original 2 vol. ed.) and
Cameron's "Tennyson and His Friends."

Thenard, Louis Jacques de (1777-1857). French chemist. (See
Gay-Lussac.) Professor in the College of France and in the Poly-
technic School. Discovered cobalt blue (Thenard's blue) and
hydrogen peroxide. With Gay-Lussac discovered boron. Dis-
covered an improved way of making white lead. A great and
genial teacher. He is said to have had 40,000 students. His
"Traite de chimie elementaire" passed through six editions and
was translated into German. Member of the Institute and Peer
of France. For portrait see Arnault. Biog. Nouvelle Contemp.
1825, 19, p. 424.

Thomas, Philippe Etienne (1843 ). French veterinarian.

Thuillier, Louis Ferdinand (1856-1883). French pathologist. A
student, then brilliant associate of Pasteur. Discovered with Pasteur
the cause of "rouget" and a vaccine for it. Collaborated on an-
thrax and on rabies. Died of cholera in Egypt where he had gone
to study a violent outbreak of the disease.

"C'etait une nature profondement meditative et silencieuse,"
(Pasteur) .

For a brief account of Thuillier by Costantin see "Le Centenaire
de I'Ecole normale," Paris, 1895, pp. 540-543.

There is in the Normal School a bust and a portrait of Thuillier
and a marble tablet which says: "Thuillier, mort pour la science."

Thuret, Gustave Adolphe (1817-1875). Distinguished French algologist.
For a biographic notice and a list of his publications by Ed. Bornet
see Ann. Sci. Nat. Bot. 6se, Tome II, pp. 308-360. For portrait
see Wittrock II, Tafl. 76.

Tiegel, Ernst (1849 ). Swiss bacteriologist. Associate of Klebs.

Toussaint, Jean Joseph Henri (1847-1900). French veterinarian.
Professor in the school at Toulouse. Toussaint's report to the Min-
ister of Agriculture on anthrax is in "Archives Veterinaires," 1879.
See also "C. R. d. s. de I'Acad. des Sci.," 1880, p. 155.
25

350 ANNOTATED LIST OF PERSONS

Trecul, Auguste Adolphe Lucien (1818-1896). French botanist. Mem-
ber of the Academy of Sciences and Chevaher of the Legion of Honor.
Made botanical collections in the United States and North Mexico.
Adversary of Pasteur.

"Heterogenesis is a natural operation by which life, on the point
of abandoning an organized body, concentrates its action on some
particles of that body and forms thereof beings quite different
from that of the substance which has been borrowed" (Trecul,
1867).

Turpin, Pierre Jean Frangois (1775-1840). French artist and botanist.
Wrote "Iconographie vegetale" (Paris, 1841). Illustrated Hum-
boldt's works.

Tyndall, John (1820-1893). English physicist. Studied under Bunsen
at Marburg. Professor in the Royal Institution in London. Wrote
with Huxley, and independently, on glaciers and showed their move-
ment to be due to fracture and refreezing. Studied heat, light, sound
and fermentation. Discovered intermittent sterilization. Presi-
dent of the British Association for the Advancement of Science
at the Belfast meeting. A friend of Pasteur and opponent of Bastian.
A great teacher and popularizer of modern science. For portraits
see Pop. Sci. Monthly, Nov., 1872, Harper's Mag., 1888, p. 831,
and Critic, 1893, p. 382.

Van't Hoff, Jacobus Hendrikus (1852-1911). Dutch chemist and
physicist. Professor in Amsterdam and then in Berlin. A great
stereo-chemist and one of the founders of physical chemistry. Born
in Rotterdam. In 1876 he was docent in physics in the veterinary
school in Utrecht, hence one of the German chemists, who was worsted
in an argument, called him "horse doctor." For portraits see "Chem-
isch Weekblad" Amsterdam, Oct. 15, 1910, and Les prix Nobel en
1901, p. 76.

Van Tieghem, Philippe Edouard Leon (1839-1914). French botanist.
Entered the Normal School in 1S58. Professor in the Normal School,
in the Sorbonne and in the Museum of Natural History. Member of
the Academy of Sciences and of the Legion of Honor. Friend of
Pasteur. Author of numerous important researches, chiefly anatom-
ical and morphological. The second edition of his important "Traite
de Botanique" (pp. xxxi, 1855) was published in Paris in 1S91. Editor
of "Ann. des Sci. Nat. Bot." for thirty-two years. For portrait see
Ann. des Sci. Nat. Bot., Tome XIX, No. 1, 1914.

Varro, or Varrone. Roman poet and prose writer of the Second Century.
Among many other things he wrote "Rerum rusticarum."

Vergnette-Lamotte, Gerard Alfred Vicomte de (1806-1886).

ANNOTATED LIST OF PERSONS 351

Viala, Eugene ( ). Assistant in rabies vaccinations at the

Pasteur Institute. A boy educated by Pasteur, who became a de-
voted and skillful assistant.

Virchow, Rudolph (1821-1902). Distinguished German physician, path-
ologist, sanitarian, anthropologist, and politician (Prussian). Ge-
heimrat, Medicinalrat. Professor in Wiirzburg and in Berlin. A
man of good judgment, broad views and tremendous energy. Founder
of a system of cellular pathology, which has had great influence
on modern medicine. His book "Cellular Pathology" passed through
four editions. A copious writer. Founded with Reinhardt the
"Archiv fur pathologische Anatomie und Physiologie." Wrote
"The Pathology of Tumors" (1863-67) 3 vols. Had much to do
with the canalization and sanitation of Berlin. For portraits see
Garrison, p. 603, Pagel, p. 1775, and Werckmeister, 1899, 3, pi.
261.

Vittadini, Carlo ( 186.5). Italian mycologist (Milan). His method

of distinguishing good silkworm eggs from bad was published in
Milan in 1859 ("Actes de I'lnstitut Lombard," Tome I).

Voigt, ( ). French professor in Lyons. Duclaux's

friend.

Vulpian, Edme Felix Alfred (1826-1887). French physician, pathologist
and physiologist. Professor of Pathological Anatomy in Paris.
Perpetual Secretary of the Academy of Sciences. Greatly interested
in rabies inoculations. For portrait see Pop. Sci. Monthly, Dec,

1888.

Waldeyer, Heinrich Wilhelm Gottfried (1836 ). German anato-
mist, pathologist, and histologist. Student of Henle. Professor
in Strassburg and in University of Berlin. Director of the Anatom-
ical Institute. One of the founders of the "Archiv fiir mikroskop-
ische Anatomie." Member of various foreign Academies. For
portraits see Garrison, p. 548, and Pagel, p. 1806.

Weigert, Carl (1845-1904). Celebrated German histologist. Assistant
to Waldeyer, to Lebert, and to Cohnheim. Professor in Frankfort -am-
Main and in Leipzig. The first to stain bacteria. Wrote "Erste
Farbung von Bakterienhaufen" (1871) and "Farbung der Bakterien
mit Anilinfarben" (1875). For portrait see Pagel, p. 1826.

Weiss, Christian Samuel (1780-1856). German physicist, mineralogist
and crystallographer. Professor in Berlin.

Willis, Thomas (1621-1675). English anatomist and physiologist of
the brain. For portrait see Garrison, p. 253.

Wohler, Friedrich (1800-1882). German physician and chemist. Studied
in Stockholm under Berzelius. Professor in Gottingen. Fellow of
the Royal Society of London. Collaborated with Liebig. Studied

352 ANNOTATED LIST OF PERSONS

the cyanides and benzol compounds, isolated aluminium, berj-Uium
and yttrium. Made many contributions to science. Taught many
students. For portraits see Pop. Sci. Monthly, Aug., 1880, and Wcrck-
mcister, 1899, vol. 3, pi. 287.

Yersin, Alexandre (1863 ). French physician and pathologist.

Collaborator of Roux in the Pasteur Institute. Studied in the French
colonies where he discovered the plague bacillus independently of
Kitasato.

Yonrievitch, Serge ( ). Attache of the Russian legation in

Paris. Eulogist of Duclaux "Bull, de I'Inst. general psychologique,"
4 annee, No. 4, 1904.

I

OW Jrf^ 0«- vi-(

«^w

^^^^K-^

PASTKIli IX HIS OLD AGE
(From "Le Centonaire dc I'ficole normal." 1895.)

INDEX

Aerobic, coming of word, 124
life, 82

of anaerobic species, 202
Aging of wine, 140
Air, germs in, 91, 93
distribution of, 101
fewer than first supposed, 103,
191, 268
Alcoholic fermentation, 51, 56, 73
Anaerobic, coining of word, 124
life, 82

changed structure due to, 200
of aerobic species, 198
Aspergillus niger, 199
Bail, 198, 201
Mucor mucedo, 198
Mycoderma of wine, 201
Penicillium glaucum, 199
Anthrax, 233

bacteridium of, 234, 237, 245
augmentation of virulence of,

309, 311
diminution of virulence of, 307,

310
preservation of virulence of,

309
reaction of host, Pasteur's

chief interest, 253
return to virulence, 308
spore of, 241

zone of attenuation, 305, 306
Bert, 244, 259
Bouley, 238
Brauell, 233, 238
cursed fields and dangerous moun-
tains, 236
Davaine, 233, 237, 247, 248, 250,

257
Delafond, 235, 242

Anthrax, earth-worms and, 287
endemic and epidemic nature of,

288
etiology of, 237, 242, 245, 250
Jaillard, 238, 257, 259
Joubert, 252
Klebs, uses porous earthen filter,

239
Koch, Robert, 241, 247, 248,

250
Leplat, 238, 257, 259
Pasteur, what interested him in,
250
contributions to our knowledge
of, 251,252,286
Pollender, 233
Payer, 233
Sanson, 238
Signol, 238
spore of, 241
Tiegel, 239
vaccine for, 289, 291, 292

savings due to, 293
a virus disease, 285
Appert, Emile, IX, X

Francois, 60, 90, 143
Arloing, 305, 315

Aseptic methods advised by Pas-
teur in dressing of wounds, 267,
271
Aspartates, 20

Aspergillus niger, growth in ab-
sence of air, 199
Raulin's culture medium, best
for, 225, 226
Attenuation, chemicals in, role of,
Chamberland and Roux on, 306
heat in, role of, Toussaint and
Chauveau on, 305

353

354

INDEX

Attenuation, light in, role of,

Duclaux and Arloing on, 305

oxygen in, role of, Bert and

Chauveau on, 305
physiological differences between
bacteridia unequally attenu-
ated, 306, 307
virulence and, 304
Autoclave, introduction into bac-
teriology, 118

Bacillus subtilis, 118, 242

Bacteria, associations of, role of,
264
role in pathology, 247-249

Bacterial secretion producing symp-
tom of a disease, first example of,
255

Bacteriotherapy, first example of,
256

Bail, 192, 198, 201

Balard, characterization of, 107

Barbet, X, XI

Bastian, 101, 111, 114, 119

Bechamp, 197

Becher, 53

Beer, diseases of, 188
studies on, 187

Bellamy, 211

Bellotti, 160

Berkeley, 192

Bernard, Claude, 206, 209, 219, 321

Bert, 244, 248, 259, 306

Berthelot, 28, 137, 206, 210, 212

Berlin, 189

Berzelius, 28, 76, 77

Biot, 8, 10, 11, 20

Black, 55

Blanchard, 280

Bloch, XIX

Blood corj)usclcs, red, comparison
with acetic ferment, 127

Bornet, 81

Bouley, 293

Boullay, 58

Boussingault, 137

Boutron, 79
Boyle, 53

Brauell, 233, 234, 238
Bremer, 44

Brewing, Pasteur's studies on, 187
Broussais, 230
Briicke, 231
Buffon, 87, 148
Burdon-Sanderson, 116
Butyric fermentation, 79, 80, 82
vibrio of, 80

CAGNiARD-Latour, 61, 64, 65, 69
Cantani, 256
Cantoni, 153, 157, 160
Cellular life, dissymmetry of, 28
Chamberland, 114, 191, 226, 291,

293, 297, 306
Chassang, 124
Chauveau, 191, 245, 247, 248, 277,

305, 315
Chemiotaxis, 319
Chicken cholera, 276
parasite of, 277
Cohn, 118, 242
Colin, 65

Columella, 227, 229
Contagion, ideas of, prior to 1866,
225

state of scientific mind on, in
1876, 226
Cornalia, 152, 160
Cornevin, 315
Corpuscular disease of silkworms,

149
Cowpox, protection against small-
pox (Jenner), 282
Coze, 232, 274
Crystallography, 1

aspartates, Pasteur's work, 20

Biot, 8, 10, 11,20

Bromcr, 44

cellular life, dissymmetry-, com-
pared with, 28

Dclafosse, 5, 6, 10, 11, 12

dissymmetry, 5

I

INDEX

355

Crystallography, dyssymmetry, cel-
lular life and, 28

molecular, 23

substances inactive through
loss of, 32
general conclusions on, 46
Gernez, separation of tartrates

by decoy, 44
Haiiy, 2, 6, 9, 10, 12
hemihedrism, 5, 6, 13, 14
Herschel, 10, 13
isomorphism, 3
Le Bel, 37

malates, Pasteur's work, 20
Mitscherlich, 4, 13, 17
molecular dissymmetry, 23
molecular structure, theories prior

to 1840, 2
molecules, active, combinations

between, 39
para tartrates, 16

Mitscherlich, 17

Pasteur, 16
Pasteur's predecessors, 1

work (See Pasteur)
Provostaye, 13
right and left-handed substances,

means of separating, 43
rotary power, depends on consti-
tution of molecule, 12
rotation of plane of polarization,

8, 11, 13, 14
tartrates, 12

Mitscherlich, 13

Pasteur, 12

Provostaye, 13

Weiss, 6
Culture media, suited to organisms

225
Cultures, Pasteur's early knowl-
edge of how to make a series, 252

Darwin, 192, 201

Davaine on anthrax, 182, 191, 232,

233, 237, 245, 247, 248, 250, 257,

259, 274

Declat, 191

Delafond, 235, 242, 245
Delafosse, 5, 10, 11
Descartes, 55
Desmazieres, 61
Dessaignes, 32, 33
Dissymmetry, molecular, 23
substances inactive through loss

of, 32
cellular life and, 28
Dobereiner, 75, 121
Dry sterilization, introduction of,

119
Du Bois Reymond, 231
Duboue, 295

Duclaux, Emile, life of, VII
Madame, VII
Pierre-Justin, VII
Duclauxian high lights: a blast of
heat, a blast of cold, 123
a corner of the veil raised, 125
a dream which goes somewhere, 84
a fact is nothing by itself, 213
a hard necessity, 148
a new world was opened to him,

283
a sure beginning of things, 253
Bastian's contribution to science,

119
Bernard, very respectful with

facts, 208
Broussais' cloud of dust, 230
chemical mutations govern every-
thing, 318
chemist to his finger-tips, 107
chemistry, physics and life, 272
chemistry in medicine, 321
choice of food among bacteria,

126
deceptiveness of words, 80, 227
discoveries, that reveal vast hori-
zons, 303
discussions, mediocre value of,

212
experimental method, its power,
295

356

INDEX

Duclauxian high lights: faith, in-
tolerance of, 144
Gay-Lussac's coup de pouce, 58
general debility of intelligences,

213
Grand Turk and Republic of

Venice, 130
guess or be devoured, 154
Herschel's drop of oil, 10
historic stumbling stones, 1, 52,

227
honor to Davaine, 237
how Davaine failed, 257, 258
how one falls, 122
how to understand the past, 227
Jenner's eternal glory, 282
judgments revised without ceas-
ing, 111
Klebs and mineral solutions, 225
Liebig, extractor of quintescence,
75
he only remained a little
melancholy, 132
life in struggle with a compound
endowed with rotary power,
45
modern surgery full fledged, 268
multicolored lanterns, 230
obedient to what mysterious call,

319
old age and mental inertia, 128,

133
only with difficulty do great
minds understand one another,
206
on pathology in, 1876, 226
on seeing simply, 88, 89
Pasteur, a concjueror in the realm
of his dream, 281
a pioneer, 84, 232
man of largo horizons, 273
struggling with error, 149
the apostle, 290
twenty years old in microbiol-
ogy, 226
where he is without equal, 232

Duclauxian high lights: Pasteur's
debate with a shade, 206

dogmatic style, 276

first camp on a route wherein
he found immortality, 147

good fortune, 34

guardian spirit, 186

imagination, 27, 45, 273

iron on punk, 105

Olympian silence, 147

politeness and personal opin-
ion, 208

posthumous writings and one's
friends, 209

Pouchet's imagination, 93

progress in science from change
of view, 7

raging victims, bound and
howling, 294

researches a la Lavoisier, 123
revolutionary phrase, 71
role of a good technique, 191
slave of one's education, 272
struggle for existence vs. struggle

for oxygen, 256
struggles in the dark, 206
the enchanted grotto, 280
theory: it need not be true, it

suffices that it be fertile, 36,

38, 55, 111, 130
there are not on the palette of

any painter, 285
the weather vane has turned,

248
the whipstroke of departure,

218
value of a theory, 130
Virchow's terminolog\' and sys-
tem, 231, 232
virulence is a state of perpetual
becoming, 311

sums up the result of conflict,
308
vital force, 231, 300, 301
we have not the same sort of

brain, 106

INDEX

357

Duclauxian high hghts: what secret
instinct, what spirit of divina-
tion, 289
why turn the carpet to see the
design? 88

Dujardin, 80

Dumas, 58, 87, 107, 145, 148, 154

Dusch, 91, 94, 101

Duval, 197

Ehrenberg, 80

Epidemics, Pasteur on suppression

of, 173, 223, 224
Eremacausis, 121
Erysipelas of the pig, 310
Etiology of microbial diseases,

studies on, 225

Fabroni, 60
Feltz, 232, 274
Fermentation, 51

aerobic and anaerobic life of, 79,

82, 205
alcoholic, 73

and spontaneous generation, 85
Appert, preserving methods of,

60
balance in chemistry, introduc-
tion of, 56
Becher, 53
Bernard, 206
Berzelius, 76, 77
Boullay, 58
Boutron, 79
Boyle, 53

Cagniard-Latour, 61, 64, 65
cause of, theory as to, Gay-Lus-
sac's, 218
Liebig's, 218
Pasteur's, 205, 218
Colin's work, 65

disease, association between phe-
nomena of fermentation and,
53
Dobereiner, 75
Dujardin, 80

Fermentation, Dumas, 58
Ehrenberg, 80
Fabroni, 60
Fremy, 79, 213
Gay-Lussac, 57, 58, 59, 62
Helmholtz, 63, 64, 84
knowledge of, before Lavoisier,

51
lactic, 67, 79
Lavoisier, 55, 56, 57, 58
Liebig, 54, 64, 68, 69, 75, 76, 80,

130
Mitscherlich, 65
oxygen, role of, in, 61
Paracelsus, 53

Pasteur, discussion with Ber-
nard, 206
lactic fermentation, 67
Quevenne, 65
Schwann, 61, 62, 63, 65
specificity of, 71
Stahl, 54, 55, 66
Thenard, 57, 59, 61, 65, 74, 78
Turpin, 65
Van Helmont, 53, 55
Willis, 54, 66

yeast, role of, in, Berzelius, 76
Gay-Lussac, 60
Helmholtz, 63
Liebig, 64
Pasteur, 73, 74, 75
Schwann, 62
Fermenting power of Mycoderma

aceti, 125
Flacherie, 173'
Flaming glassware, Pasteur's

method of, 119
Fracastoro, 229
Fraenkel, 304
Fremy, 79, 111, 213
Frey, 152

Gay-Lussac, 57, 58, 59, 62, 90, 91,

102, 119, 218
Germination in absence of air, 264
Germs in air, 91, 93

358

INDEX

Germs in air, distribution of, 101
not everywhere abundant, 103,
191, 268
reaction to acid liquids, 117
rejuvenescence of, air necessary
for, 118
Gernez, 44, 166
Gibier, 272
Grancher, 299
Guerin, Alphonse, 191
Gucrin, Jules, 104
Guerin-Meneville, 152
Guyon, 191

Hales, 55

Hallier, 192

Hameau, 229, 230

Haiiy, 2, 6, 9, 10

Helmholtz, 63, 64, 84, 92, 101, 231

Henle, 228, 230

Herschel, 10, 13, 35

Heterochronia, 231

Heterotopy, 231

Hoffmann, 192, 197

Immunity, 313

cellular theory of, 317

chemical and humoral theories

of, 312
problem of, 299
relative, 278

Jaillard, 238, 257, 259, 261
Jenner, 232, 275, 282
Joly, 106, 118

Joubcrt, associated with Pasteur,
114, 115, 191, 226, 252

Klebs, 225, 239, 248

Koch, Robert, adverse criticisms of,

293
distinguished contributions of,

226, 242, 245, 247, 248, 250,

286
Kutzing, 61

Lackerbauer, 165

Lactic fermentation, 67, 79

Lannelongue, 270

Lavoisier, 55-59

Le Bel, 37

Lebert, 152

Lechartier, 211

Lefevre, 55

Lemery, 55

Leplat, 238, 257, 259, 261

Leuwenhoeck, 61

Liebig, 54, 64, 65, 66, 68, 69, 75, 76,

80, 121, 122, 128, 134, 206, 218,

231
Linnaeus, 230
Lister, 104, 191. 269
Loffler, adverse criticisms of, 293
Ludwig, 231

Malaxes, 20

Metastatic abscesses, 266

Metchnikoff, 317, 318, 319

Microbial diseases and virus dis-
eases, 273

Microbial pathology, great teach-
ings of, in Pasteur's book on
silkworms, 182

Milk, sterilization of, 101

Mitscherlich, 4, 13, 17, 65

Moitrel d'Element, 55

Molecular dissymmetry of tartrates,
23
relation to nutritive character, 46

Molecular structure, theories prior
to 1840, 2

Molecules, active, combinations be-
tween, 39

Moliere, 90

Morts-flats, 164, 173

Mucor mucedo, anaerobic life of,
198, 200

Miintz, 212

Mussct, 106,118

Mycodcrma aceti, 124

supposed transformation of,
197

INDEX

359

Mycoderma vini, growth in absence
of air, 201
supposed transformation into
an alcoholic ferment, 192,
197

Needham, 89, 90

Obermeier, 249

Organized ferments, Pasteur's the-
ory, 69, 78, 79

Osimo, 153, 157, 160

Oxidation in contact with air, 121

Oxygen, role of, in fermentation,
61, 123, 125, 205
toxic role of, 306

Paracelsus, 53, 229

Parasite, reaction of host, Pasteur's

interest in, 254
Paratartrates, 16

Pasteur, aerobic and anaerobic life,
discovery of, 79, 82
aerobic life of anaerobic species,

202
alcoholic fermentation, 73
anaerobic life of aerobic species,

198
anthrax, endemic and epidemic
nature of, 287
etiology of, contributions to,

245, 251, 252, 286
vaccine for, 289-293
virus disease, 289
antiseptics, effect of, first hint, 71
aseptic methods of dressing
wounds advocated by, 267,
271
aspartates, work on, 20, 32, 37,

38
atomic groupings, contribution

to our knowledge of, 22
bacteria, associations of, role,

264
bacterial species, conception of
action of, in disease, 301

Pasteur, Bastian, discussion with,

114
beer, studies on, 187
Bernard, discussion with, on

fermentation, 206
boil of the bone, 270
brewing, studies on, 187
butyric fermentation, 79, 81, 82

vibrio of, 80
chicken cholera, 276
combinations between active

molecules of rotary substances,

40
crystallography, 1
culture media, importance of
suitable, 76, 225

influence of acid and alkalies
on, 71
discouraged, 174
discovers motile bacteria, 80
disregard of morphology, 254
dissymmetrical molecule, three

dimensional, 37
dissymmetry of cellular life, 28
equipment, 93
erysipelas of the pig, studies of,

310
etiology of microbial diseases,

studies on, 225
fermentation, cause of, 218

physiological theory of, 85,
205
Fremy, discussion with. 111
germs in air, 93, 103
germ-specificity, 192
groping, 115, 159, 163, 164, 166,

167
heating of wines, 141
Henle and, 229

illusions of an experimenter, 280
immunity, 278, 279

cellular theory of, 317

chemical and humoral theories
of, 312, 316

problem of, strife between
cells, 300

360

INDEX

Pasteur, indifferent to perfection
of technique, 191
insight, 19, 32, 222, 254, 270, 271,

287
Institute, 299
lactic fermentation, 67, 79
Liebig, discussion with, 128
malates, work on, 20, 33, 38
masterful qualities, 72, 74, 178
microbial and virus diseases,

discovery of identity, 281
microscopical studies, 258
milk, sterilization of, 101
molecular dissymmetry and ro-
tary power, correlation of, 36
not a naturalist, 81
on human plagues, 223, 224
opinion on danger of precon-
ceived ideas, 193
organized ferments, 69, 79
osteomyelitis, 270
oxidation in air, 122
oxygen, role of, in disease, 264
parasite, reaction of host to,

254
paratartrates, work on, 16
pathological conflicts, 269
Pouchet, Joly and Musset, dis-
cussion with, 105
puerperal fever, 270
rabies, 294

cultures of, in the living organ-
ism, 296
prophylaxis, 298
rotary substances, right and left-
handed, means of separating, 43
septic vibrio, 259

silkworms, and human path-
ology, 173, 182, 186
corpuscular disease (p6brine),

149
morts-flats (flacherie), 164, 173
studies on diseases of, 145
species, transformation of one into

another, 190, 192
spontaneous generation, 93, 119

Pasteur, spores, of butyric vibrios,
241
role of, 244
staphylococcus, discovery of, 269
struggle for existence, concep-
tion of, 301, 317
susceptibihty to infection, indi-
vidual variation in, 181
tartrates, work on, 12, 16, 30, 36
technique, 226

temperature, relation of, to in-
fection, 271
There, there is its picture! 271
toxines, discovery of, 255
training in 1870, 186
transformation of species, 192
vaccines, discovery of, 280, 281
vinegar-making, phenomena of,

122
virulence, and attenuation, 304
variations in, attributed first
to several organisms, 274
virus, attenuation of, discovery
of, 302
-diseases and microbial dis-
eases, the same, 281
water, contaminating germs in,

116
wine, action of oxygen on, 136

diseases of, 134
yeast of wine, 134, 214, 217
Pathology, Pasteur's entrance into

field of, 145
Pcbrine, 149

origin of name, 152
Pcligot, 166

Penicillium glaucum, growth in
absence of air, 199
supposed transformation of
yeast into, 192
Pfeffer, 46
Pfeiffer, 319
Pliagocytosis, 317
Phihppi, 152, 160
Phylloxera, 143
Poilender, 233

INDEX

361

Pouchet, 93, 105, 118, 119
Predecessors of Pasteur in crystal-
lography, 1
Provostaye, 13
Puerperal fever, 270
Pus vibrio, 265

QUATREFAGES, 152, 154

Quevenne, 65

Rabenhorst, 81
Rabies, 294

Chamberland, 297

cultures in living host, 296

Dubouc's discovery, 295

prophylaxis, 298

Roux, 297

Thuillier, 297

virus diseases, analogies, 298
preservation of virulence of,
309
Raulin, 225
Rayer, 233, 235
Recklinghausen, 249, 250
Redi, 86

Right and left-handed rotary sub-
stances, means of separating, 43
Rindfleisch, 249
Rossignol, 291
Rotary power, depends on shape

of molecule, 12
Rotation of plane of polarization, 8,

11, 13, 14
Roux, 191, 226, 297, 306

SAiNTE-CLAiRE-Deville, 28
Sanderson, See Burdon-Sanderson
Sanson, 238
Schroeder, 91, 94, 101
Schultze, 90, 92
Schutzembach, 122
Schwann, 61-^5, 91, 95, 100
Sedillot, 268
Septic vibrio, 257

effect of air on, 265

Septicemia, 260
Signol, 238, 259
Silkworms, diseases of, 145

digestive tract full of mi-
crobes, 180
flacherie of, 164, 173

contagious nature of, 184
distribution of germs in,

widespread, 182
hereditary character of, 176
life history of, 149
morts-flats. See flacherie
pe brine (corpuscular disease),
149
Bellotti, 160
Cantoni, 153, 157, 160
cause of, 162, 170
contagious nature of, 171
Cornaha, 152, 160
Frey, 152

Gernez, 159, 166, 167, 169
Guerin-Meneville, 152
hereditary nature of, 171
Lebert, 152
Osimo, 153, 157, 160
Peligot, 166
Philippi, 152, 160
Quatrefages, 152, 154
Susani, 173
Vittadini, 153, 160
teachings of microbial pathol-
ogy in Pasteur's volumes
on, 182
Spallanzani, 89, 91, 92, 95, 96
Species, transformation of one into
another, 190, 197, 201
Bail, 192
Bechamp, 197
Berkeley, 192
Duval, 197
Hallier, 192

Hoffmann, 192, 197, 201
Mycoderma aceti, 197
Mycoderma vini, 194, 197
Trecul, 192, 197
Turpin, 192, 201

362

INDEX

Spontaneous generations, 85

and fermentation, 85

Balard, 107, 109

Bastian, 101, 111, 114, IIG,
119

Buffon, 87

Burdon-Sanderson, 116

Chamberland, 114, 116

Cohn, 118

Dumas, 107, 108, 109

Dusch, 91, 94, 101

Fremy, 111

Gay-Lussac, 90, 91, 92, 102,
118,119

Helmholtz, 92, 101

in decoction of hay, 1 10

in heated urine, 115

Joly, 106, 109, 118

Joubert, 114

Musset, 106, 109, 118

Needham, 89

Pasteur, 93

Pouchet, 93, 105, 106, 109,
115,118,119

Schroeder, 91, 94, 101

Schultze, 90, 91, 92

Schwann, 91, 95, 100

Spallanzani, 89, 92, 95, 96

Tyndall, 92, 105
Spore, conception of, 117, 118
role of, in anthrax, 241, 261,

264
vitahty of, 286, 289
Stahl, 54, 55, 66

Staphylococcus, discovery of, 269
Struggle for existence, 317

idea introduced into pathol-
ogy, 256
Susani, 173

Susceptibility to infection, individ-
ual variation in, 181

Talamon, 304
Tartrates, 12

hemihedrism and rotary power
in, 16

Temperature, relation of, to infec-
tion, 271

Thonard, 57, 59, 61, 65, 74, 78

Theory of fermentation, Pasteur's,
205

Thomas, 315

Thuillier, 297, 299, 310

Thuret, 81

Tiegel, 239

Toussaint, 305

Toxines, discovery of, 255

Trccul, 192, 197

Turpin, 65, 192, 201

Tyndall, 92, 105

Vaccines and viruses, study of, 273

discovery of, 280
Van Helmont, 53, 55
Van't Hoff, 37
Varro, 227, 229
de Vergnette-Lamotte, 144
Vinegar, manufacture of, 121
German process, 122, 127
Liebig, 122, 128
Orleans process, 123
Pasteur, 122, 132
mycoderma of, 124, 137
Virchow, 230, 232, 301
Virulence, augmentation cf, 310,
311
definitionof, 308, 311
preservation of, 309
return to, 308
variations in, 273, 297, 307
Virulence and attenuation, 304
Virus, 247, 252

attenuation of, Pasteur's dis-
covery of, 302
-diseases and microbial diseases,

273
versus parasite, 245, 250, 252
Viruses and vaccines, study of,

273
Vital phenomenon versus molecu-
lar disintegration, 130
Vittadini, 153, 160

INDEX

363

Voigt, XIV
Vulpian, 299

Waldeyer, 249

Water, distribution of bacteria in,

116
Weigert, great service of, 250
Weiss, 6
Willis, 54, 66

Wine, action of oxygen on, 136
Berthelot, 137
Boussingault, 137
Pasteur, 136
aging of, 140
diseases of, 133
Liebig, 133, 134
Pasteur, 134, 135
mycoderma of, 138, 192, 197,
201

Wine, heating of, 141
Wines and vinegars, 121
Wohler, 28

Yeast, role in fermentation, 60,
62, 65, 73
Berzelius, 76
Dobereiner, 75
Helmholtz, 63
Liebig, 64
Pasteur, 73, 75
Schwann, 62
of beer, aerobic life of, 202
of wine, 134, 135, 217

origin of, 214
supposed transformation into
other organisms, 192, 197
Yersin, XVIII
Yourievitch, V

II