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BIOLOGICAL TIME

THE MACMILLAN COMPANY
NEW YORK - BOSTON . CHICAGO - DALLAS
ATLANTA - SAN FRANCISCO

BIOLOGICAL TIME

By
P.LECOMTE DU NOUY

Chief of the Division of Molecular Biophysics,
Pasteur Institute, Paris; formerly Associate
Member of the Rockefeller Institute

With Foreword by

ALEXIS CARREL, M.D.
Rockefeller Institute for Medical Research
Author of “Man the Unknown”

New York
THE MACMILLAN COMPANY

ee

Copyright, 1937, by
THE MACMILLAN COMPANY.

All rights reserved—no part of this book
may be reproduced in any form without
permission in writing from the _ publisher,
except by a reviewer who wishes to quote brief
passages in connection with a review written
for inclusion in magazine or mewspaper.

PRINTED IN THE UNITED STATES OF AMERICA
BY THE POLYGRAPHIC COMPANY OF AMERICA,N.Y.

TO
DR. ALEXIS CARREL

THE SPIRITUAL GODFATHER OF THIS BOOK
WITH THE AFFECTIONATE GRATITUDE OF THE AUTHOR

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FOREWORD

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In this book, Lecomte du Noi discusses an aspect of our-
selves, which is both very important and little known—our
duration. To endure is an essential characteristic of all
living organisms. Time is, in fact, the fabric of life. In his
admirable ‘Creative Evolution,” Bergson has shown the
fundamental importance of time in biological phenomena.
“Wherever anything lives, there is, open somewhere, a
register in which time is being inscribed.” But the time of
our body is not the same as physical time, that is, the time
marked by a clock. Physical time is an aspect of the cosmic
world. Inward time, an aspect of ourselves. It differs as much
from physical time as the solar system differs from a man.
It is identical with the living body. For this reason, Lecomte
du Noiiy has united in the title of his book the ideas of life
and time. It is impossible to understand the nature of our
time if we ignore the nature of organic phenomena. Time
and life are one and the same thing. A better knowledge of
human duration will permit a more effective application of
the factors of our environment to the development of our
physiological and mental life.

Physiological time, like physical time, is the expression of
certain intrinsic changes within a system. While physical
time depends on the motion of the earth around the sun,
inner time is bound to some modifications of our humors
and tissues. These modifications constitute aging. Of course,
aging is an extremely well known phenomenon. But we have
only recently learned how to analyze it. In this book,
methods are described for the measurement of physiological
time, and for the study of its characteristics. Physiological
time has been estimated in two different ways: By the rate
of wound healing, and by chemical changes taking place in
blood serum. The first method was invented by Lecomte du

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Vill : FOREWORD

Noiy in the laboratories supported by the Rockefeller In-
stitute in France during the Great War, while he was study-
ing the repair of wounds. A constant relation was found to
exist between the velocity of wound healing and the age of
the patient. From the mathematical formula expressing the
repair of tissues, Lecomte du Noiy extracted a constant,
which varies from 0.4 for a child of ten years to 0.08 for an
old man of sixty. In this manner, age can be detected by rate
of healing. The other method, much less precise, is based on
certain changes that take place in blood serum. During the
course of life, blood serum progressively acquires the power
of arresting the growth of tissues when they are cultivated
in vitro. This change is probably responsible for the decrease,
in function of age, in the velocity of the repair of a wound.

The knowledge of physiological time is of obvious im-
portance because it leads to the understanding of its value.
Long ago, Minot found that the younger an animal is, the
more rapid is the rate of aging. From his experiments, it
could be inferred that physiological time has a much greater
velocity in youth than in old age. But we remained ignorant
of the extent of those differences. Their numerical value has
been determined by Lecomte du Noiy. The rate of tissue
repair is five times slower at the age of sixty than at the age
of ten.

The significance of the time of a clock depends naturally
on the characteristics of physiological time. When compared
with physiological time, physical time loses its uniform
value. Parents and children live in different temporal worlds.
They are separated by a gap that often is too large to be
bridged, even by illusions. Within the familial group, the
individuals should not be separated by too great a temporal
distance. It is, therefore, desirable for women to have chil-
dren as early in life as possible. Again, the knowledge of the
characteristics of physiological time teaches us that, at the
end of life, aging is very slow. From one year to another,
the appearance of an old man in good health hardly changes.

FOREWORD 1X

Any acceleration in the process of aging in a senescent in-
dividual signifies the incidence of a disease, which should
be detected. It also becomes obvious that the value of a day
is much greater for a child than for his parents and his
teachers. The younger a child is, the richer his life in physio-
logical and psychical values. Such a fact should not be
neglected by educators. Every moment of the existence of a
child must be utilized for his formation. A clear realization
of the enormous value of physical time for children would
bring about a real progress in education and in the quality
of individuals. The knowledge of physiological time is
equivalent to the knowledge of life itself, because time can-
not be separated from life. The deeper this knowledge, the
more successful will be our approach to the mystery of our
self. For these reasons, I am happy to present this book by
Lecomte du Noiy to the American public.

Alexis Carrel

Rockefeller Institute for Medical Research,
New York

LIBRARY

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CONTENTS

INTRODUCTION

PART Jf

THE BIOLOGICAL PROBLEM AND METHODS

CHAPTER
I, OUTLINE—BIOLOGICAL METHODS . . .

II. PHYSICAL AND CHEMICAL METHODS — CRITICISMS
AND DIFFICULTIES

III. CHEMICAL AND PHYSICAL METHODS—LIMITATIONS—
RESULTS ACQUIRED—THEIR ROLE IN IMMUNITY
AND BACTERIOLOGY

PARTY 11
CICATRIZATION OF WOUNDS AND
TISSUE-CULTURE

Iv. A BIOLOGICAL PHENOMENON—TIME—CICATRIZATION
OF WOUNDS—PRELIMINARY EXPERIMENTS .

V. CICATRIZATION OF WOUNDS (II)—EXPERIMENTAL
TECHNIQUE—CURVES—MATHEMATICAL STUDY

VI. INDEX OF CICATRIZATION—INFLUENCE OF THE AGE
OF THE PAYIENT—INFLUENCE OF THE SIZE OF THE
WOUND

VII. TISSUE-CULTURE IN VITRO

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TIME
VIII. $TIME—DEFINITIONS—MEASUREMENTS

IX. THE TIME OF ORGANIZED BEINGS—-THE CHEMICAL
CLOCK

INDEX OF NAMES .

Xl

PAGE

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23

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51

66

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102

125

145
179

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DIAGRAMS

FIG. PAGE
I. SCHEMATIC CURVE EXPRESSING THE PHENOMENON OF

CICATRIZATION . : ; : : mee
EFFECT OF A GRAFT ON THE GRANULAR CONTRACTION 59
EFFECT OF A GRAFT ON THE GRANULAR CONTRACTION 59
EFFECT OF A GRAFT ON THE GRANULAR CONTRACTION 60

2
3
4
5. EFFECT OF A GRAFT ON THE GRANULAR CONTRACTION 60
6. EFFECT OF A GRAFT ON THE GRANULAR CONTRACTION 60
f|

INFLUENCE OF THE PROXIMITY OF EPITHELIAL BORDERS

ON CICATRIZATION ; ; ‘ ; ; , 61
8. INFLUENCE OF THE PROXIMITY OF EPITHELIAL BORDERS
ON CICATRIZATION ? r 5 : p : 61
Q. EFFECT OF A GRAFT ON EPITHELIZATION . : ; 62
IO. INFLUENCE OF MECHANICAL PROTECTION ON EPI-
THELIZATION ; : ‘ si ha is 2:
II. INFLUENCE OF INFECTION : : : : Ah es
I2. REDUCED REPRODUCTION OF THE DRAWINGS OF A
WOUND, TAKEN FOUR DAYS APART ; ¢ ! 68
13. NORMAL HEALING OF A WOUND . ; Lee
14. CALCULATION OF THE FORMULA } i : ; 73
I5. LARGE ABDOMINAL WOUND, CICATRIZED IN THREE
MONTHS. s f BH oa é : : 76
16. INFLUENCE OF DIFFERENT ANTISEPTICS ON A WOUND 78
17. THE INDEX OF CICATRIZATION 3 [ j E SI
18. CICATRIZATION OF AN IRREGULAR WOUND ; : 83
I9. INFLUENCE OF THE AGE OF THE PATIENT AND OF THE
SIZE OF THE WOUND . : ; : : ne Fi
20. RATE OF HEALING AS A FUNCTION OF THE AGE OF THE
PATIENT. . Z A : ; , ree:

X1li

X1V BIOLOGICAL TIME

FIG. PAGE
21. RATE OF HEALING AS A FUNCTION OF THE SIZE OF

THE WOUND : ‘ ‘ 3 i ; aie =.
22. LONG AND NARROW WOUND . : ; hie
23. CORRECTING FACTOR IN EQUATION (6) . 230 (6

24. DURATION OF LIFE ‘IN VITRO’ OF FIBROBLASTS AS A
FUNCTION OF THE AGE OF THE ANIMALS FROM
WHICH THE PLASMA WAS TAKEN : : i Le

25. RATE OF GROWTH OF FIBROBLASTS AS A FUNCTION OF
THE AGE OF THE ANIMALS FROM WHICH THE SERUM

WAS TAKEN ; u : i : : Da i
26. INDEX OF CICATRIZATION AS A FUNCTION OF THE AGE

OF THE PATIENT : ; : : {ETO
27. COEFFICIENT ‘A’ AS A FUNCTION OF THE AGE OF THE

PATIENT. ' ’ ase
28. RELATIVE RATE OF CICATRIZATION COMPUTED FROM

CONSTANT ‘A’. : . ; Oe ht
29. FRONT WAVE CURVE : . : : E62

30. RELATIVE RATE OF CICATRIZATION AND APPRECIATION
OF THE VALUE OF TIME AS A FUNCTION OF THE AGE 167

31. RELATIVE VALUES OF OUR APPRECIATION OF THE
DURATION OF ONE SIDERAL YEAR, COMPUTED FROM
THE CONSTANT ‘A’, AND FROM THE HYPERBOLA
WITH RESPECT TO THE AGE OF TWENTY TAKEN AS
REFERENCE : : : ; ; : . 169

BIOLOGICAL TIME

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INTRODUCTION

The consequence of the progress of Science is the gradual
weakening of all the primary concepts born of ignorance. Their
only strength lies in the unknown, and as that is gradually
elucidated quarrels must cease, divergent doctrines must fade
away and be replaced by scientific truth which wiil reign supreme.

CLAUDE BERNARD (1875)

THE problem of life has always passionately interested man.
And yet there has never been a satisfactory definition of
life. Why is this? Perhaps because a distinction must be
drawn, as Claude Bernard pointed out, between the word and
the thing itself. Pascal, who so well understood all weaknesses
and illusions of the human mind, points out that in reality
true definitions are creations of the mind, or definitions of
names, and merely conventions for shortening speech. But
he admits that there are primitive words which are under-
standable without need of definition. According to Claude
Bernard, the word ‘life’ is one of these. Everybody com-
prehends the words ‘life’ and ‘death’. It is impossible to
separate these two terms, for what lives will die, and what is
dead has lived.

Ideas on life have necessarily varied with different epochs
and according to scientific progress. The reader may remem-
ber the purely verbal definition of the Encyclopedia: ‘Life is
the opposite of death’, and that of Bichat: ‘Life is the com-
bination of functions which resist death.’ In other words
life is the combination of the vital properties which resist the
physical properties. This is a vitalistic-view. It was generally
thought that Claude Bernard meant to give a definition of
life when he wrote: ‘Life is Death.’ But this is not quite
true for, in a later article, this phrase is preceded by another
which is usually overlooked and which materially restrains its
meaning: ‘If we wished to express the fact that all vital
functions are the necessary consequence of organic com-
bustion, we would repeat what we have already stated: Life

I

2 BIOLOGICAL TIME

is death, the destruction of tissues. Or we would say with .
Buffon: Life is a minotaur; it devours the organism. If on
the contrary we wished to insist on this second phase of the
problem of nutrition, that life maintains itself only by a
constant regeneration of the tissues, we would consider life as
a creation accomplished by means of a plastic and regenerating
act opposed to the vital manifestations.’

Claude Bernard was not the man to be enslaved by a formula,
as is proved by his words: ‘Facts are always more beautiful
than the most beautiful theory.’ His keen intelligence dictated
the lines which even to-day contain the clearest and truest
thoughts on the subject. In the course of this introduction
we will only express his ideas, and in spite of the rich harvest
of new facts of which he had no knowledge, it will be seen
that his admirable common sense, his respect of truth, and
his genius still dominate all physiology.

The following pages are extracted from two little-known
articles published in the Revue des Deux Mondes in 1867 and
1875. Their perusal will show why they were chosen as an
introduction to this book.

‘At the beginning of the nineteenth century, a physiologist
could still publish a volume of experiments On the Principle
of Life and the Seat of this Principle. We no longer search
for the seat of life. We know that it is everywhere, in all
the molecules of organized matter. The vital properties
are in the living cells. Everything else is but organization
and mechanism. The manifold manifestations of life are
the expression of thousands and thousands of combinations
of elementary organic properties which are themselves fixed
and invariable. It is therefore less important to know the
immense variety of vital manifestations which nature never
seems to be able to exhaust, than to determine rigorously
the properties of the tissues from which they spring. That
is why to-day all scientific effort is directed towards the
histological study of the infinitely small elements which
contain the true secret of life.

INTRODUCTION 3

‘No matter how far we delve into the phenomena per-
taining to living beings, we are always confronted with the
same question which was propounded in ancient days, at
the very beginning of Science: Is life due to a power, a
special force, or 1s 1t only a modality of the general forces
of nature? In other words, does life contain a special force
which is distinct from the physical, chemical, or mechanical
forces? The Vitalists have always claimed the impossibility
of explaining physically or mechanically all the phenomena
of life. Their opponents have always answered by giving
well-proven physico-chemical explanations to an ever-
increasing number of vital manifestations. We must admit
that the latter have constantly gained ground. Will they
succeed in explaining everything by their theories, or in
spite of their efforts will there not remain a quid proprium
of life which will always be irreducible?

‘This is the point that must be examined, for, far from
being only of philosophical interest, it is, on the contrary,
capable of showing us to what degree the fundamental
problems of all biology are dominated by chemical and
physical methods.

‘There are two classes of nutritional phenomena which
essentially constitute life and which are the origin, without
exception, of all its manifestations. One of these, organic
destruction or disassimilation, can already be classified
among the chemical actions. These decompositions in
living beings are no more mysterious than those which take
place in organic substances. As to the second class, the
phenomena of organizing genesis and nutritional regenera-
tion, they appear at first glance to be of a quite distinct vital
nature, and often irreducible to general chemical actions.
This, however, only appears to be so, and these phenomena
must be considered under the double aspect of an ordinary
chemical synthesis and of an organic evolution in progress.
Indeed, vital genesis incorporates phenomena of chemical
synthesis arranged and developed according to a particular
order which constitutes their evolution. Jt 7s zmportant to

4 BIOLOGICAL TIME

separate the chemical phenomena from their evolution, from
their correlation in time, for these are two entirely different
things.! As synthetic actions, it is evident that these
phenomena reveal only general chemical forces. By
examining them successively one by one this is clearly
demonstrated. The calcareous matter which is found in
the shells of molluscs, in birds’ eggs, in the bones of
mammals, is certainly formed according to the laws of
ordinary chemistry during embryonic evolution. Fatty and
oily substances are in the same case, and chemistry has
already succeeded in reproducing artificially, in the labora-
tory, a great number of immediate principles, of essential
oils and of complex bodies which are the apanage of the
animal and of the vegetable kingdoms. Starchy substances
which are developed in animals and which reproduce them-
selves in the green leaves of plants by the combination of
carbon and water under the influence of the sun, are also
well-characterized chemical phenomena. If the synthetic
properties of nitrogenous substances are much less clear,
this is due to the fact that organic chemistry is not far
enough advanced as yet. But it is nevertheless certain
that the substances are built up in living beings by chemical
methods. In truth, it may be said that the germs and the
cells, elements of organic synthesis, are most exceptional
agents. In respect to the phenomena of disorganization it
might also be said that enzymes are special factors charac-
terizing living matter.? The following seems to be a
general law. Chemical phenomena in the organism are
produced by special agents or processes. But this does
not alter the purely chemical nature of the phenomena
which take place, nor of the products which are their
result.

‘And now we come to organic evolution. The agents of

1 The italics are mine.—L. D.N.

2 Due to the remarkable work of Gabriel Bertrand, the funda-
mental role of infinitesimal traces of metals in the activity of the
enzymes is now known, but so far it has been possible to synthesize
artificially only one of them. (Kuhn, 1934.)

INTRODUCTION 5

chemical phenomena in living bodies do not confine them-
selves to producing chemical synthesis of extremely varied
substances. They organize them and render them appro-
priate for the morphological edification of a new being.
The most powerful and marvellous agent of this living
chemistry is, without question, the egg, the primordial cell
which contains the organizing principle of the whole body,
the germ. We cannot observe the creation of the egg ex
nihilo. It emanates from the parents, and the origin of its
evolutive potentiality is hidden from us. Science, however,
is bringing us every day nearer to the heart of the mystery.
It is by the germ, and in virtue of a kind of evolutive power
which it possesses, that the perpetuity of the species and
the descendance of beings are established. It is likewise
the germ which enables us to grasp the necessary links
which exist between nutritional phenomena and growth
phenomena. It explains, or at least allows us to conceive,
the limited duration of the living being. For death must
ensue when nutrition stops, not because food is lacking,
but because the evolutive sequence of an organism, which
must be admitted even though we do not understand it,
has reached the term of its career, and because the organizing
cellular impulse has exhausted its power.

‘The germ likewise controls the organization of the
individual by forming the living substance with the help of
the surrounding medium, and by giving it the unstable
chemical characteristics which are the cause of its unceasing
vital movements. The cells, secondary germs, similarly
dominate the organization of cellular nutrition. It is
evident that these are purely chemical actions. But it is
no less evident that these chemical actions, through which
the organism grows and is built up, are linked together and
succeed each other in view of the result, which is the
organization and growth of the individual, animal or vege-
table. It is as if a vital drawing existed which traced the
plan of each organ, so that even though each phenomenon
in the organism is tributary to the general forces of nature

ns

BIOLOGICAL TIME

when taken separately, when taken successively and as a
whole, they seem to reveal a special link. Some invisible
contingency appears to lead them in the path which they
follow and to impose the order in which they are bound.
The synthetic chemical actions of organization and of
nutrition thus manifest themselves as if they were dominated
by an impulsive force which governs matter, creates a
special chemistry appropriated to its end, and brings in
contact the blind reagents of the laboratory just as the
chemist himself would. We already know that this power
of evolution, inherent in the ovule which is to reproduce
the living being, covers the phenomena of generation as
well as those of nutrition. They both, therefore, possess
a basic evolutive character.

“This power or property of evolution, which we can just
mention here, would alone constitute the guid proprium of
life, for it is clear that this evolutive property of the egg,
which will produce a mammal, a bird, or a fish, is neither
physics nor chemistry. Vitalistic conceptions can no longer
reign over physiology as a whole. The evolutive force of
the egg and the cells is therefore the last stronghold of
vitalism. In taking refuge behind it, however, it is clear
that vitalism transforms itself into a metaphysical concept
and destroys the last link which bound it to the physical
world and to physiological science. In stating that life is
the directing idea, or evolutive force of the organism we
simply express the idea of unity in the succession of all
morphological and chemical changes linked together by the
germs from the beginning to the end of life. Our mind
grasps this unity as a concept which imposes itself, and we
explain it by a force. It would be a mistake, however, to
believe that this metaphysical force is active in the same
way as a physical force. This conceptual force does not
leave the intellectual realm in order to react upon the
phenomena for the explanation of which it was created.
Although an emanation of the physical world, it does not
act upon it retroactively. In brief, the metaphysical force

INTRODUCTION 4)

through which we can characterize life is unnecessary to
science because, being outside the physical forces, it cannot
influence them in any way. We must therefore separate
the metaphysical world from the phenomenal world which
acts as its base, but which cannot borrow anything from it.
Leibnitz expressed this delimitation in the following way:
“The body develops mechanically, and the mechanical laws
are never violated in natural movements. Everything takes
place in the soul as though there were no body, and every-
thing takes place in the body as though there were no soul.”’’

In brief, if life can be defined with the help of a special
metaphysical concept, concludes Claude Bernard, it is never-
theless true that mechanical, physical, and chemical forces
are the only efficient agents of the living organism, and that

the physiologist must take their actions alone into account.

As Descartes says, ‘We think metaphysically, but we live

physically.’

PART I
THE BIOLOGICAL PROBLEM AND METHODS

CHAPTER I
OUTLINE—BIOLOGICAL METHODS

THE preceding pages give a certain aspect of the biological
problem and of its infinite complexity. We do not propose
to study in detail all biological problems, but only those which
may lead us progressively to the notion of time. If we seem
occasionally to deviate from our plan, it is because of the
necessity to show that, in spite of the difficulties encountered
and of the criticisms that can be made, certain modern methods
more than others are capable of helping the physiological
sciences, and even medicine, to progress rapidly. We hope
that the reader will be left with a truly optimistic outlook.

In order that one may understand the general plan and
follow the directing thread between chapters which might
easily seem to possess no common link, we must state, at the
very beginning, that it is our purpose to introduce a new
concept of time, or, more exactly, to try to demonstrate that a
fundamental difference exists between physical time, the time
of the universe which flows at a uniform speed, and our
physiological, internal time, on which, so far, we had only very
vague ideas. We will show that this physiological time, which
has a beginning and an end, does nor seem to flow at a uniform
rate. We will indicate the possibility of deriving from our
Own organism a unit of time different from the classical one
derived from the rotation of the earth around its axis. We
will also attempt to show the quantitative discrepancy between
conceptual and physiological time. This will lead to an
explanation of the differences perceived in the appreciation
of the flow of time at the beginning and at the end of life,
and to a hypothesis on the relation existing between the two
times.

Now, the point upon which we must insist at the beginning
of this book is that all these results are not based on hypotheses
but on experimental biological facts obtained by two different

Il

I2 THE BIOLOGICAL PROBLEM

methods which mutually check each other. The experimental
facts have been studied quantitatively, and our conclusions
are often derived from their mathematical relation. We do
not start from one or more postulates, but from measurements
and velocities. These researches were not undertaken with
the object of arriving at a definition of time, but on the
contrary in order to elucidate certain very definite biological
problems. The conclusions imposed themselves on us when
the experimental work was ended. That is why it is necessary
to give the reader a general idea of the biological problem and
of the methods by which it can be examined in detail, so that
he may follow progressively the path which led us to these
conclusions. It is important for him to be fully convinced
of the part played by the physico-chemical and chemical
mechanisms in life phenomena in order to understand, for
example, the value of the argument derived from the demon-
stration of the activity of the temperature coefficient (Van’t
Hoff constant) in the appreciation of time. It is essential
that he should understand the role of the chemical reactions
in the organisms. It is indispensable for him to know in
detail the mechanism of the cicatrization of wounds and of
tissue-culture, so that he can trust the calculations on which
the whole work is based, and realize the importance of the
quantitative checks on which our reasoning rests. The
elementary notions to which we constantly refer will some-
times be briefly dealt with, so as to avoid the necessity for the
reader to consult technical books or papers in search of mere
definitions.

In other words, we have tried to answer beforehand the
principal questions which might be put to us and the objections
which might be raised. We are not under the illusion that
we have completely succeeded, but we have done our best.

Our plan is the following:

1. We will show that the modern conception of a living
organism enables us to study it from different points of view
which can be roughly classed in three groups, each of which
imposes a distinct category of methods:

OUTLINE 13

(A) From the point of view of its objective manifestations
as a whole, that is to say, as an entire organized indi-
vidual, either isolated or in its normal environment:
zoology, descriptive botany, etc.

(B) From the point of view of the mechanisms of the
biological actions, using what we might call the breaking-
down methods. Either dynamic, i.e. maintaining life
and entailing no serious alterations in the part played
by each mechanism in particular (physiology); or else
static methods, which start by destroying life (cytology,
etc.)

(C) From the purely physical and chemical point of view,
namely, by suppressing conventionally the difference
which distinguishes living from dead matter, and by
incorporating life with our material universe.

In the first case the unit will be the individual; in the second,
the cell; and in the third, the molecule. It can be seen that each
class corresponds to a different order of magnitude, therefore
to different methods of investigation. If we admit the
beautiful definition of Ch. E. Guye: ‘Jt is the order of magni-
tude that creates the phenomena’, we shall be in each case
confronted by different phenomena.

2. We will studyin detaila fundamental biological phenome-
non: cellular reparation. First, under its best-known and most
important practical aspect, cicatrization of wounds; secondly,
under the experimental aspect given it by Dr. Carrel: trssue-
culture in vitro. We will discuss the mathematical con-
sequences which can be derived from the experiments and
which introduce a particular concept of age and time.

3. Having introduced quantitatively the notion of time in
the experiments previously described, we will develop the
subject by explaining the conventional and relativistic concept
of time and its classical measurement.

4. Finally, we will develop the concept of duration and of
physiological time. Contrary to the customary procedure, we
will borrow a unit from our internal time, and we will use it

14 THE BIOLOGICAL PROBLEM

to measure the physical exterior time. In other words, we
will confront a time felt and lived, with a time merely con-
ceived. We will thus directly oppose /:fe, the subconscious,
to intelligence.

The study which first imposed itself on the human mind
was evidently that of whole organisms in the animal and
vegetable kingdoms. In principle, this requires neither
laboratories nor complicated apparatus. The old-time natu-
ralists and botanists began by describing what they saw.
The eye, the ear, the senses in general, are the only instru-
ments needed for these contemplative sciences. It is not even
necessary for the scientist to do the observing himself, as is
proved by the example of the great naturalist Francois Huber,
who although blind left some remarkable experiments which
he conceived on the subject of the life of bees (1814) and
which were executed and seen by his servant, who had
absolutely no scientific ideas of his own. Huber was thus the
directing spirit, but he was obliged to borrow another man’s
senses. However, the pure and simple description of nature
does not in itself constitute a scientific work. It leads to a
classification which would be extremely complex and without
significance if it did not seek to establish, behind the different
appearances of individuals, the similarities leading to kinships
which are real even though less apparent. That is why the
observer must be completed by the experimenter. Claude
Bernard wrote at the beginning of his Introduction to the
Study of Experimental Medicine some beautiful pages in which
he analysed at length these two forms of activity of the
scientist in general.

“The observer purely and simply describes the phenome-
non which takes place before his eyes. The only thing he
must ward against is an error of observation which might
lead him to see a phenomenon incompletely or define it
badly. To this end he will employ all the instruments which
can help him to make his observation more complete. The
observer must be the photographer of the phenomena, his

OUTLINE 15

observations must represent nature exactly. He must

observe without a preconceived idea. His mind must be

passive, that is to say silent. He listens to nature and
writes under her dictation.

‘But once a fact is ascertained and the phenomena
observed, the idea comes, reasoning intervenes, and the
experimenter appears in order to interpret the phenomenon.
The experimenter is he who, in virtue of a more or
less probable but anticipated interpretation of observed
phenomena, institutes an experiment so that in the logical
order of his previsions it will furnish the result which
serves to control the hypothesis or the preconceived idea.
To accomplish this, the experimenter reflects, tries, gropes,
compares and combines, so as to find the experimental
conditions which are best fitted to attain the goal which is
his aim. It is necessary to experiment with a preconceived
idea. The mind of the experimenter must be active; that
is, he must interrogate nature and question her in all
directions following the different hypotheses which are
suggested to him.

‘But when the conditions of the experiment have been
realized and the experiment itself started according to the
preconceived idea or anticipated view of the mind, the
result, as we have already said, will be a provoked or
premeditated observation. It will be followed by the
apparition of phenomena determined by the experimenter,
but which he must first study so as to know in which way
they can be used to check the experimental idea which
brought them to life.’

It is clear that these lines apply to all classes of methods
and are not confined to the one which is the object of our
first paragraph. But it seemed to us that they belonged to the
beginning of this chapter because of their evident character
of generality.

The naturalist and the zoologist can resort to a variety
of methods, depending on whether they study the isolated

16 THE BIOLOGICAL PROBLEM

organism, or whether they consider it as an element ofa social
whole. It is difficult to study certain insects, for example, with-
out taking into consideration the role of the individual in the
superior unity, namely the hive, the ant-hill or the termi-
tarilum, inasmuch as the individuals differ largely by their
morphological and physiological characters, according to the
part attributed to them: warriors, workers, queens, or males.

These observations do not entirely eliminate planned
experimentation. The great entomologist Fabre describes
ingenious experiments which were suggested to him by the
attentive examination of the habits of insects. The naturalist
can intentionally introduce an alteration or a disturbance in
the conditions of natural phenomena and make destructive
experiments with the aim of ascertaining zm vivo the use of
organs the functions of which are not evident.

In brief, this class of methods tries to comprehend the
organism as a whole. Similar to a jet of water of unvarying
aspect, to a stream for ever following the same bed, to the
flame of a candle, or to any other system which conserves its
form although composed of ever-renewed and ever-fugitive
particles, a living being is a system the fixity of which is only
apparent. It owes the constancy of its form, of its aspects,
and of its mean composition to the evolutive correlation of
the phenomena of which it is the seat. But we hasten to add
that there is a striking difference between the maintenance of
the ‘stationary systems’ just mentioned and the renovations
which are characteristic of the living being. The stationary
system is only a witness to the constancy, in time, of an
indefinitely repeated phenomenon. According to Ostwald it
is the passive result of this regularity. On the other hand,
nutrition in living organisms consists of an aggregate of
numerous, variable phenomena. The ensuing morphological
permanence is an indication of the active part played by the
organism which is its seat. This activity is all the more
evidence that these systems evolve, develop according to a
constant order, and reproduce themselves.

The idea of studying individually each of the elementary

BIOLOGICAL METHODS ET

phenomena which contribute to the edification of the living
being as a whole is therefore quite natural. No matter how
much a motor is tampered with, one cannot hope to know how
it works without taking it to pieces. This brings us to the second
class of methods, which can be called the ‘breaking-down
methods’ and on which we will say a few words.

These methods are static or dynamic. To study an
organism statically it is necessary to begin by killing it. All
descriptive sciences, such as anatomy, cytology, histology,
embryology, compel the worker, at a given moment, to act
like a curious child who breaks his toy so as to see the
mechanism. Thanks to anatomy, we have acquired a perfect
knowledge of the location and the shape of our organs, our
muscles and the levers which they command, the bones.
Anatomy, enlarging the field of its activity under the name of
comparative anatomy, established enlightening analogies
between living beings from the bottom to the top of the ladder.
And not only between those living to-day, but between these
and those which became extinct long ago. Anatomy is at the
base of our knowledge of evolution in organized beings. It
has rendered possible the notion of filiation of species and the
issuance of a good many hypotheses which probably all contain
a part of the truth, without one of them, it must be admitted,
being able by itself to account for natural evolution.

The famous theories of Lamarck, Darwin, and de Vries
have been the object of numerous critical works which are of
great interest, and the reader is referred to the many books
. which exist on the subject.

Cytology, the science of cells, depends wholly on the use of
the microscope as a tool of investigation, coupled together
with selective dyes. The tissues are usually embedded in a
block of paraffin wax which, when cool, maintains the fragile
cellular elements so that they can be sliced in extremely thin
layers, a thousandth of an inch thick. The entire sample of
tissue having thus been cut into a considerable number of
transparent pieces, it can readily be understood that the
examination of a successive series enables the scientist to

18 THE BIOLOGICAL PROBLEM

reconstitute exactly the architecture of the cell. The selective
dyes are indispensable to show up the structural details which
are otherwise invisible owing to the similarity of their refrac-
tive index, the absence of natural colour, and the thinness of
the sections. Broadly, cytological and histological techniques
consist in fixing, i.e. killing, the cells without deteriorating
them and then colouring these sections by means of
different substances (aniline dyes, for instance, or metallic
impregnations).

We will not dwell on these methods which have rendered
and continue to render great services. We will only point
out that the purely morphological study of anatomical and
cellular elements cannot furnish any information as to their
physiological functions.

Dr. Alexis Carrel writes:1

“The structure of tissues and their functions are two
aspects of the same thing. One cannot consider them
separately. Each structural detail possesses its functional
expression. It is through physiological aptitudes of their
anatomical parts that the life of the higher animals is ren-
dered possible. Likewise, the life of a community of ants
depends on the physiological aptitudes of the individuals
of which it is composed. When cells are considered only
as structural elements, they are deprived of all the properties
that make them capable of organizing as a living whole.
Within the organism, they are associated according to
certain laws. Cell sociology results from properties specific
to each type of cell. Among these properties some manifest
themselves under ordinary conditions of life, while others
remain hidden. Tissues are endowed with potentialities far
greater than those which are apparent. But these poten-
tialities become actualized only when certain modifications
of the internal environment occur, as, for instance, when
pathogenic agencies are at work within the body. The

1 A. Carrel, ‘The New Cytology’, Science, vol. 73, no. 1890, pp.
297-303 (1931).

BIOLOGICAL METHODS 19

significance of a given structural state is bound to the
knowledge of the corresponding physiological state.
Structure and function must be considered simultaneously.’

Furthermore, tissues evolve in time.

‘A tissue consists of a society of complex organisms which
does not respond in an instantaneous manner to the changes
of the environment. It may oppose such changes for a
long time before adapting itself to the new conditions
through slight or profound transformations. To study it
at only one instant of the duration is almost meaningless.
The temporal extension of a tissue is as important as its
spatial existence.’

The conception of cells and tissues which Carrel has sub-
stituted for the classical viewpoint is that of ‘a system: cells-
environment, of which the structural, functional, physical,
physico-chemical and chemical conditions are considered in
time as well as in space.’ This constitutes a dynamic concept
beside the purely static concept of the old cytology.

Physiology as a whole, one of the most fundamental
sciences of life, of which almost all the others are but chapters,
is essentially dynamic. Carrel’s great merit has been to show
that outside of a general physiology which considers complete
organs preferably studied 7m vivo, a cellular physiology could
be created which, without encroaching on the domain of
general physiology, enables one to simplify the problems and
to study the individual activities of each of the elements
composing an organ. The name of ‘breaking-down methods’
which we employed in the beginning is thus justified. The
method of tissue-culture outside of the organism enables one
to go farther in the breaking-down process than does classical
physiology. To make a rough comparison, the study of an
automobile is divided into two stages. First, the study of the
role and workings of the organs im situ and their breaking up
as complete elements: dynamo, magneto, carburettor, motor,

20 THE BIOLOGICAL PROBLEM

gears, etc. Second, the breaking up and analysis of the
workings of each of these isolated elements. The knowledge
of the whole is thus naturally enlarged. The comparison is,
however, very superficial, inasmuch as the characteristic of
Dr. Carrel’s method consists in maintaining the physiological
activity of the cellular elements, when they are detached from
the organ. This renders possible a profound analysis of the
mechanisms.

Fragments of tissue can be kept alive out of the organism.
These fragments, preferably explanted! from an embryo,
grow actively in an appropriate medium and possess the
faculty of living indefinitely. The descendance of a small
piece of chicken heart extracted from the egg in 1912 is still
alive to-day after twenty-four years and shows no signs of
ageing, that is to say that its growth-activity is the same as
at the beginning. Barring ever-possible accidents—for the
care it requires is considerable, and in spite of the precautions
taken the cessation of its development can always be feared—
there is no reason why it should ever die. It is superfluous
to add that, had the chicken from which it was extracted
lived its normal life, it would hive been dead long ago. Ten
years constitutes about the extreme limit of duration of a
chicken’s existence. This method, on which we will have
occasion to dwell in detail later on, presents tremendous
advantages over the old cytology.

“The task of the new cytology,’ says Carrel, ‘is to discover
the physiological properties which characterize each type
of cell. It is impossible to attempt the study of these
properties by any other method than that of pure cultures’
(namely, constituted by a single type of cell). ‘It is the only
method which enables one to introduce precise modifica-
tions in the conditions of life of the colonies and to show up
potentialities which often remain hidden during the normal

1 Explanted, technical expression used in tissue-culture work,
meaning ‘removed from’, ‘cut off’. The term ‘explant’ is often used
as a noun to define the fragment explanted.

BIOLOGICAL METHODS 21

life of a cell. Bacteriologists are not content to study the
shape and the reactions of microbes in connexion with
certain dyes, but also examine the aspect of their colonies,
their action on the culture-medium, the poisons they secrete,
their susceptibility to different antiseptics, the nutritive —
substances which they require, etc. The same is true of
tissue-cells. Through our new techniques a cell type can
be characterized by the appearance of its colonies, its mode
of locomotion as recorded by cinematography, its effect on
the coagulum, its rate of growth, the nature of the sub-
stances which inhibit cell-multiplication, the nature and
concentration of the nutrient substances, etc.

“The new cytology permits the identification of cells and
prediction of their conduct under given conditions. It
reveals the specific properties of each type of cell. Thanks
to it the mechanism of complex phenomena which take
place in the normal or pathological tissues can be sub-
mitted to experimental analysis. Its fecundity will neces-
sarily be greater than that of the classical cytology.’

The explanted tissues, kept alive, can be assimilated to
ideal experimental animals. First, because they are simple and
deprived of a nervous system; secondly, because they can be
manufactured at will in large quantities. It is thus possible
to experiment indefinitely on the same family of cells proceed-
ing from the same stock. This eliminates innumerable causes
of error due to the individual characteristics of animals of
different origin. Furthermore, at each stage of an experiment,
one disposes of a permanent control, since it is derived from
the original culture itself, cut in two equal parts.

We have outlined a cursory view of certain methods which
can be classed in the second category. We see that the unit
is no longer the individual, but the cell, and that the principal
tool of investigaton is the microscope, as in the case of
bacteriology. The limit of observation is what is called the
resolving power of the microscope, that is to say the order of
magnitude of the smallest objects which can be clearly

22 THE BIOLOGICAL PROBLEM

distinguished by this instrument. It can easily be under-
stood that it is useless to increase the magnification above a
certain point if one loses in sharpness what is gained in
dimensions, It is a fact of current observation for amateurs
of photography, that there is nothing to be gained by enlarging
the proofs beyond a certain size, which depends on the
quality of the initial negative.

The preceding pages show that bacteriology is a science
which belongs equally to both of the classes which we have
examined, since microbes are at the same time individuals
and isolated cells. But in fact, bacteriology studies cultures
rather than microbes, and it is the entire culture which
represents the individual rather than the microbes themselves.

CHAPTER II m\

PHYSICAL AND CHEMICAL METHODS—
CRITICISMS AND DIFFICULTIES

WE now come to the third class of methods: chemical and
physical methods. Let us listen once more to Claude
Bernard.!

“The knowledge of the definite and elementary conditions
of phenomena can only be attained in one way, namely by
experimental analysts. Analysis dissociates all the complex
phenomena successively into more and more simple
phenomena, until they are reduced if possible to just two
elementary conditions. Experimental science considers
only the definite conditions which are necessary to produte
a phenomenon. Physicists try to picture these conditions
ideally, so to speak, in mechanics and mathematical
physics. Chemists successively analyse complex matter,
and in thus reaching either elements or definite substances
(individual compounds or chemical species) they attain the
elementary or irreducible conditions of phenomena. In
the same way biologists should analyse complex organisms
and reduce the phenomena of life to conditions that cannot
be analysed in the present state of science. Experimental
physiology and medicine have no other goal.’

All the functions of life are a remote consequence of the
chemical functions of the molecules -which enter into the
constitution of each cell. Thus, one of the main problems of
the modern biologist is the-discovery of the relations existing
between the structure and the properties of the elementary
cellular substances, humours and tissues of a living organism,
and the integral phenomenon which we call Life.

This affirmation admits an identity between the determinism

' Introduction a@ l’étude de la médecine expérimentale, 4th ed., 1920
(Delagrave), p. 113.
23

24 THE BIOLOGICAL PROBLEM

of the inorganized world and that of organized matter. There
is much to be said, especially since the last few years, on the
value of this determinism, for it has lost the character of
absolute rigidity which was before attributed to it.

This question will be discussed more fully a little farther
on. At any rate, the phenomena which enter into the field
of our experimental studies are of an order of magnitude
such that it can be admitted that everything occurs as if this
determinism was absolute. In the same way, certain of our
concepts were modified by the theory of relativity, but the
description and quantitative examination of the objects of
our experiments have not been practically affected. We again
refer the reader to the Introduction to the Study of Experimental
Medicine for the development of the reasons, hardly questioned
to-day, which led to the adoption of this determinism.

Consequently, in first approximation, it can be said that all
vital phenomena are dependent on the laws of energetics, and
in particular, on the Carnot-Clausius law. They consequently
contribute to the increase in entropy of the system of which
living beings are a part, just as all the other phenomena
resorting to chemistry and physics.

On the other hand, the majority of vital phenomena take
place under conditions bordering on a state of equilibrium,
which ordinarily leaves the choice between several different
isodegradating paths. This second proposition puts in
evidence the fact that living matter, in its evolution, obeys
a law which zs not implicitly contained in the second principle
of thermo-dynamics. This important point has not escaped
famous observers, for its trace is found in an article by Lord
Kelvin, in another by von Helmholtz, in the works of Ch.
E. Guye,! and of H. Freundlich.

If it is necessary to possess a thorough knowledge of
the chemistry of living matter which alone can instruct the
physiologist and the medical man as to the nature of the
basic reactions of the phenomena which they are interested

1 See Ch. E. Guye, L’Evolution physico-chimique, Chiron, Paris,
1922.

PHYSICAL AND CHEMICAL METHODS 25

in, the experimenter must never forget that the living being
forms a complete organism. It has a personality, and the
biological phenomenon as a whole is not simply due to the
summation of elementary chemical phenomena, but to the
order in which these phenomena occur in time and space.
This order appears to be the expression of a pre-determined
purpose.

Sir Frederick Gowland Hopkins, one of the founders of
modern bio-chemistry, wrote the following lines in 1925
(Lancet), in an article protesting against the term ‘protoplasm’
taken as a definition of the elementary living substance:

“There is no such thing as living matter in a specific sense.
The special attribute of such systems from a chemical
standpoint, is that these reactions are organized, and not

_ that the molecules concerned are fundamentally different
in kind from those the chemist meets elsewhere.’

The phenomena of life considered in their different aspects
and intimate nature are thus simultaneously characterized by
special forms which distinguish them as ‘life phenomena’ and
by an identity of laws which incorporates them with the
other phenomena of the cosmic world. It must be admitted
that, if there are special procedures in all vital phenomena,
at the same time they all obey the laws of mechanics, physics,
and ordinary chemistry.

We have written, zt must, purposely. This is not a profession
of faith, for all professions of faith, be they vitalistic or
materialistic, are unscientific. But itis important to orient
research by means of a hypothesis, and it is impossible actually
to avoid this one. That experiments should absolutely con-
firm or invalidate it, is immaterial to a man of science, or
rather, to be exact, should be immaterial. Passions, which
have nothing in common with science, have weighted the
scales alternately on the vitalistic and mechanistic sides without
any real benefit, for it is not by speeches but by experiments
that human knowledge is advanced. There is much to be said

26 THE BIOLOGICAL PROBLEM

on this subject, most of the discussions resting on misunder-
standings. Religious questions, which are entirely separate,
have been injected into these discussions and walls have been
raised which prevent each party from observing what takes
place at his neighbour’s. Religion is a total stranger to these
problems. It is necessary to be absolutely convinced of this
in order to discuss them intelligently and fruitfully.

Descartes was a pure mechanist, and yet was a true believer.
Claude Bernard, like most physiologists, admits a force, a
vital impulse, but has no religious faith. From the point of
view of pure method, Claude Bernard is more strictly Cartesian
than Descartes. Ignorance of facts was at the base of Bichat’s
spiritualism, just as ignorance of facts is at the base of modern
materialism. Every doctrine a priori other than the respect
of the experimental fact is harmful and dangerous in science.
The scientist should be a man of good faith before being a
philosopher, a moralist, or even a citizen. Alas, should good
faith be rarer than faith? It is useless to add that I have not
only reference to religious but also to anti-religious faith.
Although arising from a different source, the latter results in
similar consequences and, in addition, kills hope.

To what degree can we actually accept the determinism
which was the foundation of Claude Bernard’s method?

‘Life introduces absolutely no difference in the experi-
mental scientific method which must be applied to the study
of physiological phenomena, and in this respect the physio-
logical sciences and the physico-chemical sciences depend
on identically the same principles of investigation. In
living as in inorganized matter the laws are immutable, and
the phenomena which are governed by these laws are
bound to their condition of existence by a necessary and
absolute determinism.’

These lines, extracted from the Jntroduction, constitute a
true act of faith or, if one prefers, a bold and very fruitful
extrapolation; for it was evidently impossible in 1865 to

CRITICISMS AND DIFFICULTIES 27

affirm the necessary nature of an absolute determinism, based
on undisputed experiments. It could certainly not be affirmed
to-day. Yet the exact sciences have advanced since that
period, and one of the clearest benefits which we have gained
consists precisely in the new concept of determinism which
has profoundly modified the significance of our experimental
laws. To the physico-chemical law, which we had become
accustomed to consider as fatal and ineluctable, a statistical
law has been substituted, which, theoretically at least, admits
very rare exceptions, fluctuations according to the consecrated
term.! The absolute determinism of the physical and chemi-
cal laws is now replaced by a statistical determinism which is
broader and more elastic, though practically as rigorous.
Curiously enough, Claude Bernard’s act of faith, admittedly
based on an incomplete knowledge of phenomena, acquires
in the light of the progress of mathematical physics a character
of greater plausibility and generality. But contrary to what
the great physiologist might have thought, it is not by proving
the strictness gf the determinism which he brandished as the
emblem of his scientific philosophy, that the exact sciences
have given a more probable value to his words. On the
contrary, it is by opening the door to the possibility of very
rare fluctuations practically escaping calculation. To study
living organisms we are therefore obliged to depend on two
postulates. We need not define the first, for we momentarily
admit that it concerns the unknowable, the co-ordinated
effort, the plan. The second, and only one which counts for
us, establishes the identity of the laws governing inorganic
and organized matter. The latter alone has the value of an
indispensable working hypothesis.

Our ideas have become more flexible since the works of
Gibbs and especially of Boltzmann. The ‘determined’ fact
has become a ‘probable’ fact. The law of great numbers is
at the base of all our physical laws. And now the old and

1 For the development of these fundamental ideas, we again refer
the reader to Ch. E. Guye’s book L’ Evolution physico-chimique (Chiron,
Paris, 1922), an admirably clear account of one of the most signifi-
cant and important advances of physico-chemistry.

28 THE BIOLOGICAL PROBLEM

already shaky determinism has had to undergo another
assault, which, however, like the preceding one, has not
practically changed its value as a tool.

Heisenberg, a brilliant mathematician, formulated in 1927
his ‘Principle of Indeterminacy’ which seriously modified our
old ideas, for it introduced a certain degree of indetermination
or imprevisibility of the future, as one of the fundamental
postulates of the universe. This different point of view seems
to transform the flow of time into a much more tangible
phenomenon than it used to be in classical physics. Every
moment which passes introduces something new into the world
which is not solely a mathematical extrapolation of all that
existed previously.1 The classical determinism of Laplace
which dominated science for so long stated that, if complete
information concerning the entire state of the universe, the
position and speed of each element of matter in space during
the first minute of the year 1600, for example, could be
obtained, it would be possible, by mere calculation, to deduct
all the events of the past and of the future. The future is deter-
mined by the past, just as the solution of a differential equation
is determined by the limiting conditions. Heisenberg demon-
strated on the contrary, that only one half of the elements
necessary to determine an event can be assembled (speed or
position, but not both), as the other elements only come into
existence after the accomplishment of the event. It is not
ignorance, properly speaking, but a necessary limitation. It
is the principle of indetermination which is now fully incor-
porated in modern physics. We can easily understand to
what a degree this notion upsets the old ideas, even though

1 There is in Bergson’s l’Evolution créatrice a remarkable anticipa-
~ tion of the principle of indeterminacy: ‘Thus our individuality
develops, grows, and matures incessantly. Every moment adds some-
thing new to what was before. We will say more: not only new but
unpredictable.’ These lines were published in 1907, twenty years
before Heisenberg. In 1918 Franz Exner also emitted certain doubts
as to the justification of determinism, and E. Schrédinger, who
developed the ideas of Louis de Broglie, and like him was awarded
the Nobel prize, was alone at that period in supporting Exner’s ideas
on ‘the acausality of phenomena’ (1922). See E. Schrédinger, Science
and the Human Temperament, Norton & Co., New York, 1935.

CRITICISMS AND DIFFICULTIES 29

a certain number of the most distinguished physicists refuse
to subscribe to the logical philosophical consequences that
can be deduced from it. They perhaps fear that the fragility
of their theories will be shown up by the weakening of
determinism. But this is tantamount to admitting that
determinism is a dogma, and they quite rightly profess a
violent dislike for dogmas in general. From our point of
view, we simply wanted to mention this important theory
which renders great services in undulatory mechanics,
for it is sometimes good to be reminded that even exact
sciences are far from having attained their definite form,
assuming that such an expression is not entirely mean-
ingless.

It is evident that this new concept is of a nature to upset
the ideas of many people, especially of those, who uncon-
sciously and as a result of a blind confidence in Science—
with a capital S—had launched themselves into far-fetched
extrapolations, of a purely speculative and unscientific
nature. The combination of sentiment and science is not
often a happy one, and I am inclined to think that certain
optimistic anticipations, so flattering to the human mind, are
nothing but a reaction against certain moral disciplines which
all tend to glorify humility and severely condemn pride. At
its dawn, science was greeted as a liberator. At that time the
simplicity of a theory or a doctrine appeared as a proof of its
value. New discoveries and events have taken it upon them-
selves to cure us of this candidness, which, however, has not
yet quite disappeared from the world. But we are forced to
admit to-day that science has not fulfilled the promises which
man made in her name. We can only blame ourselves for
this failure, as not a single experimental fact acquired in the
past has ceased to be true. Science has never had to retract
a single statement resulting from well-established facts within
well-determined limits. The retractations that science has had
to make were not of the domain of pure science, but concerned
precisely the prediction of the future. Facts remain, but
human anticipations fade away.

30 THE BIOLOGICAL PROBLEM

It is easy to discover the source of the fundamental error
which led to hasty conclusions. ‘The magnificent conquests
of science induced us to believe that, by increasing indefinitely
the precision of our measurements, we would be able to
predict phenomena with ever-increasing accuracy. Unfortu-
nately, experimental facts have proved that this hope was, and
will always be, vain. It was found that the most capricious
irregularities are observed when the precision of the measure-
ment exceeds a certain point and enables one to penetrate
into the realm of the up till now inaccessible small elements,
the postive and negative electron, the photon. No refinement
of techniques can enable us to predict the movements of these
corpuscles which seem to be determined by the most disordered
fantasy. We must repeat that, from a practical point of view,
this state of things not only in no way disturbs the evolution
of inorganic phenomena nor what we call the principle of
causality, but also that this disorder is the necessary condition
of our physical laws. These are only rigorous on condition
that the movements of the elementary particles are absolutely
disorderly, and if they ceased to be so, the laws would cease
to be valid. For, as we said above, the laws of great numbers,
of probability, enter into play. All our phenomena are but
‘envelope’ phenomena, and the result, at our scale, of an
immense number of elementary phenomena which escape
observation. They are statistical laws. There is therefore
only one thing changed: our old notion of determinism, our
ideas on the real significance of the relation of cause to effect.
But the possible occurrence, under certain conditions, of
fluctuations which occasionally transpose the ‘fantasy’ of the
elementary corpuscles to a higher scale, still not directly
observable, but capable of influencing vital phenomena,
limits in a certain measure our power of prediction, that is
to say our science.!

' The development of these concepts would exceed the scope of
this book. Nevertheless we think we ought to insist on the fact that
these limitations only concern the individual elementary particles and

not the current objects of our science. These, as well as all the
phenomena which we study, consist of, or bring into play, such a

CRITICISMS AND DIFFICULTIES 31

Let us take an example. If heredity depended on the play
of a considerable number of identical elements, there would
be no problem. The laws of chance would apply, excluding
all sudden mutations, or rather rendering them improbable.
The apparition of mutations seems to show on the contrary
that we are in the presence of too feeble a number of elements.
It is an analogous case to that of tiny communicating vases
containing a few molecules of gas. The displacement of one
single molecule destroys the statistical result. Boyle’s law no
longer applies. The second law of thermo-dynamics is upset.
So that the real and greatest intellectual problem of man,
which covers all the problems of life, can actually be reduced
to a very simple question: How is order born of disorder?
By ‘order’ we mean the natural sequence of perceptible
phenomena.

Let us now leave this somewhat. hallucinating realm,
admirably evoked in the last chapter of Sir James Jeans’
The Mysterious Universe, where all reality is reduced to groups

tremendous number of particles that the action of one isolated
elementary particle has absolutely no value with respect to the
phenomenon as a whole. It is in this sense that we said that practi-
cally there was nothing changed. We are incapable of predicting the
future of one particle, but there are so many of them that the calcula-
tion of probabilities enables us to establish with a very great degree
of approximation the probable statistical result of the sum of their
individual actions (kinetic theory of gases, for example) as revealed by
experiments. In the same way an insurance company is incapable of
predicting which of the insured houses will be burned or which client
will die. The only thing which interests it is the annual percentage
of each disaster, percentage which is calculated from the statistics of
the preceding years. It is thus possible with a small sum to cover
the risks representing a much larger amount. This enables one to
understand how chance can give birth to precise laws, and one compre-
hends also why it is necessary that chance alone should determine
the fate of each individual, for if a new element enters into play—for
instance a world-wide cataclysm (epidemic, earthquake)—which
superimposes itself on normal chances of individual accidents, the law
of statistics no longer applies and the company fails. That is the
so-called ‘fluctuation’.

32 THE BIOLOGICAL PROBLEM

of equations, and return to the chemical bases of vital functions.
We shall see that other difficulties await us.

The analysis of elements constituting living matter or
elaborated by it, rapidly demonstrated that it was composed
of elementary substances in no way different from those found
everywhere in nature. The carbon of coal and diamond, the
potassium, sodium, and calcium of inorganic salts, the nitrogen
and oxygen of air are identical with those of our tissues or of
our blood. There was therefore, in principle, no reason why
the classical methods of chemistry should not be applicable to
the basic substances of organized matter. In analysing these
compounds the conviction was rapidly obtained that a great
number of simple elements entered into their constitution.
In the same way any machine or any work of art can be reduced
under the mortar to a given quantity of chemical bodies and
definite elements. But a machine, a work of art, a living
organism, only exist as such by reason of an organization at
a scale superior to that of molecular magnitude. At this scale,
the properties of the constituent molecules seem to efface
themselves in order to allow the birth of new properties due
to their conjunction in space and in time, in definite propor-
tions, following an order, a plan which establishes a bond
between them, and which creates their reason of existence and
their harmony.' This brings us back to Hopkins’ observation,
quoted on page 25.

In brief, our body is made up of cells, the cells of molecules,
and the molecules of atoms. But these atoms are not ail the
reality of the human body. The way in which the atoms, the
molecules, and the cells are arranged, and which results in
the unity of the individual, is also a reality, and how much
more interesting. The molecules of any substance can always
be decomposed into their atomic elements, and these in turn
into their sub-atomic elements, the electrons and the protons.
But this dissociation results in the disappearance of the
properties which gave this molecule its chemical individuality

1 In connexion with harmony in science, the first pages of Henri
Poincaré’s admirable book, Science et Méthode, should be read.

CRITICISMS AND DIFFICULTIES 33

endowed with definite characteristics.1_ The characteristics of
the individual at a different scale always superimpose them-
selves on the characteristics of the materials.

‘Would a naturalist who had only studied an elephant
through the microscope believe that he had a thorough
knowledge of this animal?’ asks Henri Poincaré.

Thus, on the one hand, we are necessarily led to the physical
and chemical study of living matter, for without this analysis
the mechanism of the physiological functions would remain
a mystery. On the other hand, we must always consider at
the same time the organism as a whole, without ever losing
sight of the special conditions of all separate phenomena which
constitute the individual. There is, therefore, a kind of
antinomy between the aims and methods of the medical man
and those of the bio-chemist or bio-physicist. This antinomy
is only apparent, but it suffices to account for the difficulty
experienced in establishing an intimate collaboration between
these two disciplines.

In reality, the chemist and physicist seek the elementary
phenomenon by cutting up bodies fictitiously into infinitely
small cubes, because the conditions of the problem which
undergo slow and continuous variations when one passes from
one point of the body to another, can be considered as constant
in the interior of each one of these small cubes. Their
ambition is to establish the law of certain variations. This
law has a meaning only on condition that sufficiently simple

1 There is much to be said on this subject, and particularly on the
biological properties derived from the increase of the complexity and
of the molecular weight of the organic substances. Above a certain
molecular weight the definition of the chemical unit, the molecule,
does not suffice to characterize a// the properties of the unit. Simi-
larly in the atoms, radioactivity accompanies the complication and
fragility resulting from the high atomic weight. Pigmentary proteins
have been found in certain animals (snails) of enormous molecular
weight (more than five millions). These immense molecules, if they
can still be given this name, are so complicated, that it is quite possible
that in these primitive organisms, they function as complete organs.
This observation seems to be confirmed by the fact that, in this
particular case (hemocyanine of Helix’s blood) the molecular weight
varies according to the physiological activity. (Roche.)

34 THE BIOLOGICAL PROBLEM

elements are dealt with, so that the events studied have a
chance of repeating themselves. But this would not be
possible, as Henri Poincaré pointed out, if instead of ninety-
two simple elements we had ninety-two billions of them,
equally distributed in the world.

“Then each time we picked up a new pebble, there would
be a great probability of its being made of an unknown
substance. Everything known about other pebbles would
be of no help for this one. In front of each new object we
would be like a new-born child. In such a world there
would be no science. Thought and even life would perhaps
be impossible, for evolution could not have developed the
instinct of conservation.”!

The medical man, on the contrary, even though he tries,
like the chemist and the biologist, to simplify, to unify, and
to generalize with respect to the cells, the body fluids, and the
organs, is not the doctor of living beings in general. He is
not even the doctor of the human race, but of the human
individual, and what is more, of an individual in certain
morbid conditions which are special and which constitute
what has been called his idiosyncrasy. From which it seems
that medicine, contrary to the other sciences, must constitute
itself by being more and more individualized. (Claude Bernard.)

It is needless to point out that this contradiction is purely
artificial and due to the fact that the groundwork, on which
the physiologist and, later on, the medical man must rest, is
still too frail and too scarce, owing precisely to our ignorance
concerning the structure of the chemical elements of the
organism. It is therefore necessary first of all to enrich bio-
chemistry and bio-physics with facts, so as to supply physio-
logists with the foundations which are actually wanting.

But this programme, which holds in so few words, gives
rise to extreme difficulties not suspected in the time of Claude
Bernard.

1 Henri Poincaré, Science et Méthode.

CRITICISMS AND DIFFICULTIES 35

‘The brilliant beginnings of organic synthesis,’ wrote
Jacques Duclaux a short while ago, ‘had raised hopes that
this chasm which separates physics and chemistry from
biology could be crossed by the resources of organic
chemistry alone. . . . The oft-employed formula according
to which living organisms obey the same laws as inert
chemical compounds, dates of this period. The idea that
such a formula could have been seriously given makes us
smile to-day. Pushed to such a point, optimism is no longer
a quality.’

Those who have studied living matter and elementary
organisms in the laboratory by means of the most advanced
methods of physics and chemistry, and have surrounded them-
selves with the greatest precautions, know well that everything
happens as if ‘life was a struggle against the physical laws’,
as Professor Lapicque puts it. It is not without interest to
compare this phrase with that of Bichat, cited at the beginning
of this chapter: ‘Life is the combination of functions which
resist death.’ How surprised Claude Bernard would have
been had he been told that sixty years later, his successor,
instead of having more proofs of what he already considered
assured, would on the contrary express himself with far more
prudence?

Consequently, from the physical as well as the chemical
point of view, one of the obstacles which we have to surmount
is the following: we try to apply the laws of inorganized
matter to phenomena which are dependent on them without,
however, obeying them completely. The deviations which
we observe are the measure of our ignorance. Donnan’s ~
famous equilibrium is never rigorously found on both sides
of a living membrane. As far as osmotic pressure is con-
cerned, the cells do not function like a Dutrochet osmometer.
The difference of pressure which exists only maintains itself
thanks to the work produced by living matter which plays a
fundamental part. It is the phenomenon which Lapicque

menamed “Epictése’. The electric resistance of a cellular

36 THE BIOLOGICAL PROBLEM

wall falls to one-tenth of its value when the cell dies.
(Osterhout).

In brief, the vital equilibria which bring infinitely complex
structures into play are never absolutely comparable to the
physical and chemical equilibria. “True equilibrium is death,’
said Bayliss.

Now that we have shown some of the pitfalls which the
chemist and physico-chemist encounters in his study of living
matter, it is only fair to add that a great number of biological
problems can be solved by means of chemical and physical
methods, and even can only be solved that way. Amongst
these, luckily, are those which are of the greatest interest to
humanity, namely the problems of immunity in general, pro-
tection against infectious disease, as well as a great number of
pathological and therapeutical problems. After the preceding
rather discouraging pages we will try to give a slightly more
optimistic note.

CHAPTER, 11T

CHEMICAL AND PHYSICAL METHODS—
LIMITATIONS—RESULTS ACQUIRED—THEIR
ROLE IN IMMUNITY AND BACTERIOLOGY

THE difficulties which we have enumerated are important only
when we seek to understand the intimate mechanisms of
fundamental biological phenomena, the ‘irreducible principle’
of Claude Bernard. The objection based on the evolution of
the notion of determinism is purely theoretical, and in no way
changes the results of our experiments. Whenever we try to
superimpose an example borrowed from an inert body on toa
series of chemical phenomena taking place in an organism, we
observe that there is no absolute accord, even though the point
of departure and the point of arrival are identical. Usually
we are not aware of this discrepancy, as we cannot know the
real intermediary stages, but only those which we have our-
selves realized. This brings us back to Plato’s picture of the
cave, in which our senses perceive only the shadows projected
on the background. If our problem consists in the exact
analysis of the means employed by nature to obtain a certain
result, the chances are that our rough methods will fail, until
the far-off day when some kind of electronic chemistry will
be perfected. Even then we will succeed only if there is no
other point of divergence, which is not very likely.

But our ordinary chemistry can render great services if we
concern ourselves chiefly with the pomts of departure and
arrival. If, for instance, we manage artificially to obtain sub-
stances identical with—or sufficiently similar to—those which
determine pathological disturbances, by an excess or deficiency
in the organism, we will have truly progressed. We will thus
be able to neutralize them if they are too abundant, and to
replace them by purified and concentrated or even synthetic
products if they are deficient.

37

38 CHEMICAL AND PHYSICAL METHODS

This is what takes place for hormones amongst others. We
now understand the troubles brought about by lesions in
the thyroid gland. Any diminution in the secretion of the
hormone manufactured by this gland is followed by severe
accidents: cretinism, myxoedema, goitre. Physiology brought
us this far. Now, biological chemistry has not only succeeded
in purifying and obtaining in crystalline form the active
principle, thyroxin, which contains four atoms of iodine, but
has synthesized this compound,artificially. The introduction
into the organism of two milligrams a day of thyroxin is
sufficient to dispel all morbid symptoms and often brings
about a complete recovery. The result is identical, whether
thyroxin extracted from organs or the synthetic product is
employed and, as these active substances are pure, a minimum
dose, which can be indefinitely tolerated, suffices. Chemistry
has solved the practical problem which was propounded by
medicine and studied by physiology.

This is an example amongst twenty. Up tll now, only
thyroxin and adrenalin have been synthesized. The other
hormones are extracted from organs of animals. But the
constant strides made in this direction permit us to look
forward to the day when they will be manufactured directly
from pure chemicals. In the same way insulin (hormone of
Langerhan’s islets) renders the greatest services in serious
cases of diabetes. It is certain that the mechanism of the pro-
duction of thyroxin, insulin, and adrenalin in the glands
themselves eScapes us altogether. But it does not matter, if
we have understood the part they play as regulators of certain
physiological functions in the organism.

We know very well that vegetable cells chemically fix nitro-
gen at normal temperature, whereas we can only obtain the
same result, 7 vitro, around 500°C. But from a practical
point of view the important thing is to understand the role of
nitrogen in the metabolism of plants. The rest will perhaps
come later.

It might be objected that the practical point of view should
not be considered in science. But much as we believe that a

CHEMICAL AND PHYSICAL METHODS 39

purely utilitarian conception of science is as great an absurdity
as a utilitarian conception of art, we nevertheless think that
in certain cases science has nothing to lose by advancing in a
direction which, besides being fascinating by the mystery
which surrounds it and by the marvellous complexity and
harmony of its objects, may lead to the suppression of suffering
and the amelioration of human conditions.

No painter, however independent, would refuse to decorate
a beautiful monument. Hisg work can only gain by the
grandeur of the frame, and he has no reason to feel limited in
his liberty if no one imposes the subject or any other restric-
tions and if he has the impression of participating in the
edification of a masterpiece.

The new orientation of bacteriology is chemical. This
impulse seems to have come from Vienna, about thirty-five
years ago, with Obermayer, Pick, and particularly Karl
Landsteiner, who, by his remarkable and epoch-making
experiments, showed the value of this method of analysis for
the study of immunity. Should one, under pretence that the
intimate mechanism of immunity, the real nature of cellular
phenomena, will always escape us—which is not proved—
abstain from working in this path which has already enabled
us to throw so much light on the secondary mechanisms of
fundamental interest to us?

If the physicists and engineers, beginning with Ampere and
Faraday, had reasoned in this way on the subject of the nature
of electricity we would have none of the comforts which
characterize our modern material civilization; neither electric
light, telegraph, telephone, nor radio. Waterfalls could not
have been utilized. The greater part of modern metallurgical
and chemical methods would not have been brought to light.
And who knows to what degree a quantity of other industries
would not have been hampered in their development. Evi-
dently we can ask ourselves, like Tolstoy and a few others,
if this would not have been preferable. But it must be
conceded that this is quite another problem, and that man can
no more escape the current which sweeps him towards

40 THE BIOLOGICAL PROBLEM

an unknown fate than a drop of water can travel up-
stream.

We will now try to show what important results may be
obtained by applying chemical and physical methods to a
biological problem, and we will take as an example a problem
of capital importance: immunity.

The experimental work which illustrates our thesis was
chosen not only because of its recent and fundamental charac-
ter, but also because it represented the last link in a chain
which was started at the beginning of the twentieth century
and forged with scientific rigour and admirable logic by the
scientists whose names we have already mentioned: Obermayer
and Pick and, especially, Karl Landsteiner. The latter, not
long ago, obtained the Nobel Prize for Medicine for his dis-
covery of the four blood-groups. This discovery, as everybody
knows, made blood transfusions absolutely safe. Our choice
was therefore not only governed by the interest of the work
itself, but by the fact that it is solidly based on a long series
of previous discoveries which rendered it possible. It also
enables us to foresee a still longer series of discoveries to come.

We shall now briefly report the experiments of Dr. Oswald
Avery and his collaborators, Drs. Michael Heidelberger, René
Dubos, and Walter Goebel, which represent the perfect type
of research in modern biology. This work was done in the
laboratories of the Rockefeller Institute in New York.

Pneumonia is one of the diseases which cause the greatest
havoc in the United States. In the great majority of cases it
is due to a micro-organism called ‘pneumococcus’. We have
known for a long time that there are very distinct differences
in pneumococci which manifest themselves by a characteristic
specificity. They develop in the same way in artificial media,
but even though their aspect under the microscope is the
same, they can be classed in well-defined and specific types
which simply bear a number: types I, II, III, etc. The
differences existing between these types are not revealed by

CHEMICAL AND PHYSICAL METHODS AI

the ordinary bacteriological methods, but by more subtle
methods called zmmunity reactions. These reactions are essen-
tially chemical, and cover all the processes by means of which
the body tries to fight against infectious disease. For example,
we know that if a solution containing microbes, let us say
pneumococci of type I, is injected several times into the veins
of an animal, the latter will, as a reaction of defence against
the foreign cells, manufacture new substances, called ‘anti-
bodies’, in his blood. The consequence of this fact is not only
that the animal is actively immunized against a subsequent
infection of living and virulent pneumococci but that the
serum (which is the liquid part of the blood) containing the
antibodies, confers a passive immunity, when it is injected into
the body of another animal susceptible to the same infection.

What is more, when the serum of the animal immunized by
means of the pneumococci type I is mixed with the same
microbes in a test-tube, the micro-organisms act in a strange
way. They stick to each other in clusters, in masses. They
are what is called ‘agglutinated’. These reactions are strictly
type-specific, that is to say serum antipneumococcus type I only
agelutinates the pneumococci type I and has no action on the
organisms of another type. It is therefore possible, by em-
ploying specific immunized sera of each type of pneumococcus,
to classify an unknown culture by the nature of its reaction in
contact with one or other of the immunized sera.

I insist on the specificity of the different types of pneumo-
cocci and on their immunological reaction thanks to which
they can be distinguished, for this is at the base of the work
which will now be described.

The biological classification of pneumococci was established
before anything was known of the chemical nature of the sub-
stances which determine the specificity of the type. Before
going any farther we will say a few words on the importance
of having a biological classification for the chemical and
epidemiological knowledge of the malady. This classification
has made it possible to appreciate the frequency of cases of
pneumonia due to each type of microbe, to recognize the

42 THE BIOLOGICAL PROBLEM

difference of gravity, as well as the death-toll of the infections
which they determine and to understand better the mode of
dissemination of the disease, by finding the different types in
the mouths of healthy or convalescent individuals. Finally,
the notion of “type-specificity’ has provided us with the only
rational basis for the production of an immunized serum which
has proved its value in the treatment of infections of type I.

In the course of their first experiments, Avery and his
collaborators naturally asked themselves: To what could be due
this extraordinary specificity, and in what part of the microbe
it resided? How could it be possible that organisms so com-
pletely identical from a morphological point of view were so
different from the point of view of their immunological
properties? Previous observations furnished the clues that
put the searchers on the road to success.

The pneumococcus is a unicellular organism which is
surrounded, under certain well-defined conditions of growth,
by an envelope more transparent than the microbe itself,
visible under the microscope and known as the ‘capsule’.
This capsule is particularly well developed in pneumococci
which grow and multiply in the body of animals. During
their growth, the capsulated cells secrete in the midst of the
culture a diffusible substance which, in solution, presents the
characteristics of type-specificity of the organisms from which
it derives. This substance is found not only in the filtrates of
young cultures but also in the humours of animals experi-
mentally contaminated, and in the blood and urine of the
patients during the evolution of pneumonia in man. The
faculty of elaborating this product increases with the virulence
of the pneumococcus, and there is every reason to believe
that the capsule of the micro-organism is constituted mainly
by this specific substance. Thus, around each microbe, there
exists an ectoplasmic layer or capsule capable of reacting
with the serum of an animal immunized against the same
microbe, the so-called anti-serum. This reaction is remarkably
specific and occurs only when the anti-serum and the capsular
substance are of the same type. The problem, then—and it

LIMITATIONS 43

was a difficult one—was to isolate the substance in question
in a pure form, and to determine its chemical constitution
and its role in the immunological properties of the pneumo-
coccus as a whole.

The capital discovery that these soluble substances, which
are responsible for type-specificity, belong to the family of
carbohydrates, that is to say sugars, is due to Dr. Michael
Heidelberger, a brilliant chemist and one of Avery’s first
collaborators. No matter what type of pneumococcus they
are extracted from, they always possess in common the
chemical properties of the complex sugars, the polysac-
charides. But strangely enough, the polysaccharide derived
from each specific type of pneumococcus is chemically
different, and each one possesses particular properties which
distinguish it clearly from the others. What is more,
chemically purified solutions of these sugars manifest the
same specificity, from the immunological point of view, as
the microbes from which they are derived. To give an idea
of their astounding activity it suffices to mention the fact
that by means of the corresponding serum it is possible to
reveal their presence at a concentration of one five-millionth
Or 0:0000002 grams in one cubic centimetre of solution.?

From the point of view of medicine, and especially of
serology and immunology, this discovery was of capital
importance for two reasons. First, because it had been
believed up till then that immunity reactions were solely due
to extremely complicated substances the chemistry of which
is very little known—the proteins. And second, because by
demonstrating that the capsular sugars were as chemically
distinct as they were serologically specific for each type of
pneumococcus, Avery and Heidelberger brought a striking
proof of the close relation existing between the chemical
constitution and the specificity of the microbes.

1 Let us mention that Heidelberger and Avery accomplished the
same experiments, with equal success, on types A and C of Fried-
lander’s bacillus. It is interesting to note that 75 litres of an auto-

lysed, eight-day-old culture medium are needed to yield about
I gram of polysaccharide.

44 . THE BIOLOGICAL PROBLEM

It was a brilliant confirmation of the splendid work of
Landsteiner on complex antigenes. His researches led him
to conclude that biological specificity is conditioned by
chemical groups relatively small with respect to the antigenic
molecules. A new proof in favour of this thesis was given
by Avery, as we shall see presently.

Thus the specificity of different types of pneumococci
depends on the chemical nature of the sugar which forms the
capsule. What would happen if the microbe could be relieved
of this capsule. Would it die? Would it conserve its virulence?
Of what nature would be its specificity and what accidents
would it occasion in an animal? All these problems were
completely solved by Avery with the collaboration of a young
Frenchman, René Dubos. But it required several years to
do it, as no enzyme capable of attacking, dissolving, in other
words, of digesting these sugars could be found. Finally,
Dubos isolated from the bogs of New Jersey, a micrabe of
the soil, which secreted an enzyme capable of digesting the
capsule of pneumococcus type III, without killing the cell.

It was now possible to obtain cultures of pneumococci having
totally lost the type-spectficity, deprived of virulence and incap-
able of invading the animal in which they were injected.
However, these microbes had not lost the faculty of surrounding
themselves with a new capsule which restored their specific
virulence. But it became possible to give these cells the faculty
of surrounding themselves by the characteristic sugar of a
different type and of transforming themselves into pneumococ-
cus types I or II. A degenerated microbe can produce any kind of
specific saccharide, according to conditions in which it is placed.

The authors then had the idea of injecting doses of these
enzymes into the bodies of the experimental animals—mice—
so as to discover whether they would digest the capsule of the
virulent pneumococci 7m vivo and render them inoffensive.
They ascertained that their previsions were fully justified and
that it was possible to protect mice specifically against
type III, and solely against this type.

They afterwards studied the chemico-immunological

LIMITATIONS 45

properties of the capsular polysaccharides. These sugars
are not toxic and do not seem to be responsible for the
accidents which accompany a pneumococcic infection. But
certain facts indicate that they can indirectly oppose the
normal mechanisms of defence against this disease. Indeed,
by reason of the avidity with which they combine with the
antibodies, they tend to neutralize the substances resulting
from the processes of immunization, and thus prevent these
protecting agents from reaching the centres of infection.
What is more, the pneumococci enrobed in their shell of sugar
resist phagocytosis,! whilst the naked microbes divested of
their capsules are energetically absorbed and destroyed by
the phagocytes. We have already seen that pneumococci
artificially deprived of their capsule lose their virulence and
do not multiply like the others. This is due in part to the
vigorous offensive of the phagocytes which devour their
enemies bereft of their protective armour. And now we
come to a most important point, the crowning touch to the
magnificent work which demanded such long years of effort
from the scientists of the Rockefeller Institute.

The chemically purified capsular polysaccharides of the
pneumococci have lost the power to induce the formation of
antibodies in the animals to whom they are injected. In
other words, they cease to function as genuine antigenes whilst
conserving the faculty of combining with the specific anti-
bodies resulting from the injection of the integral microbe.
In this way, they are related to the important group of sub-
stances, immunologically active, which Landsteiner named
‘haptenes’,” and which behave in the same way.

As these sugars, these carbohydrates, are antigenic when
they are accompanied by the microbic cell, Avery came to

the conclusion that in this case they cannot exist as free

1 Phagocytosis, which is the process by which certain wandering
cells of the organism surround, absorb, and sometimes digest any
invading element, was discovered by Metchnikoff. The ‘phagocytes’
act as the policemen of the body.

* Haptenes are substances which react specifically, but fail to
induce immunity (i.e. to determine the appearance of antibodies)
when injected into an animal: they are not antigenic.

46 THE BIOLOGICAL PROBLEM

polysaccharides, but under some other form, forexample, chemi-
cally combined with a protein or another substance which gives
them an antigenic power of which they themselves are deprived.

In order to see what would be the consequence of the
introduction of a radical ‘carbohydrate’ in a protein molecule,
from the point of view of the orientation of the specificity of
the new compounds thus formed, Avery and Goebel chose
two simple sugars (monosaccharides), glucose and galactose.
These two substances have the same composition and the
same chemical formula. They differ one from the other
only by their configuration in space, the groups H (hydrogen)
and OH (oxhydril) fixed to one of the carbon atoms occupying
a different place in each case. Starting from these two sugars,
Goebel succeeded in synthesizing the corresponding ‘para-
aminophenol-glucosides’. Then each of these derivatives of
the sugar was combined with a protein (globulin of serum or
egg albumin) so as to obtain definite compounds (sugar-azo-
proteins), that for simplification can be called galacto-globulin,
galacto-albumin, gluco-globulin, and gluco-albumin. Rabbits
were immunized with these substances, and the sera of these
animals, containing the antibodies, were submitted to immuno-
logical reactions similar to those of which we spoke above.
It was found that the specificity of each of the compounds
thus created, was solely determined by the radical sugar, and
altogether independent of the nature of the protein to which
it was combined. This fact was capital. The introduction of
a simple sugar in a protein confers to the entire compound
a new specificity which is determined by the chemical structure
of the carbohydrate. The sugars in question differ only by
the spatial relations of the groups OH and H attached to the
fourth carbon atom. A simple rotation of 180 degrees around
this atom suffices to change completely the serological speci-
ficity of two substances otherwise identical. The marked
differences between pathological accidents can then be due
to the simple displacement of a chemical group in a molecule.!

' The similarity between the two substances, the p-aminophenol
8-glucoside and the p-aminophenol (-galactoside clearly appears in
the two structural formulas:

LIMITATIONS Bia) Be

Avery and Goebel were thus ready to attack the final
problem rich in significance and consequences, the synthesis
of an artificial bacterial antigene, obtained by combining the
polysaccharide of a pneumococcus with a foreign protein.
With this end in view they chose the sugar of type III which,
being totally deprived of nitrogen, can be considered as a
definite chemical entity and has never by itself determined
any immunological response on the part of the injected animal.
It is not only inactive in a pure form, but the microbe from
which it is isolated does not in the majority of cases possess
the power to bring forth antibodies in rabbits.

The great difficulty from the chemical point of view
consisted in preparing by synthesis the substance derived
from the polysaccharide capable of combining with a protein
without neutralizing or masking the chemical groups. This
feat was accomplished by Goebel, a young and brilliant pupil
of Heidelberger. He obtained the ‘amino-benzyle-ether’ of
sugar type III which he combined with a foreign animal
protein, the globulin of horse serum. This soluble antigene
has nothing in common with the pneumococcus type III
excepting the polysaccharide, and yet the rabbits into which
it was injected reacted by manufacturing specific antipneumo-
coccic antibodies in their serum. The serum of these animals
not only precipitates the synthetic antigene, but specifically
agglutinates the living cultures of pneumococcus type III and

Bee Fe Seni ae His Ta laa ale re ©
“RY iy SECON od Be a Pea, |

BX
H—C—OH H—C—OH

| |
Je Tg mae qatan & : HOCH
| O |
H—C—OH so vtereeeeteteees £3) Dey
Ce |
2 ae ge ee Hc

| |
H,—C—OH H,—C—OH

Glucoside Galactoside

It can be seen that the only difference consists in the position of H
and OH at the level of the fourth carbon atom.

48 THE BIOLOGICAL PROBLEM

protects mice against an infection engendered by the virulent
microbes of this type.

There are few comments to add. Asa result of this splendid
work we begin to see the dawn of a new bacteriology and
immunology, no longer founded on empiricism but on the
scientific knowledge of the mechanism and the chemistry of
the phenomena of infection and defence. Progress will be
long and tedious, but success is certain, for the path is now
traced, and though bristling with difficulties it is the only one
open to us. And if we remember the methods and principles
of Pasteur, chemist and physicist, we realize that it follows
the true Pasteurian tradition.

We have thus far taken a bird’s-eye view of biological
problems in general. In studying the methods of investigation
we have pointed out a few of the difficulties that are
encountered. Some are of a purely material nature, mostly
due to technical difficulties of all kinds resulting from the
inadequacy of methods created to solve the problems of
inorganized matter when applied to living matter. Others
are of a deeper nature; concerning either the problem in
itself or else the mechanism of our thought and the criterium
of our reasoning. Finally, however, we succeeded in con-
vincing ourselves that at the base of our normal or pathological
physiological reactions, chemical phenomena existed that could
be approached by our techniques. They are, if one might
say so, the material foundation of life, but not life itself.

Now that we are in possession of these necessary premisses
we can proceed to the study of a biological phenomenon of
fundamental importance, as it is one of the manifestations of
the tendency to persist which characterizes living beings. It
is one of the rare problems which can actually be submitted
to measurements and calculations, and which, as we will soon
see, allows us to introduce time quantitatively in the shape of
a variable depending only on the organism as a whole.

PART I}

CICATRIZATION OF WOUNDS AND
TISSUE-CULTURE

CHAPTER IV

A BIOLOGICAL PHENOMENON—THE
CICATRIZATION OF WOUNDS—TIME—
PRELIMINARY EXPERIMENTS

WE will now examine in detail a phenomenon which ts familiar
to everybody. Cicatrization can be studied either zm vivo or
in vitro and therefore belongs to the methods of Class B.

This phenomenon is too complex to lend itself to chemical
analysis as a whole. It is a manifestation of the cellular
activity of reparation and proliferation. We propose to show
the reader how the quantitative laws were established, by
making him successively participate in all the stages of the
experiments and in the reasoning which led to their discovery.

But before delving into the heart of the subject, we would
like to change the tone adopted in the preceding chapters, for
the following reasons.

Up till now we have spoken of general questions. We have
exposed the different points of view of eminent scientists,
living or dead, and we have expressed our own opinion. In
conformance to an old habit, we have avoided speaking in the
first person as is done in original papers. This is a convention,
which is not followed by everybody and which misleads no
one. The aim pursued by the author in all scientific papers
is to efface his personality as much as possible and to let the
facts speak for themselves. This, at any rate, is the end that
everybody should seek and that most of us attain, even when
‘TY’ is employed instead of ‘we’.

One of the principal tasks of the experimenter is the
elimination of the ‘individual factor’ or ‘personal coefficient’.
There are always too many causes of error, and this particular
one can take on different aspects. The observers are not
identically sensitive to light radiations, to sound. The way
in which they appreciate the equality of two juxtaposed

51

52 CICATRIZATION OF WOUNDS

coloured areas is not quite similar. Their movements are
more or less rapid, more or less precise. Their reactions
more or less slow. At different moments of the day, the same
person does not always react in the same fashion to the same
stimulus. Hence the necessity of resorting as often as possible
to automatic or recording instruments. It can be admitted
that one of the reasons for employing the pronoun ‘we’ has
the same origin. It imposes a more neutral redaction than the
‘Tl’. Another reason lies in the fact that several workers have
often materially collaborated in different ways to the dis-
covery of the experimental facts described in a paper. Still
other motives may exist.

The result of these combined considerations is that the
perusal of a totally impersonal scientific article, from which
all human element has been systematically eliminated, is
impossible for all but a student of the same subject or one
directly connected with it, and who is interested enough to
seek only facts and measurements in the text. In other words,
only a specialist reads it.

And yet there is something else in a discovery or a scientific
endeavour. First, the human element which has been care-
fully put aside, and second, all the intermediary steps between
the salient points of the reasoning, the stages which establish
the continuity, the homogeneity of the psychological evolution
which enabled the worker to reach his anticipated goal. Only
these elements could make the paper interesting to a non-
specialized reader. An article written in this fashion would
be too long and encumbered by useless details as far as the
scientist is concerned, but not without interest from the
point of view of the ‘stor# of a discovery. To be complete,
the description of researches having attained a definite result
would require the mention of a great number of facts the use-
fulness of which vanishes when the final end is achieved, but
which, at a certain moment, have served as cement, or as a
link between more important facts. The elimination of these
links leaves, instead of a continuous curve, a series of points,
the interrelationship of which is not sufficiently clear to allow

A BIOLOGICAL PHENOMENON 53

an outsider to understand their logical sequence. Such a
reader will gladly skip a table of figures, but if the work is in
itself new and original he will perhaps be interested in the
mechanism of the development of the ideas, hypotheses,
experiments, and results of the author. In other words he
would be interested in the manner in which the results have
been obtained as much as in the results themselves.

This point of view is quite different from that of vulgariza-
tion. The vulgarizer translates articles and books which are
written in a conventional jargon meant to economize thought
and time, into a language which is accessible to the unspecialized
public. He eliminates mathematics which are nothing else
but a condensed form of mental stenography. But he does
not introduce the more interesting human touch, or if he
does so, it is because a particular phase of the work in question
presents a specially picturesque, striking, or amusing aspect.
He does not try to extricate the general line, the slim psycho-
logical thread which binds together the successive stages of
the evolution or a discovery in the brain of a scientist. Yet
it is the romance of a discovery which could seemingly be
capable of fixing the attention of the layman. This novel,
once lived, is destroyed. Only the material conclusions of
each chapter are allowed to subsist.

It is true that the vulgarizer or commentator would find it
very difficult to reassemble the pieces of the puzzle furnished
by scientific papers, so as to be able to unite these elements
in the logical and harmonious order which led to their birth.
It would be quite impossible for him to divulge the succession
of psychological facts of which they are the fruit, had he not
assisted in person at all the different phases of the work or
had the author not taken him into his intimate confidence.
A few such examples, however, exist. The most celebrated is
certainly the admirable Life of Pasteur by René Vallery-Radot.
The realization of this monumental and profoundly moving
fresco is due to the family bond existing between the genial
scientist and the author.

In English-speaking countries, however, didactic works are

54 CICATRIZATION OF WOUNDS

sometimes and even quite often found, the extreme dryness
of which is attenuated by portraits, short biographies, and
reproductions of old engravings, historically connected with
the text. Bayliss’ remarkable Principles of General Physiology,
for example, is a living and fascinating book, full of pictures
which relax the mind of the student. In America, excellent
text-books such as Practical Physiological Chemistry, by Hawk
and Bergeim, and Applied Chemistry, by Morse, are illustrated
with portraits of the scientists whose works are cited.

But there is no attempt to expose the mechanism, the
genesis of a work, the interest of which, if it exists, can be
quite independent of the value of the effort or of the result.
I will, therefore, in the following pages, report my experiments
and results published in the Fournal of Experimental Medicine,
without eliminating the intermediary stages of my researches.
The reader will thus be able to follow the evolution of the work
in my mind and the succession of ideas and reasoning. I will
not vulgarize nor simplify, I will develop instead of shortening,
and will reintroduce in part the personal element which had
been smothered and hidden. The reader must excuse me if
the subject is mediocre; my choice is necessarily limited to my
own experiments, and this restriction reduces its interest.

Towards the end of 1914 I found myself at Compiégne as
Lieutenant commanding Section R.V.F. B. 26, in charge of
victualling the 61st Reserve Division. At the same period,
Dr. Carrel was transforming the Hotel du Rond Royal into
Front Hospital no. 21. This hospital was destined to become
a centre of research, for people were beginning to realize that
it might be useful to be able to recommend officially certain
methods for the treatment of infected wounds and that a
selection amongst those employed was necessary. Professional
surgeons adapted themselves rapidly to circumstances, and
owing to their experience and their knowledge inspired no
fears. This was not the case, however, with the general

A BIOLOGICAL PHENOMENON 55

practitioners who had been obliged to transform themselves
instantaneously into surgeons, and who often found themselves
brutally faced with important lesions for the immediate treat-
ment of which they possessed scant information, and no
training.

The expenses of the laboratories of Temporary Hospital 21
were supported by the Rockefeller Institute of New York.

Dr. Carrel asked me one day what method could be
employed for measuring exactly the surface of any kind of
a plane area. In fact, he was interested in estimating the surface
of wounds which he was studying with Dr. Alice Hartmann, and
which were outlined on cellophane by means of a wax pencil
or even a fountain pen. He told me that up till then he had
employed the weighing method, which consists in transferring
the first drawing obtained directly on the wound on to a sheet
of paper, which is then cut out following the lines of the
drawing as exactly as possible, and weighed.

Figures proportional to the areas of the wounds are thus
obtained on condition that the paper utilized is always of the
same thickness. He explained the inconveniences of this
technique, which was delicate, lengthy, and inaccurate. I sug-
gested employing the planimeter, an instrument well known
to engineers, which enables one to evaluate in a few minutes,
with precision, the area of any surface in square centimetres.
The problem which was occupying Dr. Carrel at the time was
the following one. He had been able to convince himself that
the cicatrization of surface wounds maintained under proper
conditions evolves according to a geometric law. This
phenomenon had not been studied quantitatively, owing to the
fact that its only interest before the war was a purely physio-
logical one. Furthermore, in order to solve it, some notion
of mathematics was necessary and, at that time, mathematical
culture was not generally found amongst biologists. Carrel
thought that I might succeed and asked me to study the
question. He believed that the solution would solve rapidly
and without possible discussion, the question of the relative
value of the different treatments proposed for the dressing of

56 ; CICATRIZATION OF WOUNDS

wounds and that of the influence of certain retarding or
accelerating factors.

He had already made some beautiful experiments on
cicatrization, that marvellous phenomenon which begins as
soon as our skin or our muscles or our tendons are wounded,
and stops when the lesion is repaired. In a cut, a burn, a
torn tissue, all the cells concerned, asleep so to speak until
then, wake up and multiply with feverish activity, reproduce
by millions, repair the damage as well as possible, and then
fall back into their latent life. We are no longer surprised
by this admirable labour because we have seen it since child-
hood. Familiarity kills wonder.

‘The cicatrization and regeneration of tissues are the
manifestations of the tendency to persist which is inherent
to all living organisms. We are profoundly ignorant of
the nature of these phenomena. They are, like the func-
tion of nutrition, a fundamental property of living matter.
It is as impossible to know their essence as it is to know the
essence of life. Moreover, this knowledge would be useless.
From a metaphysical point of view, it might be interesting
to know why a wound cicatrizes. But from a scientific
point of view, it is infinitely more important to know how
it cicatrizes. It would thus become possible to determine
the efficient causes of the complex mechanism of the
regeneration of tissues. That is why it is useful to study
the physiological phenomena of cicatrization. It is true
that the regenerating power escapes our methods of
research, but the physico-chemical processes which are
co-ordinated and harmonized by this directing force in view
of the morphological reparation can enter into our field of
experiment.’

It was in 1908 that Dr. Carrel wrote these lines which he
later communicated to me and with which I began my Thesis
in I917. At the same time, he gave me the unpublished
results of his experiments. I will summarize them here so

A BIOLOGICAL PHENOMENON eS

that the reader may have all the elements which I myself
possessed at the beginning of my work in I9gI5.

Carrel’s experiments represent the first systematic study of
these phenomena. They led him to the culture of tissues in
vitro, and this second problem caused him to abandon the
first. The work was accomplished at the Rockefeller Institute
in New York, and principally on dogs. The wounds were
obtained by resecting a piece of skin of geometrical, i.e.
rectangular, trapezoidal, or circular, shape. To distinguish
the edge of the original wound he preferably employed dogs
with a black skin, or else tattooed the outline of the wound
on the epidermis -with India ink. It was thus easy to follow
the evolution of the phenomenon of cicatrization. The
dressing consisted in an application of sterile talcum or of
hot paraffin wax. The wounds were kept as sterile as possible.
It is superfluous to add that all operations were made under
complete anaesthesia.

Under these conditions the following facts were brought
forth. Cicatrization passes through four phases or periods.

I. Quiescent or latent period. This is the period which
stretches between the moment of the resection and that when
granular contraction sets in. Granulations are small pro-
tuberances resembling somewhat a cauliflower, but of a bright
red colour. They are generally dry, shiny, and of a healthy
aspect on a sterile wound. During these first days the dimen-
sions of the wound do not change. Hence the name given to
this period, the duratien of which is variable in different
wounds (one to five days). At the end of that time, the
period of contraction suddenly starts. (Fig. 1.)

2. Period of granular contraction. At this moment the edges
of the wound begin to come closer together. Very quickly at
first, then slower. The rate of this contraction depends on the
surface of the wound and not on its age, as was believed until
then. In order to demonstrate this clearly, Carrel cut out
two rectangular wounds of different sizes on the same dog.
The large sides measured respectively 66 and 26 millimetres.
In the course of the first 48 hours the length of the larger one

58 PRELIMINARY EXPERIMENTS

(these experiments were made before the use of the plani-
meter) decreased by 20 millimetres (a little less than one third),
whereas the length of the small one decreased by only 4
millimetres, about one sixth.

For the same reason, when the wounds were of trapezoidal

Distance
AB

icatricial - -->
penod

Ss 10 15 20 25

FIG. I. (EXPERIMENTAL WOUND IN THE UPPER RIGHT-HAND CORNER.)
POINTS A AND B ARE ON THE OUTLINE TATTOOED WITH INDIA INK.
POINTS « AND § ARE ON THE NEWLY FORMED EPITHELIAL BORDER. THE
SCHEMATIC CURVE SHOWS THE SUCCESSIVE PHASES OF CICATRIZATION.
ORDINATES EXPRESS THE DISTANCE BETWEEN POINTS A AND B (SOLID
CURVE) AND « AND B (DOTTED CURVE) AS A FUNCTION OF TIME

shape, the length of the longer base tended to equalize itself
with that of the smaller one and the wounds became rectangu-
lar in a few days. The same results were obtained with
circular wounds made by punching out the skin. It was then
established that the rate of reparation during the granular
period was a function of the dimension of the wound, that is
to say, of the total effort required to repair the destroyed area.
This law had already been established by Spallanzani for
salamanders.t It was thus proved to be equally true for
mammals. This was unforeseen considering the differences
of the mechanisms brought into play. Minervini, in 1904,”
had found the same phenomena. However, as he made no
measurements, he did not conceive the existence of the curve

* Spallanzani, Experiences pour servir a V’histoire de la génération des
animaux et des plantes (1787).
2 Minervini, Virchows Ann., vol. 175, p. 238 (1904).

A BIOLOGICAL PHENOMENON 59

represented on Fig. 1. The different processes of cicatriza-
tion had not escaped him, but he thought it impossible to
succeed in formulating a law sufficiently general to cover them
all. He therefore abandoned the problem to devote himself
exclusively to the histological side of the question, which also
attracted a certain number of other workers.

This period of contraction during which the surface of the
wound decreases solely by means of a movement of the under-
lying tissue, plays an important part in the cicatrization of
large and medium-sized wounds and especially of the latter,
at any rate on dogs. When studying the rate of reparation of
different-sized wounds on these animals, it becomes apparent
that wounds which are too large do not cicatrize as quickly as
the others. It might almost be said that everything takes place
as though the activity of reparation was maximum for wounds
that dogs are likely to inflict on each other.

Strange to say, it seems that the phenomenon of contraction
is closely dependent on the presence of the granulations. It
does not exist before their apparition (latent period) and it
stops when the epidermization is complete, that is when the
granulations have been covered by a thin layer of epithelial
cells, foundation of the new skin, which slowly invades the
wound from the edges. In order to ascertain whether these
phenomena were bound together by a relation of causality,
Carrel made the following experiment.

FIGS. 2 AND 3. EFFECT OF A GRAFT ON THE GRANULAR
CONTRACTION

He grafted a small piece of skin in the corner of a rectangular
wound covered with granulations. A deformation took place,
but at the end of a few days, the wound had reassumed its

60 PRELIMINARY EXPERIMENTS

rectangular aspect (Figs. 2 and 3). ‘This proves that contraction
stopped at the level of the graft while it continued to act
everywhere else.’

In another experiment, he stimulated the epithelization of
a large square wound which showed no trace of epithelium
in the lower part by grafting a small piece of epithelium. It
is a well-established fact that a living graft increases the
production of epithelial cells. It was then observed (Figs. 4,
5, and 6) that the distance between the lines tattooed in India

FIGS. 4, 5, AND 6. EFFECT OF A GRAFT ON THE GRANULAR
CONTRACTION

ink on the edges of the wound, decreased in the lower part
(presence of granulations) while it remained constant in the
upper part (absence of granulations). The wound became
trapezoidal (Fig. 5) and when totally healed resumed its
primitive shape. It is therefore certain that epithelization
inhibits the function of contraction of the granulations.
When epithelization is precocious, the scar is large and thin.
When it is slow, the contraction is stronger and the scar is
thick and comparatively smaller.

The preparation of the surface of the wound for the migra-
tion of the epithelial cells is also a function of the granulations.
But it seems that their principal role is to bring the edges of
the wound within a certain distance of each other, about
10 or 15 millimetres ina dog. This may be deduced from the
fact that a wound which is 10 millimetres broad, no longer
contracts. The contraction becomes useless because at a
distance of 10 millimetres the secondary mechanism, namely
epithelization, functions easily, as we will show farther on.

A BIOLOGICAL PHENOMENON 61

A beautiful experiment of Carrel’s proves that an external
excitation is necessary to set the process of reparation going.
A fresh and sterile wound, carefully covered by a sheet of
cellophane glued to the skin and therefore completely protected
against any external action, does not cover itself with granula-
tions and does not cicatrize. In other words, the skin, which
is a protective element, has no reason to reappear, and therefore
does not reconstitute itself.

FIGS. 7 AND 8. AT A AND B THE DISTANCE BETWEEN THE EPITHELIAL
BORDERS BEING SMALLER (LESS THAN I 5 MILLIMETRES), EPITHELIZATION
IS MARKEDLY FASTER, AS WELL AS IN THE ANGLES C AND D

3. Period of Epithelization or Epidermization. The begin-
ning of the epithelization period can easily be observed on
a rectangular wound which hasbeen outlined with India
ink. The new epithelium, which later becomes the scar,
progresses at first very slowly at the surface of the granulations.
It is extremely thin and fragile, and there are numerous
factors which hinder its development. (The experiments
subsequently realized at the Compi¢gne Hospital showed
that the most important of them was infection). The observa-
tion of trapezoidal wounds shows the rapidity of cellular
proliferation (epidermization) at the smaller base in compari-
son with its slowness at the longer base. In wounds of

62 PRELIMINARY EXPERIMENTS

irregular shape, epithelization always begins at the sharp
angles where the distance between the edges of the wound
is smaller (Figs. 7 and 8). The new cells seem to attract one
another. Though the intimate mechanism of this phenomenon
escapes us, it explains the acceleration of cicatrization by
grafts. Carrel made the following experiment in order to
demonstrate this particular point. Fig. 9 shows a rectangular

FIG. 9. EFFECT OF A GRAFT ON EPITHELIZATION

wound in which epidermization has begun (A). A tiny
epithelial graft, less than 1 millimetre square, and taken from
the new epithelium just being formed, is disposed at point «.
A few days later the wound appears as in Fig. B. The small
graft has been rejoined and absorbed by the neighbouring
epithelium. A new graft was placed in the same manner in
front of the peninsula formed at 8 (C). Fig. D shows that
not only has the epithelial peninsula surrounded the new
graft but that the attraction due to the coming together of
the two edges can be observed on the opposite border of
the wound.!

The cellular reparation activity, the epidermization, is
therefore all the greater, the nearer the edges of the wound
are to each other. Whereas the granular contraction acts
‘when they are farther apart. When examined through the
_ microscope, the granulations assume the aspect of a relief
map, showing ranges of rounded hills separated by valleys
at the bottom of which a certain serosity can be detected.
The epithelial cells, either isolated or in groups, travel on the
surface of this liquid. Their reunion at the point where several

1 Reverdin had already signalled a similar phenomenon.

A BIOLOGICAL PHENOMENON 63

valleys converge gives birth to islets. These islets are called
spontaneous grafts.

When part of a cicatrizing wound is covered by a sheet of
sterile filter paper, it can be observed that epithelization
progresses more rapidly where the cells have been protected
by the sheet of paper. This experiment is not in contradiction

FIG. IO. INFLUENCE OF MECHANICAL PROTECTION
ON EPITHELIZATION

with the complete inhibition due to the application of cello-
phane over the entire wound mentioned above. In the first
case, the period of contraction had not begun and the cello-
phane was impermeable, whereas in the second, the period
of epidermization has already started and filter paper is not
impermeable. It acts only as a local protection. (Fig. 10.)

ae ~

yy GAs Ky

FIG. II. INFLUENCE OF INFECTION

On the other hand, the following experiment shows the
retarding action of infection (Fig. 11). A wound was cicatrizing
normally. When it had attained the dimensions of B, Fig. 11,
it was observed that there was a point of infection in a corner
of the new epithelial tissue at «. The wound was not sterilized.
A few days later, it assumed the aspect shown in C, Fig. IT.

64 CICATRIZATION OF WOUNDS

The presence of the small centre of infection had sufficed to
bring the lower edge of the wound almost back to its original
dimension.

4. Cicatricial Period. The scar left by a large wound is
proportionally smaller than that left by a small wound. A
wound 66 millimetres long left a scar of 22 millimetres, whilst
a wound 26 millimetres long, on the same animal, left a scar
of 13 millimetres. In the first case the scar represents one
third, and in the second case, one half of the size of the
original wound. In small wounds of about Io millimetres,
the scar is almost as extensive as the wound. When the
epidermization is ended and the wound healed, the scar
begins to spread and distends itself (see Fig. 1) so that points
A and B tend to come back to their original position. This
last period is very long (several months) and completes the
regeneration of the lesion.

In brief, the mechanisms of the phenomenon of cicatrization
are co-ordinated in such a fashion that the reparation 1s
continuous. For dogs, the processes are adapted to the quick
healing of small and medium-sized wounds, not wider than
40 millimetres. In a wound 30 to 4o millimetres wide the
contraction is very efficient, and in a short while the edges
are brought to within Io or 15 millimetres of each other,
a distance which is favourable to epidermization. Thus, at
the moment when the rate of reparation through contraction
tends to slow up, epithelization starts in and the work of
regeneration continues without interruption, but by means
of a different mechanism.

I have dwelt at length on these preliminary experiments
because it was necessary for the reader to know the subject
and to be familiar with the terminology. What precedes
suffices to explain the complexity of the phenomenon which
had to be translated quantitatively by the simplest possible
formula. The problem which I had to solve was perfectly
well defined. It consisted in finding a method which would
permit us to predict in advance the dimension of any kind of
wound at the end of 4, 8, 15, . . ., x days and, consequently,

PRELIMINARY EXPERIMENTS 65

to calculate how many days the wound would require to be
completely healed. The part of different retarding agents
had to be appreciated, and either the real factors which
govern the phenomenon discovered, or, more likely, the
efficient and measurable factors which, under an apparent
simplicity dissimulate an infinite number of inaccessible active
elements.

This goal once attained, it would be possible to determine
mathematically, instead of empirically as heretofore, the ad-
vantages and inconveniences of the different methods proposed
for the treatment of wounds, the effect of different antiseptics
and their respective qualities. A motivated choice could thus
be made and cicatrization obtained in as brief a time as
possible.

Was the problem soluble? Would not each case obey its
own particular laws, or rather be rendered independent of
general laws and mathematics by imponderable factors such
as the individual temperament of each invalid, his heredity,
his former life, his habits, the suffering which he had gone
through in the war? This was what I had to find out.

CHAPTER V

CICATRIZATION OF WOUNDS (ID—
EXPERIMENTAL TECHNIQUE—CURVES—
MATHEMATICAL STUDY

It was first of all necessary to establish a precise technique
whereby wounds could be maintained sterile without irritation,
and the edges outlined as accurately as possible. Dr. H. D.
Dakin had already prepared a certain number of antiseptics
and Dr. Carrel had chosen the ones which bore the numbers
30 and 142 as giving the best practical results. ‘30’, as we
called it, was the sodium hypochlorite solution which later
became famous under the name of Dakin Solution.

This slightly alkaline antiseptic, rigorously titrated at 0-5
per cent of sodium hypochlorite, differs radically from other
hypochlorite solutions used for cleaning purposes (Javel
water). These latter fluids are very irritating and can determine
grave lesions of the tissues on account of their high percentage
of free alkali. Their antiseptic power, however, is not due to
their alkalinity; that is to say, to their causticity. The Dakin
solution possesses a strong antiseptic power without being
irritating or toxic, and this constitutes a tremendous advantage.

It was furthermore necessary to avoid as much as possible
all disturbing influences on the wounds and, in particular, to
make sure, by daily checks, that their bacterial condition,
viz. the mean number of microbes per unit of surface, was
minimum and did not vary from the beginning to the end of
the experiment.

The patients had to lie in bed, preferably immobilized by
a fracture, for example, as any movement always brings about
considerable delay in cicatrization.

The bacterial condition of the wound was therefore con-
trolled every day by smears taken from different points and
examined under the microscope. If microbes were found,

66

CICATRIZATION OF WOUNDS 67

they were destroyed by appropriate treatment. The granu-
lated surface and environing skin were carefully washed with
neutral sodium oleate (soap). The granulations were then
sterilized by means of the Dakin solution (no. 30)! or no. 142
(sodium toluene—sulphonchloramide, Dakin), for short:
Chloramine-T. When the microscopic examination showed
that sterilization had been obtained, the wound was dressed
either with neutral sodium stearate containing small quantities
of antiseptic, or simply with vaseline, lanoline, or salt water
(physiological isotonic solution at 0-9 per cent of sodium
chloride). It was thus possible to maintain wounds bacterio-
logically sterile during several weeks, sometimes months. The
daily bacterial examination immediately revealed any return
of infection and permitted us to take it into account in the
interpretation of the experiment. It was on wounds thus
prepared according to Dr. Carrel’s technique that the pro-
gress of cicatrization was studied as well as the comparative
action of different antiseptics.

As I have already explained, the drawing of the wound was
obtained by means of cellophane. These thin sterile sheets
were applied on the surface of the wound with a dab of cotton.
The outline of the epithelial edge or outline of the granulations
was drawn with a dermographic or wax pencil, and also when
possible the edge of the cicatrix at the line of junction with
the healthy skin. This drawing was then reproduced on
a sheet of ordinary paper. Fig. 12 is the reproduction of
such a series of drawings from the beginning (moment when
the wound was recognized as sterile) to the end of the experi-
ment. As can be seen, the drawings were generally made
every four days. The area of each drawing could then be
obtained in square centimetres by means of the planimeter.
When the outline of the cicatrix could be taken, a second
figure was obtained.

The graphic expression of the curve was easy to establish.
As is customary, the time was carried as abscissae, that is to
say horizontally on millimetre paper (squared in millimetres)

' Later prepared according to Dr. Daufresne’s improved technique.

Pahient N° 221

Dec.13th 1915
S= 18.2 sq.cm

Dec.17 th.
S = 16.2 sq.cm,

1916

Jan.1Oth

() S00

FIG. I2. REDUCED REPRODUCTION OF THE DRAW-
INGS OF A WOUND, TAKEN FOUR DAYS APART.
THESE DRAWINGS REPRESENT THE OUTLINE OF
THE GRANULATIONS, LIMITED BY THE NEW
EPITHELIAL BORDER. (SEE FIG. 13.)

CICATRIZATION OF WOUNDS 69

and the surfaces vertically as ordinates. To every day
corresponded a given area. If the measurements were made
every four days, a curve similar to that of Fig. 13, which
represents the evolution of the wounds of Fig. 12, was obtained.
Once in possession of a certain number of similar curves,
I could begin to work, rocked day and night by the unceasing
S in sq.cm.

17
16
IS

R

ee ool oe TE At UY 8 <a Ga

17 Zl oe 29 Zz 6 (0%
December /9/5 January 7/6

FIG. 13. NORMAL HEALING OF A WOUND. THE DISCREPANCIES BETWEEN
THE TWO CURVES — OBSERVED (SOLID CURVE) AND CALCULATED (DOTTED
CURVE)— ARE SMALL. THE MAXIMUM DIFFERENCE AMOUNTS TO 0°6 SQ. CM.
ON THE 29TH OF JANUARY

bombardment which formed a sonorous background to all our
thoughts and all our actions. I intended to begin by attacking
the surface and then the length of the epithelial edge. The
first idea was to express the quantity cicatrized in one day as
a function of the dimension of the wound. For if I expressed
In square centimetres the area cicatrized in a time t, I failed
to take into account the fact that a large wound can, in an
equal time, cicatrize a surface which is larger in absolute
values, but which may be smaller in relative value, namely,
with respect to its total area.

70 CICATRIZATION OF WOUNDS

In other words, if the wound no. 221 (Fig. 12) has shrunk
by 5°5 square centimetres in four days, between the 17th
and 21st of December, and if another wound no. 263 has
diminished by 20 square centimetres (from IIo to 90 cm.?)
it is not certain that it is the first one which has been the
slower to cicatrize. In the first case, the initial surface was
16.2 cm.” (previous to that it was infected); 5-5 cm.? therefore
represents about one third of the total area of the wound;
whereas, in the case of no. 263, 20 square centimetres corre-
spond to one fifth of the area. It is the smaller one, therefore,
which healed quicker.

As a consequence it was quite natural to express the
quantity cicatrized as a fraction of the work accomplished
with respect to the total work to be accomplished, that is to say,
in relative units. To do this it sufficed to divide the area
cicatrized in a given time, by the total area at the beginning of
the experiment. S being the initial surface at the moment
when infection, one of the principal causes of delay, has been
eliminated, and S’ the surface at the end of a time t (expressed
in days), the work accomplished with respect to the total
surface S will be:

In the examples cited, the value of this ratio is 5-5 : 16-2=
0:34 for the first and 20: 110 = 0°18 for the second, in round
figures. Experience soon showed that a small wound will,
in all cases, heal relatively quicker than a large one. The
surface of the wound seemed thus to play a primary part.

On the other hand, it was necessary to introduce time into
our formula in order to express the quantity cicatrized per

/

day. This was done by dividing the quotient by ¢,
number of days elapsed between the measurement of the
area S and the measurement of area S’, just as one divides the
number of miles by the time, to obtain the mean velocity of
a distance travelled. The formula became then:

EXPERIMENTAL TECHNIQUE 71
easy

I was thus in possession of a simple element of calculation
which expressed the quantity cicatrized per day between the
two measurements as a function of the total area of the wound
in question. One of two things must happen. Either the
wound would continue to cicatrize at the same rate, or else
other factors would intervene, and influence the velocity of
repair in proportion as the wound diminished. It was hardly
probable that the first hypothesis would be verified, for it was
too simple. Hence, there were few chances that my first
formula could be applied to the following period. In fact, I
observed a certain progressive divergence. It now behoved
me to study this discrepancy and to find a new factor the
variations of which would remain proportional to it. This
factor introduced into the formula would give it a constant
value from the beginning to the end of the phenomenon. In
case of success, the problem was solved, for it would then be
possible to calculate the curve from point to point.

The difference between the biological method of approach
and the mathematical method borrowed from the physical
sciences is here clearly shown. ‘The preceding chapter gave
the reader an idea of the multiplicity of the factors and of the
complexity of the problem. The solution had not yet been
found, because those who had studied it were too familiar with
the details of the phenomenon. Knowing a great many
_ physiological factors but ignoring their relative influence, they
did not dare eliminate them, and did not know how to take
them into account. They were paralysed by their knowledge.

Like the botanist who could not see the forest because of
the trees, they could only consider the facts as a function of
microscopic biological elements with which they were familiar.
My ignorance of these elements freed me from the chains
which fettered them. Not knowing how to distinguish the
different species, I examined the forest from a distance, as a

72 CICATRIZATION OF WOUNDS

whole and quantitatively as I had been taught to do for a
physical phenomenon. Dr. Carrel had foreseen that a brain
trained in such methods was better adapted to attack this
problem than one inhibited by a mass of knowledge and by
habits of thought.

The problem was then momentarily reduced to finding a
way of obtaining a constant value for this formula by intro-
ducing a ‘new measurable element, varying in the same
manner as the differences observed between the experimental
values and those calculated from the formula.

First of all, of what order of magnitude were the dis-
crepancies, and what was the law of their variation?

Let us go back to wound no. 221. We have seen that the
cicatrized area was 5:5 square centimetres between the first
and fourth day; this gave the following values for formula (2)
fo — "6-2. — 10-7)

Se av SS
SME 3 1624
For the second period of four days, we find:

S’=10°:7; S” (surface after eight days)—6-5 therefore

So -.) =4-2 and

= 0-085 (in round figures).

S’—S” 4:2
SE AO ga

The difference is slight, but nevertheless exists. The same
calculation made for the fourth period gives o-119, the fifth
period gives 0-136 and the sixth 0-175 (the area of the wound
is now equal to one square centimetre). It was obvious that
I was far from having a.constant to deal with. Fig. 14 clearly
shows the extent of my error in the shaded area. This error,
as can be seen, was considerable and affected the last figure
calculated by Io0o per cent (0°67 instead of 0:33). On other
wounds it was still more important.

All the values of S which could be derived from the formula
were too high. Hence, it was clear that it was the denominator
which must be augmented. But it could not be increased by
a constant coefficient, for the values of the entire formula

= 0:098.

EXPERKIMENTAL TECHNIQUE 73

mounted progressively, from 0-085 to 0:175. Therefore I had
to find a correcting factor which increased in proportion as
the wound diminished.

On second thought, this was logical, for I already knew
from a number of experiments that the most important factor

NS
CCCI
CCT
AWS
NAS

Values of

Periods of 4 days.
FIG. I4. CALCULATION OF THE FORMULA

in the rate of cicatrization was the size. Now, in our example,
formula (2) was established for a wound of a certain dimension:
16:2 cm.*. At the end of twenty days its size was reduced to
I cm.*. It was therefore obvious that the first formula could
no longer be considered as valid. The correcting factor had
to be a function of the actual area of the wound; and as this

74 CICATRIZATION OF WOUNDS

area was precisely our unknown factor, it could not be
utilized.

I realized, however, that if the area itself could not be used,
there existed an element which increased regularly as the area
diminished and that the surface was necessarily a function of
this element. It was what can be called the age of the wound,
namely the number of days gone by since the beginning of the
experiment, since the moment when the wound has become
bacteriologically sterile. This age could be known at all
times. Unfortunately it increased much more rapidly than
was necessary. I fell into the opposite extreme and obtained
decreasing values with my formula. However, by turning over
this problem from all angles I noticed that the discrepancies
increased as a reciprocal function of the square root of the
successive surfaces. The solution was at hand. The decrease
of the surface being a function of the time, it sufficed to intro-
duce in the denominator the square root of the age of the
wound, necessarily a reciprocal function of the square root of
the areas.

By means of an artifice, I thus replaced the area by a factor
on which it depended quantitatively, and I corrected the
formula in function of its decreasing size, without taking
anything but the age into consideration.

It must be admitted that I had been very lucky. The
correction was much simpler than I had thought. I never
imagined, when first checking the new formula, that it would
be unnecessary to introduce auxiliary constants, which are the
terror of physicists, for they are the proof that the mechanism
of the phenomenon is far from being solved. I thought I was
only nearing the solution when I wrote the equation

ce a

S(t+V T)
T being the number of days since the beginning or the age
of the wound and & the coefficient which had to be stabilized,

I immediately deduced from formula (3) the value S”’ of the
surface at the time 7”

CURVES 75

I Sy CE, V Ait Re PS a (4)

This would enable me to calculate the curve from point to
point with only two values of the surface of the wound at
t days’ interval to start from. Practically, t is always chosen
equal to 4. I immediately verified this formula on a certain
number of experimental curves. The accord from one end
to the other was good, much better than I had hoped. I could
thus, by means of a simple formula, containing only one
coefficient, k (which, we will soon see, possessed the advantage
of not being arbitrary), express, as a function of time, the
evolution of a very complex phenomenon. This was un-
foreseen. At the beginning of my studies I thought it would
be necessary to resort to many more arbitrary coefficients.
Here is a convincing example of the fact that a definite pheno-
menon taken as a whole, can often obey a simple law, even
though it is the result of an important number of factors, each
of which obeys laws which can individually be more compli-
cated. We are almost on the verge of touching that amazing
and disturbing co-ordination which characterizes living beings.

The first practical application of the formula was the study
of antiseptics. It enabled us to establish rapidly the real
qualities of preconized antiseptics and to prick a number of
soap bubbles such as the ‘cicatrizing agents’ reputed for
accelerating the healing of wounds.

We soon became convinced at Hospital 21 that, out of
approximately two hundred substances tried, only two
possessed an exceptional number of qualities: the nos. 30 and
142, as stated before. The formula only confirmed the choice
already made empirically. The method employed for these
experiments was the following one.’ A wound was sterilized
with Dakin’s solution, prepared according to Daufresne’s
method, or with ‘Chloramine T’. The curve was calculated

1 All technical details have been given in A. Carrel and Dehelly’s
book, Le traitement des plaies infectées (Masson, 1917. Collection
Horizon). We also experimented on the action of sunlight, of

artificial light, of ultra-violet rays and of oxygen. In no case could
we detect any acceleration whatsoever.

76 CICATRIZATION OF WOUNDS

from beginning to end. When, after about eight days, we felt
sure that the wound was healing ‘normally’ we replaced the
standard dressing by another one with the antiseptic to be
tried out. If there was a slowing up of the cicatrization, that
is to say, a difference between the calculated figures and those
of the area measured, it indicated either that the new sub-

140

a

wh ee Oa se
BACCO C CCE E EET tele
0
30 PAR ts hicks NC de aCe at bs) ae
Eee
SOP SEGRE Sie ae
ame
HAS Ee

80 |

aa
a ae A 36 22 2695S (9°15) 7 21-25 9 2 RDG: 10) 18 22 26
MARCH APRIL

FIG. 15. LARGE ABDOMINAL WOUND, CICATRIZED IN THREE MONTHS.
IMPORTANT INFECTION FROM THE IOTH TO THE I8TH OF FEBRUARY,
FOLLOWED, AFTER STERILIZATION, BY A RAPID ACCELERATION

stances had not maintained the bacteriological sterility (this
fact was controlled microscopically) or else that it was irritating
and impeded epithelization. To be certain that the dis-
crepancy was not due to other factors, the dressings with the
Dakin or Chloramine solution were reapplied for four or
eight days. In general, these dressings not only brought the
cicatrization curve back to normal but determined an accelera-
tion which caused it to catch up with lost time. That is, when
the irritation due to infection had not lasted too long. This
was absolutely unforeseen. Fig. 15, which represents the

7

|
|

CURVES 77

evolution of an abdominal wound on a soldier twenty-two
years old (no. 360), shows that the accord between the experi-
ment ‘and the calculation was excellent during nearly three
months. The date of complete cicatrization was calculated
on the roth of February and gave the 6th of May as an answer.
On the 30th of April the wound had an area of 0-70 cm.” and
the calculated figure was 0-75. It was completely healed on
the 4th of May instead of the 6th, an error of two days out of
ninety. An important divergence can be noticed between the
roth and 18th of February due to a re-infection of the wound,
which at that time was kept under a plain sterile dressing.
Chloramine was applied on the 18th, and the rate was imme-
diately accelerated. The curve overtook the calculated point
on the 22nd.?

Fig. 16 shows an experiment with Flavine, an antiseptic
which was much praised at the time in England. The experi-
ment was begun on the 23rd of April, after a small infection
which manifested itself on the 15th by a slight retardation had
been conquered. The result was almost immediate. On the
25th of May not only had the wound ceased to cicatrize but it
had enlarged (from 4-3 to §-2 cm.*). The immediate applica-
tion of Chloramine brought about the renewal of cicatrization
by epidermization. On the Ist of May another trial brought
about another stop. On the 3rd of May we definitely resorted
to Chloramine, which brought the experimental curve back to
the calculated one. During all this time the wound had
remained sterile. From a purely antiseptic point of view,
Flavine was therefore excellent. But, on the other hand, its
necrotic action was so strong that it was impossible to employ
it. We could therefore, in a few days, ‘establish mathemati-
cally, without possible discussion, the real practical value of a

1 This interesting phenomenon is not due to the specific action of
the Chloramine or Dakin solutions, but to the elimination of the
retarding factors, infection or irritation. It is as if the wound accumu-
lated the necessary elements during the slowing up process, and
liberated them as soon as the inhibiting cause was suppressed. The
same phenomenon can be observed in the growth of living beings
when an impediment which retards their growth is eliminated.

78 CICATRIZATION OF WOUNDS

treatment. It was possible, for the first time, to settle, by
measurements and calculations, discussions in which self-
conceit and sentimental reasons had up till then played the
principal part.

Age
apere| a
inane
SD ina

SAR Wass a Be a Gy AS a ee ee

Wy 15 1y BS. 25.27) BY op 3) 6s Ge ieee

FIG. 16. INFLUENCE OF DIFFERENT ANTISEPTICS ON A WOUND

Now that I have explained the practical applications of the
method, I will turn back again to the study of the formula
itself and show what could be derived from it.

CHAPTER VI

INDEX OF CICATRIZATION—INFLUENCE OF
THE AGE OF THE PATIENT—INFLUENCE OF
THE-SIZE OF THE WOUND

WE have seen that the first part of the problem consisted in
finding a parameter remaining constant throughout the entire
_ phenomenon of cicatrization. Now the coefficient k, constant
for a given wound, seemed to vary from one wound to another
and from one man to another. As, however, it characterized
the rate at which a certain wound healed, I replaced it by the
letter 2 and named it index of cicatrization.

I naturally asked myself whether this index was solely
characteristic of each wound studied or whether it possessed
a more general and hidden significance. To solve this new
problem, I drew up a table in which were brought together
certain known elements corresponding to completed experi-
ments: index, dimension of the wound (area in cm.”), and age
of the patient. I had already observed that the youinger a man
was the quicker he cicatrized. It was therefore natural to try
to see whether the index did not, to a certain extent, depend
on the age of the man. The two following facts were soon
well established:

I.—Small wounds cicatrized more rapidly in relative values
than large ones; their index was therefore higher than that of
larger wounds.

2.—Wounds of the same area cicatrized more rapidly on a

young man than on an older man. The index z was therefore
a function of age as well as of the area of the wound.
These observations were of interest because the importance
_ of the index would be much increased if it could be proved
_ that it was not an individual factor but depended, on the con-
trary, on general factors such as the area of the wound and the
_ age of the patient. If it had been a function of the state of
79

80 CICATRIZATION OF WOUNDS

health of the patient, of the extent of his physical resistance,
of his antecedents, there would have been an index for each
person and for each wound. This would have eliminated all
possibility of connecting this constant to measurable physio-
logical factors, and would, in consequence, have materially
reduced its importance. No scientific laws would exist if
there were only particular cases. On the other hand, it
seemed rather strange that the general condition of the patient
did not influence the activity of reparation.

A close examination of the wounded cared for at the
hospital clearly demonstrated that outside ef certain specific
cases, such as diabetes, syphilis (in periods of accidents), and
inveterate alcoholism, the activity of reparation expressed by
the index appeared to be solely determined by the age of the
patient and the area of the wound. At any rate, the fluctua-
tions due to other factors were negligible in the experimental
conditions in which we placed ourselves. They were of an
order of magnitude inferior to the tolerable experimental
errors.

This unlooked-for result was partly due to the fact that all
our patients with few exceptions were soldiers, that is to say,
healthy men in the prime of age, between twenty and forty
years old. What is more, in spite of the hardships, the life
they led was healthy when compared to the stagnant life
in towns with all its excesses. The majority were robust
peasants, accustomed to live out of doors. The others,
nervous and morally tired city men, had generally become
stouter and gained in health. We were therefore dealing with
a selection. But this selection gave us precisely what would
have been very difficult to find in peace-time, namely nor-
mality. However, I may say that I had several occasions of
studying all sorts of different wounds after the end of the war,
such as eschars, wounds which do not heal normally, varicose
ulcers, burns, etc., on men unfit for military service. The
discrepancies observed between the ‘normal’ index and the
calculated index were much less frequent than I had supposed.

Sufficient elements were on hand to make it possible to

INDEX OF CICATRIZATION SI

establish a chart or, in other words, to draw on squared paper
a ‘family’ of curves as a function of the index and of the area
of the wound. Each curve corresponded to a determined age
between twenty and forty. Fig. 17 represents this chart. To
find the index of cicatrization corresponding to a given wound
of known area, a line parallel to the abscissae or axis of the

os war een
a
OSes
“hee Ga aa

OBA Ne
Sac

COZ OOS (008 (O05 006. O07 indext
FIG. 17. THE INDEX OF CICATRIZATION

indices (horizontal) is drawn up to the point of junction with
the curve representing the age of the patient. From this point
a perpendicular is drawn on to the same axis and its inter-
section with this axis (abscissae) gives the value of the index.
For example, a wound 60 centimetres square on a man twenty-
five years old, corresponds to a ‘normal’ index of 0:03. The
same wound on a man of thirty-two will have an index of 0:02.

This represented an improvement from several points of
view. First of all, the reader will remember that two measure-
ments of the area were necessary to calculate the index by
means of formula (3). The quantity cicatrized in four days
had to be known (experience showed that this lapse of time
was necessary and sufficient). With the chart there was no
need to let four days elapse. The calculation was made at the
start. In the second place, this procedure presented another

82 CICATRIZATION OF WOUNDS

advantage besides that of simplicity and economy of time,
namely, that of precision. For, if two measurements are made
at four days’ interval, it may happen that during this time
slight incidents escaping our observation occur, which can
momentarily retard or accelerate cicatrization. The index
calculated from the amount cicatrized during those four days
will therefore be inaccurate, and the whole curve equally so.
As we have seen above, a wound comes back to its normal
rate when the local causes of perturbation are eliminated. The
index furnished by the chart is independent of this cause of
error.

I spoke of retardation, which can be due to a traumatism or
to infection, and also of acceleration. This latter phenomenon
takes place, for example, when a wound rapidly epithelizes
small crannies like those represented in Fig. 18. The figures
below show the error that would have been made if the index
had been calculated between the 20th and 24th of May (the
patient was thirty-one years old).

May | May | May

1916 2oth | 24th | 27th

Area observed . . |e34°5 | 24:8 7 206

» calculated (index

taken from the chart) | 34:5 | 29:2 | 22-4
Area (index computed

from formula (3)) .| 34°5 | 24:8 | 16°8

If the index obtained from the chart is used, the discrepancy
between the two figures on the 24th of May is wiped out on
the 5th of June. The theoretical index obtained from the
chart was 0-032. That given by calculation was 0-047. The
error would therefore have been important, and the use of the
chart eliminates it completely. Finally, this method has the
following third serious advantage. The index obtained from
the chart being a mean value, corresponding to a normal
asceptic cicatrization on a normal individual, if, independently

INDEX OF CICATRIZATION 83

of all known errors, a more or less important discrepancy is
observed between this index and that of the wound itself
calculated by means of formula (3) it will be the indication
that the patient zs not normal. There is an unknown retarding
cause which it may be interesting to investigate. And if there

Fatient N°488 Age:31 ¢.0,03

A B

22>

FIG. 18. (A) ASPECT OF THE WOUND ON MAY 20TH. ONLY THE SHADED

PARTS ARE CICATRIZED. AREA IS EQUAL TO 34.5 SQ. CM. (B) ASPECT

OF THE WOUND ON MAY 24TH. IN FOUR DAYS IT HAS CICATRIZED ITS
NARROW PARTS. AREA EQUALS 24.8 SQ. CM.

is every reason to admit that the man 1s in good health it will
be the proof that his real physiological age 1s not the same as his
legal, official age. In other words, from then on, there was a
way of determining the difference between these two ages
expressed by the reparation activity of tissues. Later on I
wil deal with this point more thoroughly. In connexion
with this subject, however, I would like to mention the first
calculated determination of the age of aman. The great and
regretted surgeon, Dr. Tuffier, had put an engineer, Dr.
Desmarres, in charge of the calculations relative to wounds.
One day, in Compiégne, I received a letter containing an
experimental curve of cicatrization and asking for an explana-
tion. The curve calculated by means of the first formula had
given a time of cicatrization materially longer than that
actually observed.

I had studied only a few days before long and narrow
wounds which, as we have already seen, cicatrize more rapidly

84 CICATRIZATION OF WOUNDS

than others, by reason of the proximity of the epithelial
borders. I immediately concluded that the wound in question
was of this shape, and although I had not seen the drawings
I introduced the new correction (of which I shall speak
presently) and obtained a good accord. Having satisfied
myself that an elongated shape was probably the cause of the
acceleration, I consulted the chart and saw that the index
corresponded to about twenty years of age. Dr. Tuffier had
not as yet heard of the results obtained on the subject of age.
I therefore replied by telling him that his patient, assuming
that he was in good general health, must be between twenty
and twenty-two years old, and that his wound was long and
narrow. Very much surprised, Tufher answered by a letter
in which he confirmed the exactitude of the calculation. The
wounded man in question was a young soldier called Jacque-
maire, twenty-one years old and Clemenceau’s grandson.

It was therefore possible by this method to determine the
age of a wounded man with a good approximation.

These experiments, first performed on men, were taken up
again on animals and gave similar results. When, owing to
the fact that we had no facilities for breeding, it was impossible
to be certain of the age of the animals, the latter was replaced
by the weight, which in young animals is very nearly pro-
portional to age. On guinea-pigs, for example, we obtained
for wounds of the same order of magnitude (I to 1-5 cm.?)
the following values (the guinea-pig weighing 250 gr. was only
a few weeks old).

Weight (in grams.) . . 800 680 560 250
Initial area (insq.cm.) . I°5 Es 1-0 rs
fides” .. . 0046: 0075. -O°O78\), Or kam

The part played by the size of the wound is most interesting.
Wounds which are too large in comparison to the total surface
of the body of a man or an animal, do not cicatrize. Every-
thing occurs as if nature had not anticipated the reparation of

CALCULATION OF THE CURVE OF CICATRIZATION

Table giving the Two Coefficients of the Formula
S’=S [1-7 ¢++/nt)|!

Ist Coefficient—Index of Cicatrization 7 2nd Co-

Area |__| efficient
of Age of Patient Time Co-
Banana pe a a Ee eMICIEnE

20 years| 25 years| 30 years} 32 years| 40 years] !+ V nt

sq. cm.

150 0:02 0-02 0-02 0:02 6
and over 6-81
7°43
140 G02) | 0°02): "|G702/ | G02 8-00
8°45
130 0:02 0:02. | 6-02. ,)'0-02 8-90
9°3
120 0:02 0-02 0-02 0-02 9:65
| 10-00
I1IO 0-02 0-02 0-02 0-02 10:32
10:64
100 0:02 0-02 0:02 0-02 10:93
FI)
90 0'022 || 0:02 0-02 0-02 11-48
11-75
80 0-023; } 0702 0-02 0:02 12-00
12°25
70 67025, 1 0°02 0-02 0°02 12°48
12°72
60 0:03 0:0225| 0:02 0:02 12°95
13°16
50 0-034 | 0:0265] 0:0230]| 0:02 13-37
13°60
40 0:04 | 0-031 | 0-027 | 0-022
30 0-045 | 0:0375] 0:033 | 0:026
25 0:05 0-04 0:0375| 0-029
20 0:054 | 0:0465}] 0:0425] 0:0325
15 0:06 0:0525] 0:0475] 0:038
10 0-066 | 0:0625] 0-055 | 0:045
O'075 |. 0:07 0:07 0:07
and under |_

1 du Noiiy, ¥. Exp. Med., 1916, xxiv, 451, 461; 1917, XXV, 721.

86 CICATRIZATION OF WOUNDS

lesions, the dimensions of which are too important. The
index of wounds decreases progressively until it reaches a
constant value, namely: 0-02. It may decrease still further,
but we have no experimental facts to prove it. The largest
wounds which I was able to study did not attain 150 square
centimetres. But the maximum size of wounds affected by
the index 0-02 is not the same for every age. A man twenty
years old will cicatrize a wound of 150 square centimetres,
and over, with an index of 0-02, whereas the same index
characterizes a wound of 50 cm.” on a man forty years old.

Age, therefore, introduces important factors of retardation
into the rate of cicatrization. The table on page 85 shows the
extent of this action.

I had established it to facilitate the calculation of the curves
by means of formula (4). It can be seen that all the values of
t+./nt (where nt=T the age of the wound, and t=4 days)
are calculated in advance for 24 496 days (last column).
Under these conditions the calculation was rapid.

A ‘family of curves’ represented by Fig. 19 can be drawn
from this table. In the first place their geometric regularity is
impressive. It is striking that such clear quantitative relations
between the area of the wound, the age of the patient and the
index, can be obtained in a phenomenon as complex as
cicatrization. But the curves themselves are most instructive,
and propound new problems which we are incapable of solving,
for they depend on questions of a much more general order.
For instance, what is the signification of the highest curve
which corresponds to index 0-02? It signifies that all wounds
which give points located in the upper shaded region cicatrize
with the same index, or at any rate with an index very close to
0-02. It can be seen that above 150 cm.?, age no longer seems
to play any part between twenty and forty years. But though
I have no proof of the fact, it is very probable that a wound of
this size should heal much more slowly in a man of forty.
There is no doubt that things are quite different on either side
of this curve and in my experiments I was unable to find
indices inferior to 0-02 except in pathological cases, or else

INFLUENCE OF AGE OF PATIENT 87

when the wound was situated in certain regions practically
deprived of underlying conjunctive tissue: the skull, the foot,
etc. Therefore on the right hand side of the curve the
primary factors of age and area no longer intervene quantita-
tively. There are unknown factors, and reparation is very

ea)
_YYyye 7
— |) —_
GY
| WY
= (=
pt tN Uf —
wa |
as <p

Se

FIG. 19. INFLUENCE OF THE AGE OF THE PATIENT AND OF THE
SIZE OF THE WOUND

slow in all cases. On the left-hand side of the curve, on the
contrary, everything occurs as if these two factors were the
only ones that entered into play, and the considerable im-
portance of age can be seen, especially in the first curve (0°02).
But one can also observe that the influence of age decreases

88 CICATRIZATION OF WOUNDS

rapidly with the dimensions of the wound and that, when the
area is inferior to § square centimetres, the wounds cicatrize
at about the same rate between twenty and forty years of age.
In this case, as in the case of large wounds, age and area lose
their importance. In wounds less than 5 cm.? in size, the

Awbund of! 40 $q.cm hel
days pnatman of 40 yee
; ” ” 39

Be) AE Ee ao a aon TR le Sih

30

20

Time indays
Age: 20vears soho Bie
FIG. 20. RATE OF HEALING AS A FUNCTION OF THE AGE OF THE
PATIENT

edges are so close that almost all the work of reparation is due
to epidermization. Towards the end of this book we will see
that many years later, in 1933, I eliminated the area so as to
obtain a new index depending only on the age.

To recapitulate the foregoing pages clearly it suffices to
glance at Figs. 20 and 21. The first expresses the role of
age in the rate of reparation of a wound of 4o cm.”. The
second, the role of the area, the age and other conditions being
identical.

In reference to the problem propounded by Prof. Tuffier,
I pointed out that it had been necessary to introduce a correc-
tion in the case of long and narrow wounds resulting, for
instance, from longitudinal incisions along the muscles. We

cm

INFLUENCE OF AGE OF PATIENT 89

saw in the first chapter on cicatrization when speaking of
Carrel’s experiments, that epithelization is activated by the
proximity of the epithelial edges. This enabled us to under-
stand the double part played by grafts of skin. It was there-
fore important to take this into account, the total gain on the

On Bb normal] man , 249 yealrs o
\ a wound of:
40 sqcm heblsin 56/day:

\ (} 4 mu 4 ”
NaN : :
TASER ERE

4 8 6 60

Ie NGG) BO RB PB S256) RO hk BB SaaS gi
Time indays
FIG. 2I. RATE OF HEALING AS A FUNCTION OF THE SIZE OF THE
WOUND

40

20

70

date calculated being from twelve to sixteen days. Now, the
principal difference from a quantitative point of view between
such a wound and one that is round or square is that the peri-
meter, the length of the epithelial edge, is increased with
respect to the area of the wound. It is therefore the shape
which plays a part, for no perceptible differences are observed
between wounds that are more or less indented, outside of
sudden but momentary accelerations such as the one mentioned
on page 82.

I observed that the phenomenon of acceleration with respect
to the curve calculated by means of formula (4) only begins to
show slightly when the length is eight or nine times greater
than the width. When the ratio is equal to 1o (length Io cm.,
breadth 1 cm. for example), it becomes very apparent. It

90 CICATRIZATION OF WOUNDS

continues to increase, and reaches a maximum value when the
ratio approaches 20. At that moment, cicatrization is almost
complete and the absolute value of the correction is very close
to I cm.?, this being a maximum.

Therefore the maximum correction could be expressed by
aie =I (as the ratio pel Gc Se
20 1 l (width)
tion had to be subtracted from the figure normally calculated

Fatient N°409

March 7 th.1916 .S=14.65 sq.cm.

March 11 . S = 8.20 Sq.cm.

March 21 : healed
FIG. 22. LONG AND NARROW WOUND. RAPID CICATRIZATION

=20). This empirical correc-

by means of formula (4). But I could introduce neither L
nor / in the formula, as it was impossible to know at the start
what would be the length and the width of the wound at the
end of a time x. Therefore another way of expressing the
same thing had to be found.

Now, in such wounds the perimeter—let us call it P—is
practically equal to twice the length, or P=2L, and P being a
function of the square root of the area and of a certain co-
efficient which depends on the shape of the wound, one could
write:

L=kv §
where & is a coefficient to be determined experimentally. It is

|

|
|

INFLUENCE OF SIZE OF WOUND OI

superfluous to enter into the details of the calculations which
finally led me to admit that the correction could be satis-

factorily expressed by us which it sufficed to subtract from

formula (4). It may be of interest to give the reader a few
figures enabling him to realize that the accord thus obtained is
quite satisfactory. (Patient no. 409) Fig. 22 represents the
successive aspects of the wound. The table below gives the
figures.

with

correc.
March sq.cm
Fi 55

II 8:20

15 3°95

19 1-40

21 O cic

23

27

cicatrized

The formula for ordinary wounds gave March 31st as the
date of total cicatrization, or an error of ten days.
The corrected general formula, which became

S,= S_- [1 —i+- V nt] — ae BS) CON Ue a (5)

possessed the advantage of admitting a zero, whereas the
current formula, being asymptotic, forced one to admit that
the wound was cicatrized when the calculation gave a figure

inferior to 0-4 cm.*, for example.

What is more, the correction is so slight for wounds in

which the ratio 7 is small (it is never inferior to 1) that it can

be introduced at any moment, as soon as it is observed that

92 CICATRIZATION OF WOUNDS

the wound, long at the outset, shrinks rapidly. Not only is it
altogether negligible for large wounds, but by reason of the
form of the formula itself its action is compensated and it
enters automatically into play the minute it becomes useful.

I may add that from a practical point of view these calcula-
tions would be tedious did the slide rule not exist. Without
this marvellous tool it would have been much more difficult
and would have taken much longer to solve these problems.
Moreover, my mathematical treatment of them was not in the
least classical: the formula is not homogeneous, and a true
mathematician would probably judge my method rather
severely. That is why I endeavoured to find a more elegant
procedure. The reader will soon see that I succeeded in
obtaining a general equation of classical aspect. I rarely em-
ployed it, however, for it is much less convenient than the
first, and requires two coefficients instead of one.

Meanwhile, I was sent to the Rockefeller Institute in New
York for a stay of several weeks. During this time I applied
my formula to study the cicatrization of civilian wounds and
in particular of varicose ulcers.

I was able to verify that these wounds of pathological origin
cicatrized according to the formula as soon as they were dis-
infected. Curiously enough, in certain cases the cicatrization
was more rapid—there was a higher index—than would have
been the case in a war wound, that is to say, in a fresh wound.
It seemed as if nature had accumulated materials during the
long period in which the infected ulcer did not cicatrize,
which sterilization suddenly freed. We had already observed
this phenomenon in conjunction with momentary infections
of wounds previously sterile. (See Fig. 15.)

The new problem which now confronted me was the
establishment of a true equation of the curve. The one of
which we have spoken so far rendered great services and had a
real practical value. But it did not permit me to calculate the
area at a given moment; neither could I obtain the date of

INFLUENCE OF SIZE OF WOUND 93

cicatrization directly, without passing by intermediary points. I
had to proceed point by point. It was an extrapolation formula.

I spent several weeks in search of the ideal general equation.
By ‘ideal’ I mean that it must not have more than two co-
efficients and that these coefficients must necessarily be func-
tions of the index 7, which had a well-determined significance
and was itself a function of the age of the patient. I was
especially anxious to obtain these coefficients without calcula-
tion, by means of a chart. It was necessary that they should
not be arbitrary. It is always possible with a little patience to
find an equation by increasing the number of arbitrary co-
efficients. But the interest of a formula is then much slighter.
A little farther on I will mention such a case.

Mr. de Rufz de Lavison, to whom I exposed my difficulties,
agreed to collaborate with me in this work. A few weeks later
he brought me an equation which was satisfactory from the
point of view of the accord with the observed facts. Unfortu-
nately it contained two coefficients which I could not connect
with the values of 17. This equation was the following:

T=b,Log,°+2kxV Sy VS).

It can be seen that it gives the time elapsed TJ instead of the
area of the wound. To obtain the date of total cicatrization it
sufficed to replace S by 0-4 or 0-3, and T was obtained in days.
This result encouraged me to take up my calculations anew
in another way, and this is how I attempted to do it.

Let us admit that during a very short time dr (the differ-
ential notation is here employed) the cicatrized area ds remains
proportional to the total area. This is written in the following
way:

—ds=KSadt
from which by integration with respect to time one obtains:
S
ds
T=—f ;;
KS

Sy

94 CICATRIZATION OF WOUNDS

S

I fds

or ~~
S

I S
hich = 5 Log.
which is equivalent to T Kee $
or KT = Log, :
which can be written
Ss = S o¢ “T,

e being the base of natural logarithms.

In calculating the values of K for different values of T, one
sees that this coefficient increases regularly. This equation,
as could be expected, does not express the facts, and gives for
each value of T (the age of the wound) values of S which
differ more and more from those calculated by the extra-
polation formula:

SiS, rs GA ADs eee ee (4)

It was therefore necessary to introduce another coefficient
which would correct the divergence as cicatrization pro-
gressed. This coefficient had to be incorporated preferably
into the formula as an exponent. But here a problem immedi-
ately arose. Was it better to attempt to find this correction
by giving to 7 its real value and by studying the law of the
variations of K, or was it better to maintain K constant and to
study the variations of a certain coefficient « entering into the
exponent in the following manner:

—K(T-+-«).

I tried the two methods. The first revealed itself as not
practical because the coefficient being small (of the order of
0-020) with respect to the time 7, the smallest numerical
variations were of sufficient importance to destroy the con-
cordance of the curves. In other words, this correction was
too sensitive. In the second case, on the contrary, fairly

INFLUENCE OF SIZE OF WOUND 95

important variations in a certain coefficient Ky connected
with « by a relation such as

interfered very little with the accuracy of the calculation of the

entire formula.
This result was obtained by plotting on squared paper the
values of « as ordinates. These values were computed from the

formula:

The time 7 was plotted as abscissae.
We thus obtained a curve expressing the law of divergencies
between the formula
S=S,e-kT
and the formula
S,=Sn_y[1—1(t-++ Vnt)].

Now this curve (Fig. 23) is simply a perfect parabola
answering the classical equation y?—=2px, (y=T and x=a),
which is equal to saying that

T?
ae —
2p.
And in consequence the general equation of the curve became
ing e
se se Bl? UN eee LE (6)

It was possible from now on to calculate directly the area of

a wound at any date. To obtain the date of complete cicatriza-

- tion, it sufficed to solve the equation making S=o-4, as a

_ wound of 0-4 square centimetres cicatrizes in less than twenty-
four hours.

_ The two coefficients K and p were bound to the index of

_ cicatrization 7 by simple relations, and one could either calculate

96 CICATRIZATION OF WOUNDS

them directly, from the above formulae, or else compute
them from the values of 7 found in the chart. The study and
discussion of the two coefficients would require too much
space and I therefore refer the reader to the original paper.’

NEDO SEV ARE
iishae cs ese
axe} LogSs-t [TT

4 842 (20. 28 S6 “44 ‘SZ Vimesndsays

FIG. 23. CORRECTING FACTOR IN EQUATION (6)

The concordance between the curves calculated by the extra-
polation formula (4) and those obtained by the exponential
equation (6) is excellent, as shown by the table below.

But there is another advantage in employing this equation.
It may be remembered that the phenomenon of reparation is
due to a double process. First, contraction and second,
epidermization. The two formulae, (4) and (6), translate into
mathematical language the result due to the combined
mechanisms. It would be too long and fatiguing for the

1 Lecomte du Noity, ‘A general equation for the law of cicatrization
of surface wounds’. Journ. of Experimental Medicine, vol. 29, p. 392

(1919).

9 ‘ou
‘uonenbs jenusuodxy

v-o | S.0 ‘wo ‘bs (uon
-ejodeijxo jo epnu
-I10}) F ‘ou uonenby

gl ae _ skep Ul SWI],

(panuiquor) €9T ‘ON JUaNeg

LL Pole ieet 1-7 Ole be | O.Or/S0sce. | OsIy | - Ors |-9.19=|- % -OOu
‘uonenbs enuouodxg

oeoec Oleiaienoi.Ol- | ele |-9:0c.|-V.Ee 1 7-1P-] 9-08--| 9.19--12" ‘ud ‘bs (uon
-ejodemxo jo enu
-10J) F ‘ou uonenby

gt ae QZ | vz Oz gl TI g v O sep Ul OUT],

‘SO==0 2. .V10-0=-1— SOCO'O—7 60. “ON JUNE

9 ‘ON NOILVNOA AO ANY V ‘ON NOILVNOA AO SNVIW AG GNNOM Y AO
NOILVZIMLVOIO AO AAUND AHL ONILVINOIVO NI GANIVLAO JONVGYOONOOD AHL ONIMOHS ATAVL

20

98 CICATRIZATION OF WOUNDS

reader to go into the details of the reasoning which led me to
emit the hypothesis that the simple formula

S= Se-KT

quantitatively expressed the result due to the granular con-
2

yee
traction and that the factor ap in the exponent expressed the

acceleration due to epidermization. The comparison of the
two curves calculated by means of the experimental curves
and representing, on the one hand, the diminution of area due
to contraction, and, on the other hand, the total phenomenon,
contraction-++epidermization, proved that this hypothesis was
justified. We could thus express the two processes inde-
pendently,’ and the last formula was more complete and more
satisfactory than the first, though less easy to use.

I have already pointed out some practical applications of
these calculations. A few years later they enabled my friend
Dr. Ebeling, of the Rockefeller Institute, to demonstrate
clearly that the mechanisms which are at the base of all
cellular reparation are of a chemical nature. This was done
in the following fashion.?

It is known that all chemical phenomena are characterized
by a ‘temperature coefficient’, the value of which is about 2:5
(Van’t Hoff’s coefficient). This means that for every rise in
temperature of 10° C. the rate of the reaction is a little more
than doubled. Conversely, for every diminution of 10° C.,
the rate of the reaction is divided by a factor approximately
equal to 2°5. This criterium is used when one does not
exactly know how to interpret a new phenomenon nor what
hypotheses can be eliminated a priori. For example, in the
early days of radio-activity, before 1900, scientists began by
trying to measure the temperature coefficient. But no matter
what the temperature of the reaction, one hundred degrees
below zero or several hundred degrees above, the rate of the
phenomenon remained the same. The production of what

1 Lecomte du Noiiy, loc. cit., fourn. of Exp. Medicine, 1919.
2 A. H. Ebeling, Journ. of Exp. Medicine, vol. 35, p. 657 (1922).

|
y

INFLUENCE OF SIZE OF WOUND 99

were then called the «, 8, and y rays remained immutable. The
conclusion, without possible doubt, was that this was not a
chemical phenomenon but a phenomenon of atomic dis-
integration. The same is true of the photo-electric pheno-
menon, known as the Hertz-Hallwachs effect, which consists
in the discharge of a conductor of polished zinc, electrically
isolated and on which falls a beam of ultra-violet light. By
varying the temperature it was proved that this was purely an
electronic phenomenon and not a result of combination or
decomposition.

The problem was less easy to solve in the case of cicatriza-
tion, for it was necessary to work over a range of 10° or 15° C.
This immediately eliminated all ‘warm-blooded’ animals,
which could be more correctly called ‘thermo-stable’ animals.

But there are a quantity of so-called ‘cold-blooded’ animals.
These animals are not characterized by the fact that their
blood is cold, which does not signify much, but by the fact
that their blood maintains itself approximately at the tem-
perature of the surrounding medium. The reader is aware
that insects, fish, reptiles, and batrachians belong to this class.
They are deprived of the property of maintaining their
temperature constant. For evident reasons it was impossible
to work on insects or fish. But in the class of reptiles, alliga-
tors and crocodiles were particularly indicated, for they can be
kept without difficulty at temperatures varying between 10°
and 4o°C. At 10°C. they are somnolent and in a state of
latent life. At 40° C. they are in full activity.

Square, easily measurable wounds were cut out on the
abdomens of young Florida alligators and curves were estab-
lished. The animals were kept at temperatures constant from
beginning to end of each experiment, but variable for each
new wound.

It was found that the rate of cicatrization varied in the mean
ratio of 2:12 (extremes: 2-47 and 1-88) when the temperature
was raised or lowered by 10°C. For instance, at 23°C., a
crocodile weighing 314 grams cicatrized a wound of 1-3 square
centimetres in 29 days and the same animal at 38° C. (that is, a

100 CICATRIZATION OF WOUNDS

difference of 15° C.) took only 11 days to cicatrize a wound of
I-2 square centimetres. Chemical phenomena are therefore at
the base of the phenomena of tissue reparation. This was to be
expected; but in biology, as in all sciences in general, facts
alone must be considered. Farther on, we shall see that this
observation, together with another one equally based on Van’t
Hoff’s coefficient, constitutes one of the most solid links in our
reasoning concerning the appreciation of time.

The most important facts to be remembered in the preceding
pages are, first, that the evolution as a function of time of a
physiological phenomenon as complex as cellular reparation,
which involves the co-ordination, for a determined end, of a
series of physical, chemical, and biological mechanisms, can
be mathematically expressed by a very simple formula con-
taining only one well-defined coefficient. Secondly, that this
coefficient is a function of the physiological age, and that there-
fore it becomes possible to measure the process of ageing. I
do not mention the relationship to the area of the wound, for
we shall see, in the last chapter, that it is easy to eliminate this
contingency and to obtain a new constant depending solely on
the age.’

! As a result of our studies, the problem was taken up again by
other workers. Certain of the proposed formulae are not worthy of
mention. Either they did not express the facts accurately, or else
their coefficients are meaningless. The excellent work of Prof.
Gaston Backmann, however, must be mentioned. (Ergebnisse der
Physiologie, vol. 33, pp. 915 and 939, 1931). With the help of my
experiments he was able to express the curve of cicatrization by means
of a formula established by him to account for phenomena of growth
in general. This formula expresses the facts perfectly, and in certain
cases follows the experimental curve more accurately than mine.
Unfortunately, it necessitates no less than four arbitrary coefficients,
which have to be determined for every wound. From my point of
view, this suppresses all its interest, for it is less important to be able
to calculate the area of a wound within one-tenth of a square cen-
timetre than to be able to have an idea of the principal factors which
intervene in the phenomenon. Backmann’s formula is the following:

log d=k, +k, . log (k3—T)+k, . log? (k;— T)
where d=the absolute rate of growth or cicatrization in square centi-
metres. It can be seen that the calculation of a wound by this formula
would take a certain length of time.

INFLUENCE OF SIZE OF WOUND IOI

I have dwelt at length on the details of these calculations
and have taken the reader ‘behind the scenes’, a thing which
by tradition or modesty the scientist usually avoids, because
it was necessary that he should have absolute confidence in the
results published. This confidence can only be acquired in
three ways. By repeating the experiments, by knowing the
author personally, or by possessing as many elements as
possible to enable one to follow step by step all the reasonings
which have led to the final conclusion. The two first methods
were difficult of realization, and I was therefore obliged to have
recourse to the third.

In order to define more clearly the notion of time and the
mechanism of ageing in certain biological processes as well as
to check the results obtained zm vivo, we shall now study the
admirable method of tissue-culture outside the organism,
which Carrel established in I912 at the Rockefeller Institute
of New York. I shall be obliged to dwell on it at length, for
this method has made it possible to detect the existence of the
chemical changes underlying the process of ageing, and also
to understand the accumulative processes registering the flow
of time. It is therefore a new and indispensable element for
our ulterior reasoning.

CHAPTER VII
TISSUE-CULTURE IN VITRO

CHAPTER I demonstrated the fundamental differences existing
between classical cytology, a science of pure observation which
suppresses evolution in time by killing the cells, and what
Carrel calls ‘the new cytology’. This new experimental science
enables the searcher to consider the cells in their environment
and to observe the reactions determined by modifications in
the surrounding medium, as a function of time. To make a
comparison, the classical cytology corresponds to the dissec-
tion of corpses, whereas tissue-culture is related to medicine,
physiology and, one might even say, to elementary sociology.
Taken in a restricted sense, this expression is not exaggerated.
Indeed, cinematographic films of cell-cultures have revealed
totally unknown and unforeseen facts related to the behaviour
of the free cells such as the leucocytes (white cells of the blood)
and macrophages. These cells, instead of living in a consistent
mass, bound one to another like the tissue-cells, disseminate
themselves in the culture-medium ‘like children let loose in a
school-yard’. The pictures are taken, According to the
activity of the culture, every 10, 15, 20, or 30 seconds, during
periods varying from 24 to 72 hours. They are projected at
the ordinary rate of 16 per second or less. Every motion of
the cells is therefore considerably accelerated (from I60 to
500 times or more). It is thus possible to discern unsuspected
movements and mutual reactions, otherwise imperceptible, just
as in the well-known films which revealed to us the opening
of a bud and the blossoming of flowers. Unleashed leucocytes
can be observed attacking a nervous fibre which resembles
a taut string. The fragile and tenuous fibre is bent by the
shocks like the string of a bow in the hand of an archer. One
sees the macrophages in blood-plasma surrounding themselves
with a large undulating membrane resembling a sequence of
wavelets in a calm sea at low tide when they die without
I02

TISSUE-CULTURE IN VITRO 103

breaking on a smooth sandy beach. The meetings, the bumps,
the flights, the struggles often ending in absorption, the
envelopment of one by the other, are all portrayed. We
observe, in short, at a scale of a thousandth of a millimetre,
all that we are accustomed to see every day around us.

It is in this sense that one can speak of ‘sociology’, even
though the strict meaning of the word is perhaps different.
But I cannot think of any other to replace it adequately.

These observations which enable us to witness the incessant
activities of the cells and to assist like an indiscreet onlooker
at their birth, nourishment, battles, and death, form a new
science of which great things can be expected.

Not only can we contemplate them alive and magnified
thousands of times on the screen, but we dispose, thanks to the
cinematographic technique, of the apparently superhuman
power of contracting their time in comparison to ours. Like
the character in a remarkable story by Wells,’ we can accel-
erate the rhythm of the life of our constitutive elements. In
other words, we have the faculty of influencing the fourth
dimension.

Different workers, and especially Harrison, had tried before
Carrel to maintain pieces of tissue alive outside the organism.
But no one succeeded in prolonging the life of these ex-
planted? fragments beyond a few days for lack of proper
nourishment. It was therefore a momentary extension of life
which they obtained, and not an independent and unlimited
existence. Dr. Carrel was the first to prevent death setting in.
The explanted tissues which are kept in special containers
with tremendous aseptic precautions, for one single microbe
suffices to infect the culture and to kill it, can be assimilated
to immortal experimental animals. We have already men-
tioned in the first part of this book the fact that a strain of
cells derived from a small fraction of embryonic heart in 1912

1H. G. Wells, ‘The New Accelerator’, Twelve Stories and a Dream.
2 See footnote, page 20.

104 CICATRIZATION OF WOUNDS

is still alive to-day. The cultures are as young as they ever
were and show no signs of ageing as measured by their growth
activity, which has not varied since the beginning. There is
actually no reason why those fragments of living flesh should
ever die, except accidentally. If it were not necessary, as we
shall soon see, to cut these cultures in half every two days, if
they could have been left to grow unrestrictedly, they would
now occupy a literally inconceivable volume. For, as their
size doubles in forty-eight hours, they would already have
attained 6,130,000,000,000,000,000,000,000,000,000,000,000,
000,000,000 cubic metres at the end of the first year (218? cubic
millimetres or 613 X 10%"). At the end of twenty-four years the
calculated volume would be 24° or 5,862 followed by one
thousand three hundred and three zeros, in cubic metres. At
the end of one year they would have been more than thirteen
quatrillion times bigger than the sun. I hasten to add that
these calculations are absurd and devoid of significance as, if
the culture is not periodically divided in two, the growth of
volume brings about its death in a few days. Owing to the
fact that there is no circulating system, the interior cells are
not nourished and cannot eliminate the toxic products result-
ing from the reactions which they engender. They therefore
die, and in doing so liberate poisons which accelerate the death
of the other cells. The culture can persist only in very thin
layers or in very small fragments where all the exchanges can
take place on the surface.

Nevertheless it is possible to experiment indefinitely on the
same family of cells proceeding from the same strain. A much
greater precision is possible than when operating im wivo
because of the elimination of innumerable causes of error due
to the individual characteristics of animals of different origin.
We have already mentioned these advantages in the first
chapter, but they are not the only ones inherent to this method.

To preserve these tissues in a state of activity they must be
divided at short intervals of time, viz. every other day. Two
cultures rigorously identical from a biological point of view
are therefore available instead of one. Consequently, for each

TISSUE-CULTURE IN VITRO I0§

experiment and for every stage of the experiment, one obtains
every second day a control which in turn will be the originator
of a new family of cultures, the biological, chemical, and
physical properties of which can be compared at any ulterior
date with those of the cultures issued from the fragment sub-
mitted to experimentation. It is thus possible during a series
of experiments lasting several months and bringing about
hereditary modifications of the cells Gmmunity, for instance),
to compare cultures proceeding from successive stages of the
experiment. The reader is aware that for the majority of
biological experiments it is necessary to have one or two
controls on which no experiment has been made. This
enables one, by comparison, to appreciate the results obtained.
But two animals are never identical, whereas the two parts of
a same culture are as identical as possible.

This is not all. To study the characteristics and properties
of certain species of microbes it is necessary to dispose of pure
cultures; that is to say, cultures composed of one kind of
microbe excluding every other micro-organism. It is quite
evident that, when there is a mixture of different microbes, it
is impossible to define the function of each species in the
lesions and accidents determined on an animal by the culture.
Science has no use for anonymity. Its aim, on the contrary,
is to discover responsibilities. It would also be impossible to
prepare preventive vaccine or curative sera against one of
these organisms; in other words, we could not manufacture
‘specific’ vaccines or sera.

This is equally true of tissue-cultures. To be able to study
the cytological and physiological characteristics of a certain
species of cells, it is necessary to obtain pure cultures. First,
Carrel and then, under his direct guidance, Albert Fischer of
Copenhagen, Albert H. Ebeling, Raymond Parker, and one or
two others have succeeded in isolating absolutely pure strains
of fibroblasts (conjunctive cells), osteoblasts (bone-producing
cells), cartilage, epithelium, cancer cells, leucocytes, etc.
These strains are generally capable of living indefinitely zn
vitro while reproducing and conserving all their specific

106 CICATRIZATION OF WOUNDS

characteristics. This fundamental discovery was not accepted
without a struggle by certain biologists, particularly in France.
A few scientists pretended that it was impossible, simply
because their own imperfect techniques had prevented them
from succeeding. These facts, however, are now classical and
no longer discussed by any one.

I have spoken of ‘technique’. It will be necessary to say a
few words on the subject so as to enable the reader to follow
the mechanism of the experiments on ageing which will be
described farther on and which established the link between
the experiments on cicatrization and those on tissue-cultures.

The subject of tissue-culture techniques is vast enough to
fill a voluminous book written by Fischer, and I shall therefore
make a very brief summary. The principle is simple. It
consists in cutting out a fragment of living flesh and incor-
porating it to a medium capable of sustaining and nourishing
it. The products of excretion are eliminated by washing every
other day and the cultures, divided in two equal parts by
cutting with a sharp knife, are then transplanted separately
into a new medium. One of them serves as control. The
cultures are naturally maintained at the temperature which is
normal for the animal from which they proceed (about 38° C.
or 100° to 103° F. for chicken embryos).

Realization is less simple. Indeed, as I have already stated,
the most important thing was first to find the nutritive medium
capable of indefinitely prolonging the life of the cells. Carrel’s
idea of using embryonic juice was a stroke of genius and laid
the foundation of the whole method. The ‘Juice’ is obtained
by mincing eight-day-old chicken embryos. To this end,
fecundated eggs are maintained in an incubator and, after
eight days, are brought into the operating room, which must
be as dust-free as possible. The operator, masked and in a
sterile blouse, breaks the shell after having washed and
sterilized it, and extracts the embryo which he cuts into small
pieces. These pieces are then crushed (in a ‘Latapie’ crusher,
for instance) and form a kind of pulp which is mixed with a
complex, rigorously balanced saline solution. This mixture

LISSUE-CULTURE IN VITRO 107

centrifuged and decanted is the ‘embryo juice’. No one so far
has ever been able to replace it by any synthetic medium.
This product is now also employed medically to avert surgical
shocks.

Needless to say, these operations must all be accomplished
with infinite aseptic precautions, far greater than for a surgical
operation. The preparation of the saline solutions (Tyrode
and Ringer solutions) also demands great care. The sub-
stances employed must be rigorously pure and the degree of
alkalinity (measured by the concentration in hydrogen ions
expressed by the symbol pH) is controlled electrically or
colorimetrically. In addition to the ‘juice’ there is also the
‘support’ which is composed of a drop of coagulated chicken
plasma. (We remind the reader that the blood is composed of
red and white blood-cells suspended in a liquid called the
plasma, which coagulates under different influences.) The
culture, one or two square millimetres in size, is placed in this
drop or on its surface, according to the nature of the cells to
be cultivated. The blood is taken from a young and healthy
chicken by means of a sterile operation made under anaes-
thesia. The blood-cells are separated from the plasma by
centrifugation in tubes previously paraffined and cooled at
O° C. so as to prevent coagulation.

When these elements have been prepared, all that remains
to be done is to take an incubated egg, about nine or ten days
old, remove the embryo, dissect the heart, or any other part
of the animal, cut out a certain number of small pieces without
tearing them and incorporate them on a thin slide into a drop
of plasma mixed with a drop of embryo juice. The mica is
then covered by a thick glass slide hollowed out in the middle,
sealed with hot paraffin, and put into an incubator at 38° C.
Forty-eight hours later, the fragments are extracted and cut
with a cataract knife, the blade of which is only three milli-
metres long. They are then washed in Tyrode solution and
quickly replanted into a new nutritive drop before the latter
has had time to coagulate. This is done every two or three
days according to the nature of the tissue. The small pieces

108 CICATRIZATION OF WOUNDS

of heart, rapidly surrounded by a transparent and fragile circle
of new cells, often continue to beat during two or three weeks,
sometimes longer. They can be seen through the microscope,
contracting spasmodically, and nothing is more impressive
than to observe this fundamental and marvellous mechanism
which is still so mysterious. This famous experiment gave
rise to the legend of the ‘ever-beating heart’. But there is no
example of these heart fragments having beaten for more than
three months. A month is already a limit rarely attained.
The beats become more and more distant as the culture ages,
and generally last only from fifteen to twenty days. The con-
tracting muscular cells are progressively replaced in the culture
by inert cells of conjunctive tissue, the fibroblasts, whose
reproductive energy is greater and which finally reign alone. It
must not be forgotten that at the end of fifteen days the initial
fragment has been cut seven times and that after cach division
it has reconstituted itself mainly with fibroblasts. At the end
of a fortnight, the beats are already much weaker and some-
times only perceptible every ten seconds. They often cease
altogether when the culture is examined under the microscope,
and the temperature must be raised—for instance, by placing
the whole microscope in a small incubator—in order to see
them reappear.

Tissue-culture is neither simple nor easy if one wishes to
maintain pure strains in good health for any length of time.
The technique has been so marvellously perfected by Carrel
that it is easy to keep them alive during two or three weeks.
The difficulties come later, and it requires a long experience
to be able to prolong their existence beyond three months. It
even seems as if the difficulties increased with age. This
explains the fact that the only laboratory where cultures have
been kept alive for twenty-four years is that of Dr. Carrel,
which is splendidly organized and has several ‘culture doctors’.

For cultures, like human beings, often have slight illnesses.
These must be known and the consequences attenuated or
annulled. A fatty degeneration shown by the apparition of
small refractive globules, or a variation in structure, is an

PISSUE-CULTURE/IN .ViTRO I09

indication that the diet must be momentarily changed and the
concentration of the ‘juice’ modified. The cultures are some-
times even submitted to a period of fasting. The treatment to
be applied differs according to the case, and there are no
precise rules. Everything depends on the experience and
‘clinical’ sense of the operator.

The material organization of a laboratory for tissue-culture
is not very complicated. The difficulties which arise can gener-
ally be traced to the lack of rigorous care that must be given
to the slightest detail and the long experience that is necessary
to keep them in good health.

The development of this science depends entirely on the
possibility of maintaining the principal types of cells in a state
of pure cultures. Carrel has demonstrated that this is
possible. The study of these cultures has revealed that each
cellular type is characterized not only by its morphological
aspect but also by an aggregate of special physiological proper-
ties. These properties remained unknown up till now because
they were hidden by the tremendous complexity of the pheno-
mena which take place in the organism. It is impossible to
know the physiological state of the cells and, consequently,
the significance of what is observed, if cells taken from a
living animal or an impure culture (mixture of cells of different
species) are studied by means of the old techniques as was done
and is still done by certain workers. It is only by means of
colonies composed of a single-cell type, placed in flasks con-
taining a medium of known composition, and manifesting a
measurable form of activity, that it becomes possible to
establish a relation between the morphological state (as seen
under the microscope) and the functiorial state of the cells.

The culture of tissues has already considerably increased
our knowledge of cell physiology, and we are only at the
beginning. For in spite of the fact that this method is already
fairly old, there are few scientific centres where it is employed.
This is due to the difficulties mentioned above, to the expense
involved, and to the fact that, to be fruitful, it requires real
talent, great manual dexterity, patience, and imagination.

IIo CICATRIZATION OF WOUNDS

However, it will certainly be fruitful in the hands of the new
generation of biologists.

Besides the fundamental classical problems which can be
attacked, this method will certainly reveal, and has already
revealed, new problems which otherwise might always have
remained ignored. I shall illustrate this statement by two
suggestive examples.

We have seen that the fragments of muscular tissue, removed
from the heart of a chicken embryo, frequently continue to
beat in the culture. Fisher made the following remarkable
experiment.

If two palpitating fragments, proceeding from the same
heart, are put next to each other, but without touching, one
usually observes that their rhythm is not identical. One frag-
ment beats eighty times a minute, for instance, the other fifty.
If it so happens, which is rare, that their pulsations are identi-
cal, they are nevertheless not synchronous. But these frag-
ments proliferate and gradually surround themselves with a
circle of new cells which penetrate into the medium in the
shape of a thin, translucid, living layer. After a certain length
of time these membranes issued from the two fragments come
into contact. At that very moment, the rhythm becomes
identical. The synchronism is re-established; the two frag-
ments beat as one.

The bird has been long dead; the small pieces of muscle
separated from its heart have neither blood circulation nor a
nervous system connected to a main trunk, and yet they seem
to recognize each other as soon as they come in contact. They
persist in accomplishing the work for which their cells were
created, not in a haphazard independent fashion but together
and co-ordinately. Needless to say, there is not the beginning
of an explanation for this curious phenomenon.

Another example: a single isolated celi does not proliferate
by mitosis. It cannot reproduce and dies without offspring,
even though it appears to be identically in the same conditions
as the healthy culture from which it has been separated and
the ceils of which proliferate rapidly. Cellular growth and

TISSUE=CULTURE IN VITRO III

multiplication requires the presence of a certain number of
cells in the same medium. Everything occurs, in brief, as if
certain substances secreted by the cells were required to set
free the mechanism of proliferation of the other cells. In
other words, they have to be fecundated. What are these sub-
stances; what is the mechanism? Can it in some way be com-
pared to a particular form of sexuality, or is this phenomenon
connected with the oxidation-reduction potential of the
medium? All these problems are still very mysterious.

We have insisted on the necessity of employing pure cul-
tures, composed of a single type of cell. This is a capital point,
but also the most delicate of the method. Its importance was
not fully realized by many workers who at the start were filled
with enthusiasm by the possibilities which they foresaw. Some
of them, when they finally understood, were soon discouraged
by the meticulous care, the patience, the time, and the techni-
cal equipment required to conduct successfully constructive
experiments. The tissue-culture laboratory at the Rockefeller
Institute comprises about fifteen people: experimenters,
assistants, women technicians, and orderlies.

Even though certain species of cells can now be isolated by
well-established techniques, there are other varieties which
have only been isolated once or twice, thanks to a sequence of
circumstances not always reproducible. One or more factors
remain undetermined. The general method of selection con-
sists in finding culture media of such composition that they
will favour the proliferation of the cells which are to be isolated
whilst discouraging the others. Small variations in the con-
centration of the embryonic juice, addition of blood-serum,
and modification in the rhythm of the transplantations are
amongst the principal means employed. But there are others,
depending on the nature of the cells. Epithelial cells, for
instance, live only on condition that they are placed at the
surface of the coagulated plasma drop. Naturally it is im-
portant to obtain the fragments of tissue from the embryo in
as pure a state as possible. This is not always easy. The
dissection of a thyroid gland on an eight- or ten-day embryo

TI2 CICATRIZATION OF WOUNDS

does not always succeed. It is not exactly child’s play to
dissect the eye of an embryo in order to secure the pigmented
epithelium which surrounds the iris.

Experiments can be conducted only with cultures at least
three months old. At that age they constitute relatively
homogeneous units. They can then be submitted to different
diets so as to permit the study of either their morphological
modifications, their physiological reactions, or alterations in
their general behaviour and mobility.

These modifications can be reversible as, for instance, altera-
tions of the structures or dimensions of the cells and of their
elements, or irreversible, such as the transformation of one
type of cell into another. Certain cells develop only in groups
and form tissues (fibroblasts, epithelium, etc.). Others, on
the contrary, are independent, and manifest a certain individual
activity. Leucocytes (white cells) and macrophages are in this
category. The latter are found almost everywhere in the
organism. In blood, in lymph, in bone marrow, in conjunctive
tissue. When cultivated in plasma, macrophages transform
themselves into large cells surrounded by an undulating mem-
brane. The addition of certain substances such as amino-
peptones, organic enzymes, brings about the disappearance of
these membranes and the transformation of the mobile cells
into fixed cells. But these changes are reversible. The mem-
branes reappear after a few days in an appropriate medium.
On the contrary, when the cells of a culture of macrophages
are transformed into fibroblasts by the addition of an extract
of Rous sarcoma (spontaneous chicken cancer) the change is
irreversible. The same is true of fibroblasts treated with
plasma containing heparin (heparin is a substance which
keeps plasma from coagulating). The fibroblasts turn into
macrophages, acquire all the physiological properties of the
latter—mobility and the power of phagocytosis—and conserve
them.

A culture does not completely cease growing when it is
made to fast. Its life is, however, very much slowed down, as
was shown by Fischer. The conditions resemble much more

LISSUE-CULTURE IN: VITRO II3

the normal conditions in the organism. But its activity
manifests itself in other ways. The cells function physiologi-
cally. Instead of proliferating rapidly they accomplish the
tasks which they fill in the organism and begin to secrete the
substances which they produce normally. In my laboratory
at the Pasteur Institute where a pure liver-culture had been
isolated (Doljansky) it had been noticed that the well-fed cells
no longer manufactured ‘glycogene’, a substance which
transforms itself into sugar (glucose) and is one of the most
important products normally elaborated by this organ. When,
however, the culture had been submitted to a reduced diet
by the suppression of the embryo juice, the glycogenic func-
tions started working again exactly as in the organism. The
same phenomenon was observed with the pigment cells of
the iris. When too well nourished, the cells proliferate
abundantly but without producing any pigment or colouring
matter. When dieted, they cease growing in number, but
secrete the black pigment which characterizes them in vivo.

It is evident that this method is particularly adapted to the
study of cancer. It suffices to compare pure cultures pro-
ceeding from malignant cells to cells of the same type but
devoid of malignancy. It was thus soon ascertained that
macrophages proceeding from Rous sarcoma are unhealthy
abnormal cells which degenerate rapidly and do not live long.
They require the same nourishment as normal macrophages,
but unlike the latter they actively digest the coagulum. The
fibroblasts proceeding from another tumour, the ‘Crocker no.
10’ are, on the other hand, strong and healthy, require the same
nourishment as normal fibroblasts, but also digest the coagulum.
Epithelial cells from the Ehrlich carcinoma are unhealthy and
delicate cells like those of the Rous sarcoma. They /zkewise
digest the coagulum.

Other types of malignant cells have been studied, and it
was found that no matter how divergent they are on certain
points they all have properties in common, such as this faculty
of digesting and liquefying the solid part of the coagulum, the
fibrin. Furthermore, they can assimilate substances which do

I14 CICATRIZATION OF WOUNDS

not nourish normal cells. It is therefore possible to conclude,
as does Dr. Carrel, that cancerous cells acquire their malig-
nancy im vivo because of their faculty of manufacturing
nutritive substances from the surrounding tissues and fluids.
This enables them to proliferate in an unlimited fashion.
The mutability of certain types of cells, which we spoke of
above, takes on all its importance at this point. Malignant
cultures are varieties of normal types from which they differ
only slightly through certain properties. These differences
are not qualitative but quantitative and irreversible. After
several years of culture zm vitro they have not regressed to the
original type. They are fixed varieties.

The hypothesis of the microbic nature of cancer has been
definitely abandoned as a result of these experiments and of
many others which it would take too long to describe in
detail. Unfortunately, the knowledge thus obtained has not
yet resulted in any practical progress towards the eradication
of this scourge. But these researches have only started and
every hope is permissible.

The almost unlimited applications of this method are easy
to conceive. Thanks to it we can study the problems of
immunity. A tissue behaves like an organism and reacts
against the poisoning due to the toxic substances carried by
microbes by manufacturing the specific antidote substances
called antibodies. From a practical point of view, Carrel and
Rivers succeeded in cultivating smallpox vaccine by inocu-
lating it to cultures of cornea, skin, and embryonic tissue.
The virus multiplies rapidly, and it is probable that a chicken
embryo reduced to a fine pulp can produce as much vaccine
as a calf.

The reader had to have precise notions on tissue-culture in
general so as to be able to follow the development of the
technique employed in checking the method of quantitative
study of cicatrization expounded in the preceding chapters.
That is why I have kept this problem for the end.

Dr. Carrel was induced to study these problems by former
experiments on the ageing of animals. These experiments

TISSUE~CULTURE IN VITRO Ils

had led him to admit that with age blood-serum accumulates
toxines which are increasingly noxious or abundant. He had
convinced himself of this fact by a series of experiments.
One of these is particularly striking and deserves to be men-
tioned, especially as it was never published.

There was at the Rockefeller Institute, before the war, a
dog nearly eighteen years old. This poor animal never stirred
from its corner and could hardly get up to eat. He slept all
day, his coat was coming out, his eyes were dim, and his
eyelids stuck together.

This animal was anaesthetized, put on the operating table
and treated as follows. Carrel bled him by the carotid
artery and removed nearly two-thirds of his blood. This
blood was collected aseptically and immediately centrifuged,
sO as to separate the red cells from the serum. The red cells
were washed in Ringer solution, recentrifuged and mixed
with fresh Ringer solution to re-establish the initial volume of
the blood. This was then re-injected to the dog. The cir-
culation was restored by massaging the heart, and the skin
was sewn up. A prince of royal blood, heir to the throne, on
whom the peace of the world depended, could not have been
the object of more attentive care than this old animal. After
several days he had regained strength and appetite. The
same operation was repeated so as to eliminate practically all
the serum of his blood and replace it by this artificial solution
which, besides the blood cells, contained only salts such as
chlorides of sodium, potassium, and calcium in the same
proportion as those found in the blood. The animal lived.
Not only did he live, but, once over the operative shock, he
was a different dog. He ran and barked, a thing he had not
done for years. His eyes were clear, his eyelids normal. His
coat started to come in; he was gay, active, and most important
of all, he was no longer indifferent to the charms of the other
sex. He was regenerated.

The logical conclusion which Carrel deduced from this re-
markable experiment was that his hypothesis on the increase of
toxicity of serum with age was verified, and that the symptoms

116 CICATRIZATION OF WOUNDS

of senescence are the expression of profound physico-
chemical and chemical changes occurring in the organism
through the influence of time. When the war was over and
he had come back to New York he decided to prove this
point.

The first experiments simply consisted in cultivating the
conjunctive tissue of chick embryo in plasma taken from
chickens of different ages. He ascertained that growth was
more active in the plasma of young animals than in that of
old ones. This fact demonstrated the possibility of employing
fibroblast cultures to put in evidence the modifications
introduced into the serum by age. The technique was then
improved so as to eliminate the most palpable causes of error
and to obtain quantitative values.1 Experiments were per-
formed in the following way: an equal quantity of serum
taken from six-week to nine-year-old chickens was added to
the culture medium. It was observed that the growth of the
cultures was hardly or not at all affected by the serum of a
chick six weeks old. Growth was retarded, however, by the
addition of serum removed from older animals, and all the
more so the older the animal was. Furthermore, under well-
determined conditions, the span of life of a culture was
affected in the same way. That is to say that, if a culture
lived four or six days in the plasma of a nine-year-old cock,
it would live forty-six days or more in that of a chick six
weeks old. The rate of growth is modified in a similar
fashion, and decreases as a function of the age of the animal
from which the serum proceeds.

Through further experiments Carrel convinced himself
that this retardation was not due to the neutralization of
accelerating substances but to the accumulation of toxic
products. The curves shown in Figs. 24 and 25 were ob-
tained by taking arbitrarily as base (100 per cent) the rate
attained when employing the plasma of three-month-old
chickens. This was the age of the animals which furnished

1 A. Carrel and A. H. Ebeling, Fourn. of Exp. Medicine, vol. 34,
Pp. 599 (1921).

TISSUE-CULTURE IN VITRO ti

the plasma in the ordinary technique, and it was therefore of
interest to use it. These curves express in percentage the
part played by age in the duration of life and in the activity
of proliferation.

It can be seen that the drop is much more rapid in the

120
“Se cea ES a
ooalmonng | | | | | | tt
eee Ope ARS a)
EA Be
eR adi Oa a
cy RN aN RW
oe SO 2 a
oo a ss
50 = Ue
20 ES oe SR
1” SoaemenR a
iO SP a)

Pe 9 OIG Fl di Oo Yeats

FIG. 24. DURATION OF LIFE ‘IN VITRO’ OF FIBROBLASTS AS A FUNCTION
OF THE AGE OF THE ANIMALS FROM WHICH THE PLASMA WAS TAKEN

first years and especially in the first months. This indicates
that the inhibiting power of the plasma increases much more
rapidly at the beginning than at the end of life, and tends
towards a constant value. If these curves are now compared
with that of Fig. 26 representing the variations of the index
of cicatrization studied previously, it is obvious that a striking
similarity exists between them. This last curve represents the
evolution of z for a wound of 40 sq. cm.

The growth index which can be deduced from Carrel’s expert-
ments is therefore closely related to the index of cicatrization.
Both these indices are a measure of the irreversible trans-
formations progressively introduced into an organism by age.

118 CICATRIZATION OF WOUNDS

A certain relationship on general lines could evidently be
foreseen a priori. But nothing authorized the prediction that
the differences due to age would be more important at the
beginning than at the end of life. In other words, it was in
no way evident that the plasma of an animal would reflect

Average relative increase

ie

SeauRenee. °

AEC BI Rl
LBP 4G 6 7 om oye

FIG. 25. RATE OF GROWTH OF FIBROBLASTS AS A FUNCTION OF THE
AGE OF THE ANIMALS FROM WHICH THE SERUM WAS TAKEN

so exactly the complex variations due to the ageing of a
human being.

It is true that many of the characteristics of cicatrization
can be found in tissue-cultures. For instance, the considerable
acceleration of cellular proliferation brought about by a lesion.
Fischer put this phenomenon in evidence by placing cultures
under such conditions that their rate of growth became very

HLISSUE-CULTURE IN (\ViTRO II9

slow and that they could be maintained for several days
without transplanting. Hecutoutasmallsquare on a relatively
large culture the proliferating activity of which was very
slow. The proliferation immediately became very active
around the wound, which healed rapidly. This proliferation

ae ee
0.09 Wound 40!sqcm
aotted cur
extrp polaté
008
oe ae a
0.06 ue ard
0.05 ie
04
0.03
0.028
0.01

FIG. 26. INDEX OF CICATRIZATION AS A FUNCTION OF
THE AGE OF THE PATIENT

ceased as soon as cicatrization was complete. In short, there
is an almost absolute identity with the biological phenomenon
of cicatrization 7 vivo, and we are faced with the same
problems. How is this proliferation started and how is it
stopped? This is a most important point, for it is one of the

120 CICATRIZATION OF WOUNDS

differences between healthy and cancerous tissues. In a
cancerous tissue the cells do not receive the order to stop,
or if they receive it, they are incapable of obeying.

Thus, we are in possession of two methods enabling us to
study age and the process of ageing. The first im vivo, by
means of a complete organism, manifesting differences in the
rate of reparation at different periods of its evolution. The
second zm vitro, by means of a living reagent which is eternal
in comparison with the short duration of our existence and
the activity of which is checked proportionally to the toxic
power developed in the serum of a normal animal by the simple
fact that it undergoes the limited evolutive cycle due to its rank
in the hierarchy of organized beings. In the first case we
observe the result of the accumulation of toxins and of
other unknown phenomena on an organism whose entire vital
activity is governed by the immutable cycle characterizing
our human condition. In the second and much simpler case,
we dispose of a living element, artificially removed from the
periodical evolution necessary to all organized beings and of
which only the constituent parts—the cells—eventually obey
the universal law of ageing and death. The tissue-culture
does not age and does not die, barring accidents. It has no
consciousness comparable to ours. It has no ‘individual’ exist-
ence, and only represents the summation of an infinity of
elementary lives. From this angle it is comparable to a species
rather than to an individual, for the species persists with all its
characteristics and without taking into account the death of its
members.* And yet if a culture is treated with normal serum
from an animal of the same species, its activity is reduced to a
value corresponding to the age of this animal. The flow of time
has therefore not had the same action on the culture as on the
chicken. It affects the first no more than it would an inert
body, whereas it inevitably sweeps the bird to its death in
obedience to a millennial rhythm. Not only does it affect an
organized being from birth, but the rate of ageing is different

TISSUE-CULTURE IN VITRO IZ}

at the beginning and at the end of life and much more rapid
during youth.

Consequently, there are two kinds of time. One corre-
sponding to the classical notion, the sideral, physical time,
without beginning and without end, flowing in a continuous,
uniform, rigid fashion. The other, the physiological time, the
duration of our organism, which begins and ends with us,
and which does not affect identically in our youth and our old
age the phenomena of which we are the seat. It is a time which
remembers. It is no longer the impersonal, rigorous time
measured by the rotation of the earth, the immutable and
arithmetical time in which the universe evolves. Its flow
seems to be submitted to periodical fluctuations. It rebounds
with each germ: a living time.

But, on the whole, what is time? Is it not absurd to say that
it flows? Can we measure physiological time with the same
units as the other, the time of inert things? Are they really
differentiable? We will now try to study these questions
successively.

PART LI
TIME

CHAPTER VELI
TIME—DEFINITIONS—MEASUREMENTS

A GREAT deal has been said and written about time. When
speaking of it we have been obliged to employ current,
ordinary words coined for other purposes. This has resulted
in paradoxes, misunderstandings, and endless discussions.
The majority of words employed to define an object, a force,
cr a tendency, necessarily imply the notion of time, for they
evoke movements, relations, successions. The verb ‘to be’,
which is indispensable, implies the idea of existence, and the
idea of existence imposes the notion of time. All words are
therefore inadequate, for one can only define a thing accurately
by means of words which do not evoke ideas incorporating
the very thing which has to be defined.

We conceive space as something which surrounds us, and
time as something which flows beside us and through us.
These projections of our thought are at the same time logical
and illusory. Ideas on this subject have evolved, however.
We shall attempt to explain them.

There are notable analogies and also flagrant differences
between space and time. It is impossible to separate these
two concepts, for we constantly use one to measure the other.
A distance, that is to say, a dimension of space, has a mean-
ing only if a certain time is needed to cover it. Ifthe distance
which separates two points could be covered in null time, it
would be rigorously equivalent to a definition of a null distance
or to the superposition of two points, identical to one. The
very existence of matter is inseparable from time by the mere
fact that the word ‘existence’ has been pronounced. It ts
impossible to conceive a material object existing instantaneously.

The certitude that we have of finding it similar to itself
after a given time, be it ever so short, gives it what we call
its existence, its reality. Just as space marks the coexistence
of perceptions at one period of time—we measure the scope

125

126 TIME

of our domain—so time marks the progression of perceptions
to a position in space. The combination of these two modes
or change of position with change of time is motion, which is
the basic condition of our perception.

At first glance it seems, however, that there are certain
fundamental differences between space and time. For
instance, space, taken as a method of perceiving coexisting
objects, according to the idea developed amongst others by
Karl Pearson! and as a mode of perception enabling us to
distinguish groups of immediate sense-impressions, is asso-
ciated with the world of actual phenomena which we project
beyond us. For this reason it has been called a mode of
external perception.

On the other hand, time is the perception of sequence in
the accumulated sense-impressions. It is the relation between
past perceptions and present perceptions. Thus, time in its
essence, implies memory and thought, or in other words:
consciousness. In reality consciousness could be defined as
the power to perceive things separately in succession. From
this standpoint, time has been called an internal mode of
perception. This is in substance Bergson’s idea of duration
which we will take up again later. A moment’s reflection
soon shows, however, that this differentiation has no value, for
no distinction based on the words ‘external’ or ‘internal’ can
exist. Indeed, the perceptions of exterior objects can always
be traced back to the simple sense-impressions through which
we know these objects. It is therefore clear that the arbitrary
difference between the exterior and the interior of our ego is
nothing but a simple distinction of daily practical convention.

“Take a needle,’ says Pearson. ‘We say that it is thin,
bright, pointed and so forth. What are these properties
but a group of sense-impressions relating to form and
colour associated with conceptions drawn from past sense-
impressions? Their immediate source is the activity of
certain optic nerves. These sense-impressions form for us
‘ Pearson, Karl, The Grammar of Science, 3rd ed., 1911, London.

TIME 127

the reality of the needle. Nevertheless, they and the
resulting construct are projected outside ourselves, and
supposed to reside in an external thing “‘the needle”. Now,
by mischance we run the needle into our finger; another
nerve is excited and an unpleasant sense-impression, one
which we term painful, arises. This, on the other hand,
we term “in ourselves”, and do not project into the needle.
Yet the colour and form which constitute for us the needle
are just as much sense-impressions within us as the pain
produced by its prick. The distinction between ourselves
and the outside world is thus only an arbitrary, if a practi-
cally convenient, division between one type of sense-
impression and another. The group of sense-impressions
forming what I term myself is only a small subdivision of
the vast world of sense-impressions.’

Bergson disengaged very clearly the necessary but vague
notion of physical time from the more precise notion of duration
which had been perceived by other authors and the meaning
of which we summarized above. May I here cite a few sen-
tences borrowed from his book Durée et Simultanéité,! which
the reader might have difficulty in finding as the last edition
is exhausted.

‘How do we pass from this interior time to the time of
things? We perceive the material world, and this perception
seems to us, rightly, or wrongly, to be at the same time in
us and outside us. From one point of view, it is a state of
consciousness. From the other it is a superficial film of
matter in which the sentient and the sensed would coincide.
At every moment of our interior life corresponds a moment
of our body and of all surrounding matter which would be
simultaneous to it. This matter appears to participate in
our conscious duration. Gradually, we extend this duration
to the material world as a whole because we do not see any
reason for limiting it to the immediate neighbourhood of

1 Paris, Alcan, 5¢ édition, 1929.

128 TIME

our body. The universe seems to us to form a whole.
We think that if the part which surrounds us lasts in the
same manner as we do, the same must be true for that which
surrounds this first part, and so on indefinitely. Thus is
born the idea of a duration of the universe, that is to say,
of an impersonal consciousness which would be the con-
necting link between all the individual ones as well as
between these and the rest of nature... .

“Thus our duration and a certain felt and lived participa-
tion of our material environment to this interior duration,
are experimental facts. One cannot speak of a reality which
lasts without introducing consciousness. The metaphysician
will bring into play the direct intervention of a universal
consciousness. The common mortal will only think about
it vaguely. The mathematician will not need to take it
into consideration, for he is interested in the measurement
of things and not in their nature. But should he ask himself
what he measures, and fix his attention on time itself, he
would necessarily visualize succession, and in consequence
the before and the after, and therefore a bridge between
the two (otherwise there would only be one of the two,
a pure instantaneity). Now, we repeat once more, it 1s
impossible to imagine or to conceive a hyphen between the
before and the after, without an element of memory and,
consequently, of consciousness.

‘The use of this word may perhaps repel if an anthropo-
morphic meaning is attached to it. But to visualize a thing
which lasts, it is not necessary to transport into the interior
of the object one’s personal memory, even though attenuated.
No matter how much it is diminished in its intensity a
certain amount of the variety and richness of the interior
life would remain there and it would therefore conserve its
personal or, at any rate, human character. We should
consider one moment of the unrolling of the universe, that
is an instantaneity existing independently of all conscious-
ness, then try to evoke conjointly another moment as close
as possible to the first, and thus bring into the world a

TIME 129

minimum of time without allowing the faintest gleam of
memory to pass with it. Without an elementary memory
linking one instant to another there will only be one or the
other of the two, consequently, a unique instant, and no
before and after, no succession, no time. This elementary
memory can be reduced to only just what is needed to make
this link. It can be the link itself, a simple prolongation of
the before into the immediate after with a perpetually
renewed forgetfulness of what is not the immediate anterior
moment. Nevertheless, memory will have been introduced.
In truth it is impossible to distinguish between duration,
no matter how short, which separates two instants, and a
memory which binds them together, for duration is essen-
tially a continuation of what is no more in what is. This
is the true time, I mean the time perceived and lived. It
is also every kind of conceived time, for it is impossible to
conceive time without depicting it as perceived and lived.
Duration, then, implies consciousness, and we put conscious-
ness into things by the very fact that we attribute to them
a time which lasts.”?

One might almost say that these ideas of Bergson are
contained implicitly in Descarte’s phrase: ‘Je pense donc je
suis.’ (‘I think; hence I am.”)

Here we have the notion of universal time perfectly defined;
for, on the subject of knowing whether the universe is divisible
or not into worlds independent one from another, Bergson
adds: ‘. . . If the question had to be resolved we would choose
in the actual state of our knowledge, the hypothesis of a
material time, one and universal.’ .

But there is another difference between space and time
which appears to be fundamental. We can travel in every
direction in a three-dimensional space. We can, at will,
displace ourselves rapidly or slowly, stay motionless or even
come back on our footsteps. The same is not true of time.
Not only is it impossible to remain motionless, but one cannot

! Durée et Simultanéité, 5& édition, p. 60 and following.

130 TIME

travel backwards in it, and no one can boast of being able to
regulate its rate of flow. ‘It does not cease,’ says Sir James
Jeans, ‘to unfold itself at a uniform and uncontrollable rate
which is the same for each one of us.” What is the significance
of this difference between space and time?

It is probably solely due to a misunderstanding, to a faulty
symbolical representation of relatively clear notions.’ Indeed,
in effectuating any kind of a displacement, the first condition
to be fulfilled is to exist; in other words, if a conscious being
is concerned, to begin to register an evolution through memory.
The very distance which has to be covered exists only at the
moment when it is covered—no matter in which way, materially
or conceptually—and by the very fact that it is covered. It
may be objected that it suffices to conceive it for it to exist.
But a moment’s reflection shows that there is a gulf between
a concept and a reality. The proof being that we can easily
conceive or imagine things which we know to be impossible,
for instance, the cessation of the flow of time or its inverted
flow. The important thing for us is reality. It may also be
objected that to separate two points A and B in space, it
suffices to see a distance without having to cover it ourselves.
But our notion of distance between A and B, no matter how
short it is, implies that it exists in time, and it exists for us
only from the moment when we have seen it. Hence I take the
word ‘cover’ in the very broad sense of perceiving, for the
simple fact of perceiving two points even simultaneously,
implies that it would take a certain time to go from one to
another. No distance exists, and naturally no displacement
can be executed outside of time. We have points of reference
in space, systems of reference such as the three axes of
co-ordinates, for instance, thanks to which we know that we

1] have already spoken of the fact that we are forced to employ
words that have been coined for our current thoughts and daily life.
This makes it very difficult to express relations which we seize
intuitively and which we must translate in a language necessarily
inadequate. It is certain that a great number of discussions and
divergencies of opinion are due to this state of things. It is as if one
tried to construct a flower with a puzzle representing a locomotive.

TIME 131

are going in a certain direction or coming back on our steps.
There is nothing similar in time. Time is the very condition
of the existence of the three directions of space, which, we
repeat, begin to exist for us only from the moment we see
them. If we cover a distance in a certain direction, stop and
then come back on our footsteps, we have in all evidence
evolved in time. But time, which is concreted by the succes-
sion of our states of consciousness, cannot distinguish between
the different directions which we have taken. We say that it
has been simply unrolled, and we mean by this that we have
lasted. It is therefore absurd to try to compare time and
space, for space has no significance for us outside of time. It is
as absurd as trying to compare the wavelength 0-589 » to
yellow light. The colour or impression which we translate
by the word ‘yellow’ and which has a very definite meaning
for us, exists only if an electromagnetic radiation of a wave-
length equal to 0-589 u is intercepted on its path by a human
eye. The same is true of a rainbow, so clearly seen and which
we carry with us in the rain. In reality it exists, as we see it,
only at the back of our eye. We carry our time with us, and
it is through its intermediary that we construct universe and
space. A traveller in time, in a remarkable story by H. G.
Wells says: ‘There is no difference between Time and any of
the three dimensions of Space, except that our consciousness
moves along it.’ (The Time Machine.) In citing this phrase
Silberstein,’ one of the first commentators on the theory of
relativity, stated that Wells had thus marvellously anticipated
this theory.

The preceding lines have been written with the aim of
preparing the reader to accept the modern conception
deduced by Minkowski from the first works of Einstein. This
concept is based on altogether different reasoning, but also re-
sults in the intimate fusion of time and space. Itis admitted that
matter is electric in its structure, so that all physical and chem-
ical phenomena are, in the last resort, electrical phenomena.
Minkowski demonstrated that the theory of relativity requires

' Silberstein, The Theory of Relativity. London, 1914, p. 134.

132 TIME

that all electric phenomena be considered as taking place, not
in separate time and space, as had been thought so far, but in
a space and time welded together so intimately that, following
Sir James Jeans’ expression, it is impossible to separate space
from time in any absolute manner. None of the phenomena
of nature is capable of dissociating the result into a separate
space and time.

There is nothing in this statement to astonish the reader if
he has followed the preceding paragraphs. On the contrary,
a different conclusion would surprise him if he has thoroughly
grasped Bergson’s and Pearson’s notion of duration in which
consciousness necessarily intervenes, and also the simple
elementary fact that nothing can exist instantaneously, seeing
that the verb ‘to exist’ in itself implies the notion of time.
If the reader is thoroughly impregnated by these purely
logical ideas, he will not be able to conceive how it is possible
to think otherwise. As a result, the notion of time as a fourth
dimension not of space, as has often erroneously been said,
but of the universe, imposes itself as being not only plausible
but necessary.?

I must say that I cannot see any difficulty in conceiving
what Minkowski calls ‘the four-dimensional continuum’. The
perusal of works such as those of Eddington, Jeans, and
Bergson’s Durée et Simultanéité, give the impression that it
requires a kind of intellectual feat.

‘It is difficult to imagine a new dimension if one starts ©
from three-dimensional space,’ writes Bergson, ‘seeing that

experience does not show us a fourth one... .’
‘It is difficult enough to imagine the four-dimensional
continuum. . . .” writes Sir James Jeans.

I wonder if this is not another snare set for us by ‘words’.
In other terms is it not principally the word ‘dimension’
which makes things difficult? For if we persist in trying to
imagine a supernumerary dimension of space we cannot help
considering it as being of the same order, of the same nature

‘In the Encyclopedia of 1754, d’Alembert had foreseen this con-
ception, or more exactly had mentioned ‘a clever man of his acquain-
tance who believes that time could be considered as a fourth dimension’.

TIME 133

as the others: it bears the same name. Now, if the three
dimensions are necessary for the conception of all the directions
in space, they are also sufficient to account for our material
universe, and there is no place for the intruder in the familiar
trihedron of Euclidean space. As the dimensions of space
are schematized by three straight lines converging rectangularly
the layman tries to figure the ‘fourth’ in spite of himself as
another ‘direction’. At any rate this is the impression I
received when talking to most people. And this notion is
absolutely erroneous. The fourth dimension, as stated above,
only represents the existence of the three others, the existence
of the trihedron or any other system of reference. It simply
indicates the birth in our consciousness of the notion of the
three-dimensional space. The history of material points,
whether stationary or not, in the system of reference deter-
mined by our three rectangular co-ordinates begins the moment
this birth has taken place. The phenomena have a point of
departure; they evolve; our senses and our memory register
them and draw conclusions and laws from them. They are
alive for us. Suppress time and nothing remains. The
antithesis can be found in Herodotus: ‘Let time be lavished
and all that is possible will come to pass.’ The theory of
probability gives this sentence a profound meaning.
Minkowski’s own words: ‘Space and time considered in
themselves and individually must henceforth retire into the
shade, and only a kind of combination of the two must keep
a certain reality’, do not sufficiently bring out the fact that
all reality 1s the direct consequence of the conjugation of space
and time. The physicist does not have the same difficulty in
conceiving the fourth dimension, perhaps because of the
habit he has of giving a much broader meaning to the word
‘dimension’. He reduces the quantities which he measures
to three units: centimetre, gram, second, with which he can
describe his universe. But the C.G.S. system comprises
precisely the four dimensions and, in addition, a more complex
dimension of mass. The physicist brings the most diverse
magnitudes back to these three basic units and establishes

134 TIME

dimensional formulae in which the fundamental dimensions
are fused into a single magnitude endowed with different
material properties. For example, he expresses the unit of
volume by L’, seeing that the measurement of a volume is
obtained by multiplying three lengths one by the other. For
the unit, these lengths are equal and give Lx Lx L=L?.
He likewise expresses the unit of velocity by Aor LT—*, since
velocity is length divided by time. Acceleration, which is
the quotient of velocity by time becomes LT”. But with the
same symbols he can write the formulae of very complex
units such as that of quantity of electricity: L?M?T-! of
potential difference: L?M?T-? of magnetic moment L?M?T-!
or simply that of work or of moment of force: L?MT~?.
Absolute notions, such as that of energy, are naturally beyond
the scope of these definitions. Thus, the physicist, accustomed
as he is to juggling with various dimensions, escapes the tempta-
tion of comparing them to each other except to bring them back
to conventional units. For instance, he will say that a
magnitude ‘has the dimensions of a velocity’. This is a steno-
graphic expression which simply means that time enters into
the formula as a denominator. If he speaks of ‘the dimensions
of an acceleration’ it means that time is to be found as a
denominator but at the power 2.

Though everybody is aware of the fact that in order to
measure time one must resort to the displacement of an object
in space, we will develop this subject a little further. If we
perceived only two dimensions instead of three, it would be
almost impossible to assure oneself that time flows uniformly.
Indeed, let us suppose that a distant mobile body travels along
a path in the plane of our vision. Let us suppose, for example,
that we are examining the movement of a body on the earth
from a great height, say from the moon. If this body—a marble,
for instance—covers equal distances in equal times, we cannot
infer that its movement is uniform, for by definition, we have
no means of knowing if the ground on which the marble

DEFINITIONS 135

rolls is rigorously plane. Should this not be the case, if there
are hollows and bumps, ascents and descents, we cannot
speak of equal distances as we do not know the value of the
angles of the route in the plane of observation. A yardstick
appears to be only 3-6 inches long if looked at from a certain
angle. In this case, if an ant takes two minutes to go from
one end to another of this yardstick we will be under the
impression that it has taken two minutes to cover 3-6 inches,
that is at a rate ten times slower than the reality. Let us take
another illustration. An observer on the moon seeing a scenic
railway on earth as a simple railroad could not explain the
variations of speed observed even if the cars were propelled
by a motor imparting a uniform velocity to them. He can
only see the projection of the undulated track on the ground,
the trace of his plane of vision. In order to detect the undula-
tions he would have to look sidewise, namely to move in the
third dimension. One can conceive that it would be easy to
give this observer the impression that the speed is uniform
by imparting to the wagon, by means of a motor, such speeds
as to make up for the apparent slowing up due to the descents
and ascents. The three dimensions are thus necessary to
allow the measurement of time just as time is necessary for
the perception of dimensions; that is to say, of matter.

I trust that the notion of the ‘four-dimensional continuum’
is now clear in the mind of the reader. In all the formulae
of Relativity the fourth dimension is not expressed by the
symbol of time, z, but by another, proportional to it, obtained
by multiplying t, for practical reasons which I cannot explain
here, by the square root of —1 (ct\/-1); that is by the symbol
of the ‘imaginary’ numbers.! ;

If the idea of the four-dimensional continuum, our universe,

1 The symbol t introduced by Minkowski does not express time in
current units, that is to say, in seconds, but in units represented by
the reciprocal of the velocity of light. —These mathematical expedients,
by which it was. possible to materialize Minkowski’s conception, have
given it all its value. We are reminded by Houllevigue (Revue de
Paris, April 15th 1935) that Pfliger when mentioning this discovery
said, ‘One must be a mathematician to appreciate fully the aesthetic
joy given by this conception.’

136 TIME

is clear, that of a deformed continuum is less so. And yet the
general theory of Relativity explains gravitation by a deforma-
tion of the continuum. The existence of a ‘force’ which acts
in inverse ratio to the square root of the distance and deflects
the normally rectilinear course of bodies in space, is admitted
in the classical theory of Newton. But the theory of Relativity
does not accept mysterious ‘unknowable’ forces.1 The
formulae which define its continuum, based, it is true, on a
certain number of undemonstrated postulates, must explain
everything. From the relativistic point of view, the criticism
of Newton’s theory can be summarily expressed in the follow-
ing fashion. This theory is based on a hypothetical motion
never observed by any one: the straight-line motion, arbitrarily
named natural motion. To explain all natural motions we
have to bring into play unknown forces the existence of which
can only be proved by the hypothesis from which we started
and which cannot be verified. In all evidence we are facing
a petitio principi. A straight line exists as a geometrical
concept, but motion in a straight line does not exist as an
objective reality, or at any rate it has never been observed.
What I mean is, that if we trace a straight line on paper with
a ruler, we have before our eyes a picture which concretes
our concept of a straight line, providing that all its points are
simultaneously perceived by the eye. But the course of the
pencil which has traced this line is far from having been a
straight line in the universe. Our hand participated in the
complex movements of the earth around its axis, of the earth
around the sun, and of the entire solar system in space. The
trajectory, as seen by an observer in Sirius, would have been
very complicated indeed. It was only in relation to ourselves
that it was in a straight line. Thus, when Newton says

1 We can easily imagine in a one-dimensional space (straight line)
the apparition of a force as a simple consequence of a curve (second
dimension). For example, the ‘centrifugal force’ which throws the
passengers of an automobile towards the exterior as soon as it aban-
dons a straight line to take a curve (P. Martignan). The single
presence of matter deforms the space-time continuum and the force
of gravitation is the result. We will take up again this question of
deformations a little farther on.

DEFINITIONS a7

‘A body in motion which is not influenced by any force
travels in a straight line and its velocity is invariable. There-
fore planets follow a curved trajectory because they are
continually deviated from their course by forces which act
upon them’, Einstein simply answers: ‘Planets follow their
orbits not because they are deviated from their course, but
because SUCH IS THEIR NATURAL COURSE.’

What, then, becomes of the straight-line motion? ‘The
straight-line motion,’ answers Einstein, ‘is possible only in a
Euclidean space; we have never observed it.’ We must then
admit that our universe is not Euclidean; it is a curved space-
time continuum.

The important point which must be grasped here is that
this reasoning makes sense only if, as I explained above, the
intimate welding of time and space is conceived. If all idea
of motion and time could be suppressed, Euclidean space
could easily be conceived. But there exists an unbridgeable
chasm between this pure, abstract, static geometrical concept
and our universe which is essentially ‘motion’. It is the chasm
which separates the pure idea from reality. All the obscurities
invoked, the revolt and the repugnance which have been
expressed on the subject of Relativity derive, I think, from
our old habit of separating time and space. The idea must
become well rooted in our minds that this is an unconscious
metaphysical reasoning, whereas Relativity brings us down
to earth, face to face with the real, tangible universe. It is
above all a practical theory.

This does not mean that the theory itself is true in all its
details, nor that it will remain immutable. It never had this
pretension. It will evolve, be transformed and adapted to
new facts. This is the role of a hypothesis. But it has given
us a certain number of new concepts which have made it
possible to interpret with greater precision an important
number of phenomena. Above all, it has renewed our way of
thinking, cleared up many obscurities (has it not suppressed
that paradoxical and disturbing entity, Ether?) and steered the
science of our epoch in a fruitful direction.

138 TIME

Before passing on to the measurement of time let us come
back for an instant to the notion of the deformed—curved—
space-time continuum. It 1s impossible to have a clear picture
of this if one considers the three-dimensional space. But a
sufficiently close if not absolutely rigorous analogy can be
drawn from the idea of a two-dimensional space which we
used to show the necessity of the third dimension in the
measurement of time. Indeed, time is measured by means
of the mcvement of a mobile body in space. It cannot be
measured without displacement. The reader may remember
that in the example of a scenic railway mentioned above,
we came to the conclusion that the observer in the moon,
ignoring the existence of the third dimension which would
alone enable him to ascertain that the wagon ascends and
descends, could only conceive the acceleration and slowing up
observed as being due to variations in the actual velocity of
the moving body. On the other hand, if the rate of the
moving body was variable as a function of the slope, so that
the distance travelled im projection was always the same in
equal times, the observer would have the impression of a
uniform velocity. Thus, curvatures in a path contained in
the plane of observation, in a two-dimensional space, would
entail gross errors in the determination of the fourth dimension,
time. And reciprocally, fluctuations in speed, the cause of
which are unknown, would entail errors in the estimation of
the distance travelled; that is to say, of space. I repeat once
more that this is only an analogy, but it seems to me that this
rough comparison enables one to grasp how the deformations
of space can affect the measurement of time and how the
deformations or variations of velocity, which are the only
magnitude at our disposal for measuring time, affect space.

If I have insisted at length on this point, it is because we
shall soon see that there is perhaps another means of
measuring our time which escapes the causes of error just
enumerated.

MEASUREMENTS 139

How do we measure time?

‘Fortunately for us,’ says Karl Pearson, ‘we are not
compelled to measure it by a description of the sequence
of our states of consciousness. There are certain sense-
impressions which in our experience repeat themselves
identical to themselves, and which correspond, on an
average, to the same routine of consciousness. In the first
instance, the alternation of night and day has been employed
since the first ages of the history of man to register approxi-
mately the same sequence of sense-impressions. A day
and a night became the measurement of a certain interval
of consciousness. We feel but cannot prove that the same
amount of states of consciousness can be approximately
contained for a normal human being in each interval of a
day and a night. It is a matter of experience rather than a
demonstrated fact.

‘Many identical things happen at intervals of identical
time,’ continues Pearson, from whom we will borrow the
following exceptionally clear lines. ‘When we say it is four
hours since breakfast, we mean in the first place that the
large hand of our clock or watch has gone round the dial
four times, a repeated sense-impression which we could, if
we please, have observed. But how shall we decide
whether each of these four hours represents equal amounts
of consciousness, and the same amount to-day as yesterday?
It may possibly be that our time-keeper has been compared
with a standard clock regulated perhaps from Greenwich
Observatory. But what regulates the Greenwich clock?
Briefly, without entering into details, it is ultimately regu-
lated by the motion of the earth around the sun. Assuming,
however, as a result of astronomical experience, that the
intervals day and year have a constant relation, we can
throw back the regulation of our clock on the motion of
the earth about its axis. We may regulate what is termed
the “mean solar time”’ of an ordinary clock by “‘astronomical
time” of which the day corresponds to a complete turn of
the earth on its axis. Now if an observer watches a

~ 140 TIME

so-called circumpolar star, or one that remains all day and
night above the horizon, it will appear, like the end of
his astronomical clock-hand, to describe a circle; the star
ought to appear to the observer to describe equal parts of
its circle in equal times by his clock, or while the end of the
clock-hand describes equal parts of its circle. In this
manner the hours on the Greenwich astronomical clock,
and ultimately on all ordinary watches and clocks regulated
by it, will correspond to the earth turning through equal
angles on its axis. We thus throw back our measurement
of time on the earth which is taken as a time-keeper. We
admit that equal rotations correspond to equal intervals of
conscience. But all clocks being set by the earth, how shall
we be certain that the earth itself is a regular time-keeper?
If the earth were gradually to turn more slowly upon its
axis, how should we know it was losing time, and how
measure the amount? It might be replied that we should
find that the year had fewer days in it. But then, how could
we settle that it was the day that was growing longer and
not the year that was growing shorter. Again, it may be
objected that we know a great number of astronomical
periods relating to the motion of the planets expressed in
terms of days, and that we should be able to tell by com-
parison with these periods. To this we must answer that
the relation of these periods expressed in days and in terms
of each other, appears now indeed invariable. But what
if all these relations are found to have slightly changed a
thousand years hence? Which body shall we say has been
moving uniformly? Which bodies have been gaining or
losing? Or, what if the ratios of their periods remaining
the same, they were all to have lost or gained? How shall
we, with such a possibility in view, assert that the hour
to-day is the ‘‘same interval” as it was a thousand or
perhaps a million years back? Now, certain investigations
with regard to the frictional action of the tides make it
highly probable that the earth is not a perfect time-keeper
nor are we able to postulate that regularity of motion by

MEASUREMENTS I4I

which alone we could reach absolute time, of any body in
our perceptual experience.

‘Astronomy says it is not in me, nor do we get a more
definite answer from physics. Suppose an observer to
measure the distance traversed by light in one second? Is
this at all times a fixed standard of the length of a second?
A thousand years later another observer again measures the
distance for one of zs seconds and finds it differs from the
old determination. What shall he infer? Is the speed of
light really variable, has the planetary system reached a
denser portion of the ether, has the second changed its
value, or does the fault lie with one or other observer? No
more than the astronomer can the physicist provide us
with an absolute measure of time. So soon as we grasp
this, we appear to lose our hold on time. The earth, the
sole clock by which we can measure millions of years, fails
us when we once doubt its regularity. Why should a year
now represent the same amount of consciousness as it
might have done a few million years back? The absolutely
uniform motion by which alone we could reach an absolute
measurement of time, fails us in perceptual experience. It
is, like the geometrical surface, reached in conception and
in conception only, by carrying to a limit there the approxi-
mate sameness and uniformity which we observe in certain
perceptual movements.’

Newton, when defining what Pearson will later on call
‘conceptual time’, thus expresses himself:

“That absolute, true, and mathematical time is conceived
as flowing at a constant rate, unaffected by the speed or
slowness of the motions of material things.’

Clearly, such a time is a pure ideal, for how can we measure
it if there be nothing in the sphere of our perception which
we are certain flows at a constant rate? ‘Uniform flow’, like
any other scientific concept, is an ideal limit drawn from the

142 TIME

actual acceleration or slowing up of the motions of material
things. But, like other scientific concepts, it is invaluable as
a shorthand method of description. Perceptual time is the
pure order of succession of our sense-impressions and involves
no idea of absolute interval. Conceptual time is like a piece
of blank paper ruled with equidistant lines upon which we
may inscribe the sequence of our perceptions; both the known
sequence of the past and the predicted sequence of the future.
The fact that, upon the ruled lines, we have inscribed some
standard recurring sense-impression (as the daily transit of a
heavenly body over the meridian of Greenwich), must not be
taken as signifying that states of consciousness succeed each
other uniformly or that a ‘uniform flow’ of consciousness is
in some way a measure of absolute time. It denotes no more
than this: that from noon to noon the average human being
experiences much the same sequence of sense-impressions
and that the same space in our conceptual time-log may be
conveniently allotted for their inscription.

How does life fit into the preceding theories? Can all the
very special phenomena which characterize living beings be
assimilated to the phenomena of inorganized matter? Is there
not a difference between this physical world and the beings
who evolve between birth and death according to a hereditary
rhythm, and recommence their ancestral cycle indefinitely?
Does not this fact alone introduce something special into this
consciousness without which, by definition, the very notion
of duration would not exist? It may be objected that we have
no proof that the mineral, inorganized world does not also
evolve according to a cycle imperceptible only by reason of
its tremendous duration. If this period were only of a hundred
million years it would entirely escape the scope of our intelli-
gence, and it could be far greater than that. In favour of this
theory, we might say that the evolution of our universe is
proved by the notion of entropy, a magnitude which grows
indefinitely. I will not enter into a discussion which even

MEASUREMENTS 143

though interesting would certainly be vain, but will restrict
myself to reminding the reader that, in respect to ourselves,
to the ephemeral duration of our existence, the difference
between the rates of evolution, admitting that this difference
exists, would by its colossal size in itself suffice to introduce
fundamental differences in the phenomena observed. Indeed,
it is known that a great number of the physical properties of
matter are determined by the speed of the objects. For
instance, by the velocity of the electrons or of the molecules.
Mass itself, a basic quality of matter, is a function of velocity.
If electrons, or any other projectile, could attain the velocity
of light, their mass would become infinite. These are not
simple views of the mind, but result from experiments made,
amongst others, by Kaufman in 1901 and by Bucherer more
than twenty years ago, in which they studied quantitatively
the variations of the mass of the electron as a function of its
velocity. At our scale, it is a well-known fact that there is
a big difference if we are hit by a bullet having a velocity of
One metre per second or by one travelling at six hundred
metres a second. A spout of water a few centimetres in
diameter falling from the height of the Eiffel Tower has the
rigidity of an iron bar and cannot be cut by the stroke of
a sword.

We are therefore authorized to think that, from the point
of view of our senses and of our consciousness, things can be
different according to whether the cycle of existence is longer
or shorter and according to whether the rhythm of the reactions
is more or less accelerated. For a given species, the persistence
of life is a discontinuous phenomenon. The individual, like
a rocket tracing its luminous trajectory in space, gives birth
to another individual, just as if the rocket on coming back to
earth put fire to another rocket and so on.' This sequence of

' “Life appears like a current which goes from germ to germ by
the intermediary of a developed organism’ (Bergson). We do not
know, but it is perhaps the current alone which counts in the history
of the universe. For man, on the contrary, it is the intermediary
which counts, and the integral phenomenon of which he is only an
element escapes him.
|

ee ———

144 TIME

brilliant parabolas traced by the rockets themselves at varying
velocities, rapidly at the start, when rising, then more slowly
as they near their apogee, is only perceived by us, thanks to
our eyes and to our memory. We only see it behind the rocket,
as it rises in darkness. Just as for a living being, we perceive
its past but not its future. But we can calculate the latter
with fairly great precision. Our observer in the moon, even
though he possessed powerful means of observation, would
see only the trace of these brilliant trajectories, and if thousands
of rockets were disposed in a straight line so that each one in
falling put fire to another, he would be under the impression
that the same little luminous line was advancing slowly on the
surface of our globe. The distance would be too great, and
the rockets too close to each other for him to be able to per-
ceive the variations of speed. The latter would appear uniform.

This picture applies in a certain measure to life, to the
species which perpetuates itself almost uniformly by means of
individuals of limited duration. Practically speaking, the time
of the species represents an immortality based on mortality. It
is the envelope curve of elementary phenomena. But all
consciousness is contained in this elementary phenomenon
and, as I said above, nothing proves that the ‘flow of conscious-
ness’, or what amounts to the same thing, the perception of
time, is in all consciences and at every moment of their
individual cycle, directly proportional to the physical time, the
uniform flow of which is purely conceptual and independent
of the life of the individual.

According to Bergson, living matter represents ‘a system of
growth comparable to an avalanche, where there is no repeti-
tion, but where each step forward is a creation, a manifestation
of liberty. The living organism is then a reality which creates
itself; inorganic matter, on the contrary, is a reality which
destroys itself.’ (Creative Evolution.)

From whatever angle we look at it, on condition that we
are of good faith, we are led to the conclusion that it would
be interesting to borrow solely from a living organism the
units which are used to define it.

CHAPTER IX

THE TIME OF ORGANIZED BEINGS—
THE GHEMICAL CLOCK

THE visual impression obtained by the observer in the moon
mentioned in the preceding chapter, gives rise in his mind to
an idea of continuity. This continuity which, neglecting the
individual, uniformly pursues its course, would be for us the
expression of immortality, or the prolongation beyond death
of the individual, and through him, of the characteristics which
he had himself inherited from his parents. No matter what
mechanisms (sexual or asexual reproduction) are brought into
play by nature to impart this immortality, we know that it
exists; we can control it. Woodruff, Metalnikov and others
have shown that, with unicellular animals (infusoria) one could
start with a single individual which spontaneously divides
itself in two, then in four and so on, and obtain on an average
from six to seven hundred generations a year (about 1-74
generations per day). The experiments were followed for
several years (seven years by Woodruff and more than twenty-
three years by Metalnikov). It is evidently impossible to
speak of the absolute immortality of the cell on the basis of
experiments having lasted only a few years. But the idea in
itself has become commonplace since the works of Pasteur
and the failure of all attempts to create living matter from
inorganic matter. To-day as formerly we admit that: ‘Omnis
cellula a cellula.” The important fact from our point of view
is relative immortality, that is, with respect to the duration of
the mean individual cycle, between two cellular divisions or
between two births. In unicellular animals the cells do not
die—except accidentally—as each one at a given time divides
itself in two and starts off again. In superior organisms, the
immortal cells are the sexual cells. All the others grow old
and die, following a determined rhythm. But the gametes,
or sexual cells, are the origin of every organized being which

145

146 TIME

always proceeds from an egg—the female cell—fecundated by
the male cell. This fecundated egg develops, and at a certain
moment of its evolution becomes an adult organism. This
organism manufactures gametes, male or female according to
its Own sex, and these gametes will in their turn originate
identical new organisms. The being which created them will
continue its cycle and die. But a part of it will remain, the
sexual cell which it has put forth and which alone indefinitely
perpetuates the species. Everything therefore occurs as if an
organism was nothing but the momentary and mortal inter-
mediary by means of which life can pass from one germ to
another, as Bergson expresses it. It is in this sense that we
said that sexual cells were immortal.

We have, nevertheless, seen that it was possible, under
certain conditions, to assure eternal life, or at any rate a much
longer span of existence than is normal, to cells of vertebrates
such as birds. It was even shown that these cells do not age.
In this case it is difficult to speak of individual consciousness.
One can at the most speak of a ‘chemical memory’. The word
‘memory’ is here taken in a very special sense, for it is possible
to immunize these cells against certain substances.’ But,
strangely enough, several authors, and amongst others
Jennings, Day, and Bertlay in America, have independently
observed disturbing facts tending to prove that the paramecia,
microscopic infusoria, are endowed with real memory, or in
other words, that these unicellular beings can profit from their
past experience. This would indicate the existence of some
kind of consciousness. The study of these problems 1s
fascinating, and Metalnikov has written a remarkable book on
this subject which should be read.?

Now, from the point of view which concerns us, if life is
inherited with its specific characteristics for each species, the
same is not true of consciousness. Each birth marks a begin-
ning, and each being who begins to live, or what amounts to

1*The cellular element when energetically solicited keeps the
memory of its reaction for a long time’ (Bordet).

9

2S. Metalnikov, Jmmortalité et Rajeunissement dans la Biologie
moderne. Flammarion, 1924.

:
|
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THE TIME OF ORGANIZED BEINGS 147

the same, to age, must learn anew what his parents learned
before him. It is the rocket which rises only to fall again.
The individual, therefore, evolves in a personal time which
has a beginning and an end. But the time of the species to
which he belongs, the ‘wave front’ time, has practically no
beginning and no end. As we have already stated, it 1s a con-
cept which can have no real value for any of us, any more than
the concept of the uniform flow of physical time. The only
time which counts for man is his own time, the time which
extends between a cradle and a tomb.

We can attain this physiological time directly by means of
the two methods described in this book. The method based
on the cicatrization of wounds and that based on tissue-
cultures. We have already seen that it was possible thus to
obtain a measurement of the real physiological age. We shall
now see how a measurement of time can be derived from it.

The reader may remember that we obtained an index of
Cicatrization 7 from the rate of cicatrization of the surface
wounds. The following pages will show why we insisted at
length on the value of this coefficient, the discovery of which
was of greater scientific interest than the simple fact that it
enabled us to calculate from beginning to end the successive
dimensions of a wound. Thanks to it we could for the first
time, aS was pointed out by Carrel in his admirable book,
Man, the Unknown, measure the flow of physiological time.

Now, the value of this index (see page 79 et al.) depends
both on the area and on the age of the patient. It is all the
higher the smaller is the wound and the younger is the man.
It was therefore important to eliminate the part played by
the area and to find a new coefficient, independent of the
dimensions of the wound and truly expressing the physiological
activity characteristic of a given age.

The study of a large number of experimental figures showed
the possibility of obtaining such a coefficient as well as the
limits between which it would be applicable. So as to enable

148 TIME

the reader to follow up to the very end in all their details
the successive steps of reasoning and thoroughly to under-
stand the way in which the results were obtained, I shall once
more take him behind the scenes. He will thus appreciate
the extreme simplicity of the method. Let us examine the
following table:

CONSTANT OF PHYSIOLOGICAL ACTIVITY A
For the age of twenty

+ 5

Index Agee

Z oe

(20 years) iv’S
0°0200 0°244
0:0210 0:248
0:0220 0-251
0°0225 0°245
0:0240 0'252
0:0250 0:250
0:0275 0-252
0:0300 0-268
0°0325 0°270
0°0355 0°274
0:0400 0:282
0:0445 0:282
0:0500 0°274
0-0540 0°274
0-0580 0:259
0:0645 0:250
0:0700 0-222
AA 99=0'260

Here we have five columns of figures. The first column
expresses the areas of the wounds. The second, the values of

|

THE TIME OF ORGANIZED BEINGS 149

the square roots of the figures in the first column. The third,
the reciprocal value of the figures of the second. The fourth,
the values of the index of cicatrization corresponding to each
dimension of a wound for the age of twenty. And finally the
fifth, the quotient of the figures of the fourth column (index 7)
by the corresponding figures of the third or, what amounts
exactly to the same thing, the values of the product of 7 by the
figures of the second column (square roots).

Why these figures? For the following reasons: As the area
decreases the index of cicatrization increases. But the area
decreases more rapidly than the index increases. This is
obvious: we see in the table that when the area diminishes by
one half, from 140 to 70 sq. cm. for instance, the index only
increases from 0-210 to 0:0325. When the wound is reduced
to one third of its size (from 150 sq. cm. to 50 sq. cm.) the
index has only just doubled (from 0-020 to 0-040). It is pre-
cisely this absence of proportionality which makes it necessary
to take the area into account. But when a quantity decreases,
its reciprocal increases. Consequently, when one considers
the reciprocal of the area, it varies in the same direction as the
index but always with greater rapidity. The aim being to
obtain a constant, for then the area could be eliminated, it
behoved us to try to see if a quantity did not exist which
would be a simple function of the area, and the variations of
which would follow as closely as possible the variations of the
reciprocal of the index. Now it may be remembered that in
establishing the formula, I took only the area into account,
except in the case of long, narrow wounds where the role of
the epithelial edge is preponderant. In this case, we have
seen that the experimental facts could be quantitatively ex-
pressed by introducing the square root of the area multiplied
by a certain coefficient. It is known that the square root of a
square area expresses quantitatively the length of one of the
sides. For a square, the product 4 ./§ is therefore equal
to the length of the sum of the four sides. If the figure is not
a square the coefficient 4 alone changes. If the figure con-
tracts, if its area decreases without the shape being altered, the

150 TIME

formula Kx VS will always express the length of the
sides. On the other hand, we also know that, if the area of a
figure decreases, the length of the sides of the outline also
decreases, but less rapidly. The relation of the two figures
expressing length and area is that of a number to its square.

The idea which immediately imposed itself was to calculate
the square roots of the areas and to take their reciprocals
(3rd column) so as to see if by chance the increase of 7 was not
proportional to these reciprocals. Now, at first sight, this is
actually what happens. Let us take at random a figure in
column 3. For example, o-1 and 0-2, its double in value. We
see that the corresponding indices are respectively 0:0250 and
0°0540, a little more than double (ratio exactly equal to 2-15).
Let us now take two values of the index, the ratio of which is
approximately three: 0-02I10 and 0-0645 (ratio equal to 3:07).
The corresponding values in the third column are 0-085 and
0258: the second figure is very nearly treble of the first (ratio
equal to 3:04).

From then on the problem was practically solved. As the
indices seem to vary proportionally to the reciprocals of the
square root of the areas, it suffices to multiply 7 by VS to
obtain a constant factor, the increase of one being exactly
balanced by the decrease of the other. This amounts to
saying that the area no longer intervenes in this quantity,
which will be solely determined by the age of the patient.
It is the solution of the problem which we had propounded.

The new coefficient thus calculated, and which shall be
designated by the letter A, can then be considered as the
coefficient or constant of physiological activity of reparation
for a given age, and can be written in the following manner:

A= Ss
The fifth column of the table on page 148 gives the values
of this coefficient. It can be seen at a glance that they are only
approximately constant. They vary between 0:24 and 0:22 at
the beginning and the end and go up to values attaining 0:28.
Does this mean that this coefficient is not sufficiently stable,

THE TIME OF ORGANIZED BEINGS ISI

and that we rejoiced prematurely? It suffices to reflect on the
manner in which it is calculated to understand that the reason
for these fluctuations lies not so much in an error of reasoning
as in the method employed to calculate the values of 7. Indeed,
these values are obtained from table, p. 85. Most of them
are interpolated, and even though the experimental values of 2
are established on a fairly large number of experiments (about
six hundred), it is impossible to affirm that all these values
are rigorously exact. Ten thousand experiments would be
needed in order to consider the mean values as being really
representative. We stated above that the individual differences
due to the state of health, to the physiological age, were at first
glance negligible, with the exception of certain special cases
such as syphilis, diabetes, alcoholism. But it is probable that
they nevertheless exist, and that the indices drawn from the
chart (p. 87) are only the approximate expression of the true
index. Furthermore, differences can exist according to the
part of the body on which the wound is located, when the
granular contraction depending on the elasticity of the sub-
jacent conjunctive tissue is less efficient. For example,
wounds on the skull, on the antero-internal part of the leg (on
the tibia), those on the foot or the back of the hand, are
characterized by a lower index, owing to the fact that the skin
lies almost directly on the bone. Not only is the contraction
weaker in these wounds, but blood irrigation through the
conjunctive tissue is diminished and can even be null if the
bone is bared. All these causes of error introduce small varia-
tions in the calculation, but can be easily taken into account by
slightly correcting the index if one wishes to establish the
curve of a particular wound. :

We can, moreover, assure ourselves that the variations of A
are due to fluctuations of a negligible magnitude in the values
of 7. From a practical point of view, only the two first
characteristic figures of the values of 7 are significant, and it
can be said that a satisfactory mean accuracy corresponds to
values which are correct within +-0:002. Now, if we take the
value A which represents the largest divergence from the

152 TIME

mean 0-260, that is to say 0-282, we can see that the difference
0022 represents a divergence of 0-003 in the value of 7, which
is not very far off from the acceptable value 0-002. The sole
and exceptional divergence of 0-038 observed for the wound of
IO sq. cm. indicates that, when wounds inferior to this dimen-
sion are dealt with, the preponderant role of epithelization
destroys the accord which characterizes the phenomenon as a
whole: contraction plus epithelization. We already know
(Fig. 19, p. 87) that small wounds, just as very large ones, no
longer show the marked differences in their indices exhibited
by the majority of lesions between Io and 150 sq. cm. for the
age of twenty.

But there is a better way to convince ourselves of the value
of the coefficient A. It consists in computing it for different
ages. Inasmuch as it is precisely the age which interests us,
we can in this way make the crucial experiment. The calcula-
tion of A for 30 years and for 4o years gives the figures of
the table on page 153. It will be noticed that the columns are
shorter than those of the preceding table (20 years). This
is due to the fact that the index, as may be remembered (see
p. 87) remains constant above a certain area. The coefficient
A being the product of the index 7 by the square root of the
area would have increased indefinitely beyond this limit and
would have become meaningless. We are therefore obliged to
keep within the limits imposed by the variations of 7.

An examination of the figures in the columns 3 and § (values

of the coefficient A—=7V S) shows that the constancy is in the
first case as good as, and in the second case better than, for the
values corresponding to the age of twenty. Indeed, the maxi-
mum divergence for 20 years was 0-038, whereas for 30 years
it is only 0-025 and for 40 years 0-006. The maximum diver-
gences from the mean values are 0:022, 0-018, and 0-003
respectively. Considering that we are dealing with biological
phenomena, in which the same precision as in physical
phenomena cannot be obtained, that we have not taken into
account the causes of error enumerated above, and that,
moreover, it was especially important to put in evidence the

THE TIME OF ORGANIZED BEINGS 153

differences between mean values, it can be admitted that the
coefficient A is very close to the activity constant of reparation
within the accepted limits. The relative maximum errors

I 2 3 | 4

5
Area of Index 7 Coefficient Index 7 Coefficient
the wound 30 years A 30 years 40 years | A 40 years
sq. cm.
80 0:0200 0-180 —
70 0:0220 0'184 a=
60 0:0250 O-Ig4 —
50 0:0275 0-194 0:0200 O-I4I
40 0:0310 0°196 0:0225 0°143
30 0:0375 0°205 0:0260 O°143
25 0:0400 0*200 0:0290 O-145
20 0:0465 0:207 0:0325 O'145
15 0°0525 0°204 0:0380 0-147
IO 0:0625 0-198 0:0450 0-142
Mean value 0-198 0-144

expressed as a percentage of the mean value are 8-5 per cent
in the first case (20 years), 9 per cent in the second (30 years),
and 2 per cent in the third (40 years). These errors are
inferior to those accepted for the index and are certainly less
than those which affect the majority of measurements per-
formed on living organisms. :

Basing ourselves on the values of 7 for intermediary ages,
we finally obtain the following mean values of A:

20 years 25 years 30years 32years 40 years
H==0-260 0°225 0-198 0-188 0-144

We had only two patients of fifty under observation. They

154 TIME

gave the value of o-103 for A. One single case for sixty:
A=o-08; and only one case also for ten years of age: A=o-4.
These values are therefore very doubtful. Fig. 27 expresses

these results.
Dotted curve vs
exthapolated

0.40

0.30

020

Constant A~14VS~

0./0

I BO! 130... 40, 50 80. 70" Se

FIG. 27. COEFFICIENT ‘A’ AS A FUNCTION OF THE AGE OF THE
PATIENT
What do these figures mean? It is extremely simple.
These values of constant A signify that, if a child of ten will
cicatrize a wound of 20 sq. cm. in twenty days (I purposely
take an arbitrary round number), a man of twenty will cicatrize
a wound of the same dimension in thirty-one days (20 is in the

THE TIME OF ORGANIZED BEINGS 155

same ratio to 3I as 0:26 to 0-40), a man of thirty, in forty-one
days; a man of forty, in fifty-five days; a man of fifty, in seventy-
eight days; and a man of sixty, in a hundred days. A wounded
man, forty years old, therefore cicatrizes at a rate which is
almost twice as slow (exactly 1:8 times) as that of a man of

_—

200
190
180
170
/60

wlan ay ee,

140

120

100

Relative rate of cicatrization , computed from the values ofA

SO 20 30 40 50 60 JO 80 90
Age

FIG. 28. RELATIVE RATE OF CICATRIZATION COMPUTED FROM
CONSTANT ‘A’

~

twenty. And a child of ten cicatrizes five times more quickly
than a man of sixty. If the activities of cicatrization are
referred to that of the age of twenty taken as the unit (100) the
curve shown in Fig. 28 is obtained. This, like the preceding
one, clearly shows the very rapid decrease of this activity in
the first years of life and the tendency to reach a low and
constant value towards the end of life.

156 TIME

Now, when a wound cicatrizes, what does it do? It effectu-
ates a piece of work. Just as a mason closes up a breach in a
wall, nature repairs a breach in our organism. When we
measure the velocity at which this work is accomplished, by
means of the sideral, physical time, we observe that it is very
great at the beginning of life, slower at the middle and slower
still towards the end of life. We can see on Fig. 28 that if 100
represents the velocity at twenty years of age, at thirty it is
only 76 and at sixty 31. But it is expressed by 155 at ten
years of age. It is therefore not constant with respect to our
unit of measurement, the 24-hour day. At different ages it
takes different lengths of time to accomplish THE SAME AMOUNT
OF WORK: the cicatrization of one square centimetre of a wound.

On the other hand, it is possible to evaluate time by referring
to a travelled distance or to a work done, if one is reasonably
sure that the speed of displacement has been constant in the
interval or if the workman has not changed the rhythm of his
movements. We often employ expressions such as: the time
to go to the post office, the time to dress, the time to write a
page. In olden days, the hours of a trained labourer, working
regularly, were often estimated by the work accomplished, for
instance by the area mowed. Supposing he cuts, on an
average, two hundred and fifty square yards an hour. If he
has worked four hours we know that he has cut a thousand
square yards. But if we have no watch and do not know how
long he has worked, the measurement of the mowed area, two
thousand square yards, for example, enables us to conclude
that he has worked eight hours. We have therefore measured
time by the amount of work performed. Consequently, if we
reason in the same way for the work represented by the
cicatrization of a wound, we can measure sideral time in units
of physiological time.

An objection immediately imposes itself. We have just
demonstrated that this work is accomplished at different
velocities at different moments of our life. We are therefore
no longer under the required condition. Not only is it im-
possible for us to affirm that the work has been accomplished

THE TIME OF ORGANIZED BEINGS P57

at a constant rate of speed but we demonstrate precisely the
contrary. Weare here facing an absolute contradiction. This
contradiction, however, is more apparent than real. Indeed,
on what do we base ourselves to say that the velocity of repair
is not uniform? We base ourselves on physical time, on the
regular rhythm of our clocks. We therefore implicitly admit
that this rhythm is invariable. But if, as was pointed out in
the preceding chapter, this rhythm ceased to be uniform for
any reason whatsoever, we could not know it and we would
measure our phenomenon by means of a variable, elastic unit,
which would destroy all the value of our conclusions. We
would have no means of ascertaining whether the velocity of
cellular reparation or that of the flow of the time employed to
measure it, fluctuates.

Now, this unit, in which we have complete confidence, and
to which we conventionally attribute an absolute rigidity and
undeformability, is borrowed from our inorganic material
universe. The use of this unit for measuring the evolution
of our physiological and psychological ego is practical, but is it
legitimate? As we have before remarked, there is a difference
between the physical, sideral time based on the co-ordination
of our sense impressions, but which remains nevertheless
outside us, and our human duration which is a constituent of
our ego as much as the space in which we evolve. It is our
intelligence which ‘thinks’ the world. Our consciousness is
born, ages, and dies. But in coming to life it inherits an
enormous quantity of observations relative to this world which
have been accumulated by preceding consciences and trans-
mitted by word or by letter. It is this tradition which enables
it to acquire the notion of the continuity of the universe.! It
is this tradition which enables us to see and to locate ourselves
in the world. A unique, isolated consciousness, without con-
tact with those which have preceded it, would have very
different notions. Our short and fragmentary human duration

' And many other ‘notions’ also, which our intelligence, our science
have proved to be false or, if one prefers, relative; for example, the
notion of the vertical, the trajectory in a straight line, the parallelism
of two plumb-lines, etc.

158 TIME

is dependent on our organism as a whole, as well as the notion of
this duration which is characterized by a discrepancy with the
notion of uniform duration of inert things. Sideral, physical
time perhaps also characterizes evolutions, but of such colossal
duration that, in comparison to ours, it can be considered as
infinite. We measure it by certain periodical phenomena such
as the rotation of the earth around its axis, and without being
able to verify our assertion, we conclude that it flows uni-
formly. This is perhaps an illusion due to the fact that we
can perceive only a limited portion of a curve. Its radius of
curvature might be so gigantic that it appears to us as a
straight line. As we shall see later on, it is perhaps also
because we conceive it as a wave front or an ‘envelope’ surface,
which borrows its reality from the infinity of curves or
determining elementary surfaces underlying it. It would be
the time of species as opposed to individual time. The time of
tissue-cultures, of the generations of infusoria; the statistical,
conceptual, uniform time, projected by us into the universe
but not lived.

Be that as it may, it would seem logical to borrow a standard
of time from our specific evolutive cycle, and to refer all our
internal phenomena to this unit, which is no more arbitrary
than the one we commonly employed up till now. We have
inside of us a machine which registers time: i.e. our sub-
conscience. We also have a machine which conceives time:
our intelligence. The two mechanisms, though different, are
based on memory. Our subconscience gives our intelligence
a crude information: time seems to flow quicker in proportion
as we age. Our intelligence, a reflection of the external
universe, only reveals to us the time of things, which leaps
from individual to individual, and flows uniformly. These
two notions are correlated but not interchangeable.

Even to a superficial observer, our internal physiological
time does not seem to flow at a constant rate within the frame
of external sideral time. Real age, as we have seen, can differ
from legal age. From a psychological point of view, the value
of a day is not identical for ephemeral insects and for animals

THE TIME OF ORGANIZED BEINGS 159

that live to be sixty years old. Even for one individual, this
value seems to vary during the course of life. Our duration
would therefore be, in a certain measure, independent of
sideral time. Each human being constitutes a universe in a
state of continuous transformation. It is the rate of this
transformation which can be considered as characteristic of
our brief specific duration, of our physiological time itself,
inseparable from our consciousness.

In short, seeing that this physiological time is truly our own,
an interior time, and that humoral reactions and vital pheno-
mena as a whole are governed by it more than by the rhythm
of the earth’s rotation; seeing that, in all likelihood, it is from
our physiological reactions as a whole that we derive our notion
of time which is inseparable from these reactions, since we
must admit that consciousness is conditioned by them, we are
authorized to carry to its logical conclusion the reasoning
which motivated this digression and which brings us to the
comparison of sideral time with physiological time. We are
authorized to do it, not only by logic, but, what is more con-
vincing, by experiments also. M. Marcel Frangois, in a
communication presented by Prof. Piéron at the Société de
Biologie, entitled ‘Sur l’influence de la température interne
sur u0tre appreciation du temps’, concerns himself with the
question of whether the perception of time is influenced by
the increase in velocity of our internal chemical reactions. In
order to verify this, he exposed patients to high-frequency
currents (short waves). The test consisted in striking a Morse
key three times a second—or rather the number of times
which corresponded to a personal estimation of three per
second—before and after a diathermic application. After the
application, the internal temperature rose about 0-6° C. on an
average (between 0-4° and 1° C.). He observed an accelera-
tion in the temporal standard, corresponding to a shortening in
the appreciation of time, in respect to the increase in temperature.
This is in conformity with what might have been expected
from the application of Van’t Hoff’s acceleration coefficient

*G.R» Soc; Brol., vol. 98,'p. 152 (1928). :

160 TIME

in chemical reactions. These experiments led him to a value
of this coefficient comprised between 2-75 and 2°85. This is
a satisfactory accord—if one takes into account the difficulties
of the experiment and the small difference in temperature—
with the mean value of 2:5 for an increase of 10° C. (It may
be remembered that I mentioned (page 98) experiments
made at the Rockefeller Institute on cold-blooded animals
(crocodiles) which clearly demonstrate the influence of the
Van’t Hoff coefficient in the cicatrization of wounds.)
M. Francois’ interesting results were entirely confirmed and
extended by Hoagland in 1933.' Finally Wahl, Graben-
berger, and Kolmus published very curious facts which also
confirm our thesis and establish the chemical nature of the
mechanisms which result in our psychological appreciation of
time. When studying bees, ants, and termites, trained to
come at a certain hour and take their food, the authors ascer-
tained, by modifying the temperature, that an increase in
temperature forced these insects to shorten the interval of
time between two meals. This is the equivalent of an apparent
dilatation of the time perceived by them. A decrease in
temperature brought about a contrary effect. There can
therefore be no doubt as to the nature of these phenomena.”
The comparison of these two series of experiments demon-
strates clearly the relation between the rate of cicatrization of
wounds and the psychological appreciation of time. They
both rest in last analysis on a chemical basis. There is no
break of continuity in the chain of our reasoning, every link
of which derives its solidity from an experimental confirmation.

Consequently, when we refer to sideral time as being the
canvas on which the pattern of our existence is spread, we
notice that the time needed to effectuate a certain unit of
physiological work of repair is about four times greater at
fifty than at ten years of age. Everything, therefore, occurs as if

1H. Hoagland, Pace-makers in Relation to Aspects of Behaviour.
MacMillan, New York, 1935.

2 This information was given to me by Prof. Piéron, to whom I
express my thanks.

THE TIME OF ‘ORGANIZED BEINGS 161

sideral time flowed four times faster for a man of fifty than for
a child of ten. It is evident, on the other hand, that from
a psychological point of view many more things happen to a
child in a year than to an old man. The year therefore seems
much longer to the child, and it is probable that the figures
established—the constant A—enable us to realize quantita-
tively, not only by how much our physiological activity
decreases, but also by how much physical time is apparently
accelerated in respect to ourselves.

Thus, we find that when we take physiological time as a
unit of comparison, physical time no longer flows uniformly.
This affirmation revolts one if the words are taken in a literal
sense. But we pointed out in the preceding chapter that if
the expression ‘flow of time’ is in current use, it is nevertheless
entirely false and does not correspond to a reality. We have
seen that time is inseparable from space and matter and that
the four-dimensional continuum, in conformity to the relative
concept, is alone capable of furnishing a satisfactory frame for
Our universe. When, therefore, we say that physical time
measured by means of a unit borrowed from our physiological
time, no longer flows uniformly, it simply means that it does
not seem to flow uniformly. At the bottom of our conscious-
ness we perceive a discrepancy between the notion of our
external time, without beginning or end, based on our science,
our past experience or inherited documents, in other words
between the notion of the uniform time of species, and the
notion of individual, sensed time, limited by birth and death,
which corresponds to the elementary curves of short period
and variable velocity.

We can separate these two notions by an intellectual effort,
but physiological time alone has a reality with respect to us.
The envelope curve—the uniform sideral time—is perhaps
nothing else but the resultant of the infinity of elementary
curves, just as a light wave, or rather the wave front, is the
perceptible resultant of the elementary group of waves given
out by a luminous source, as shown in Fig. 29.

The envelope wave expands spherically, and each of its

162 TIME

vibrating points becomes in turn the centre of an elementary
spherical wave, according to Huyghen’s conception. The
uniformity of external physical time would thus be a simple
concept resting in last analysis on an infinity of individual non-
uniform elements, the continuity of which is assured by
memory and tradition.

ware front

we

Each point 2,6,c, etc. is theorigin ofa wave

FIG. 29. FRONT WAVE CURVE

It is evident that we do not intend to establish a parallel
between the propagation of light waves and time. We have
simply tried to clarify the notion of ‘envelope’. A parallel
could only exist provided each elementary wave issuing from
a vibrating centre were damped in such a way as to progress
more rapidly at the start than at the end. The discrepancy
between the order of magnitude of the small individual waves
and that of the envelope bubble is so great that the observer
who perceives only the latter ignores its origin. Just as an
observer of the universe cannot perceive the difference
between the two times unless he succeeds in finding an
internal standard of time: the physiological time defined above.

It seems to me that the extension of this notion of physio-
logical time to the notion of appreciation of time is legitimate.
On the one hand, our appreciation of time is one of the
properties of our consciousness, and our consciousness is
dependent on our physiological cellular reactions. It is there-
fore logical to admit that all slowing up of the activity of these
reactions must result in a modification of our appreciation of
time. We have demonstrated the fact that such was the case
and, on the other hand, we know that time seems to flow more
quickly as we grow older. This is a commonplace observation

CHEMICAL CLOCK 163

which is at least qualitatively in good accord with our experi-
ments and our reasoning. Thus only the quantitative accord
might be questioned, and we will take this up later.

It may be rightly objected that not all biological phenomena
are slowed up by age in the same proportion as cellular
activity. The answer to this is that it is necessary to differen-
tiate between fundamental biological phenomena and the
others. Phenomena such as cicatrization and cellular proli-
feration, which are life itself, i.e. the edification of living
matter, must not be confused with certain physico-chemical
phenomena which underlie our biological activities but which,
as was shown at the beginning of this book, are different in
many ways. If, for instance, one objects that the velocity of
the nervous influx or irritability as a function of time—
measured by ‘chronaxy’—is far from being modified by age
in the same proportion, one can answer that irritation is a
property of living matter which is fundamental in that it
determines the conditions of muscle and nerve action, but
which is, however, less fundamental than the manufacture
of the cells themselves. Irritability is an epiphenomenon.
Cellular proliferation is the basic phenomenon of the building
up of living matter. The remarkable notion of chronaxy, so
ably developed by the French physiologist Lapicque, should
be no more influenced by age than fundamental phenomena
such as the beating of the heart, for example. On the other
hand, it can be plausibly admitted that hematopoiesis—the
manufacture of red blood cells—is affected in the same pro-
portion as cicatrization. The measurement of chronaxy
cannot give any information concerning the age of the organ-
ism because it is only the measurement of a property of living
matter and not a measurement of the vital activity of the cells.
Tissue-cultures live and cicatrize their wounds without a
nervous system.

A more serious objection is that the impression of the more
rapid flight of time is simply due to the varying ratio of the
length of the time unit—a year, for instance—to the total
duration of life. For example, a year seems longer to a child

164 TIME

of five than to a man of fifty because it represents the fifth of
his existence, whereas it represents only the fiftieth part of the
life of the older man. This would imply a notion of time based
on memory, and a permanent subconscious confrontation of
the time which flows with the time elapsed since birth. This
objection is important because it is full of common sense.
Let us examine it with the attention it deserves.

First of all, what can be the mechanism of this memory?
We are not speaking of the memory of precise facts standing
out against the moving background of our existence, but of the
registration of the very motion of this mobile background. It
is somewhat as if we were in a theatre watching the play of
actors—representing our internal perceptions projected out-
side of us—and as if the scenery were being shifted always in
the same direction, unwinding itself on the right and being
rolled up on the left. From a mechanical point of view it is
easy to conceive that the more canvas is wound the larger
will be the diameter of the roll and the greater will be the
velocity. But this is much too crude a comparison. Can we
find among known biological facts a basis which would allow
us to visualize this quantitative recording of past time?
Indeed we can, for we know that ageing introduces chemical
modifications into our organism, the effect of which is pro-
gressively to increase the toxicity of our serum, that mirror of
our physiological reactions. This fact stands out clearly in
the experiments of Carrel and Ebeling, described in detail on
p. 116. There is, consequently, an accumulation of toxic
products in the fluids of our organism. We know, on the other
hand, that the activity of physiological reparation evolves
parallel to this phenomenon and that the curves representing
the growth-index of tissue-cultures and the index of cicatriza-
tion assume very nearly the same aspect. The two pheno-
mena can almost be superposed. It may be inferred that they
are basically very similar. The older the individual from
which a serum proceeds, the more toxic his serum becomes
for tissue-cultures and the slower will the individual cicatrize.
Here is a biological fact which indicates that each year in

CHEMICAL CLOCK 165

passing Jeaves an indelible trace in us, just as in a motor-car
every turn of the wheels registers in the speedometer a figure
which is added on to the preceding figures. Nature does not
dispose of mechanical systems such as speedometers, but the
result is approximately the same. It seems difficult to call
upon another procedure for the explanation of the existence
of this type of memory, for there can be no question of a
mechanism identical with that of our sense memory which
retains and easily evokes events registered by our senses, but.
without respecting the dimensions of time. A proof of this
is given by dreams in which the scale of time is often strangely
contracted. But, when the registration of the flight of time
is concerned there can only be question of a passive, sub-
conscious memory, of physico-chemical or chemical nature,
which would be only one of the manifestations of ageing, and
the very foundation of our notion of duration.

Should this really be the case we would have answered the
objection, for we would have demonstrated that the fact of
admitting an estimation of the apparent length of a year, based
on the comparison of the number of years gone by since birth,
would imply a subconscious totalizing system which might
well be one of the psychological manifestations of the physio-
logical and chemical transformations introduced by age.
Instead of eliminating the objection we would, on the contrary,
have incorporated it into the totality of phenomena which
are correlative to ageing. But the whole question would still
remain hypothetical.

To confirm the reasoning as a whole or, at least, bolster up
its probability by facts, the two series of calculations used to
express quantitatively the apparent shortening of duration of
one year, based, the first, on the coefficient A of physiological
activity, the second, on the value of a year expressed in frac-
tions of the age of a man, should coincide at least approximately.
If only the order of magnitude of the shortening were the
same in both cases, it would supply an impressive argument
in favour of the thesis expounded in this book.

Nothing is easier than to confront the two hypotheses. If

166 TIME

age intervenes numerically in the estimation of the duration
of a year, the curve representing the value of one year for each
age can be drawn by simply plotting as ordinates the values
of the reciprocal of the ages plotted as abscissae. We have
stated that the year of a five-year-old child seems long to him
because it represents one-fifth of his existence, or 0-20. Toa
man of twenty, a year (ome-twentieth of his existence or 0-05)
will seem shorter in the same proportion as I to 4. For a man
of fifty it will be only one-fiftieth or 0-02. To the latter, time
will seem to flow ten times faster than to the child of five.
We thus obtain the solid curve of Fig. 30. It is a very simple
curve, an equilateral hyperbola, the branches of which are
asymptotic of the axes of co-ordinates and which answers to

I
the elementary equation: xy=I or y=—. Let us now super-
x

pose this curve on that of Fig. 28, p. 155. The values of the
abscissae (age) coincide. For the ordinates we must keep the
scales comparable; namely the figures, although different,
must be proportional to those of the preceding diagram. We
obtain the dotted curve of Fig. 30 and we notice at once a
similarity which, if not absolute, is nevertheless very remark-
able. There is no complete coincidence, but it is indisputable
that the aspect is nearly the same between the ages of fifteen
and sixty. We must not forget that, as we said on p. 154, our
experimental figures are doubtful before twenty and after
fifty years of age.

Does this mean that the reactions registered by age inside of
us, faithful witnesses of the flight of years, evolve according to
a hyperbolic law? We cannot affirm this, for it would imply
the admission that no other process enters into play, and
nothing authorizes at present the formulation of such a postu-
late. We may, however, note that such curves are not infre-
quent in chemistry: the dissociation curve of Nernst (iso-
thermal dissociation) is precisely an equilateral hyperbola.
This curve gives the number of ions produced in a solution
by dissociation, as a function of the concentration in mole-
cules. It shows that the phenomenon decreases when the

CHEMICAL CLOCK 167

concentration increases, following a hyperbolic law. We do
not wish to draw any conclusion from this. We simply

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“ah cee ge
a ds a
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0.15 Ne

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Se aenl

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=
+

—-
oa

y of
oro
oe
N @

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ee ee Se A
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1OMn2OW 504-0) 150 io Oia 90 100

FIG. 30. RELATIVE RATE OF CICATRIZATION AND APPRECIATION
OF THE VALUE OF TIME AS A FUNCTION OF THE AGE

Relative rate of cicatrization (Acurve, dotted line )
es eae 5)
oo 50 Oo Or
Sye(Sj- teks) :
wo + on fe.)

wanted to recall this classical example so as to remind one
that chemical phenomena obeying this law exist.

This concordance between a curve obtained by quantitative
experiments on the cicatrization of wounds, a curve which

168 TIME

summarizes the results of a great number of measurements made
without any preconceived idea, and a curve obtained by expressing
quantitatively the consequences of a simple reasoning based on
common sense and psychological observation 1s very striking.

A year is thus physiologically and psychologically much
longer for a child than for its parents. Supposing the parents
to be forty years old and the child ten, one year will represent
for the child about the same length of time as three (derived
from constant A) or four (derived from the hyperbola) years
for the parents. If the child is younger the difference will be
still more marked, but we have no experimental figures where-
from it could be computed. The hyperbola of Fig. 30 might
furnish them, but it is probable that a satisfactory accord can
be obtained only between the extreme limits of fifteen and
sixty years of age. The diagram of Fig. 31 represents the
apparent values of one year at different ages with respect to
its value at the age of twenty, taken as unit. It can be seen
that we limited ourselves to the age of ten.

There is nothing, moreover, to prove that the hyperbolical
rate is valid beyond this age. It is impossible to speak of the
notion of time in a very young child and it is extremely
probable that the rate of cicatrization is not increased in the
proportion indicated by the curve. The extrapolation, repre-
sented by the vertical branch which attains an infinite velocity
for o years of age, has no meaning. No more meaning than
the expression, 0 years of age, itself; for should one start
counting it from the beginning of the time of the fecundation
of the egg or from birth? These are purely intellectual bouts.

The region of maximum curvature, that of our material and
conscious existence, is situated exactly midway between
infinite velocity and infinite slowness, astride on the hyper-
bolic axis which cuts the curve at the point corresponding to
thirty-one years and a half. It is impossible not to notice that
for a pure relativist it would be very tempting to assimilate
every living being to a simple deformation of the four-
dimensional space-time continuum so as to explain the non-
uniform flow of our time as compared to universal time.

CHEMICAL CLOCK 169

Young and old, united in the same space, live in a separate
universe where the value of time is radically different. Peda-
gogues and psychologists do not seem as yet to have taken
into account the considerable importance of this disaccord.
Obviously, the manner in which this could be done is by no
means evident. But this is another problem.

L H Ui U hyperbola
reek g o iz] Constant A
A ee ee eat ak 8c

yeers

10 20 30 40 = 50 60 70 Age

FIG. 31. RELATIVE VALUES OF OUR APPRECIATION OF THE DURATION

OF ONE SIDERAL YEAR, COMPUTED FROM THE CONSTANT ‘A’ (SECOND ROW),

AND FROM THE HYPERBOLA (FIRST ROW), WITH RESPECT TO THE AGE
OF TWENTY TAKEN AS REFERENCE

Thus there is a physiological time which has no signification
excepting for organisms capable of being born, of ageing, and
of dying normally. This word ‘normally’ contains in sub-
stance the greater part of unsolved biological problems. It
implies, for instance, the action of the organic regulating
mechanisms which establish the fundamental difference
between the healthy normal growth of cells and the abnormal,
anarchical growth of cancerous cells, between an immortal
tissue-culture and an individual who is born, lives, and dies.

Between a malignant tumour and a healing wound which
cicatrizes by rapid cellular proliferation let loose in the healthy
tissue by the wound itself there is, barring the morphological
difference of the cells, only the following difference: prolifera-
tion stops instantaneously when reparation is ended in a
healthy flesh, whereas a cancerous tissue ignores this regu-
lating mechanism and continues to proliferate until death
follows. Similarly, when a tissue-culture is cut in two and
placed in a fresh drop of nutritive medium after washing, the
cells, which proliferate slowly in the organism, are taken with
a frenzy of growth and reproduce with great rapidity. We
have seen that a tissue-culture two square millimetres in size
doubles its volume in forty-eight hours indefatigably and

170 TIME

indefinitely. The elimination by washing of the toxic waste
products due to the metabolism, suppresses ageing in this
fragment of tissue, just as for cancer cells, individual physio-
logical time no longer exists or rather is blended into sideral
time, ‘envelope’ time. Like all animal species considered as a
whole in their secular evolution, this little piece of flesh registers
only the uniformly flowing physical time. Each of its cells,
considered separately, probably evolves in the physiological
time, the same as all individuals. But everything occurs
as if continuous flowing time, the ‘wave front’ time, which is
perceptible to our intelligence but is not our time, played a
much more important though more mysterious role than
individual time. The death of the individual is of no im-
portance. It is the species which counts, and we cannot know
if the species is endowed with consciousness. Just as the
personality of a molecule is abolished in a crystal, so does the
individual disappear in the evolution of organized beings,
drowned in the mysterious stream which he contributes to form.

The conclusion at which we arrive of a ‘granular’, variable,
individual time, differing from the continuous, integral, uni-
versal time, has nothing in it which should surprise us. A
genial intelligence could have foreseen it, for, since more than a
century ago, science has tended to destroy the palpable notion
of continuity and to replace it by the impalpable one of dis-
continuity. Our senses, which are the intermediaries between
the universe and ourselves, translate discontinuity into con-
tinuity, air pulsations into sound, groups of waves, accom-
panying photons, into light. The first success—foreseen by
Democritus—was the demonstration of the granular, fragmen-
tary nature of matter. Imperceptible molecules and atoms
give us, by reason of their immense number in any body whatso-
ever, the impression of continuity. The second was the dis-
covery of the electron, which established the granular nature
of electricity. The third was the discovery of the quantum
of action, which destroyed our clear idea of continuity of
energy. Matter, electricity, energy, all our material universe,
are but ‘envelope’ manifestations of statistical phenomena

CHEMICAL CLOCK ET

resulting from the play of isolated elements which are them-
selves deprived of dimensions. There is therefore nothing
astonishing in the fact that we are brought to the conclusion
that the very essence of time is granular and that its continuity
is only the statistical appearance given it by individuals so as
to class all the other external statistical phenomena in their
consciousness and in their memory.'

We know that the major laws which govern our material
bodies—Newton’s law, the electrostatic law of Coulomb, and
others—apply only at a certain scale, and cease to apply at the
electronic scale. We see that the law of flow, the succession of
our internal phenomena, is also different from the law of flow
of the external phenomena of the universe. Must one con-
sider this fact as the indication of a difference of magnitude
between our short individual period and the immense periods
of the universe? Must we see a proof of the existence of such
periods? Who knows? All that we can say at present is that
our crude language, lacking appropriate words, translates this
knowledge into improper, inadequate expressions such as:

'It is evidently absurd to speak of ‘the very essence of time’.
Space, time, energy, are beyond our terminology. However, to dis-
tinguish between these two concepts, of continuity and discontinuity,
we are forced to employ current expressions. All our experience and
all our science lead us to the admission that continuity exists nowhere,
and that one of the roles of consciousness is to manufacture con-
tinuity from discontinuity. The notion of continuity is essentially
human. It is normal that this tendency of our consciousness should
have been applied to time as well as to the material universe. How-
ever, if all our universe is discontinuous we nevertheless observe the
existence of many phenomena the continuity of which is indisputable
and likewise based on elementary discontinuous phenomena. The
persistence of species, for instance, or the manifestations of ‘the spirit
of the hive’, in bees as well as in ants and termites. M. Jean Rostand
could give us many examples borrowed from insects. Here, also,
something continuous is born in our consciousness from discon-
tinuity, but from a discontinuity of quite another order of magnitude
than electronic, quantic, or even molecular discontinuity. There is
nothing shocking in speaking of our physiological time as a constitu-
tive element of our concept of a uniformly flowing time. The latter
is perhaps a mere product of our intelligence. It is, moreover,
possible that outside of the major tendencies cited above (persistence
of species, etc.), thought alone is continuous. But this would be very
difficult to prove.

172 TIME

“There are two species of time’, or ‘Physiological time does not
flow uniformly like physical time.” We must not be duped
by these words; we must not let ourselves be bound by them.
We must try to perceive, beyond them, the reality which they
vainly strive to translate: ‘The flow which does not imply a
flowing thing, and the passage which does not presuppose
states through which one passes’, as says Bergson, who was
led to conceive different durations diversely rhythmed, when
living species are concerned. But this was only a hypothesis.
In pages 58 and 61 of Durée et Simultanéité, he arrives, by pure
reasoning, at conclusions very similar to ours, in the sense
that he develops the idea of ‘the unity of an impersonal time
in which all things flow’ and which is the result of the time
registered simultaneously by all human consciences. One
feels that he lacked the clear experimental facts capable of
substantiating his reasoning, i.e. the difference between uni-
versal time and individual physiological time. But his in-
tuition and immense talent had almost supplied the deficiency,
even though he was finally led to admit a unique universal
time. His intelligence was apparently revolted, if one may
say so, by the fragility of deductions resting on no measurable
phenomenon.

The fact that we conceive the universal time as a mere
conceptual envelope of our physiological, individual time,
does not mean that we intend to affirm that it would no longer
exist if all life were swept from the universe. Let us pass over
the absurdity of the expression: “Time which exists’, on which
we have already insisted, and define our meaning. From
all that precedes, it seems to us that the reader must have
already disengaged the fact that our universe, the universe
which we perceive and conceive, exists as such only in our
consciousness. Let man, his senses and his memory, be
suppressed, and the universe is reduced to vibrations, to
forces, to velocities deprived of the familiar aspects which we
lend them by placing ourselves in their path. We gather
them and transform them by means of our sense organs. We
translate them in our consciousness and baptize them Reality.

CHEMICAL CLOCK 173

This is our only reality. But there is, behind this shadow, the
object which projects it, and which ever since Plato we have
vainly tried to conceive. The intersideral spaces are black
and cold. ‘Energy quanta’ circulate through them in every
direction and in infinite numbers.’ Without an adequate
receptor to intercept, accumulate, totalize and transform them,
they are nothing but quanta. In the absence of human beings,
light, heat, sound, do not exist as such. In the absence of
radio sets, waves emitted by the broadcasting stations are
inexistent for us. Each one of our senses acts as a receiving
set and translates for our consciousness the silent, invisible,
and abstract message of the quanta of energy. It is in this
sense that we have occasionally called our physiological time
real time. It is owing to this time that the summation of
quanta takes place in our brain, and that we perceive the
universe as we perceive it. The other, the time of things, the
time of the obscure and mute .universe, unknown and un-
knowable, has no more reality for us than radio waves in the
absence of receiving sets. ‘In this time without duration,
events could not succeed each other, nor things subsist, nor
beings age’ (Bergson). If it governs us as a combination of
atoms and molecules, it does not govern us as a living individual
destined to die. It is, on the contrary, our physiological time
which enables us to conceive, through our intelligence, the
uniformity of flow impossible of perception. Should it be
demonstrated some day that universal time can be resolved
into quanta, then the same would be true of our physiological
time. The quantum of physiological time would then be a
function of the period of our existence, and would be different
for each species. The picture of a curve, or of a wave front,
which we have proposed in order to explain our concept of
universal time would, in this case, be materially strengthened.
But this draws us into a speculative domain, and that is pre-
cisely what we have tried to avoid.

1 Before Planck and Einstein one would have said, ‘waves or
vibrations of ether’.

174 TIME

We have now come to the end of this study, which has led
us from the biological problem in general to the notion of
time. The first part of this book can be compared to a trip in
an aeroplane at a low altitude above a poorly explored country
of varying aspects. From on high, without going through the
fatigues and deceptions of the explorer, we have been able to
realize the enormous and various difficulties which he would
encounter on his way. Then, choosing with care our landing-
place, we alighted in a region more easy of access than the
others, though still barren. We then reported in detail the
material labour of the pioneer, the clearing of the land, the
organization of the conquered ground, the tracing of roads
leading to already colonized regions, the blazing of trails
towards the unknown. Once this programme accomplished,
we again stepped into the aeroplane and rose to a greater
height, losing sight of the details but embracing in a single
sweep of the eye our universe and the relations between
certain external causes and their subjective effects. Chance
decreed that some of our experiments were of a nature to
throw a little light on the fundamental notions which form the
frame of our concepts. We deducted therefrom a few con-
clusions which seemed to us legitimate. We do not doubt
that we will be criticized for it. And yet, is it not logical to
try to throw a bridge between the external world and our
consciousness, considering that we can now approach the
problems which have preoccupied men for centuries: problems
of space, of matter, of time? The pure physicist cannot do
this for, a priori, he neglects consciousness, which is not of his
domain. Progress in this direction can therefore come only by
the path of biology.

The purely imaginary, philosophical concepts of olden days
are outdistanced. Our ideas on matter are infinitely more
mysterious than the wildest lucubrations of philosophers. We
cannot, and will not, doubt the evidence of our senses, the
indications of our instruments, and the deductions of our
intelligence. We admit that the properties of things are due
to the motion of elements which seem to have no existence ©

CHEMICAL CLOCK 175

outside of this motion. We ascertain that all reality can be
traced back to a conjunction of space and time, that immobi-
lity is synonymous with nullity, and yet we hesitate, not without
a certain hypocrisy, to look things in the face. We have been
frightened of philosophy. We have been warned, and rightly
sO, against mere intellectual exercises. But now that science
brings us back to measurable, concrete facts, which raise new
problems, we are forced to attack them, if the conquests of the
human mind are to continue, even though these problems
have been listed sixty years ago amongst the ‘untouch-
able’ questions reserved for philosophers. We cannot help
but smile nowadays when thinking of the ancient quarrels.
There is no more room for such childishness, which only
existed because of our ignorance and because, the problems
being wrongly stated, the extrapolations were false. The
modern experimental results have made a hecatomb of theories
in ‘ism’. A harvest of disturbing facts arises in their place.
As they are solidly established, they can hardly give birth to
quarrels, but in front of them, deprived of the magnificent
confidence of our predecessors, we often feel our reason falter.

It must be admitted that these results have sometimes
dashed the hopes prematurely expressed with great publicity
by certain scientists of the last century who had given rein to
their enthusiasm and sentimental convictions to the detriment
of those primordial qualities of a scientist: prudence and
humility. This cannot be helped. Our immense progress is
measured principally by the fact that we now admit that we
know nothing—or very little—and that it is quite possible that
we shall never know much more. Our science will assuredly
progress, and the material conditions of our existence will be
transformed—I hesitate to say ameliorated. Day by day we
will learn to use with greater skill the elements composed
ultimately of pure velocity, that is to say, of space and time.
But what benefit will our consciousness, which transforms
these velocities into a universe, derive therefrom? How will
our happiness be increased? These are vain questions. There
‘is no doubt that a new era is beginning from a philosophical

176 TIME

point of view. Those who are tempted to deny it need only
pass in review the conquests of physics since the discovery of
radio-activity. Whether they wish it or not, they will be
obliged to admit that our brain has reduced the universe, as
we said above, to velocities and accelerations; that is to say, to
space and time. Even ether, the unreal reality which could
give our predecessors the illusion of a substratum of pheno-
mena, has been suppressed.’ We find ourselves confronted
by a world characterized by a number of statistical properties,”
the resultant at our scale of different elementary phenomena.
These elementary phenomena escape us because we ourselves
are a Statistical resultant. But it is they which are the Universe
itself, the universe considered in the absence of Man.

Man is too curious not to ask himself whether the universe
exists outside of him. He already agitated the question in
olden days when his intelligence, genius, and faith were the
only elements he possessed to solve this immense problem.
We have progressed since Leibnitz and his monads, but we
seem to travel in a closed circuit. One of two things: either
we shall continue to accumulate facts which will raise an
unsurmountable wall around us, or else we shall have the
courage to climb to the top of the tower in which we imprison
ourselves, so as to throw a circular glance around and take our
bearings without any preconceived ideas. We never sus-
pected, when we decided to abandon dialectics and philosophy
and to lean exclusively on science, that the latter would lead
us so rapidly to the edge of the abyss. We are the victims of
a “Cartesianism’ pushed to the extreme limit, and now we
are caught in our own trap. We must jump the fence or stay
where we are. We will not be able to experiment on pure
time and space by means of our beautiful instruments, nor
can we apply to them the reasoning and rigorous laws which
have no value outside of our presence. How shall we manage

1 There are many excellent books on the subject. I have cited a
few of them, but new ones appear continually in every country.

2 One should read the admirable book of Ch. E. Guye on this

subject, L’ Evolution physico-chimique, to which I have already referred
the reader (note, pp. 24, 27).

CHEMICAL CLOCK 77

to suppress, in thought, this presence outside of which we
cannot speak of reality?

So far, only mathematicians have dared to venture into the
domain of the imponderable. They speak a language the
symbols of which express solely pure ideas or relations.
Thanks to this privilege they can explore the most abstract
regions and emit daring theories without incurring the
thunder of the enemies of philosophy, the rationalists. It
must be admitted that mathematical methods possess a
rigorousness never attained by ancient philosophers, which
enables a greater number of men to reason with a seeming of
truth. Yet, there as elsewhere, the value of the conclusions
depends on the value and legitimacy of the premises and
postulates, that is to say, on the genius of man and not on the
rigour of the intermediate reasoning.

Nowadays our philosophers are mathematicians. Their
aim, if not their ambition, is not to explain, but to translate
quantitatively the facts perceived by our conscience. This is
undoubtedly a marked progress. Nevertheless, the question
now arises as to whether quantitative symbols will ever be
able to express life, psychological phenomena in general,
intelligence, and mathematical reasoning itself, including the
principle of beauty which it so often embodies.

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INDEX OF NAMES

Alembert, d’, 132

Ampere, 39

Avery, Oswald, 40, 42, 43, 44,
45, 46, 47

Backmann, Gaston, 100

Bayliss, 36, §4

Bergeim, 54

Bereson,. 28, 126, 127,129; 132,
143, 144, 146, 172, 173

Berard, Claude, 1, 2,7, 14; 23,
26, 275 34, 35> 37

Bertlay, 146

Bertrand, Gabriel, 4

Bichat, 1, 26,35

Boltzmann, 27

Bordet, 146

Boyle, 31

Broglie, Louis de, 28

Bucherer, 143

Buffon, 2

Carnot-Clausius, 24

arte). VAexIS:, .F33\,16,' 19,20;
54 55, 56, 57, 62, 66, 67, 72,
TOT, 1C2,, 1035 1055, 106, TOS,
109, WEAy L155 L1G, T175)-1475
164

Clemenceau, 84

Coulomb, I71

Crocker, 113

Dakin, 66, 67, 75, 76; 77
Darwin, 17

Daufresne, Maurice, 67, 75
Day, 146

Dehelly, 75

Democritus, 170
Descartes, 7, 26, 129
Desmarres, 83
Doljansky, 113

Donnan, 35

Dubos, René, 40, 44
Duclaux, Jacques, 35
Dutrochet, 35

Ebeling, A. H., 98, 105, 116, 164
Eddington, 132

Ehrlich, 113

Esistein, 53s 1373-073

Bener, Franz, 25

Fabre, 16

Faraday, 39

Fischer, Albert, 105, 106, I10,
LUZ, Tus

Francois, Marcel, 159, 160

Freundlich, 24

Friedlander, 43

Gibbs, 27

Goebel, Walter, 40, 46, 47

Grabenberger, 160

Gye, ‘Charles Hug:, 13, 24,27:
176

Hallwachs, 99

Hartmann, Alice, 55

Harrison, 103

Hawk, 54

Heidelberger, Michaél, 40, 43, 47

Heisenberg, 28

Helix, 33

Helmholtz, von, 24

Herodotus, 133

Hertz, 99

Hoagland, 160

Hopkins, Sir Frederick Gow-
land..25,. 32

Houllevigue, 135

Huber, Francois, 14

Huyghen, 162

Jacquemaire, 84
Jeans, James, 31, 130, 132
Jennings, 146

Kaufman, 143
Kelvin, 24
Kolmus, 160
Kuhn, 4

180 BIOLOGICAL TIME

Lamarck, 17

Landsteiner, 39, 40, 44, 45
Langerhan, 38

Lapicque, 35, 163
Laplace, 28

Latapie, 106

Lecomte du Nouy, 96, 98
Leibnitz, 7, 176

Martignan, 136

Metalnikov, 145, 146
Metchnikoff, 45

Minervini, 58

Minkowski, 131, 132, 133, 135
Morse, 54

Newton, 136, 141, I7I

Obermayer, 39, 40
Osterhout, 36
Ostwald, 16

Parker, Raymond, 105
Pascal, I
Pasteur, 48, 53, 145

Pearson, Karl, 126, 132, 139, I4I

Pfluger, 135
Pick, 39, 40

Pieron, 159, 160

Plato, 37> 173

Planck, 173

Poincare, Henri, 32, 33, 34

Reverdin, 62
Ringer, 107, II5
Rivers, 114

Roche, 33

Rostand, Jean, 171
Rous, I13

Rufz de Lavison, 93

Schrédinger, E., 28
Spallanzani, 58
Silberstein, 131

Tolstoy, 39
Tuffier, 83, 84, 88
Tyrode, 107

Vallery-Radot, 53

Van ’t Hoff, 12, 98, 100, 159, 160

Vries, de, 17

Wahl, 160
Wells, H. G., 103, 131
Woodruff, 145

8