Biology and social problems

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JHemortal lectures

THE RELIGIOUS REVOLUTION OF TO-DAY.
By JAMES T. SHOTWBLL. 1913.

BIOLOGY AND SOCIAL PROBLEMS. By GEORGE
HOWARD PARKER. 1914.

HOUGHTON MIFFLIN COMPANY
BOSTON AND NEW YORK

€1)0 William 2&rcto£ter Ciarfc

Jlcctureg
1914

All figures after Castle

PLATE IV. OVARIAN TRANSPLANTATION

Fig. 1. A young, black guinea-pig like the one whose ovaries were transplanted into the
albino shown in Fig. 2. Fig. 2. An albino guinea-pig whose ovaries were replaced by
those from such a guinea-pig as that shown in Fig. 1. Fig. 3. An albino male guinea-pig
with which the one shown in Fig. 2 was mated. Figs. 4 and 5. Two of the six offspring
of the matings of the guinea-pigs shown in Figs. 2 and 3. All the offspring were black.

B^iHiam S&rctogter Clarfe

3lecture£
1914

BIOLOGY AND SOCIAL
PROBLEMS

BY

GEORGE HOWARD PARKER, S.

PROFESSOR OF ZOOLOGY IN HARVARD UNIVERSI
AND WILLIAM BREWSTER CLARK LECTURER
AT AMHERST COLLEGE FOR 1914

BOSTON AND NEW YORK
HOUGHTON MIFFLIN COMPANY

prc^" Cambridge
1914

COPYRIGHT, 1914, BY GEORGE HOWARD PARKER
ALL RIGHTS RESERVED

Published November zqi4

TO

L. M. P.

FOREWOED

THE unique characteristic of modern times
— one which gives every indication of being
permanent — is that the world, both personal
and external, is to an apparently increasing
degree in a state of change. The immense
significance of this fact is as yet but dimly
perceived. The new modifies the old or dis-
places it in every department of life without
exception and with increasing rapidity. New
ideas, new movements, new ways of looking
at things present themselves for attention for
the first time or call upon people to change
their attitude towards things they had con-
sidered settled. This state of the world ren-
ders the practical problems of personal con-
duct and social policy increasingly vital and
complex, and makes the task of a college in
its relation to them as much more difficult as
an institution is less mobile than an indi-
vidual.

To assist Amherst College, therefore, in
throwing light in a genuinely scientific spirit
upon the relation of the research, discovery,

viii FOREWORD

and thought of the day to individual attitude
and social policy is our aim in the founda-
tion of these lectures. Such light may come
through a recent discovery in natural or ap-
plied science, through a new tendency in art,
literature, or music; it may be the result of
some painstaking research in history or an-
thropology ; or it may be found in some vital
movement, religious, philosophic, economic, or
political. It is our wish that men and women
who are in the position of leaders in such
phases of the life of the day shall give to
Amherst College and the world an exposition
of their particular work in its relation to what
they conceive to be a modern outlook.

We give these lectures in memory of Wil-
liam Brewster Clark, M.D., who graduated
from Amherst in the class of 1876. We be-
lieve that no place for a memorial to him
could be more fitting than the college which
he loved with a devotion characteristically
rich and sincere, nor any form more suitable
than lectures on subjects which to him would
be most absorbing.

FANNY H. CLARK,
W. EVANS CLARK.

NEW YORK CITY, 11 March, 1913.

POSTSCRIPT

SINCE the publication of the first series of
lectures it has seemed advisable to limit the
scope of future series more definitely. Should
the field of subjects include all of those which
affect "individual attitude and social policy/7
it would make for a loss of coherence and
continuity in the lectures as a whole. Accord-
ingly, we have decided to confine the subjects,
for the present at least, to those which bear
directly upon a most important phase of the
general problem of " social policy " — that of
Social Control.

The idea of unlimited human progress is
but four centuries old. The idea of the con-
scious direction of that progress is yet in its
infancy. Few indeed there are who do not
still consider human characteristics, institu-
tions, and environment to be as immutably
fixed as the hills and the ocean. The merest
scattering of human beings realizes that with
knowledge and cooperative effort large masses
of people can, in great measure, seize their
destiny and mold it to their conscious aims.

With the birth of this idea of Social Con-
trol among the few have come large plans of

x POSTSCRIPT

social reorganization and improvement to
affect the many. The salient feature of most
of these plans, however, is their speculative
and dogmatic quality. They lack, quite nat-
urally, the basis of positive knowledge and
experience. Social Control to-day is more
prophecy than science.

It is our hope, therefore, that in these lec-
tures we may contribute toward this new sci-
ence by providing a forum for those who have
data relating to the problem.

With this limitation of their scope the lec-
tures will be continued along the lines origin-
ally planned.

F. H. a
w. E. a

ARDNAMURCHAN

LOWER ARGYLE, N.S.

12 August, 1914.

CONTENTS

INTRODUCTION xv

I. THE NERVOUS SYSTEM 1

II. HORMONES 39

III. EEPRODUCTION ,63

IV. EVOLUTION 98

ILLUSTRATIONS

OVARIAN TRANSPLANTATION (Plate IV)

(p. Ill) Frontispiece

From photographs in the possession of Professor
W. E. Castle.

FEMINIZED GUINEA-PIGS (Plate I) ... 52

By courtesy of Professor E. Steinach.

MENDELIAN INHERITANCE (Plate II) ... 86

From photographs in the possession of Professor
W. E. Castle.

UNIT CHARACTERS (Plate III) 92

From photographs in the possession of Professor
W. E. Castle,

INTRODUCTION

IN our endeavor to better the conditions of
man, probably no facts are more worthy of
consideration than those included in his natu-
ral history, a science which in its wider aspects
has done more in the last few centuries than
any other body of knowledge to change our
opinion of man's real nature and of his place
in the world. How great this change has been
will be evident if we compare the ancient view
of man's relation to the universe with the
opinions of to-day. In early times the heavens
were supposed to be a dome from which show-
ers descended upon the expanse of earth be-
neath, fertilizing it and rendering it a fit abode
for man. Here he built habitations, cultivated
the soil, and peopled the earth with his off-
spring. To him the earth seemed the center
of the universe, and he believed that its crea-
tion was for his convenience and welfare.

But this anthropocentric conception was
not without its difficulties. Even as early as
the days of Aristotle, good reasons were given
for the belief that the earth was not a plain

xvi INTRODUCTION

under the vaulted heavens, but a globe. This
conclusion was accepted by many of the early
astronomers, and much speculation was pro-
voked by it as to the condition of the antip-
odes and the relation of the earth to the
heavenly bodies. In the system devised by
Ptolemy in the early part of our era, the earth
was placed at the center of things and the
heavenly bodies were supposed to move around
it. This geocentric theory was for a long time
the prevailing opinion of the structure of the
universe. It permeated much of the Middle
Ages and afforded the physical setting for
such great works of art as the Divine Comedy.
It was, however, eventually replaced by the
Copernican theory, according to which the
sun, not the earth, is the central body around
which the others move. So completely does
this heliocentric theory meet the facts of as-
tronomy that its truth is beyond dispute. But
in abandoning the old for the new, man was
obliged to give up his idea of a centrally lo-
cated habitation. In fact it may be said that
the Copernican theory removed the last physi-
cal vestige of the support for the anthropo-
centric conception and left this idea to survive
merely as a poetic figure.

INTRODUCTION xvii

But modern astronomy has done vastly
more than displace the habitation of man from
an assumed central position. It has given us
a view of the structure of the universe such
as was never dreamed of before. Not only is
the earth one of the smaller members of an
association of heavenly bodies traveling at
enormous speed around a centrally located
sun, but the whole solar system thus consti-
tuted, though its diameter is between five and
six thousand millions of miles, is small com-
pared with even the measurable space beyond
it. The star nearest to us is alpha centauri,
distant between four and five thousand times
the diameter of our system. Light from this
star takes over four years to reach us. No
means are known for measuring the distances
of the most remote stars. Some of them have
been estimated to be from seven to eight thou-
sand light-years from us ; that many of them
are removed by more than one hundred light-
years is certain. This distance amounts to
over one hundred thousand times the diame-
ter of our solar system and is unquestionably
far short of the actual distances of many stars.
None of us in this audience will live to see the
light which at this moment is starting toward

xviii INTRODUCTION

the earth from many of these bodies. Such
expanses of space as are implied in these meas-
urements were probably never imagined by
even the astronomers of olden times and cer-
tainly never by those who held the ancient
opinion of a flat earth vaulted by the heavens.
The immensity of these stretches in relation
to the earth and to man brings us to a realiza-
tion of our own insignificance. Man is as the
merest atom among these magnitudes; and
the nations " are counted as the small dust
of the balance."

If, then, the human race can no longer claim
the central place in the universe, is not the
observed of all observers, what can be said of
it? To this question natural science has re-
plied that man is the product of his immedi-
ate environment. And it therefore behooves
those who have his welfare at heart to ac-
quaint themselves with this environment as
well as with man regarded as one of its prod-
ucts. It is the object of these lectures to at-
tempt to sketch in outline something of man's
nature from this standpoint.

Viewed near at hand and as a part of his im-
mediate surroundings, man has a twofold in-
terest. He is, first of all, an incessantly re-

INTRODUCTION

xix

sponsive organism performing an enormous
variety of complicated and intricate acts some
of which are indicative of the highest order
of intelligence; and, secondly, he possesses
powers of reproduction in that he can leave
behind him offspring who, while they carry
with them the vast inheritance of the race,
are also the means of that gradual change
which has made his own coming possible. In
dealing with the natural history of man in
the following lectures these two aspects of his
nature will be the chief topics for consider^
ation.

BIOLOGY AND SOCIAL
PROBLEMS

THE NERVOUS SYSTEM

OF the sixteen hundred millions of human
beings that populate the earth to-day expe-
rience has shown us that we usually have no
difficulty in learning to distinguish one from
another with perfect certainty. Physical traits,
such as stature, color of hair or eyes, facial
form and proportions, are the elements usually
employed in this discrimination ; but only a
finger print may suffice. When, however, we
ask ourselves what constitutes the real in-
dividual whom we have learned to know, we
are less inclined to dwell on physical traits
than on the innumerable characteristic move-
ments in the form of common acts, responses,
and replies which are habitual with him and
which we believe to indicate in him certain
mental states and attitudes that we have come
to associate with him as part of his nature.

2 BIOLOGY AND SOCIAL PROBLEMS

These traits seem to us to indicate the real in-
dividual more truly than such obvious physi-
cal peculiarities as stature, color of hair, and
the like, for the reason probably that expe-
rience has taught us that, though the physi-
cal traits may change with time, the others
remain relatively stable and may be counted
upon as more or less permanently present.
We group these relatively stable traits under
the head of personality, and we think of
these collectively as constituting the core and
essence of the individual, the real and effec-
tive part under cover of the more obviously
physical, the ego or soul of the situation. It
is the possession of a centralized nature, of
an active personality, that makes each normal
human being an effective and responsible unit
in society. His attitudes are the result of this
possession ; his acts are determined by it ; it is
in fact his inmost self.

What can be said about personality so far
as its natural history is concerned? How is it,
for instance, related to the body? Many of the
ancients believed personality to permeate more
or less completely the whole human frame ; it
was a shade or shadow that simulated the form
of the material body in all its details, but was

THE NERVOUS SYSTEM 3

airy in its lightness and transparency, and,
like a shadow, it might separate itself some-
what from the body. More accustomed to
think of an animal as a whole than as an as-
semblage of parts, they were prone to conceive
of functions as more or less diffusely related
to the body. Yet that a certain degree of local-
ization was admitted is seen in the opinion
ascribed to Galen that the brain is the seat
of the rational soul, the heart the location of
courage and fear, and the liver that of love.
This localization became more or less restricted
in later times. Thus, Vesalius taught, in the
sixteenth century, that the chief soul was en-
gendered in the brain by virtue of the powers
of the proper material and form of that organ.
And, although Stahl attempted, a century and
a half later, to revive the belief that the soul
and the sensorium commune were diffused over
the whole body, that is, were resident as well
in the tip of the finger as in the brain, the idea
of the localization of these active properties
in the nervous system became so well grounded
through the investigations of the physicians of
that time, particularly Haller, as to assume the
form of permanency. This growth of knowl-
edge led directly to the modern view that

4 BIOLOGY AND SOCIAL PROBLEMS

personality is, strictly speaking, a property of
the nervous system and is in no true sense the
direct result of any other system of organs.
The nervous system, to be sure, is embedded
among other organs of the body, and the
environment thus provided influences pro-
foundly its condition and action; but what is
meant by individual personality, acuteness or
dullness of sense, quickness or slowness of
action, temperamental traits, such as a gloomy
or bright disposition, incapacity, shiftless-
ness, honesty, thrif tiness, or sweetness, are all,
strictly speaking, functions of the nervous
system. All these traits, then, that count for
so much in making the individual an effec-
tive or ineffective member of society, are the
direct product of his nervous system, a system
which is equaled in its importance in social
problems only by the reproductive system.

How the nervous system subserves person-
ality, and how in man it has come to be the
seat of that general function, are questions
whose solutions are to be sought in the condi-
tions of our nervous organs to-day and in the
course which their evolution has taken.

The body of man, like that of other higher
animals, is composed of an immense aggre-

THE NERVOUS SYSTEM 5

gation of cells, such as skin cells, bone
cells, muscle cells, gland cells, and so forth,
arranged so as to constitute its organs. The
nervous system in the higher animals, like their
other sets of organs, is also composed of cells,
but nerve cells are very unlike other cells.
Although the analysis of the body from this
standpoint was undertaken three quarters of a
century ago, the unique character of the nerve
cell was only first fully grasped by Waldeyer
in 1891. Each nerve cell, or neurone, as Wal-
deyer designated it, consists of a nucleated cell
body, the so-called ganglion cell of the older
neurologists, from which extremely attenuated
processes, the nerve fibers, reach out to the
most distant parts of the animal. These proc-
esses, which for a long time were not recog-
nized as belonging to the nerve cell, are the
most characteristic parts of its structure. Ex-
tending as they do in the larger animals for even
some meters from their cell bodies, they afford
an example of the special extension of a single
cell such as is seen in no other histological
element. In man, for instance, neurone proc-
esses are known to begin in the middle of the
back and extend to the toes, a distance well
over a meter. Although the human body con-

6 BIOLOGY AND SOCIAL PROBLEMS

tains other elongated organs than nerves, as,
for example, muscles and, particularly, blood
vessels, the cells of these parts are in no wise
elongated as the cells of the nervous system
are. In this respect the nervous system seems
to be unique.

Described from the standpoint of the histo-
logical elements composing it, the nervous
system of man and the other higher animals
may be said to be made up of an enormously
intricate system of interwoven neurones. The
number of these elements in such a nervous
system is incredibly great and certainly reaches
many, many millions. The complexity of their
arrangement is familiar to every reader of
textbooks on neurology, but even the most
involved descriptions in the texts are as sim-
plicity itself compared with the real complex-
ity in such a nervous system as that of any of
the higher animals, not to mention man.

Yet, notwithstanding the enormous com-
plexity in the arrangement of the neurones in
such animals, these elements are capable of a
relatively simple classification. A large num-
ber of them extend from the skin and the or-
gans of special sense, such as the nose, the
tongue, the ear, and the like, to the central

THE NERVOUS SYSTEM 7

nervous organs. These neurones become ac-
tive when their sense organs are appropriately
stimulated and transmit impulses from the
periphery to the central organs. They are,
therefore, classed as afferent or sensory neu-
rones. Another set of neurones transmit im-
pulses from the central organs to the muscles
and other mechanisms of response. These are
called efferent neurones. It might seem that
the afferent neurones leading into the central
organs and the efferent neurones leading out
from them were all that were necessary for
even a complex nervous system, but as a mat-
ter of fact there is a host of other neurones
which never reach beyond the limits of the
central nervous system and which are con-
cerned with bringing one part of this system
into communication with another. As a rule
these neurones cannot be designated appro-
priately as either afferent or efferent. They
have, therefore, been termed internuncial. In
the higher animals they certainly far outnum-
ber the afferent and the efferent elements col-
lectively and constitute the bulk of the central
nervous system in these forms. Thus, not-
withstanding the enormous numbers of neu-
rones in the higher animals and the intricacy

8 BIOLOGY AND SOCIAL PROBLEMS

and complexity of their arrangement, they
can be grouped conveniently under the three
classes, afferent, efferent, and internuncial.

The general arrangement of the neurones
in any complex nervous system, as indicated
in the preceding classification, foreshadows in
a way the simplest complete nervous act, the
reflex. When an animal is stimulated, it usu-
ally responds almost immediately by a move-
ment. In most animals this operation is carried
out by the nervous system and the appended
motor organs, the muscles. Such a simple
neuromuscular operation is called a reflex. It
involves the stimulation and activity of an
afferent neurone, whereby a nervous impulse
is sent into the central organ from which issues
over an efferent neurone a motor impulse that
brings a muscle or a group of muscles into
play. Such an action can be conceived to be
restricted to the two classes of neurones men-
tioned, namely, the afferent and the efferent,
but probably in the great majority of actual
occurrences internuncial neurones are included,
and these strictly central elements mediate be-
tween the central ends of the efferent and of
the afferent neurones. The reflex is thus a
physiological unit, so to speak, in the action

THE NERVOUS SYSTEM 9

of the nervous system, and though it can
scarcely be said to exist in the bald way in
which it has just been described, the idea of
the reflex has been certainly a most important
conception in the analysis of nervous opera-
tions.

Many of the elemental movements which
the body of man is continually exhibiting par-
take of the nature of reflexes, and if we ex-
tend this term to include operations which in-
volve consciousness, and there seems to be no
good reason why we should not so extend it,
almost every form of nervous activity may be
classed under it. Many of our daily acts are
reflexes of the simplest possible kind ; our in-
stinctive movements and our habits are groups
of these reflexes more or less complex in their
associations and in their sequences. In fact
the ensemble of nervous activity that we rec-
ognize in personality rests on a background
of reflex operation and is itself made up in
large part of just this mode of action. Let us
turn now to a consideration of some of the
chief classes of nervous activity in man, that
we may see something of their significance to
him as a social organism.

If at the outset we attempt to discover

10 BIOLOGY AND SOCIAL PROBLEMS %

those reflex operations of our bodies which
seem to us to exhibit the most primitive forms
of activity, we may well turn to the responses
of our internal organs. The heart of a normal
adult man in repose beats at a rate of about
seventy pulses per minute. If he rises and
stands, it usually increases its beats to about
eighty per minute; if he lies down, the rate
may fall to some sixty per minute. Unusual
exercise, as in running and other forms of
vigorous muscular work, calls forth a marked
increase in the rate which may last for some
time after the exercise has ceased. All these
changes in the action of the heart are con-
cerned with the appropriate supply of blood
to the working body, particularly its muscles,
and are of an obviously adaptive kind. Since
they follow with great precision and regular-
ity the changes in the state of the individual,
they might be looked upon as good examples
of simple reflexes. But a careful inspection
of them will show that this is not strictly
true.

The heart of man, like that of other higher
animals, receives at least two kinds of nerve
fibers, sympathetic and vagus fibers. The
first of these on stimulation accelerates the

THE NERVOUS SYSTEM 11

heart-beat; the second retards it and may
even bring it to a complete standstill. Such
a control of a muscle is by no means usual
and suggests at once that the heart must
be an exceptional organ. But what is of still
more significance than this peculiar form of
control is the fact that the heart will keep on
beating for many hours after all its nervous
connections with the rest of the body have been
severed. This condition would be very difficult
to explain from the usual standpoint of the
relation of nerve to muscle, were it not known,
from the time of Remak, over half a century
ago, that the heart muscle is permeated with a
network of nerve cells and thus may be said
to carry its own nervous mechanism within it-
self. Hence it is clear that the sympathetic and
vagus nerves are not related to the heart mus-
cle as ordinary motor nerves are to the muscles
that they control, but are to be regarded as an
auxiliary nervous apparatus superimposed on
the heart whose true nervous mechanism may
be within its own substance.

It is not my purpose to enter here into the
vexed question of the nature of the heart-beat
in the adult vertebrate. As you are probably
aware, this question has divided physiologists

BIOLOGY AND SOCIAL PROBLEMS

into two opposing camps, the neurogenists
who believe that the heart-beat is essentially
nervous in its origin and the myogenists who
hold that it is muscular in source. But quite
aside from the way in which this question
may be settled, one point seems to be well es-
tablished, and that is that in the embryo of
such a vertebrate as the chick, the heart be-
gins to beat before any nervous tissue what-
ever can be discovered in it. At this stage,
then, the heart-beat must be purely muscular
and the nervous complications such as they
are in the adult must be of later origin.

The peculiar condition seen in the embry-
onic heart suggests that in primitive animals
muscle may have preceded nerve in its evo-
lution, and in fact confirmation of this view
seems to be presented by sponges. In these
animals the presence of muscular tissue was
long ago recognized, and recent studies on
their activities have shown that sponges are
enabled by means of this tissue to close their
pores and other apertures, and change slightly
the form of their bodies. They are not known
to possess any nervous tissues whatever, and
the responses which they exhibit, like those
of the embryonic vertebrate heart, are appar-

THE NERVOUS SYSTEM 13

ently dependent entirely upon the direct stim-
ulation of muscle.

In the adult human body there is at least
one muscle which, like the embryonic heart,
is open normally to a certain degree of direct
stimulation. This is the sphincter pupillaB by
means of which the pupil of the eye is con-
stricted. This muscle is ordinarily under the
control of the oculomotor nerve, and it re-
sponds reflexly by contracting when the ret-
ina is brightly illuminated. But it can also
be made to contract by direct stimulation. If,
in a blind person, a strong beam of light is
thrown through the pupil on to the retina,
but without illuminating the iris, the muscle
does not shorten, thus showing that the or-
dinary reflex arc is inoperative. If, now, the
same beam is directed against the iris, in
which the muscle is embedded, a contraction
follows, thus giving evidence of the direct
stimulation of the muscle. Certain parts of
the musculature of our bodies, then, exhibit
forms of response that are more primitive than
the reflex and that indicate something of the
probable nature of the beginnings of neuro-
mu scalar activity.

If the embryonic vertebrate heart illustrates

14 BIOLOGY AND SOCIAL PROBLEMS

a stage in the evolution of neuromuscular
mechanisms at which no reflex can occur, the
adult organ shows, in certain relations at least,
a simple form of true reflex. The heart of the
rabbit is invaded by a small nerve which arises
as a branch from the vagus and which has
been called the depressor nerve of the heart.
If this nerve is cut and its peripheral end is
stimulated, no result follows, thus showing
that the nerve has no motor relations with
the heart. If, on the other hand, the central
end is stimulated, a general fall in blood pres-
sure follows, demonstrating that this nerve
is an afferent nerve whose activity induces
through the central nervous system an en-
largement of the blood vessels of the body.
The receptor endings for this nerve are in
large part in the heart and are stimulated by
each stroke of that organ. When, therefore,
the action of the heart is vigorous the effect
on the endings of the depressor nerve is such
as to call forth a general enlargement of the
blood vessels of the body, thus providing the
heart, in a simple reflex way, with an ample
outlet for the blood. Since this adjustment
goes on quite without our knowledge, it is
correctly described as a reflex unassociated

THE NERVOUS SYSTEM 15

with consciousness, and in this respect is like
other deep-seated reflexes such as those by
which the food is moved through the digestive
tube. Operations of this kind constitute, per-
haps, the most primitive class of reflex move-
ments with which we are acquainted. Al-
though they may be absolutely unassociated
with consciousness, they exhibit a nicety of
adjustment that is most baffling when explan-
ation is attempted, for they show every appear-
ance of intelligent control. They, therefore,
afford evidence for that conception of the or-
ganism which has recently been so vigorously
advanced by the neovitalists, namely, that
the organism continually exhibits conditions
which, when we attempt to explain them, seem
to necessitate the assumption of an element of
intelligence.

The class of reflexes just mentioned, that
is, those unassociated with consciousness, make
up in all probability the large part if not the
whole of the nervous life of many of the lower
animals. While such a statement can be at best
only a judgment without the possibility of
final proof, it seems more probable that the
nervous life of sea anemones, jelly fishes, and
other lowly organized forms is made up of sim-

16 BIOLOGY AND SOCIAL PROBLEMS

pie nervous acts like the one just described than
that these animals have any real conscious ex-
istence. They are probably much more correctly
described as animal automata than as beings
possessing even a low degree of intelligence.
Many reflexes of the human body take place
with the certainty and precision of those just
discribed, but, unlike them, are associated
with consciousness. If we irritate the surface
of the eye by touching it, we involuntarily
wink. Here, then, is a simple reflex which is
associated with an irritating sensation, though
the response itself is involuntary. Sneezing
and coughing are similar reflexes. If we re-
peatedly strike a dog on one side of the mid-
dle of the back, he will begin scratching move-
ments with the hind leg of that side. Not only
are muscles thus reflexly brought into action,
but glands also serve as the efferent organs for
such reflex activity. When the surface of the
eye is irritated, not only does the lid move,
but the eye waters, that is, there is a reflex oper-
ation of the lachrymal glands whereby tears
flow. In addition to muscles and glands, elec<
trie organs and luminous organs, found among
fishes and other lower animals, are apparently
also reflexly excitable.

THE NERVOUS SYSTEM 17

Reflexes of the kind just mentioned are al-
most invariably congenital. The animal is born
into the world with the particular reflex mech-
anism fully formed and awaiting merely the
appropriate sensory stimulation that the new
mechanism may come into full operation. The
new-born babe sucks, coughs, and sneezes
without lessons or advice. Bees artificially
reared, and without the example of the work-
ing hive, make perfect comb. Many female
insects, mostly in response to odors, lay their
eggs upon materials which are appropriate
food for their young. Thus a great variety
of animal responses have the qualifications of
simple reflexes, and the daily life of many of
the simpler forms, like the worms, crabs, in-
sects, and so forth, are probably made up al-
most exclusively of this kind of activity. That
these responses in the lower animals are always
associated with conscious states even of a sim-
ple kind cannot be maintained with certainty,
but the evidence, on the whole, indicates that
most of them are like our coughing, or the
flow of tears from the irritated eye, involun-
tary operations, but with the stirrings of con-
sciousness on the sensory side.

The interrelations of these reflexes in ani-

18 BIOLOGY AND SOCIAL PROBLEMS

mals midway in the zoological scale, such as
the insects, for instance, are not without in-
terest. A fly in the neighborhood of food
moves, now this way, now that, partakes of
a little moisture, and, if disturbed by the ap-
proach of a person, rises in the air, circles
once or twice, and settles near the food to be-
gin again its irregular foraging. Evidently in
these responses smell, touch, and sight are
in continual play exciting various reflexes, no
one class of which predominates over another.
There is a condition of approximate balance
with momentary fluctuations, now this way,
now that. Catch such a fly in the hand and,
after a moment, liberate it ; it speeds with the
utmost rapidity to the nearest window. To the
casual observer the movements of the fly in
foraging were of the same mixed nature as
those which we exhibit in many of our daily
occupations, and the rush to the window seems
to be an effort to escape. But the same rush
is made to a closed as to an open window, and,
if the room in which the trial is made is dark-
ened by having the blinds drawn and is illu-
minated by a single artificial light, the rush is
made not at the window or even at the open
door, if it leads to darkness, but at the source

THE NERVOUS SYSTEM 19

of light, even though the fly meets its death
thereby. Clearly the movements of the fly are
not so like those of a human being, after all.
As the test with the artificial light shows, the
animal simply seeks light, not freedom. To be
sure, in most instances to fly toward the light
means to escape, but the insect's behavior is
rather in the nature of a reflex than of a cal-
culated action, and in that sense lacks intelli-
gence. The fly, like many other animals of its
own rank, is ordinarily in a state of what may
be called balanced reflexes, but after having
been especially stimulated by being caught
and roughly handled, this balance is greatly
disturbed and one set of reflexes, those con-
cerned with flight toward the light, becomes
supreme. Under such circumstances the fly,
without reference to food, drink, or other fac-
tor in its environment, rushes headlong at the
most considerable light within its range. Of
these two states, the one of balanced and the
other of unbalanced reflexes, the former is
more nearly representative of the condition in
man, though at first sight the reverse seems
to be true.

Turning to man, it is evident that, not-
withstanding his many powerful and assertive

20 BIOLOGY AND SOCIAL PROBLEMS

reflexes, he is not so much within the grip
of these agents as a fly is under the dominance
of its own reflexes. From the standpoint of
his nervous organization he is a much more
truly balanced organism than a fly. His acts
are not so abundantly purely reflex, but the
state of his higher nervous activities suggests
not only a condition of balanced reflexes, but
one that might be conceived to have resulted
from the disintegration of reflexes. The higher
nervous life of man, his intellectual life, seems
built upon two processes, the reception of im-
pressions through the sensory mechanism of
the body, and the production of voluntary acts.
These two operations represent in a way the
two parts of a reflex, and since they are abun-
dantly present in the higher nervous activities
of the human being in an essentially independ-
ent way, it is possible that the phylogenetic
beginnings of this form of intelligence may
have been associated with a disintegration of
reflexes. Certain it is that our sense organs
are almost continuously pouring into the cen-
tral organ a varied stream of impulses indica-
tive of the changes in the outside and yet with-
out calling forth any obvious responses in our
musculature. In a like manner, our central or-

THE NERVOUS SYSTEM 21

gans are discharging impulses to motion with-
out having been subjected to any particular
sensory stimulation. These two classes of ac-
tivities are continually exhibited in our higher
nervous life and afford some of its most dif-
ficult problems.

So far as our intellectual activities are con-
cerned, our sense organs may be said to be re-
ceiving incessantly notices of external changes
and to be transmitting these notices to the
central organs rather as information than as
incentives to action. From the eyes, the ears,
from the nose, the tongue, from the organs
of touch, from the cold and heat spots,
from the organs of pain and the deep-lying
muscle receptors, and from myriads of other
and unknown sensory mechanisms a steady
flow of impulses pours into the central organs.
The vast volume of this flood is of no spe-
cial service except in so far as it enables us,
partly consciously and partly unconsciously,
to adjust ourselves to the momentary state of
the environment. But certain currents in the
general flow influence us much more than the
rest and come to be more or less permanent
eddies in our mental stream. These eddies be-
gin to catch in early childhood, and as mem-

BIOLOGY AND SOCIAL PROBLEMS

ories continue to accumulate throughout life
till the obliterations of old age and death. In
many respects this accumulation is most di-
verse, for from the best remembered circum-
stance to the fact that is just about to be for-
gotten there is every gradation, and apparently
no circumstance remains long in the same
state of vividness, but all is drifting toward
oblivion, some portions more rapidly than
others, while the new is ever replacing the
old.

In practical life we come to regard our re-
membrances as having a certain degree of com-
pleteness, but in reality they are the merest
shred of our past. Think of a vivid experience
in the last ten years or so and recount to your-
self the occurrences of the day on which it
happened. Very little but the most shadowy
outline is left. Even yesterday, so near at
hand, is mostly gone, and as a test for the pres-
ent who among us here can give again from
memory the first sentence of this lecture?
We all heard it and I read it, but even I can-
not repeat it. Yet if memory were in this re-
spect only as perfect as a dictagraph, this sen-
tence could be recovered from every one in
the room. I am fully aware that in certain

THE NERVOUS SYSTEM 23

unusual mental states, such as hypnosis, the
individual can deliver information about mat-
ters which in his normally wakeful condition
he seems to be incompetent to produce, and
that in this way evidence of memory activity
in the subconscious regions of the mind is ad-

o

duced. But that this additional accumulation
would bring the shadowy past into anything
like the completeness of the present is not for
a moment to be imagined. Marvelous as all
these processes are, in that they are sugges-
tive of hidden and unseen powers, we must
still admit, I believe, that memory at best is
a most fragmentary affair. This opinion is
well expressed by Walt Whitman when, in
speaking of the insufficiency of biography, he
declares - —

Why, even I myself, I often think, know little or

nothing of my real life ;
Only a few hints — a few diffused, faint clues and

indirections.

But fragmentary as memory is, it is that
which binds our personality together ; without
it social responsibility would cease to exist.
We admit its frailness by translating our ideas
into the permanency of the written record.
This supplement to memory penetrates our

£4 BIOLOGY AND SOCIAL PROBLEMS

whole life, from the memorandum on a scrap
of paper to the inscription on the living rock,
and thus aids enormously one of our mental
processes at its weakest point.

How is memory related to the nervous sys-
tem ? By appropriate methods of experimen-
tation we can determine with great accuracy
the tracts of the nervous system over which a
given reflex runs. Is such a localization pos-
sible for memory, or is this function rather the
general property of the nervous system as a
whole? Strange as it may seem, memory is
almost if not quite the exclusive function of
one part of our nervous organs, namely, the
cerebral cortex. This gray layer covers the ex-
terior of the cerebral hemispheres and thus
lies on the surface of the brain separated from
the outer world by only the skull and the
superimposed scalp. In man it varies in thick-
ness from one and a half to five millimeters
and covers a convoluted field, which, were it
flattened out, would measure on the average
2352 square centimeters, equal to an area a
little over a foot and a half square. This re-
markable layer is the organ in which all our
sensations arise and where the processes of
memory go on. It is, therefore, the location

THE NERVOUS SYSTEM 25

of one of the most important aspects of per-
sonality.

Experimental demonstrations of this truth
have been abundantly carried out. By a care-
ful surgical operation the cerebral cortex of a
bird or even of a mammal, such as a dog, can
be removed and the animal can be kept alive
for as much as a year or more after the oper-
ation. Such animals yield most important
evidence as to the function of the cerebral
cortex. After recovery from the operation,
they exhibit no permanent motor disturbances,
such as paralyses and so forth, and they re-
spond to practically all forms of stimulation,
but their responses are not what would be
called intelligent. A pigeon from which the
cortex has been removed, when placed on a
hot plate will raise first one foot, then the
other, and finally squat rather than fly away.
A dog without a cortex will respond to a
painful stimulation of the skin by a growl or
a bark and will turn its head toward the spot
stimulated, but will not attempt to bite. Ca-
ressing calls forth no sign of pleasure, threat-
ening no sign of fear. In sleep there is no
evidence of dreaming. Such animals thus re-
spond to the immediate stimulus, but as

26 BIOLOGY AND SOCIAL PROBLEMS

though they were without experience and in a
way essentially stupid. Memory seems to have
vanished from them and with it the basis for
intelligent action. The animal responds to
stimulation like a nervous machine and with-
out reference to past or future.

What it is that the cortex contains and
that molds our responses into intelligent acts
is our store of experience. During normal life,
as we have already seen, a flood of impulses
due to the stimulation of sense organs by ex-
ternal changes pours into the central nervous
organs; many of these reach the cortex and
some leave on this organ a more or less per-
manent impression. These elemental impres-
sions are the materials out of which our men-
tal life is built. All our thinking is made up
of a redistribution and readjustment of these
elements. From the highest flights of poetic
imagination, from the aspirations of the most
devout to the extreme speculations of the
philosopher, mathematician, and devotee of
science, all are but readjustments and deriva-
tions of this mass of incoming material. With-
out this spring of supply the human brain
would be a barren and arid waste incapable
of bringing forth signs of intelligence. The

THE NERVOUS SYSTEM 27

brain of the developing child is a veritable ta-
bula rasa on which environment through the
sense organs writes the story of life. Innate
ideas there are none. The uninvaded mind is
like a machine in readiness for operation, but
awaiting the arrival of that first flow of power
to initiate its processes. Like the lung, it
stands in perfect physical readiness for action ;
at birth the stimulus for the first inspiration
occurs and the respiratory mechanism that is
to run till the end of life is started.

In stating briefly the modern conception
concerning the source of the contents of the
mind, I have put the matter almost in the
words of Locke, but the present aspect of this
subject is not based upon philosophical spec-
ulation ; it is grounded upon observed fact. We
know that when we sleep we revert to a con-
dition of relatively simple reflexes and that
intelligence vanishes in the assumption of the
unconscious state. To induce this condition
under normal circumstances, we check as far
as possible all sensory inflow by lying down
in a darkened, quiet situation. The impulses
from the organs of touch, equilibrium, and
especially of hearing and sight, having been
reduced to a minimum, the activity of the

28 BIOLOGY AND SOCIAL PROBLEMS

cortex quickly subsides, and with this sub-
sidence consciousness gives place to uncon-
sciousness. Thus, even a mind stored with rec-
ollections lapses into unconsciousness when,
under appropriate conditions, the flow of new
material from without is largely reduced. Not
only does the inflow of sensory impulses thus
condition the activity of the normal mind, but
it has also been found to be of like importance
in certain abnormal cases. Striimpeirs boy
was a defective who was insensitive to touch,
had no muscular sense, no taste, or smell, or
sense of pain, and was deaf in the right ear
and blind in the left eye. His sensory impulses
were received therefore, chiefly if not exclu-
sively, through the left ear and the right eye.
If the left ear was stopped and the right eye
bandaged, so that the sensory inflow practi-
cally ceased, he passed in a few minutes into
what seemed to be a state of sleep, thus dem-
onstrating the significance of the current from
the sense organs for his mental life. The ah*
normal, as well as the normal, thus gives evi-
dence of the general conclusion that, though
the mode of operation of the mind may be
determined by the inborn structure of the
brain, the content of the mind is supplied

THE NERVOUS SYSTEM 29

ultimately through sensory impulses from the
exterior.

Fragmentary and incomplete as memory is,
its performances continually excite our won-
der and curiosity, and even from the scien-
tific standpoint we are prone to speculate on
the methods by which it is brought about.
Our common habit of recording and storing
as evidence of our experience written or
printed signs has given us a figurative concep-
tion of the process of memory which is in
many respects misleading. We often think of
the organ of memory, the cortex, as a place in
which is set aside, in some such manner as
that just indicated, signs of our experience to
be drawn upon as needed. But the cortex is
a living portion of our body, and, like other
living parts, its life is expressed better in its
activity than in its structure, for its structure
is forever changing. Memory, therefore, is
rather a duplication of a process than the re-
appearance of a symbol. It is rather like a
current eddy in the flow of our mental life
than like a material sign. But it is an eddy
which only partially represents the original
and carries with it something that separates
it from real present experience and marks it

30 BIOLOGY AND SOCIAL PROBLEMS

as a shadow of the past. What memory really
is, however, is rather a matter for investiga-
tion than speculation. Of one thing we can
be fairly certain, memory is not a general
property of the nervous system, but is an op-
eration carried on in the cerebral cortex.

This portion of the brain is also the part
concerned with that second set of operations
which seem to result from the disintegration
of simple reflexes, namely, the voluntary acts.
That the impulses to voluntary movements in
man take their course from the cerebral cortex,
over definite neurone tracts through the cord
and nerves to the muscles concerned, is a fact
well attested by anatomy, pathology, and the
study of cortical localization. But it is not my
purpose to undertake to trace out the nervous
mechanism by which we control that enor-
mous complication of musculature that moves
when we wish to move, and that fails to act
when by reason of accident or disease nerve
tracts are interfered with or destroyed. Suffice
it to say that the impulses for the multitude
of our voluntary acts emanate from the cortex.
Whether they originate there de novo, or are
some delayed overtime sensory impulses mak-
ing their way deliberately through the central

THE NERVOUS SYSTEM 31

organs to a final effective outcome, cannot be
stated, and is perhaps, after all, a question of
no significance. For the nervous system, even
at its lowest physiological ebb, is never quies-
cent. It exhibits continuous activity. Even
in sleep our muscles show a slight contraction
due to a faint but incessant stimulation from
the nervous centers. The passage of a reflex
impulse through the nervous system, then, is
not so much like a brief period of activity in
an otherwise motionless machine as it is like
a momentary increase of motion in a slow con-
tinuous operation. From such a continuum
the voluntary impulses emerge. To seek their
origin is perhaps to look for that which does
not exist, at least in the definite and crystal-
lized form in which we often think of it.

Just as memory affords a most taxing and
perplexing problem for science, so the volun-
tary act is a process about which there is very
little real understanding. The difficulty lies in
its freedom. Such acts give us every evidence
both outward and inward of self-control. They
seem to be self -determining and in this respect
to violate those principles of sequence that we
find to underlie so much of nature.

Attempts have been made to show that the

32 BIOLOGY AND SOCIAL PROBLEMS

freedom of the voluntary act is not without
its counterpart in the more rigid aspects of
science. The answer to the question what two
digits will add together to make ten is not
single, but may be with equal truth any one
of several ; four and six is as correct an an-
swer as eight and two. But this kind of free-
dom is after all a formal freedom in a mental
operation rather than a freedom in a material
sequence in nature.

From the standpoint of science the solution
of the problem of the voluntary act, like that
of memory, is to be sought in investigation
rather than speculation. But the scientific
study of this question must be undertaken
without prejudice. Physics and chemistry are
branches of science to which the biologist has
come to attribute a certain fundamental im-
portance in that organisms are believed to be
enormously complex physico-chemical combi-
nations. Day by day facts of organic nature
are yielding to this conception, and such prog-
ress is being made as to give rise in the
minds of many investigators to the opinion
that in the end all will thus be subdued. But
voluntary acts, if not incorrectly described,
seem to be fundamentally contrary to the gen-

THE NERVOUS SYSTEM 33

eral principles of physics and chemistry, and
are, therefore, grounds for opposition to the
opinion just alluded to. However, in consid-
ering this opposition it must not be forgotten
that these sciences are still in process of ac-
tive growth, and that what we regard as their
general principles to-day are principles devel-
oped chiefly from a study of inorganic na-
ture. In only a most tentative way have these
sciences begun to touch matter and energy as
exhibited in organisms. How their principles
will be modified when they really begin a suc-
cessful attack on living beings remains to be

o o

seen, but that these principles will be modified
there can be not the least doubt. Then will be
the time to raise the question of the nature
of the voluntary act and other such problems if,
indeed, these problems really remain serious
in the light of the new knowledge, for often
what seems to be a perplexing question to-day
becomes insignificant to-morrow. Who con-
cerns himself now with the number of angels
that can stand on the point of a needle ?

But I cannot leave this matter of memory
and the voluntary operations without consid-
ering somewhat further the part of the human
nervous system in which these functions occur.

34 BIOLOGY AND SOCIAL PROBLEMS

The human cerebral cortex, as already men-
tioned, is a superficial layer of the brain with
a thickness varying from one and a half to
five millimeters and covering an average of
2352 square centimeters. This cortex is esti-
mated to weigh about 658 grammes. It is
composed chiefly of blood vessels, supporting
tissues, and nerve cells. The blood vessels and
supporting tissues are merely mechanical ac-
companiments of an apparatus the real func-
tions of which are carried on by the nerve
cells. These cells have been carefully studied,
their arrangement and distribution made out,
and it is estimated that in a single cortex
their number is not far from 9,200,000,000.
Notwithstanding this prodigious number,
these cells and their processes represent only
two per cent of the total weight of the cor-
tex ; in other words, the cortical nerve cells
and their processes in the average man weigh
about thirteen grammes. This amount repre-
sents a little less than a cubic inch of mate-
rial, or, to be more accurate, it will just fill a
cube whose edge is 2.35 centimeters. In a man
who weighs approximately one hundred and
fifty pounds, this amount of substance would
represent about one five-thousandth of his

THE NERVOUS SYSTEM 35

total weight, yet this very small proportion of
his body serves him as the material basis for a
whole life of intelligent activity and is the part
of the nervous system chiefly concerned in
yielding that almost impalpable product, hu-
man personality. Had Descartes been truly
scientific, and had he known in his time the
anatomy and physiology of the nervous sys-
tem as it is known to-day, he would have de-
clared that the cerebral cortex and not the
pineal body was the seat of the soul.

From the foregoing sketch some idea can
be gathered of the significance of the nervous
system for man as a social organism and of
the part it plays in his daily life. From a back-
ground of simple reflexes which attend to a
long range of his bodily needs, and which
are unassociated or only slightly associated
with consciousness, rise the superstructures
concerned with his higher nervous functions
such as memory and voluntary action. These
general nervous functions have done more to
make an individual of him than any other el-
ements in his nature. His circulatory mechan-
ism with its centralized heart has added much
to this unity, but even such organs are secon-
dary to the nervous system. When we reflect

36 BIOLOGY AND SOCIAL PROBLEMS

that many of the lower animals, like the sea
anemones, for instance, have only the merest
rudiments of a nervous system, and that this
system is there concerned simply in calling
muscles into action and exhibits practically
no central functions, we begin to appreciate
how strikingly different the conditions are in
higher and lower forms. Each tentacle of a
sea anemone contains its own neuro-muscular
mechanism and will continue to respond to
food particles after it has been severed from
the body. Its action is as independent of the
rest of the animal as the vertebrate heart is of
the body in which it grew. But the sea anem-
one, instead of possessing only a few such
organs as the vertebrate does, is constructed
almost entirely upon this plan. Its nervous
functions are most diffuse and subordinate;
its chief activities are feeding and reproduc-
tion. If man can be described as an organism
whose tour-de-force is intellectual, the sea
anemone is one whose culminating activities are
assimilation and growth. This condition of
affairs is characteristic of most of the lower an-
imals and represents unquestionably a primitive
stage before which the nervous system could
scarcely be said to have existed. In the higher

THE NERVOUS SYSTEM 37

forms, however, this system has far outstripped
the others in its growth, till in the mammals
and especially in man it has reached a position
of supreme dignity. Thus the nervous system,
though it originated later than some other sets
of organs, has in the higher forms attained to
paramount importance.

With the evolution of the nervous system
and the differentiation of the cerebral cortex
came the possibilities of that form of compli-
cated intellectual life that we know in our-
selves. Though less than a cubic inch of our
substance is really devoted to this form of ac-
tivity, it is as precious a cubic inch as any we
possess. By means of it we cherish the tradi-
tions of the past; its activities include all our
conscious states, our simple sensations, desires,
hopes, and aspirations, our sense of shame and
regret at deeds of unworthiness, our joy in
generous acts, our knowledge of all these
things; from it emanate the impulses to
those steps which mark us as dishonest or hon-
est, extravagant or thrifty, secretive and de-
ceptive or frank, open, and free, cold or affec-
tionate, in short all those signs which stand
for personality. Socially no part of our body
is more precious than this cubic inch of cortex.

38 BIOLOGY AND SOCIAL PROBLEMS

From the cradle to the grave we work to train
it. Our early childish plays and lessons are in-
tended to awaken it into activity. The school,
the college, the university work upon it ; our
whole educational system is devised to bring
into full efficiency this cubic inch of our body.
It must be enriched with experience ; it must
be trained to make wise decisions, to call forth
acts of friendly service. If you have doubts
of the enormous social significance of this cu-
bic inch of nervous tissue, look upon the in-
dividual in which it permanently breaks down,
a useless member of society, a charge upon
the state, if not upon the race.

n

HORMONES

IN olden times the theory and practice of
medicine was more or less permeated by the
doctrine of the humors. Those of you who
are conversant with medical history will recall
that, according to this doctrine, there were
supposed to be four cardinal humors : blood,
yellow bile or choler, phlegm, and black bile.
Many distempers of mind and body were at-
tributed to disturbances in these fluids, and
their conditions and proportions were sup-
posed to determine the physical and mental
qualities as well as the disposition of the indi-
vidual. Various kinds of insanity, known un-
der the general name of melancholy, were
supposed to be associated, as this term implies,
with the black bile. And we still describe tem-
peraments as sanguine, choleric, or phleg-
matic. But with the growth of our knowledge
of the nervous system and with the recognition
of its significance as the chief means of con-
trol for the body as well as the seat of person-

40 BIOLOGY AND SOCIAL PROBLEMS

ality, the doctrine of the humors was relegated
to the rubbish heap of worn-out ideas and dis-
appeared from view. Within late years, how-
ever, this doctrine, in principle at least, has
been revived, and recent investigations prom-
ise to give it renewed life, though not of such
general scope as it once enjoyed. The fluids
circulating in the bodies of animals, including
man, are undoubtedly highly important and
significant means of controlling the responses
of these forms and of determining their states,
mental and otherwise. Among the recent dis-
coveries which have been important in open-
ing up this point of view are those concerning
the action of the pancreas, a gland which was
supposed to be brought into activity through
the ordinary channels of nervous reflex.

The pancreas is a long, narrow gland ex-
tending from the neighborhood of the spleen
on the left side of the abdomen to the right
side of that cavity where its duct opens into
that portion of the small intestine known as
the duodenum. This opening is three or four
inches from the outlet of the stomach, there-
fore near the beginning of the duodenum, and
very close to the opening of the bile duct from
the liver. The pancreas is popularly known as

HORMONES 41

the sweetbread, or, better, the stomach sweet-
bread, to distinguish it from the thyroid gland
which is called by butchers, from its location,
throat sweetbread.

The pancreas in man produces a copious
secretion, as much as from five hundred to
eight hundred cubic centimeters per day.
This secretion is poured into the duodenum
through the pancreatic duct and is one of the
most important digestive juices. It aids in the
solution of almost all the constituents of our
food. The pancreatic juice is apparently pro-
duced in small amounts continuously, but the
major production and discharge is associated
with the taking of food. The increase of pro-
duction begins soon after food has entered
the stomach and develops to a maximum in
from two to four hours; it then gradually
falls off with the completion of digestion.

Almost two decades ago it was shown that
when acid solutions were applied to the mu-
cous surface of the duodenum, the flow of pan-
creatic juice was excited, and as the natural
contents of the stomach are acid, it was be-
lieved that, after they had passed into the
duodenum, their acidity was the normal stim-
ulus for the reflex mechanism controlling the

42 BIOLOGY AND SOCIAL PROBLEMS

pancreas. As the food arrived in the duodenum
from the stomach, the contained acid was sup-
posed to stimulate the nerve terminals in the
mucous membrane of that portion of the in-
testine and thus to set up nerve impulses which
were reflected back from the central organs
to the gland as excitants of its activity. This
opinion was consonant with the fact that arti-
ficial stimulation of the vagus nerve was fol-
lowed by pancreatic secretion. But the secre-
tion of juice by the pancreas was subsequently
shown also to occur even after the nerves
which supply that organ, namely, the vagus
and the splanchnic, were cut.

The difficulty thus introduced was removed
by the work of Bayliss and Starling about a
decade ago. They demonstrated that if some
of the mucous membrane of the duodenum
was scraped off and mixed with a weak solu-
tion of acid, an extract could be obtained
which when injected into the blood would call
forth an active secretion of pancreatic juice
even in an animal in which the nerves to the
pancreas had been severed. Hence they con-
cluded that the secretory activity of the pan-
creas was not necessarily dependent upon
nerves, but could be induced by a substance

HORMONES 43

which resulted from the action of the acid
food on the mucous walls of the intestine and
which was taken up by the blood and in this
way carried to the gland. Thus, what seemed
to be a reflex action proved in reality to be
the effect upon one organ of a substance
formed in another. The particular substance
in the case of the pancreas is known as secre-
tin. This substance is not of the nature of an
enzyme, for it is not destroyed by boiling
or by treatment with alcohol. It is, however,
a representative of what is probably a large
class of substances now recognized under the
general name of hormones, whose function it
is to excite activity in organs usually situated
at a distance from the region in which the
given hormone is produced; in other words,
to enable one part of the organism to control
another and distant part. As is shown by the
pancreas, hormone action strikingly simulates
in its results nervous activity, and yet on an
entirely different principle, a principle which
in fact revives the discarded doctrine of the
humors.

The extent to which hormones control the
body is only just beginning to be appreciated.
For a long time anatomists have recognized

44 BIOLOGY AND SOCIAL PROBLEMS

in the higher animals, including man, a num-
ber of so-called ductless glands, such as the
thyroid gland, the pineal gland, the hypophy-
sis, the adrenal bodies, and so forth. These
have often been passed over as unimportant
functionless organs whose presence was to be
explained as an inheritance from some remote
ancestor. But such a conception is far from
correct. If the thyroids are removed from a
dog, death follows in from one to four weeks.
If the adrenal bodies are excised, the animal
dies in from two to three days. Such results
show beyond doubt that at least some of these
organs are of vital importance, and more re-
cent studies have demonstrated that most of
them produce substances which have all the
properties of hormones. A number of these
organs, like the thyroids, the adrenals, and
the sexual glands, have been studied from the
standpoint of their internal secretions and
have more than a passing biological interest.
The thyroid gland in man consists of two
moderately large lobes closely applied to either
side of the windpipe just below the larynx or
Adam's apple. As previously stated, the gland
is popularly known as the throat sweetbread
in contrast with the stomach sweetbread or

HORMONES 45

pancreas. The two lobes of the thyroid are
united across the front of the windpipe by a
narrow band of their own substance, the so-
called isthmus. The thyroid gland is inti-
mately associated with a group of glands, the
parathyroids, whose presence was not always
recognized by the earlier investigators. Some
of the confusion which entered into the ear-
lier physiological work on the thyroid was
probably due to the accidental removal of the
parathyroids with the thyroid, a condition
which leads to very different results from
those observed in the simple removal of the thy-
roid itself. The circumstances which brought
about an investigation of the thyroid may now
be briefly stated.

In any large community individuals appear
from time to time who from childhood on fail
to grow and develop. They therefore are of
dwarfish stature, their hands are large and
misshapen, their features dull and expression-
less. All these signs, together with the actions
and habits of such individuals, give the im-
pression to the casual observer of low mental
capacity, if not idiocy, and such in truth is
their real state. As members of society they
are usually more or less helpless and are either

46 BIOLOGY AND SOCIAL PROBLEMS

private or public charges. They have long
been known under the name of cretins.

An examination of the physical condition
of these persons has disclosed the significant
fact that they all possess deficient thyroid
glands, and this discovery has led to the as-
sumption that the thyroid produces a hormone
which is essential to the growth and devel-
opment of the normal person. This belief is
abundantly supported by the success with
which cretinism and tendencies toward cretin-
ism can be in large part counteracted by thy-
roid treatment. Many of our so-called defec-
tive children are known to be cases in which
thyroid activity is reduced, and they approxi-
mate in many ways a mild form of cretinism.
In these cases, as well as in true cretinism, the
feeding of the patient with thyroid material,
with the throat sweetbreads of sheep, has been
followed almost invariably by most beneficial
results both physical and intellectual. In this
way children on a downward path of develop-
ment have been rescued from a trying form
of dissolution.

Defective thyroids, however, are not limited
to childhood ; they may appear in adult life.
At this stage they cannot, of course, produce

HORMONES 47

cretinism, but in other respects they call forth
the same set of changes ; intelligence declines
even to dementia ; bodily activity subsides till
only animal sluggishness is left ; a condition
known as myxedema supervenes, after which
in the course of some years the cases termin-
ate fatally. These mature cases are also im-
mensely alleviated by the thyroid treatment.
In cases of myxedema it was found that in-
jection of thyroid extract under the skin, or
better still, simple feeding of thyroid mate-
rial, gave favorable results. Only from sixty to
one hundred and thirty milligrams of sub-
stance administered every three or four days
was found sufficient to keep a patient in
health.

I cannot better picture to you the signifi-
cance of this treatment both for the child and
the adult than by quoting from Moore the
words of a well-known medical authority, Dr.
William Osier, who, in speaking of this side
of medicine, has said : " Our art has made no
more brilliant advance than in the cure of
these disorders due to the disturbed function
of the thyroid gland. That we can to-day res-
cue children otherwise doomed to helpless
idiocy, that we can restore to life the hopeless

48 BIOLOGY AND SOCIAL PROBLEMS

victims of myxedema, is a triumph of experi-
mental medicine." " The results as a rule are
most astounding — unparalleled by anything in
the whole range of curative measures. Within
six weeks a poor, feeble-minded, toad-like
caricature of humanity may be restored to
mental and bodily health. The skin becomes
moist, the pulse rate quickens, and the mental
torpor lessens." Thus thyroid deficiency, with
all its sad consequences for the individual and
society, can be largely overcome by the simple
introduction into the body of an appropriate
material from the outside.

But man is not only open to troubles from
deficient thyroids ; he may also suffer from the
excessive activity of these glands. In the dis-
ease known as exophthalmic goitre the patient
is nerved up to a high pitch of excitement, the
eyes protrude, and in general the symptoms
are the reverse of those exhibited by cases of
deficient thyroid. This state can be more or
less artificially produced by excessive thyroid
feeding, and the disease thus imitated, as well
as that dependent upon deficient thyroids, is
important for us in showing how essential for
our welfare and efficiency in the social organ-
ism is the proper amount of that hormone

HORMONES 40

which is produced by a few ounces of glan-
dular tissue in our necks,

Another important set of organs in the pro-
duction of hormones are the adrenal bodies.
These are paired, gland-like bodies situated
in the fat, one at the anterior margin of each
kidney ; hence their name. Each adrenal body
consists of an outer, firm, yellowish layer, the
cortex, and of an inner, soft, gray or brownish
mass, the medulla. Like the thyroid, the ad-
renals are unprovided with ducts. As already
mentioned, their removal from an animal is
invariably followed by its death in a few days
or even hours. They have long been known to
be associated with an obscure, fatal disease,
known as " Addison's Disease," which is
marked by the appearance of bronze patches
upon the skin. From their medullary portion
there has been extracted a substance variously
named epinephrin, adrenin, or adrenalin, and
capable of producing profound bodily changes.
This substance is apparently normally present
in the blood in very small amounts. If a strip
of intestine is placed in a warm oxygenated
Ringer's solution, it will show rhythmic con-
tractions. If, now, to one hundred million
parts of this solution only one part of adre-

50 BIOLOGY AND SOCIAL PROBLEMS

nalin is added, these contractions cease and the
bit of intestine relaxes. On the basis of such
observations as this, it has been estimated that
the adrenalin in our blood is normally about
one in two hundred millions.

Adrenalin has been isolated and is well
known chemically. It has in fact been pro-
duced synthetically. It is important as a means
of checking hemorrhages in minor surgery, for,
on local application, it quickly brings about a
constriction of the walls of the blood vessels.

No one knows with certainty what purpose
the small, constant amount of adrenalin in the
blood serves, but when more of this substance
appears, certain profound and significant
changes occur. These changes may be stated
briefly as follows : a cessation of the activities
of the alimentary canal ; a notable shifting of
the volume of the blood, from the abdominal
organs, to the lungs, heart, central nervous
organs, and limbs ; an increased cardiac vigor,
an augmentation of the sugar content of the
blood ; a hastening of its power to coagulate ;
and a rapid recovery of muscle from the con-
dition of fatigue. At first sight this seems to
be a heterogeneous assembly of physiological
effects such as might constitute a formal de-

HORMONES 51

scription of the action of any substance on the
body. But such is not in reality the case. As
Cannon has pointed out, all these facts gather
around a central condition of no small biolog-
ical interest, namely, preparation for physical
struggle. The cessation of abdominal activity
and the transfer of blood to the lungs, heart,
nervous system, and limbs is an adjustment
whereby the nutritive fluids are concentrated
in regions important for muscular activity.
Increased cardiac vigor improves the circula-
tion in these regions. The increase of sugar
in the blood adds to its nutritive value for
muscular work. The quickened coagulability
serves as an increased safeguard in case of

o

injury. And the improvement in recovery of
muscle from fatigue lengthens the time dur-
ing which an animal may continue a struggle.
Thus all the changes induced in the body by
an increase of adrenalin in the blood may be
regarded as emergency measures for times of
intense struggle. It is, therefore, entirely
natural to find that the extra adrenalin neces-
sary for all these changes is produced by the
glands whenever the animal is driven into a
condition of fear, rage, or pain. These nervous
states reflexly excite in the adrenal bodies

52 BIOLOGY AND SOCIAL PROBLEMS

such a production of adrenalin that the con-
ditions already described are almost immedi-
ately present ; in other words, when an animal
is excited to fear or rage or subjected to phys-
ical pain, its whole neuromuscular mechanism
and related parts are thrown into a condition
most favorable for vigorous and protracted
response. The biological significance of this
set of relations from the standpoint of the
struggle for existence must be clearly evident,
and we see again how a highly complex sys-
tem of organic interrelations can be developed
on a principle other than that of nervous
control.

Just as the thyroid and the adrenals can
exert a profound influence on the activities of
the body through their hormones, so the sex-
ual glands can effect changes in a like manner
and quite independently of their usual prod-
ucts. This subject has been worked upon
recently with very interesting results by Stein-
ach. The method employed by this investi-
gator was as follows : Young male rats and
guinea-pigs were first castrated, after which
the ovaries from a young female of the appro-
priate species were grafted under the abdom-
inal skin of each castrated male. The animals

..(IP

Or..

.Ov

.. GP

After Steiuach

PLATE I. FEMINIZED GUINEA-PIGS

Fig. 1. Normal male guinea-pig. Fig. 2. Feminized male guinea-pig. Bw, nipple; GP,
glans penis ; Ov, position of implanted ovary ; Wh, areola.

HORMONES 53

were then allowed to grow to maturity and
the development of the secondary sexual char-
acters was closely watched. (Plate I.) The
implanted ovaries, even though simply under
the skin, grew and ripened. None of these ani-
mals developed male secondary sexual charac-
ters ; the male external genitalia, for instance,
remained immature, and the body assumed the
form of the smaller sex, the female. The growth
of hair and the deposition of fat were in the
direction of the female type. The mammary
glands, the nipples, and their surrounding
areolaB were typically female. None of these
animals showed the characteristic male sexual
excitability even in the presence of a female
in heat. They very commonly did exhibit the
" tail reflex" and the " protective reflex," both
characteristics of the female, and they were
sought by males, though of course ineffec-
tively. Thus, so far as the secondary sexual
characters were concerned, a male animal had
been converted, both structurally and func-
tionally, into a female.

When in a very young male animal the
testes were transplanted from one region to
another, development was seen to proceed
along normal lines. Such an animal in the

54 BIOLOGY AND SOCIAL PROBLEMS

course of time assumed all the male secondary
sexual characteristics and exhibited sexual
desire. On examining its transplanted testes,
however, it was found that all the reproduc-
tive cells had disappeared and that the inter-
stitial cells had crowded in and taken their
place. For this reason it is believed that the
hormones which are given out by the repro-
ductive glands, and which serve to excite the
development of the secondary sexual charac-
teristics, are not the products of the germ cells
proper, the egg cells and sperm cells, but
come from the interstitial cells which are in
no wise concerned with reproduction.

Enough is known concerning operations
and transplantations in the human being to
justify the conclusion that the results obtained
by Steinach on the lower mammals will be
found to apply with full force to man. The
complete removal of the ovaries from a woman
is always followed by a premature menopause.
In the case of a woman who had been for two
years without ovaries and who during that
period had not menstruated, the successful
grafting into her body of a live ovary from
another woman was followed by a return of
menstruation and sexual desire. The profound

HORMONES 55

effect of castration on the male body, as seen
in the eunuchs of the East, is too well known
to require comment. All these instances show
that the effects of the reproductive hormones
in man are quite as profound and significant
as they are in the lower mammals, and that
in time we may expect to see confirmation in
man of many of the facts already ascertained
for these lower forms. Not only is this to be
expected, but it is reasonable to suppose that
the solution of some of the social questions
with which human civilization is beset to-day
may well be formulated on the basis of such
observations as those of Steinach already al-
luded to.

In fact, one of the important social problems
turns on the very points that have just been
discussed. The question is as to the best
method to be employed in the sterilization of
defective males. Two general lines are possi-
ble, either castration, that is the complete re-
moval of the reproductive glands, or some
such operation as the cutting of the spermatic
ducts or other treatment whereby the repro-
ductive cells are eventually destroyed. Both
methods render the individual incapable of
having offspring, but, judging from Stein-

56 BIOLOGY AND SOCIAL PROBLEMS

ach's results on the guinea-pigs and rats, the
first would probably also profoundly change
his character, in that among other things he
would lose sexual desire, whereas the second
would leave him much the same as he had
been except as to this ability to form sperm
cells. Thus, depending upon what society
wished as a result, one or other course might
be adopted.

Another interesting line of hormone activ-
ity of broad, biological significance is that of
the relation of the mammalian embryo to the
mother. It is well known that as the mamma-
lian embryo matures many preparatory changes
take place in the maternal body. Prominent
among these are the steps taken by the mam-
mary glands in preparation for the flow of
milk which must be in readiness for the young
at birth. How are these preparatory changes
initiated ? It is well known that there are no
nervous connections between the mother and
the embryo, and if the latter influences the
former it must be through some such means
as hormones. Working upon this suggestion,
Starling and Lane-Claypon attempted to as-
certain whether in the rabbit the embryos
gave out hormones which gradually brought

HORMONES 57

the mammary glands into activity. To test this
hypothesis, they made an extract from a num-
ber of rabbit embryos and injected this sub-
cutaneously into virgin female rabbits. The
result of this treatment was that the mammary
glands of these rabbits underwent the prepar-
atory growth that would have been character-
istic of them had there been a real pregnancy.
Further evidence of the same kind is furnished
by the interesting case of the Blazek sisters,
to quote from Howell. These twins were joined
like the Siamese twins; they had a common
circulation but separate nervous systems. Preg-
nancy and parturition in one was followed
by a secretion of the mammary glands of
both. Thus it seems quite clear that the devel-
oping mammalian embryo gives out hormones
to the maternal body and that these hormones
excite activity in those maternal organs which
are to serve the young after birth. It would
be superfluous to point out here the signifi-
cance of these relations to the practice of
dairying. In my opinion a step has been taken
in the laboratory which when properly fol-
lowed up may revolutionize our methods of
dealing with the milch cow. The time may
not be very distant when an extract of calf

58 BIOLOGY AND SOCIAL PROBLEMS \

may be more generally effective than the
bull.

Even from what is known at this early
stage in the study of hormones, it must be evi-
dent that they are most important substances
for the correlation of one part of the body
with another, and that in certain instances
they may rival though they never equal in
importance nervous methods of correlation.
Of course the whole plan of hormone interre-
lation is such that nothing can be expected
to spring from it, as the higher nervous func-
tions have grown from the simpler nervous
operations ; but, from the instances cited, it
must be clear that next to the nervous system
nothing will be found so potent for the con-
trol of animal activity as the hormones.

In much of the preceding account, I have
dealt with the nervous system and the hor-
mones as though they were distinct and sep-
arate means of accomplishing very similar
ends. But as might be suspected by any one
who is conversant with the conditions in organ-
isms, both means are often most complexly
and intricately interwoven in the perform-
ance of a single act. This is well illustrated
in our respiration. Nothing seems simpler or

HORMONES 59

easier than the regular filling and emptying
of our lungs with air, and yet the operation
is carried on in a way that illustrates prac-
tically all the forms of nervous and hormone
action of which I have spoken.

The muscles concerned with the respiratory
movements are those of the lower neck, the
chest, and the upper abdomen. They are con-
trolled from a pair of centers closely connected
and lying in the midst of the medulla oblon-
gata. Although these centers can be influ-
enced from almost any part of the central
nervous system, they will continue to give
out impulses to respiratory movements even
after they have been separated from practi-
cally all afferent tracts. This independence of
afferent control has led to the conclusion, well
supported from other directions, that the res-
piratory centers are stimulated by the quality
of the blood that passes through them. It has
been shown that when the blood that reaches
them is very impure, their action results in
vigorous breathing, and that when it is more
nearly pure, they subside in their activity or
even cease altogether. The constituent of
the blood which is effective in this respect
seems to be the carbon dioxid, and, as this is

60 BIOLOGY AND SOCIAL PROBLEMS

produced in many parts of the body, it may be
regarded as the hormone for the respiratory
centers. Thus a somewhat regulated interaction
between the amount of carbon dioxid in the
blood and the activity of the respiratory mech-
anism takes place, in that with an increase of
carbon dioxid comes an increase in the activity
of the respiratory mechanism whereby the or-
ganism is relieved of this excess of waste. Thus
an equilibrium between the amount of carbon
dioxid and the efficiency of respiratory move-
ment is quickly established.

But the respiratory rhythm is not one de-
pendent simply upon carbon dioxid. The lungs
are supplied with afferent nerve fibers which
make their way to the central organs through
the vagus nerves, and when these nerves are
cut the respiratory movements are consider-
ably changed, becoming slower and deeper.
Under normal conditions a given respiratory
movement apparently stimulates these afferent
fibers in such a way that they bring about in
a purely reflex fashion a hastening of the next
response. Thus this reflex mechanism has a
marked influence on the respiratory rate.

Although the respiratory movements ordi-
narily proceed without relation to voluntary

HORMONES 61

operations, we know that within a certain
range, we can alter them to suit our will.
They may be hastened, or slowed, or stopped
altogether, though not indefinitely; in other
words, they are more or less voluntary. The
respiratory movements then include not only
hormone control, but reflexes of the simplest
class and willed actions, a range which, as I
intimated before, involves almost every form
of control known in the body.

The fact that hormone action is often com-
bined with nerve action brings us face to
face with the ancient doctrine of the humors.
These were supposed to determine personality
in a way already indicated. Many substances
produced in the body, though not specifically
hormones, may affect our cerebral cortex in
such a manner as to color our whole lives, in
fact determine our temperaments. We all rec-
ognize the passing effect of tea, coffee, or al-
cohol. When these materials are not taken in
sufficient quantities to prove poisonous, they
serve as intellectual alteratives, and the tem-
porary condition called forth by them leads
us to suspect that the naturally vivacious or
taciturn person may have within him a spring
that generates unceasingly the appropriate

X

Vi

62 BIOLOGY AND SOCIAL PROBLEMS

humor. Every one is familiar with the feeling
of utter exhaustion after protracted strenuous
physical exercise. Probably most of you know
that if the blood of a dog in this state of
overwork is transfused into the body of a
rested dog, the second animal shows all the
signs of lassitude that the first one did. Thus
excessive muscular exercise must change the
composition of the blood in such a way that
when it acts upon the conscious centers, it
generates those vague sensations that we de-
scribe as utter tiredness, a condition which can
be easily interpreted from the standpoint of
the hormones. These substances, then, not
only interrelate distant parts and activities of
the human body as in its simpler phases the
nervous system does, but they play the part
of the ancient humors, and color momentarily

' V

or even permanently that aspect of our nerv-
ous systems which we call temperament.

Ill

KEPKODUCTION

REPRODUCTION is one of the most charac-
teristic and fundamental activities of living
things. Almost every organism, plant or an-
imal, possesses this power during some period
in its life. In a few instances it is lacking, as,
for example, in the worker bee, a sterile fe-
male, but in the vast majority of plants and
animals it is characteristically present. Every
species must contain at least certain individu-
als concerned with this function, else the spe-
cies would become extinct.

The methods by which reproduction is ac-
complished are extremely diverse. In the sim-
pler instances the fully grown body of one
individual divides into two and thus produces
material for two new individuals. Examples
of this kind occur among the unicellular an-
imals and the simpler multicellular forms
such as the corals, worms, and the like. The
more complex methods of reproduction are
accomplished by means of two kinds of cells,

64 BIOLOGY AND SOCIAL PROBLEMS

and these are usually produced by different
individuals. Individuals that produce sperm
cells are called males, those that produce egg
cells, females. The production of a new indi-
vidual is initiated as a rule by the fusion of
a sperm cell from one individual with an egg
cell from another. For obvious reasons this
method of reproduction is designated as sex-
ual in contrast with non-sexual reproduction,
which is the term used for the simpler type.

Sexual reproduction is the common method
of increase among the multicellular animals,
especially the more complex forms, but it can-
not be said to be entirely absent from the
unicellular organisms. In man reproduction is
accomplished almost exclusively by the sexual
method, there being only a few somewhat ob-
scure and rare occurrences that can be inter-
preted otherwise.

When we reflect on the enormous struc-
tural complexity of the human body, its count-
less myriads of cells appropriately disposed to
form its organs, and particularly when we
attempt to realize the immense variety of proc-
esses which go on within it, many of which
are essential to its continuance, it seems as
though a reproduction of such a complex

REPRODUCTION 65

would be open to so many accidents and
fraught with such difficulties as to be well-nigh
impossible. And yet, with every well-born
child that comes into the world, this is accom-
plished. But a human being is vastly more
than a successfully adjusted complex of cells
whose activities are sufficiently intricate and
adaptable to meet with success the ever-chang-
ing conditions around it. A human being is
a vast sum of conscious past experience, a
longing, desiring creature that seeks to mold
the future, a dreamer in hours of wakef ulness,
a thing of affections and feelings. And this
side of man's nature, too, is reproduced.
But by what process ? As in former cases we
shall attack this problem from its material
side. What are the physical conditions under
which reproduction is accomplished ?

William Harvey, the discoverer of the cir-
culation of the blood, in his treatise on gen-
eration published in 1651, maintained that
" even on the same grounds, and in the same
manner and order in which a chick is engen-
dered and developed from an egg, is the em-
bryo of viviparous animals engendered from
a preexisting conception." This " preexisting
conception" was in Harvey's mind the exact

66 BIOLOGY AND SOCIAL PROBLEMS

equivalent of an egg and justified the phrase
used in the earlier part of his treatise and so
often associated with his name, " Omne vivum
ex ovo," every living thing from an egg. To
this declaration, as Harvey explicitly states,
the human being is no exception. But it was
not vouchsafed to Harvey to see the egg of
man or of any other viviparous animal except
dimly in his mind's eye.

The egg of the mammal was discovered late
in the spring of 1827 by Von Baer. The first
egg seen was that of a dog, but subsequently
the eggs of other mammals, including man,
were found, and an account of the whole re-
search was published in the latter part of that
year. This matter-of-fact statement of an in-
vestigation, the repetition of which would be
a simple affair in the hands of even an elemen-
tary student to-day, gives no idea of what it
cost its discoverer. In his autobiography Von
Baer speaks of the physical strain and damage
to health from the long hours he spent over
his microscope and his worktable, and because
of his reluctance to leave his workshop, he com-
pares himself to a hermit crab. "And so it
happened/' he says, " that in the course of a
year, I shut myself up in my shell while the

REPRODUCTION 67

snow was still on the ground, and when I
again ventured out to cross the garden wall
only a hundred steps from me, I was as-
tounded to find that the fields of rye were in
the ear." This is the application and energy
that brought to light the mammalian egg.
The fact is a commonplace now, but let us
not forget that it took a genius to point it out
to us.

The human egg is a minute spherical body
just about visible to the unaided human eye.
It has a diameter of about one fifth of a milli-
meter. Aside from a slight envelope, it is com-
posed of a mass of protoplasm containing some
fine yolk granules and a spherical nucleus
whose diameter is about one seventh or one
eighth that of the whole structure. Thus the

o

human egg, like that of many other animals,
exhibits all the characteristics of a simple cell.
The two ovaries of a woman shortly after
the onset of puberty are estimated to contain
seventy-two thousand so-called primitive eggs,
of which, it is believed, not more than about
four hundred become mature and are dis-
charged. These mature egg cells are liberated
with more or less regularity over the period
of sexual maturity. This is ordinarily from

68 BIOLOGY AND SOCIAL PROBLEMS

about the fourteenth to the fiftieth year,
though the fact that pregnancy may occur as
early as the seventh year shows that occasion-
ally puberty begins very early. As a rule only
a single egg cell is discharged from the ovary
at each period of ovulation, but, as the con-
dition of multiple births shows, there may pos-
sibly be as many as seven eggs freed at once.
Quintuplets have occurred often enough to
place this number beyond doubt, and there
have been apparently a few good cases of sex-
tuplets. An instance of seven at a birth is
said to be recorded in Haineln-an-der-Weser,
in Germany, on a memorial tablet of the year
1600, and this, so far as I can ascertain, is the
largest well-authenticated number of children
delivered at a birth, for the case of eight re-
ported in 1872 from Trumbull County, Ohio,
seems on good authority to be spurious. Al-
though, as we shall see presently, there is good
reason to believe that some eggs divide in a
way to give rise to more than one child, it is
likewise well established that many multiple
births are due to the liberation of several eggs;
how many as a maximum cannot be stated,
but from the cases just quoted it is not neces-
sary to assume more than seven. In such in-

REPRODUCTION 69

stances the total number of eggs discharged
by a woman in the course of her life would
probably be several times four hundred, but
the ordinary rule seems to be a single egg at
each of the four hundred or more ovulations.
You are probably aware that the discharge of
the egg is supposed to take place periodically
and to be related to menstruation, but if there
is an exact relation between these events, it
has yet to be discovered.

As it is the characteristic of the female to
produce egg cells, so it is that of the male to
produce sperm cells. The human sperm cell, or
spermatozoon, as it is commonly called, was
discovered in 1677 by Hamm, a student in
Leyden, whose master, Leeuwenhoek, gave an
accurate description of it. In man each sper-
matozoon is a minute, elongated, lashlike body,
one end of which is somewhat enlarged. The
whole has some resemblance to a much atten-
uated tadpole. Each spermatozoon measures
ordinarily about one twentieth of a millimeter
in length, or roughly a quarter of the diame-
ter of the human egg. Its enlarged end cor-
responds to the nucleus of a cell, and its lash
to the protoplasm, so that the spermatozoon,
like the egg, is a single cell, though its form

70 BIOLOGY AND SOCIAL PROBLEMS

at first sight is not so suggestive of this com-
parison.

The testes in man produce spermatozoa
more or less continuously from the beginning
of puberty, at about the fifteenth year, on to
old age. Spermatozoa are often absent in old
men, but they have been found in individuals
as late as the ninetieth year. It has been esti-
mated that in the period of thirty years be-
tween the twenty-fifth and the fifty-fifth year
of manhood, one individual will produce the
prodigious number of 339,385,500,000 sper-
matozoa, a number incredibly large compared
with the egg cells probably liberated by the
normal woman during her sexually active life.

When the human egg cell is fully formed,
it is discharged on the surface of the ovary,
whence it makes its way down the Fallopian
tube toward the uterus and the exterior. If it
is not fertilized, it disintegrates and is lost,
but if copulation has occurred and sperm cells
abound in the tube, one may enter the egg
and thereby fertilize it. The fertilized egg then
passes down the Fallopian tube into the uterus,
where, instead of disintegrating, it attaches it-
self and develops into an embryo and eventu-
ally into a fully formed child.

REPRODUCTION 71

It is evident from these brief statements
that the two parents supply very unequal
amounts of material to the offspring. The
father contributes merely one spermatozoon
whose volume is surely not over 50 cubic micra
or thousandths of a millimeter; the mother
contributes the substance of the egg cell,
which, if it be regarded as spherical and with
a diameter of 150 micra, would have a volume
of 1,767,150 cubic micra, or over 35,000 times
that of the sperm cell. Not only is this true,
but the mother likewise contributes from the
substance of her body all the nourishment that
enables the diminutive egg to grow to a fully
formed babe. Hence the material of the child's
body is vastly more maternal than paternal in
its origin.

Notwithstanding the disparity between the
amounts of material contributed by the two
parents to the offspring, it is well established
that in any population as a whole the children
show about as much resemblance to the father
as to the mother ; in other words, in inheri-
tance the mother has no more influence than
the father. This condition has led to a closer
scrutiny of the actual contributions of the two
parents.

72 BIOLOGY AND SOCIAL PROBLEMS

The mature egg about to be fertilized rep-
resents all the material of maternal origin at
this early stage in development. This mate-
rial consists of the protoplasm of the egg and
of certain nuclear bodies called chromosomes
because of the ease with which they become
colored in artificially stained preparations.
These chromosomes are peculiar in that they
are very constant in number for the eggs,
sperm, or other cells of a given animal. In
the human being, because of the unfavorable-
ness of the material and of the difficulty in
getting it in a well-preserved condition, the
number of chromosomes has probably not
been finally determined. According to the re-
searches of Winiwarter, published in the last
few years, the number of chromosomes in the
ordinary cells of the human body is forty-
seven in the male and probably forty-eight in
the female. As just intimated, however, these
determinations may not be final, but whatever
the number may actually prove to be, it is
probably not far from what has just been
mentioned. It is remarkable that in practically
all animals the number of chromosomes in the
mature egg cell is half that found in the ordi-
nary cells of the body of the female for the

REPRODUCTION 73

given species. Hence in man we would expect
the number of chromosomes in the mature egg
cell to be twenty-four.

In the operation of reproduction the father
contributes a spermatozoon which, when it
enters the egg, carries with it a negligible
amount of protoplasm, a minute body called
a centrosome, and a group of chromosomes
essentially like those from the mother, and
about equal to them in number. Thus the fer-
tilized egg consists of protoplasm almost en-
tirely from the mother, of a centrosome from
the father, and of chromosomes in about equal
numbers from each parent. If children always
took after their mother, we might suspect that
part of the fertilized egg which came exclusively
from the maternal side, namely, the protoplasm,
to be the bearer of hereditary traits. If they
regularly took after the father, we might, with
equal right, suspect the centrosome as the
organ of transmission. But as children take
more or less after both parents and as the only
parts of the fertilized egg which are derived
from both sources are the chromosomes,
these bodies are believed to be the means by
which inheritance is accomplished. If this
opinion is correct, one must conclude that all

74 BIOLOGY AND SOCIAL PROBLEMS

those details of stature, color of hair, facial
and bodily form, inborn acts, and other traits
that make the child resemble the parent are
dependent upon this infinitely small amount
of living substance which is thus handed on
from parent to offspring. Although this doc-
trine is not without its opponents, it is so well
substantiated in many ways as to have gained
very general credence.

One of the recent lines of evidence that
supports this view is that touching on sex de-
termination. From the most ancient times the
question of sex has been one of great theo-
retical and practical interest, and many hy-
potheses have been advanced and advice of
all kinds has been sought and given without
resulting in any evident control over this mat-
ter in either man or the lower animals. Many
have believed that the resting posture of the
body of the mother during pregnancy or the
character and amount of the food given her
would determine the sex of the developing
child. But all such theories were rendered
very improbable by the occurrence of identi-
cal twins, triplets, quadruplets, and so forth.
In man ordinary twins usually have separate
sets of foatal membranes and always separate

REPRODUCTION 75

chorions. They give every evidence of having
descended separately from two fertilized eggs.
They may be of the same or opposite sex.
After birth they resemble each other no more
than any other two children in the same fam-
ily. Identical twins, on the other hand, possess
only one chorion and are otherwise so related
to their foetal membranes as to give evidence
that they have descended from a single egg.
They are invariably of the same sex, and in
after life they are commonly very similar in
appearance. This similarity is often so marked
as to lead to their confusion even among their
near associates ; hence the ludicrous situations
furnished by the two Dromios and their mas-
ters in " Comedy of Errors ' ' as well as by their
classical progenitors, the Mensechmi. Identical
twins are never of opposite sex, as Viola and
Sebastian in "Twelfth Night," who, though
" born in an hour," must have been descend-
ants from separate eggs, if not the pure prod-
uct of a poet's imagination. The fact that iden-
tical twins are always of the same sex, and that
ordinary twins may or may not be, shows
that sex determination must be an operation
that occurs in the very early stages of devel-
opment and before the material ordinarily des-

76 BIOLOGY AND SOCIAL PROBLEMS

lined to give rise to one individual divides in
the case of identical twins into two. Therefore
the subsequent history of the embryo, such as
the position afforded it in the mother's body or
the character and amount of nourishment pro-
vided for it, can have no influence on its sex.
This interpretation of the condition in man
is abundantly supported by recent work on
one of the primitive mammals, the armadillo.
It was long ago known that all the young in
a single litter of this animal were of the same
sex. Newman and Patterson have recently
shown that in the armadillo only one egg is
discharged from the ovary at each period of
heat, and that, if this egg is fertilized, four
embryos usually result, all of the same sex.
These four embryos, to use Morgan's state-
ment of the case, are more like each other
than like the embryos of any other litter, or
even more like each other than they are like
their own mother. In other words they are
identical quadruplets exactly comparable to
identical twins in man. The fact that they are
always of the same sex and are positively
known to come from one egg cell supports
most completely the conclusion arrived at
from the study of human twins.

REPRODUCTION 77

It is the process of forming two or more
human embryos from the substance of one
egg that has given color to the statement that
man does exhibit at times non-sexual repro-
duction, for the differentiation of two or more
embryos from the mass of cells that would
ordinarily produce a single one is apparently
a process of budding, and in this respect it
may be maintained that man occasionally re-
produces non-sexually.

But this aspect of identical twins, interest-
ing as it may be to the philosophical zoologist,
is of much less significance than that which
touches on the determination of sex. This oper-
ation is not only known through the condi-
tion in identical twins to be associated with a
very early stage of development, but evidence
from certain lower animals, chiefly the insects,
indicates that it is involved in the very earliest
stages of the differentiation of egg cells and
sperm cells. This is well illustrated in Pro-
tenor belfrageiy an insect closely related to the
squash bug. When the ordinary cells in the
body of the female of this insect divide,
the number of those peculiar nuclear bodies
known as chromosomes is seen to be fourteen.
In the formation of the egg cells, as might be

78 BIOLOGY AND SOCIAL PROBLEMS

expected, these chromosomes become reduced
in number to half that characteristic of the
cells of the body ; in other words, each mature
egg cell contains seven chromosomes. When
the ordinary cells in the body of the male of
this insect divide, the number of chromosomes
is seen to be thirteen, one less than in the
female, and when the spermatozoa in this ani-
mal are formed, the reduction in the original
number of thirteen results in the formation
of two classes of sperm cells, one with seven
chromosomes and the other with six. These
sperm cells are formed in equal numbers and
are apparently the means of sex determina-
tion. For, when an egg with its seven chromo-
somes is fertilized with a sperm having the
same number, an individual arises whose body
cells exhibit fourteen chromosomes, and such
animals are females. When, on the other
hand, an egg is fertilized by a sperm with only
six chromosomes, an individual whose body
cells contain only thirteen chromosomes re-
sults, and the animal is a male. It is thus
clear that in this instance the fertilizing sper-
matozoon determines the sex of the offspring
and that the material which is concerned in
this is that contained in the chromosome. Not

REPRODUCTION 79

only are the chromosomes thus concerned with
sex determination, but from the fact that they
possess somewhat different forms, there is rea-
son to believe that a particular chromosome is
responsible for this determination. Thus in
Protenor an especially large chromosome is
always found in those sperm cells that have
seven such bodies, that is, in those that pro-
duce females, and it is as regularly absent
from those that produce males. Hence this
chromosome is sometimes called the sex chro-
mosome.

Sex determination from the point of view
just presented has been studied in many other
animals and, though the process presents a
great variety of details, it seems to turn reg-
ularly on the chromosome composition of the
reproductive cells. In man, as already stated,
the reproductive elements are not so favorable
for this kind of study as in many other ani-
mals, but within a few years Winiwarter has
shown that human spermatozoa, like those of
Protenor, are probably of two classes, one
characterized by the presence in each cell of
twenty-three chromosomes and the other by
twenty-four such bodies. If this is true, sex
determination in man is brought about prob-

80 BIOLOGY AND SOCIAL PROBLEMS

ably by the same means as in animals like
Protenor, in that when the human egg is
fertilized by a sperm with twenty-three chro-
mosomes a male results and when by a sperm
with twenty-four chromosomes a female is the
outcome. If, as in insects, the two kinds of
spermatozoa in man are about equally numer-
ous, we can understand why male and female
human births are so nearly equal in number.

From what has been stated concerning the
composition of the fertilized egg and the na-
ture of sex determination, it must be clear
that the chromosomes are most significant
bodies in inheritance, in fact they seem to be
the vehicles of this process. The reason we
inherit from our two parents those character-
istics of feature and action which mark us as
their descendants is because they have each
contributed a certain number of chromosomes
to our make-up.

Simple as this statement is, when we face
the full actualities of the case, it strains even
the imagination. That so small an amount of
material as that represented in the chromo-
somes of the fertilized egg should influence in
so rigid a way so large an amount as that con-
tained in the adult body seems almost incredi-

REPRODUCTION 81

ble. The human egg is approximately a sphere
with a diameter, in the case of a large exam-
ple, of about one fifth of a millimeter, and with
a specific gravity about that of water ; conse-
quently its weight must be about 0.004 of
a milligram. The volume of the chromosomes
in a fertilized mouse egg has been determined
to be somewhat less than one thousandth of
the volume of the whole egg, and, assuming
that this proportion hold for the human egg,
and that its chromosomes have about the same
specific gravity as water, the weight of this
material would be about 0.000,004 of a milli-
gram. Yet this minute amount of substance
is believed to determine to a nicety that infin-
ity of adult traits wherein a man resembles
his parents. If we assume the weight of the
average human being to be sixty-five kilo-
grams, then the weight of the determining
material to that which is determined is as 1 to
16,250,000,000,000. In attempting to grasp
this almost inconceivable relation, it must be
borne in mind that the material of the chromo-
somes in the egg is living and that, in the
growth of the individual, it assimilates and in-
creases in volume like other living material ;
it is not spread through the growing body in

82 BIOLOGY AND SOCIAL PROBLEMS

ever increasing dilution. Nevertheless it is this
extremely minute amount of material in the
egg cell that gives rise to that which deter-
mines in the adult.

The fullness of this determining power is
seldom appreciated for the reason that, in or-
dinary births, we have nothing as a standard
whereby to judge of the looseness or rigidity
of the process of inheritance. But in identical
twins, triplets, and so forth, one individual in
each group may be taken as a standard for the
rest in the group, and we can judge from the
similarity of the members in a single group
how closely the process works. Wilder gives
us good evidence on this point taken from a
set of identical triplet girls by a person who
was familiar with them. This person described
them in the following terms : " I have seen
twins that looked very much alike, but I could
see a difference when they were together. I
could not see any difference in these triplets
when they stood in a row before me, and I
never saw any one else who could, except their
mother. She said she could, but I doubted it ;
they used to fool her often. When they were
babies she kept different colored beads around
their necks to tell them by. They always

REPRODUCTION 83

weighed on the same notch until they were
seven years old, then one gained half a pound
more than the others." When they were little
girls, one of them confided one day to a friend
that she had been bathed three times that
morning, while the others confessed that they
had not been bathed at all, an accident that
emphasized their complete bodily identity at
that period. Their lives must have been, in-
deed, a modern " Comedy of Errors." But for
us they are significant in that they show how
enormously powerful in determining traits was
that infinitesimally small amount of chromatic
material contained in the one microscopic egg
from which they all came, a power which when
spread through three persons instead of one
seems still to be undiminished. But we must
remember that the human body, like that of
many other animals, is often very sensitive to
minute amounts of material. Cats are known
to be affected by 0.0001 of a milligram of ad-
renalin, and our olfactory organs are stimu-
lated by 0.000,000,002 of a milligram of mer-
captan. Is it, therefore, after all, so surprising
that 0.000,004 of a milligram of chromatic
material should have so profound an influence
on our development ? Small as these amounts

84 BIOLOGY AND SOCIAL PROBLEMS

are, they are far from molecular limits, for
Von Frey has calculated that the extremely
minute amount of mercaptan which we can
just smell contains about a fifth of a billion of
molecules. Nevertheless, as compared with the
smallest amount of material that the physi-
cist or chemist can weigh directly and accu-
rately, namely, about 0.001 of a milligram, the
amounts of the various materials just men-
tioned are undeniably small.

We have thus seen how each human being
starts life from a minute egg cell charged with
an infiu itesimally small amount of material
which is destined to determine with surprising
accuracy his configuration and responsiveness.
The process that the egg cell undergoes in
changing into an adult person is first of all
cell division. The simple spherical egg cell di-
vides by a somewhat complex process into two
cells, and these into four, and so forth, till
the millions upon millions of cells which con-
stitute the adult body are formed. At each di-
vision the chromosomes divide and are shared
by the descendant cells so that both maternal
and paternal influences are handed on to each
cell in the growing individual. The great ag-
gregate of cells which thus constitute the adult

REPRODUCTION 85

body, and which are all descendants from the
single original egg cell, falls naturally into two
classes ; first, somatic cells, such as those which
form the skin, muscles, bone, nerve, and other
parts of the adult body, and, secondly, the re-
productive cells, the egg cells in the female
and the sperm cells in the male, which are des-
tined to give rise to new individuals. Of these
two sets of cells the one which by its collective
arrangement and activity exhibits those as-
pects of the child wherein it shows its likeness
to its parents are the somatic cells, and the
discovery of the way in which these cells be-
come impressed with the parental traits is one
of the chief problems of genetics.

Before 1900 scarcely anything of value in
genetics could be said to have been in the
hands of the working biologist, but with that
year the discovery of Mendel's writings, lost
for about a generation, gave to the study of
heredity such an impetus as it had never ex-
perienced before. The Mendelian principles,
to which this revival is due, are already popu-
larly known. You are aware that inheritance
in accordance with these principles is accom-
plished by the association of characteristics re-
lated in pairs and that these characteristics

86 BIOLOGY AND SOCIAL PROBLEMS

appear in the offspring unmixed and in highly
significant proportions. Thus in guinea-pigs
the white coat-color of a pure albino stock
and the black coat-color of a pure melanic
stock can be made to associate by crossing
these two stocks. The animals that result
from this cross are not, as you well know, gray
individuals midway between the white and
black parents, but all strictly black individ-
uals to all appearances like their black an-
cestor. That they are not, however, exactly
like this ancestor is seen from the fact that
when they are bred among themselves, in-
stead of producing nothing but black indi-
viduals as their black parent would have done
if mated with his kind, they bring forth pure
white stock as well as black stock and in the
proportion of one of the former to three of
the latter. Thus these black individuals can
be shown to carry hidden in their bodies the
white characteristic, though they show noth-
ing of this on their exteriors. Of such pairs
of characteristics, the one which may thus be
hidden is spoken of as recessive, the other
dominant. (Plate II.)

The black and the white descendants of
such individuals occur in the very remarkable

All figures after Castle

PLATE II. MENDELIAN INHERITANCE

Fig. 1. A black female guinea-pig. Fig. 2. An albino male guinea-pig. Fig. 3. A black
female guinea-pig with young by an albino male such as that shown in Fig. 2. Fig. 4.
Adult black guinea-pigs from a litter such as that shown in Fig. 3. Fig. 5. Albino and
black guinea-pigs whose parents are shown in Fig. 4.

REPRODUCTION 87

proportions just mentioned and present con-
ditions of great interest. The twenty-five per
cent of white individuals, when bred among
themselves, have been proved to be pure whites
like their white grandparent. The seventy-
five per cent of black individuals, when tested
in a like fashion, have been shown to be, in
the case of twenty-five per cent, pure black like
their black grandparent, and, in the case of
the remaining fifty per cent, black but with
the ability to produce white offspring exactly
as their parents did. Thus the grandchildren
of the original pure black and white mating
fall into three classes: twenty-five per cent
pure white, twenty-five per cent pure black ;
and fifty per cent black, but capable of pro-
ducing a definite proportion of white off-
spring.

You are familiar with the explanation that
Mendel offered for this remarkable state of
affairs, an explanation that is still generally
accepted. Briefly it is to the effect that each
reproductive element, egg cell or sperm cell,
can carry only one of any pair of characteris-
tics, and that in this respect each reproduc-
tive cell, be it either egg or sperm, is pure.
If we assume this segregation of characteris-

88 BIOLOGY AND SOCIAL PROBLEMS

tics together with the principle of dominance,
we shall find it easy to understand the condi-
tions just mentioned for the guinea-pig.

In the original pair of animals for such a
series of breeding experiments as have been
briefly mentioned, it makes no difference how
the sexes are combined ; the male may be
white or black, the outcome will be the same.
But for simplicity we may assume that the
male is black and the female white. As each
individual comes from a pure stock, the male
will produce sperm cells, all of which will carry
the black characteristic, and the female, for
the same reason, will produce egg cells, all
of which will carry the white characteristic.
Their offspring, then, will be the product of
a white egg, so to speak, fertilized by a black
sperm. Such animals, as is well known, are al-
ways black in color. But as already indicated
they possess within them the recessive white
characteristic. If we assume, now, that their
reproductive elements are pure like those of
their parents, then we should expect each male
of this stock to produce, not one kind of sperm,
but two, one with the white characteristic and
the other with the black, and that these ele-
ments would be present in equal numbers. The

REPRODUCTION 89

same would hold true of the females ; each one
would give rise to equal numbers of black
eggs and of white eggs.

If, now, we imagine these two kinds of eggs
to be fertilized by the two kinds of sperm and
that the combinations be purely fortuitous, we
would expect four classes of fertilized eggs of
equal frequency ; once in four a white egg
would be fertilized by a white sperm, once in
four a black egg by a black sperm ; once in
four a black egg by a white sperm ; and once
in four a white egg by a black sperm. The
first class would yield the twenty-five per cent
of pure white individuals, the second the same
per cent of pure black individuals, and the
third and fourth the fifty per cent of black
individuals which are, however, capable of
producing white as well as black offspring.
Thus the assumption of the purity of the
germ, the segregation of characteristics, makes
clear these very remarkable proportions as
seen in the actual experiments in heredity.

The conception of the hereditary proc-
ess which has grown out of this idea and

o

the way in which this process is supposed
to have impressed itself upon the face of
nature is well seen in the mutation theory

90 BIOLOGY AND SOCIAL PROBLEMS

of De Vries. According to De Vries the
significant hereditary differences between in-
dividual organisms, plants as well as animals,
depend upon the presence of unit characters,
so called, such as those of black or white coat-
color in the example of Mendelian inheritance
just described. These unit characters were be-
lieved by De Vries to be of a stability com-
parable with that of the chemical elements ;
there were no intergrades. Many of these
unit characters are known, and every individ-
ual organism can be regarded as a special
combination of them. Thus animals and plants
can be grouped in accordance with the unit
characters that enter into their composition ;
all those having the same unit characters con-
stitute what De Vries calls an elementary
species and when they differ in this respect
they belong to different elementary species.
Thus, guinea-pigs that differ in coat-color,
like the examples previously cited, would con-
stitute two elementary species separable by
the specific unit characters of black and of
white coat-color. It is to be observed that the
conception of elementary species is quite dif-
ferent from that of the old Linna3an species.
Two members of the same elementary species,

REPRODUCTION 91

such, for instance, as two black guinea-pigs,
may produce offspring some of which may be
black and some white. In other words, mem-
bers of one elementary species may have in
their immediate offspring members of other
elementary species. Thus the idea of contin-
uity of breed, usually attached to the defi-
nition of a Linnsean species, is quite absent
from that of the elementary species. But the
main fact that underlies the whole De Vriesian
conception is the fixity of unit characters.
That there is a large body of truth in this, for
certain characters at least, cannot be denied,
but that the difference is comparable with
that between chemical elements, as originally
claimed by De Vries, is far from probable.
Evidence on this point comes from a number
of sources, but I shall cite only one instance.
The hooded rat is a domesticated form in
which the fur is dark over the head and down
the middle of the back, but is otherwise light-
colored. Thus the rat has the appearance of
a light animal wearing a dark hood. When
this stock is crossed with the uniformly dark
wild rat, the hooded character is found to be-
have as a Mendelian recessive ; that is, in the
first generation of descendants all individuals

92 BIOLOGY AND SOCIAL PROBLEMS

have the coat-color of the wild parent, but
of their progeny one fourth show the mark-
ings of the hooded stock. This hooded char-
acter, then, is what may be called a unit char-
acter.

Castle has attempted to ascertain whether
this unit character can be modified by a proc-
ess of selection, the object being to produce
from the hooded stock by selection two ex-
treme conditions : a completely light animal,
and a completely dark one. In the beginning
there were selected from the common hooded
forms, two' sets of individuals : one with as
little pigmentation as possible, the other with
as much. These two sets afforded the mate-
rial with which the test began. Their descend-
ants were selected in the desired directions
generation by generation till, after somewhat
more than six years of work on over twenty-
five thousand rats, two clearly divergent stocks
were produced. One of these was composed
of members entirely light except for a small
amount of dark on the head, and the other
was made up of individuals completely dark
except for some light on the belly. Thus two
stocks were obtained that bred true and ap-
proximated closely to the two extremes aimed

7

8

All figures after Castle

PLATE III. UNIT CHARACTERS

Tig. 1. A wild gray rat. Fig. 2. A hooded rat with the hood much reduced by selection.
Fig. 3. A normal hooded rat. Fig. 4. A hooded rat with the hood much extended by selec-
tion. Figs. 5 and 6. Grandchildren from such animals as those shown in Figs. 1 and 2,
which they respectively resemble. Their parents were like the rat shown in Fig. 1. Figs.
1 and 8. Grandchildren from such animals as those shown in Figs. 1 and 4, which they
respectively resemble. Their parents were like the rat shown in Fig. 1.

REPRODUCTION 93

at, if they did not absolutely arrive there.
(Plate III.)

Does this condition indicate that the unit
character of the original hooded stock has
gradually been pushed along in one derived
stock in one direction and in the other in the
opposite, or is this whole change a purely
superficial one and does the unit character
still remain in both stocks unmodified? An
answer to this question was found by cross-
ing: females from each extreme stock with a

o

single wild dark male and by breeding grand-
children separately from each of the two sets
of descendants. Under such circumstances we
should expect to find that three fourths of
the grandchildren of both sets would be dark

o

and that one fourth in each set would show
the condition of the hooded character. Such
proportions were practically realized, and the
hooded individuals in the two sets were found
to be, not like the original hooded stock, but
like their modified grandparents. The hooded
individuals from the light grandmother were
mostly light; those from the dark grand-
mother, mostly dark. These results show that
a unit character is not necessarily fixed, as
De Vries originally maintained, but can be

94, BIOLOGY AND SOCIAL PROBLEMS

modified in that it may be gradually moved, by
selection, for instance, in one direction or an-
other. Marvelously stable as the unit charac-
ters are, they are not in their stability com-
parable with the chemical elements, for they
exhibit gradual changes. Whether these
changes are to be accounted for on the basis
of inherited modifiers, a kind of additional
demon behind the demon unit character, or
by some other process, is a question for the
future to decide. Of one point we can feel
fairly certain, unit characters are modifiable.
Although these results have been worked
out almost exclusively on the smaller, rapidly
breeding animals, there is no reason to sup-
pose that they do not apply with full force
to the human being. Already a long list of
characteristics, which are inherited in man in
accordance with one form or another of the
Mendelian principles, is known. This list in-
cludes certain eye colors ; certain hair colors
and hair forms, such as straight, wavy, and
curly ; certain skin colors, such as that of the
blond and the brunette ; pale, fresh, and col-
ored complexions in the white race ; stature,
form of head, and nose in certain races ; mu-
sical and non-musical temperaments ; various

REPRODUCTION 95

deformities and defects, such as short fingers,
aborted fingers, split fingers, split foot, catar-
act, certain hair deficiencies, stationary night-
blindness, certain sex-limited diseases like
hemophilia, and color-blindness; and certain
kinds of deaf-mutism, insanity, and imbecil-
ity. Thus even at this early stage in the
study of human heredity, there is good reason
to believe that many of our traits Mendelize.
But the question that confronts the modern
student of genetics is the extent to which
Mendelism may be said to apply. Are all
characteristics in man and other animals in-
herited in accordance with these principles, or
are only a part of them so handed on ? Man
himself seems to offer some very interesting
examples that are very difficult to bring un-
der the Mendelian rules. Thus, when the white
man is crossed with the negro neither one nor
the other is produced, but an intergrade, the
mulatto. Inheritance of this kind is called
blended and is represented by many examples.
Whether it is a form of Mendelism in which
dominance is absent is not clear. Possiblv it

V

is a totally different method of inheritance
from that exemplified in the Mendelian cases.
Certainly so long as instances of this and other

96 BIOLOGY AND SOCIAL PROBLEMS

forms of inheritance remain unanalyzable from
the Mendelian standpoint, we may conclude
that this explanation does not exhaust the
field of heredity. But even if Mendelism is an
explanation of only a part of the phenomena
of heredity, it represents an advance in all
respects the most important that the science
of genetics has yet made, and it opens up a
prospect to the experimentalist which is no
less alluring than it is full of promise.

Notwithstanding the fragmentary character
of our knowledge of reproduction, we know
that a child takes after its parents because the
fertilized egg from which it has grown is made
up of living material part of which came from
each immediate ancestor. The amount of all
the material in the egg is immensely small
compared with that of the person who devel-
ops from it, and the amount of that material
in the egg concerned with heredity is probably
not over a thousandth part of the whole egg ;
nevertheless this infinitely minute quantity of
material, rather than the environment, stamps
upon us with an iron hand the configuration
of our early life, a configuration which is so
rigidly determined that where two or more
individuals come from the same egg almost

REPRODUCTION 97

complete identity results. Yet this operation
of the rigid transfer of traits from individual
to individual is an essential step, perhaps the
essential step, in the process of racial progress^
Without it the evolution of man would have
been impossible. In the last lecture I shall en-
deavor to show the relations of this process
of reproduction to that of evolution as seen in
the human species.

IV

EVOLUTION

ASSUMING that the population of the globe
is about sixteen hundred millions and that the
average length of human life is forty years, a
number that represents the present condition
in only the more favored states and nations,
about forty million persons must die annually.
Of such persons those who reach maturity
have usually gathered about them material
devices as protections against the inclemen-
cies of nature and as means to their personal
comfort. Such persons, moreover, in the course
of their lifetime develop or acquire lines of ac-
tion which yield continuance of life and hap-
piness. At their death their material property
is commonly inherited by other members of
society, often those to whom the deceased had
blood ties ; their lines of action, remembered
or otherwise recorded, serve as examples for
avoidance, imitation, or improvement. Thus,
generation by generation, the composition of
human society changes, its material acquisi-

EVOLUTION 99

tions accumulate, and its combined forces and
activities turn now this way, now that. We
think of the totality of these changes as tak-
ing place through a process of evolution by
which not only novel features arise, but the
rich inheritance of the past is preserved and
handed on. When we reflect on the means by
which this social growth is accomplished, we
are driven to admit that it is in reality the indi-
vidual man. He it is, who, working with his fel-
lows, accomplishes all. What he inherits, what
he devises, what he can hand on, these are the
elements that make up the totality of social
evolution. Did we but know with certainty
how all this change comes about, many of
our most momentous social problems would be
solved.

To many naturalists of the Darwinian period
an experimental laboratory for the study of
evolution would have seemed to be resources
thrown away. These older workers supposed
evolution to proceed at so slow a pace that an
experimental investigation of it would be im-
possible, but for somewhat over a decade and
mainly in consequence of the discovery of Men-
del's writings, the study of evolutionary prob-
lems from the experimental standpoint has

100 BIOLOGY AND SOCIAL PROBLEMS

made great progress. In fact, since the open-
ing of the twentieth century a more substan-
tial advance has been made in the solution of
evolutionary questions than in the whole pe-
riod between 1859, the year in which the
" Origin of Species" was published, and 1900.

But the Darwinian period of evolutionary
activity was not the first. It was preceded by
a series of preliminary skirmishes fought out
mostly upon French soil. In 1809, Lamarck,
then about sixty-five years old, published his
"Philosophic Zoologique" in which was con-
tained the first well-ordered attempt at a
general theory of organic evolution. But this
fell on unsympathetic ears. It was, moreover,
opposed by Cuvier, whose scientific authority
was such that the whole movement for the
time being was swept aside, and Lamarck, in
a measure unrecognized and after an old age
of blindness, died in 1829.

But among the French contemporaries of
Lamarck, to quote freely from Delage, was
Etienne Geoffroi Saint-Hilaire. He it was who
in 1830 took his stand against Cuvier in the
Academy of Sciences in a sensational debate
which lasted almost six months, a duel, so to
speak, between the theory of transmutation

EVOLUTION 101

and the theory of the invariability of species.
This controversy became noised throughout
the scientific world. Goethe, then eighty-one
years old, took a keen interest in it and de-
voted his last work, completed in 1832, to a
review of the debate, pointing out its great
scientific and philosophic import. Yet the out-
come of this far-famed contest was not favor-
able to the new ideas. In the opinion of the
majority, the victory remained on the side of
Cuvier, and the doctrine of transmutation lost
ground.

The general theory advanced by Lamarck
contained much of significance and impor-
tance, and was in part accepted by Darwin. In
recent years it has been revived, at least in
certain particulars, by those who class them-
selves as Neo-Lamarckians. Lamarck was much
impressed by what he believed to be the direct
effects of the environment upon organisms,
particularly plants, and he attributed evolution
in the main to changes in this factor. His idea

o

of the way in which animals had been trans-
formed was through what might be called the
indirect rather than the direct influence of the
environment and may be briefly stated as fol-
lows : changes in an animal's surroundings in-

102 BIOLOGY AND SOCIAL PROBLEMS

duce changes in its habits, and changes in its
habits bring about changes in its structure.
Be these structural changes ever so slight, if
they recur regularly from generation to gen-
eration and are accumulated, they will even-
tually so modify an animal that a transmu-
tation of species may be said to occur. Thus
in an indirect way the ever changing environ-
ment is responsible for animal transformation.

The Lamarckian hypothesis, thus stated,
appeals to the student of evolution through
its simplicity and directness. The ease with
which we may induce modifications in our own
bodies by voluntary change of habits is too
well known to require comment. The special
exercise of a set of muscles induces an increase
in their size and that of all their connected
parts, and the reverse of this is followed by
their shrinkage and decline. What could be
simpler than to conceive of a given animal
being what it is in consequence of its own ac-
tivities and those of its race ? Such an animal
may be assumed to possess its present form
in consequence of its racial habits.

The application of this hypothesis to man
is most readily and easily accomplished, and
few organisms can be shown to afford a bet-

EVOLUTION 103

ter apparent example of its mode of action
than the human species. The considerable in-
fluence that the kind of life that an individual
leads has upon his body has long been well
recognized, and the direct effect of this, fa-
vorable or unfavorable, on his offspring has
underlain the claims of the moralist for gen-
erations past. Thus the Lamarckian hypothe-
sis, though an impersonal explanation of trans-
mutation, can be easily brought into relation
with man's higher nature and made to point
a moral.

But a very serious obstacle to the accept-
ance of this hypothesis has gradually arisen
in the otherwise easy path of the Lamarckian.
The slight changes which nearly every organ-
ism exhibits as the effects of its environment
and which, for Lamarck, are the actual steps
in evolution, are as a matter of fact just the
class of changes in favor of the inheritance
of which there is the least evidence. Any pe-
culiarity that an animal exhibits and that is
not an inheritance, but is the result of an in-
dividual change due either to an alteration of
habit or to the direct influence of the envi-
ronment, is called an acquired character ; and
the assumption that acquired characters are

104 BIOLOGY AND SOCIAL PROBLEMS

inherited is a most doubtful biological propo-
sition.

The clarification of this whole matter, and
the present attitude of the majority of biolo-
gists toward it, are the results chiefly of Weis-
mann's work. Weismann pointed out very
clearly that the multitude of cells that arose
by the division of the egg cell, and that
eventually constituted the body of an adult
animal, could be grouped into two sets, the
somatic cells and the germ cells. The somatic
cells are represented by those cells that give
rise to skin, bone, muscle, nerve, and other
non-reproductive tissues. They constitute the
great mass of the body and carry on all its
functions except that of sexual reproduction.
The germ cells are those that give rise to
sperm cells or egg cells, and that are there-
fore primarily concerned with reproduction.
Both the germ cells and the somatic cells in
any individuals are descendants of the egg
cell from which that individual arose, but they
are not derived one from the other. Germ
cells are cells that are differentiated directly
from certain of the unmodified cells that re-
sult from the division of the egg cell and
never from cells that begin to show a tend-

EVOLUTION 105

ency to become somatic cells. In a similar
way, somatic cells are never derived from cells
which have begun to assume the character of
germ cells, but are also directly derived from
the segmented egg. The two classes of cells
are thus fundamentally distinct, and it is not
inappropriate to describe the body of one of
the higher animals as composed of an enor-
mous aggregation of somatic cells in which is
harbored and protected a certain number of
germ cells.

What has been defined as acquired charac-
ters, namely, those changes which are not the
products of inheritance, but which are the di-
rect results of some change in the environ-
ment or in the activities of an animal, are
necessarily alterations in its somatic cells. The
change in a muscle in consequence of a new
form of exercise is a change in somatic cells ;
the alteration that the skin exhibits under a
new exposure is of the same kind ; the change
in the nervous mechanism by which a new
habit is established is also somatic. If acquired
characters, then, are modifications in the so-
matic cells, and these cells are distinct from
the germ cells, it is difficult to see how a change
which may affect a group of somatic cells,

106 BIOLOGY AND SOCIAL PROBLEMS

skin cells, for instance, can so influence the
germ cells of the same animal as to produce
the newly acquired trait in its offspring. That
the germ cells are influenced by the somatic
cells there can be not the least doubt, but
that this influence shall result in repro-
ducing in the somatic cells of the offspring
exactly the condition acquired by the cor-
responding cells of the parents is almost in-
conceivable. Since there is no known means
either in descent or otherwise of transferring
the changes which occur in the somatic cells
of an individual to its own germ cells so as
to insure that these changes may be handed on
as such to its offspring, Weismann was led to
suspect that acquired characters were not in-
herited, and that, therefore, the Lamarckian
hypothesis, natural and simple as it appeared
on the surface, was untenable.

The experimental evidence that has been
gathered concerning this question has been
largely in support of Weismann's contention.
One of the first lines of experimental work to
be instituted in this direction was that on mu-
tilations. The tails of rats and mice were cut
off generation after generation with the inten-
tion of discovering whether this process tended

EVOLUTION 107

to induce a shorter tail in the descendants.
All such experiments yielded absolutely nega-
tive results and fell in line with what was
known of the oft-repeated mutilations of the
human body as, for instance, in the Jewish
practice of circumcision. From observations of
this kind it was soon concluded that such ac-
quired characters as mutilations were not in-
herited.

The effects of changes of temperature on
one generation and their inheritance by the
next were likewise tested. Certain butterflies,
when in the pupal stage, were subjected to ab-
normal temperatures and in consequence the
wing-markings were much modified. These
changes were shown to be inherited by their
descendants. But it was pointed out with cor-
rectness that the pupal insects on which the
abnormal temperatures acted carried in their
bodies, almost fully formed, the germ cells for
the next generation, and that these germ cells
were just as much open to the effects of the
change in temperature as the somatic cells of
the parent were. Hence such instances were
set aside as not crucial.

The same is true of the effect of light in
producing pigmented individuals of the sala-

108 BIOLOGY AND SOCIAL PROBLEMS

mander Proteus. This inhabitant of caves
when reared in its natural dark surroundings
is without much pigment and consequently of
a delicate flesh-tint. When reared in the light,
it develops a well-marked dark coloration. The
newly born descendants of such dark parents
emerge at once as dark individuals as though
this peculiarity had been transmitted to them
from their parents. But as Kammerer, who
has recently studied this problem, has pointed
out, the body of Proteus is so translucent that
the light can reach and affect its germ cells
and thereby influence the next generation, as
well as modify its somatic cells. In conse-
quence of this semi-transparency light can
affect the interior of Proteus as a temperature
change can that of most lower animals. Possi-

o

bly in some such way as this are to be explained
Kammerer's later results on the spotted sala-
mander of Europe. This animal becomes
lighter in color when reared on a light clay
background and darker when reared on a dark-
earth background, and the descendants of two
such stocks show at once the parental acqui-
sitions. Kammerer regards this as a conclusive
case of the inheritance of acquired characters,
but before it can be so accepted, it must be

EVOLUTION 109

shown beyond the vestige o£ doubt that the
germ cells are not affected in some such way
as that assumed for Proteus, and the observa-
tions themselves should be confirmed by other
workers. These experiments, like those on mu-
tilations, though they have yielded interesting
material, have not yet produced indubitable
evidence of the inheritance of acquired char-
acters.

If such characters were really inherited, it
ought not to be difficult to show that the so-
matic cells of a given animal can exert a con-
siderable influence on the germ cells contained
within the body. Experimental attempts in this
direction have been made by the transplanta-
tion of ovaries. Magnus removed the ovaries
from a black rabbit and grafted into their places
those from an albino rabbit. The black rabbit
was then paired with a white male and gave
birth to two offspring, one white and the other
black. A similar experiment was then tried
by Guthrie on the hen and with similar re-
sults. Both these experiments were, however,
inconclusive, for the stock on which the tests
were made was not well known and its pu-
rity, therefore, was not established. Castle and
Phillips, in 1911, reported similar experiments

110 BIOLOGY AND SOCIAL PROBLEMS

on pedigreed guinea-pigs and with results of a
more conclusive character. I shall state these
in Castle's own words : " A female albino
guinea-pig, just attaining sexual maturity, was
by an operation deprived of its ovaries, and
instead of the removed ovaries there were in-
troduced into her body the ovaries of a young
black female guinea-pig, not yet sexually ma-
ture, aged about three weeks. The grafted
animal was now mated with a male albino
guinea-pig. From numerous experiments with
albino guinea-pigs it may be stated emphatic-
ally that normal albinos mated together, with-
out exception, produce only albino young, and
the presumption is strong, therefore, that had
this female not been operated on she would
have done the same. She produced, however,
by the albino male three litters of young which
together consisted of six individuals." " The
first litter . . . was produced about six months
after the operation, the last one about a year.
The transplanted ovarian tissue must have re-
mained in its new environment, therefore, from
four to ten months before the eggs attained
full growth and were discharged, ample time,
it would seem, for the influence of the foreign
body upon the inheritance to show itself were

EVOLUTION 111

such influence possible." All the young were
black. The white body of the foster mother,
then, had no influence on the transplanted
egg cells, thus demonstrating in this respect
the independence of germ cells and somatic
cells in one individual. (Plate IV.)

The evidence from experiments on the in-
heritance of mutilations, as well as on the
transmission of changes of a more normal
kind, and from observations on the effects
of a foster parent body on transplanted egg
cell, is thus unfavorable to the view that ac-
quired characters are heritable. If such char-
acters are inherited, it ought to be easy to
demonstrate the truth of this proposition,
but the fact that there is not a single un-
equivocal case in its favor, though the prop-
osition has been tested in many ways, is much
against it. The adverse evidence is all nega-
tive, and though conclusive negative evidence
is most difficult to obtain, that which is at
hand is so strongly negative that, inviting as
the proposition is, the inheritance of acquired
characters cannot be said to be supported by
present-day biological observation.

That man is not an exception to the rule
just laid down seems at first sight startling,

BIOLOGY AND SOCIAL PROBLEMS

if not absurd. To maintain that what we ac-
quire during life has no effect upon our de-
scendants seems to be flying into the face of
observed fact and, if true, to remove one of
the main springs that activate social progress.
That the right or wrong course of the par-
ent's life flows on more or less through that
of the child is one of the fundamental beliefs
of human nature and has long been held out
by moralists as an incentive to upright living.
This doctrine, however, seems to be in direct
opposition to the attitude of most modern
biologists toward the question of the inherit-
ance of acquired characters. But the contrast
thus set up, when carefully scrutinized, is found
to be not a contrast, after all, but rather a
confusion due to the complexities of human
inheritance.

The transmission of traits from parent to
offspring, as we see it exhibited in guinea-pigs
and other organisms, is so like the transmis-
sion of property from parent to child in every-
day life that we call both by the same name,
inheritance. But we must never forget that

o

the inheritance of property is the original
process and that the other is but a figure of
speech. That there are fundamental differ-

EVOLUTION 115

ences between the two cannot for a moment
be doubted. In the inheritance of property
the same article is passed on from parent to
child, but in what we call inheritance in sexual
reproduction, the part inherited is not passed
on from the parent through the egg to the
offspring, but only a tendency or activity rep-
resenting such a part. Moreover, as we have
already seen, such tendencies do not even
emanate from the parental part in question,
but come directly from the racial store con-
tained in the germ cells. Thus it must be evi-
dent that the inheritance of property and the
inheritance of traits are very different proc-
esses, and, since both occur in the human be-
ing, it is important that, though we use the
same name with which to designate them, we
keep the two processes clearly separated in
our minds.

That the inheritance of property in the
ordinary sense of the word is a most significant
factor in human affairs needs no comment. It
is, however, a practice that few other animals
have adopted. Ants continue to inhabit the
same hill generation after generation and thus
inherit and enjoy the results of their ancestors'
labors. Other social animals may afford similar

114 BIOLOGY AND SOCIAL PROBLEMS

examples, but the instance par excellence of
the inheritance of property is to be found
in the human species. As a social proposition
this practice has its advantages, though its
effect on many individuals in removing their
incentive to normal activity shows that the
curse of the Nibelungs' hoard is more than a
poetic fancy.

But is everything that we inherit from our
parents either an object handed down to us
in a physical sense or a tendency or other in-
direct influence transmitted to us through the
egg ? Probably not ! A large part, perhaps
the larger part, of what we are accustomed to
say makes up our lives is obtained neither as an
inherited object nor as a transmitted tendency,
but has reached us in a somewhat different
way. What comes to us over this third route
may be put briefly as our heritable intelligence.
As I pointed out in the first lecture, the mind
of the young child is an unwritten page on
which the environment, acting through the
sense organs, inscribes the story of life. Much
of the sensory inflow is controlled and directed
by the parent, and thus in the early stages
of life he can exert a most profound influence
on the personality of the child. With the

EVOLUTION 115

awakening of the emotions and the develop-
ment of attachments, the parent usually comes
to be an example to the child, and imitation
adds greatly to the obvious similarity of the
two minds. With the development of mental
independence on the part of the offspring,
the parental attitudes and acts may, however,
prove repugnant to the maturing individual
and lead to some courses of action directly
the opposite of those of the ancestor. Thus,
a dissimilarity, which, however, may rest upon
a more deep-seated agreement, may make its
appearance ; the children of the over-religious
may seek irreligion; those of the drunkard,
total abstinence. Into the quickening mind
of the developing individual, with its growing
knowledge, its expanding sympathies, and its
increasing capacity for action, the inheritance
of the race is poured ; knowledge representing
the past experience of mankind with all the
power it gives, the imagery of times gone by
with its capacity to awaken the emotions, in
short the total record of human effort in so
far as it is preserved. This race inheritance
comes to us from human memory, from the
written page, and from a thousand other
sources. It meets us on every side, but it is

116 BIOLOGY AND SOCIAL PROBLEMS

the special office of our educational institu-
tions to preserve it and hand it on. From the
child at the knee to the university student,
all are learning from the same general source.
Thus the process of acquisition goes on, and
as a result we expect an individual not only
with a well-stored mind, but capable of using
his mental equipment in the performance of
serviceable acts, the broadening of sympathies,
and the discovery of new truths.

Such a result is the exclusive outcome of
neither one nor the other of the two methods
of inheritance that we have described. If we
designate that through the germ cell as organic
and that by direct transfer as social inherit-
ance, we can say that our intellectual outfit
comes to us more in the nature of a social
contribution than of an organic one. The
content of the mind is not congenital ; it is a
vast mass of subsequent acquisition. It is in
every sense a veritable body of acquired char-
acters. It is, therefore, not to be expected that
it will ever become hereditary. The rudiments

«/

of learning must be acquired by all ; even the
genius must begin with the alphabet ; and
there is no reason to suppose that the time
will ever come when a pedigreed birth certif-

EVOLUTION 117

icate will take the place of a college entrance
examination. As educators our task is limited
only by the supply of human beings. The
automobile may drive out the horse, but the
educator, whatever the community may think
of him, has come to stay.

If, however, the content of the mind is of
the nature of acquired traits and hence not
heritable, the mental machinery by which this
content is handled is, in part at least, heredi-
tary. The inheritances of feeble-mindedness,
insanity, and other defects, as well as of favor-
able traits, such as predisposition to music
and so forth, are too well established as ger-
minal features to admit of dispute. They re-
semble a more stable background on which
our somewhat plastic natures rest, and, though
their well-being is essential to our success,
they of themselves afford only that founda-
tion on which such a success may be built.
Thus our personality springs from a heredi-
tary soil, but the direction of its growth is
more a matter of environment than of ger-
minal determination. Although the Lamarck-
ian hypothesis seems to have no assured place
as a real factor in the process of organic evo-
lution, if we widen our conception of this

118 BIOLOGY AND SOCIAL PROBLEMS

process to include the mental growth of man,
Lamarckism affords an accurate statement of
the way by which much of our mental equip-
ment has come to us, though this statement,
as compared with that advanced by Lamarck
and his followers, is figurative rather than
real. What we do not get by social inherit-
ance, however, we obtain by the strictest kind
of organic transmission. Thus our personal-
ity is in part an organic and in part a social
heritage.

With the evidence so preponderatingly
against Lamarckism as an effective factor in
organic evolution, there is left as a guiding
principle for the transmutationists little more
than Darwin's theory of natural selection.
This theory is so well known in its general
outlines as to require no special exposition.
Every species, according to Darwin, produces
many more offspring than can possibly reach
maturity. These offspring all differ somewhat
one from another. In consequence, at any pe-
riod of stress those individuals whose differ-
ences lie in the directions favorable for life
are more likely to survive than those that ex-
hibit unfavorable differences. Thus the more
favored individuals tend to be preserved and

EVOLUTION 119

to become the progenitors of a new stock
bearing the favorable traits.

The individual differences which Darwin be-
lieved to afford a basis for this process are
not the characters acquired during life, but
are those features with which the young or-
ganism is born. These differences are germinal
in their origin, and therefore may be handed
on ; in other words, Darwin's theory avoids
the difficulty of the inheritance of acquired
characters and is based upon what is known
to be heritable differences.

That natural selection is a process that oc-
curs in nature seems to be beyond dispute.
A single instance may suffice to show this.
After a severe winter storm in Providence,
Rhode Island, on February 1, 1898, many of
the English sparrows of that region were found
to be much spent and exhausted. Of these
birds, one hundred and thirty-six were col-
lected and brought within doors, and of this
number seventy-two revived and sixty-four
died. A close comparison of these two sets
disclosed the fact that the birds that died
were less near the normal than those that sur-
vived, showing that, for instance, a heavy body
with small wings or a light body with large

120 BIOLOGY AND SOCIAL PROBLEMS

wings was less advantageous under stress of
circumstances than a body of average weight
carrying wings of average extent. In this in-
stance, then, natural selection could be said
to take place in that extreme inclemency tended
to eliminate the less fit. Other instances of a
like kind have shown that this process is of
common occurrence in nature.

But though we may feel confident that nat-
ural selection is of actual occurrence, it is by
no means certain that it is of first importance.
Numerous serious and valid objections to it
have been raised from time to time. The most
telling of these is the difficulty experienced in
understanding how in a given species new
characters can get a foothold. The slight in-
dividual differences that Darwin assumed to
be the beginnings of new traits are altogether
too insignificant to be of selectional value, and
hence it seems impossible that the initial step
in the origin of such a trait could be taken
by natural selection. This objection has been
fairly met by the mutation theory of De Yries.
According to this theory the differences ef-
fective in evolution are not the small individ-
ual variations, such as were considered so
important by Darwin, but the considerable

EVOLUTION

sudden changes, or mutations as they have
been called, and which, since the revival of
Mendel's work, have been found to occur in
most animals and plants. These differences,
like Minerva, are born in their fullness, and
selection may act upon them at once. Thus it
is well known that from time to time albino
individuals appear in stocks of wild as well as
of domesticated animals. Such an appearance
is a mutation, and in the case of wild animals
living in a district where dark coloration is of
protective importance, the individuals bearing
this trait would probably be quickly exter-
minated ; but in an environment like the
polar regions where whiteness is an advan-
tage, such individuals might well be preserved
and in the end give rise to a white stock.

Such hypothetical cases show us how nat-
ural selection may take place, and yet we have
reason to suspect that the process itself is not
so simple. Selection is supposed to act on what
Weismann might call the somatic qualities of
individuals, coat-color, size of body, strength
of muscle, and so forth, and it is assumed that
these traits, since they are germinal in origin,
would be reproduced in the offspring. But, as
we saw from the breeding experiments with

122 BIOLOGY AND SOCIAL PROBLEMS

the black and white guinea-pigs already al-
luded to, we may have two individuals with
indistinguishable exteriors and yet with very
different germinal possibilities. One stock of
black guinea-pigs, depending upon its ances-
try, is able to produce nothing but black de-
scendants, and another stock of black indi-
viduals, indistinguishable externally from the
first but differing from it in its ancestry, can
bring forth white offspring as well as black.
In the preservation of black individuals, nat-
ural selection would act the same in the two
stocks, but one stock would be more effective
than the other in establishing a black race.
Thus germinal composition may be a factor of
no small importance in limiting the effective-
ness of natural selection, a process which is
of undoubted significance in nature, but which
may be much more restricted in its applica-
tion and effectiveness than its advocates have
suspected.

That natural selection influences man as it
does other organisms is an undoubted fact.
Every epidemic that carries off human beings
acts selectively, and if it affects individuals in
early life and before the period of reproduc-
tive activity, it may have great importance

EVOLUTION 123

from the standpoint of natural selection. Un-
doubtedly the differences in the immunity to
various diseases characteristic of different hu-
man races are to be attributed to this kind of
influence. But that natural selection has been
the main driving force in the evolution of
man is no more to be admitted than it is in re-
spect to the other organisms. Natural selection
seems to be a real but subordinate factor in
organic evolution, the mechanism of which is
still to be discovered.

In man much of his social practice tends to
reduce rather than to preserve the efficiency
of natural selection. In ancient times and in
primitive races to-day the malformed or other-
wise defective infant is often destroyed, thus
anticipating what is likely to happen later
through purely natural causes. With the
growth in our civilization of the sense of value
in human life, these practices have become
mostly illegal and have been largely sup-
pressed. As a result we have developed a large
body of institutions for the care of our defec-
tives, institutions supported by a strong pub-
lic opinion. Such social undertakings are in
direct opposition to the workings of natural
selection. They are a drain on the social body,

124 BIOLOGY AND SOCIAL PROBLEMS

but they are justifiable for the reason that they
inculcate a respect for life and a public habit
of humane treatment of unfortunates, charac-
teristics without which no race can afford to
be. But they are not unqualified blessings.
And when we examine them from the stand-
point of evolution, they seem to contain an
element of no small danger to the state. While
it is avowedly advantageous to the community
as a whole to treat with all reasonable care its
defective members, it is quite clear that this
class, so far as its traits are hereditary, is not
the class from which the future of society
should be recruited. It seems proper, therefore,
since our social institutions have counteracted
to a certain degree the effects of natural selec-
tion and have thus brought about conditions
that are unduly burdensome to the common-
wealth, if not really menacing to the welfare
of society itself, that the state should regulate
the reproductive activity of certain classes of
defective individuals. This can be done in two
ways : first, by educating all persons to a sense
of their social responsibilities in reproduction
and then relying upon them to act in accord-
ance with this training; and, secondly, where
such education is impossible, by sterilizing the

EVOLUTION 125

individual through means that are effective,
but that are as little disturbing to his person-
ality as possible. By these methods reasonable
self-restraint can be brought into play or a
final barrier set in the way of the irresponsi-
ble. That so radical a course as the latter is
justifiable will be apparent to any one who
follows the history of many of the charges
in our public institutions for the feeble-
minded.

In the programme of the eugenicists, I
heartily agree with that portion which is di-
rected toward the complete elimination of re-
production by the irresponsible defective. Such
a step is merely a reinstitution in modern hu-
man evolution of a rapidly disappearing phase
of natural selection. When, however, the ac-
tivity of eugenics is shifted from that of the
elimination of the most undesirable to exclu-
sive reproduction by the most desirable, I find
it difficult to settle in my own mind how this
high-grade stock is to be selected. My neigh-
bors are charitably inclined, but some of them,
I am sure, would give what seemed to them
good reasons for not having my particular
personality repeated in the future, and yet,
with all due respect to the welfare of society,

126 BIOLOGY AND SOCIAL PROBLEMS

I confess to a slight measure of feeling that
I be allowed some individual freedom in this
matter.

And this brings me to another aspect of
the social evolution in man. We have seen
how immensely powerful and compelling the
forces of organic inheritance are, but we have
also seen that what we call ourselves is a
growth built up in our nervous organization
in part directly by daily experience and in
part indirectly by what I have called social
inheritance. The personality thus developed,
though it must depend upon a certain or-
ganically inherited soil and cannot rightly
flourish unless this is wholesome, is in itself
no whit less important a factor in the evolu-
tion of man than that of inheritance through
the substance of the egg. Memory and above
all the ability to act voluntarily are most sig-
nificant factors in our daily affairs. Without
them the fabric of human society would never
have come into existence. Voluntary action is
a basic fact upon which all social responsibil-
ity rests. It makes a code of morals effective.
By education this capacity can be greatly
improved and set forward and no small part
of human progress has depended upon this

EVOLUTION 127

fact. Improvement of this kind through a
favorable environment, educational or other-
wise, can transform a being whose hereditary
outlook is poor into one whose service to so-
ciety may be great, for a new discovery, a sub-
lime idea, or even a kind act has its place in
the evolution of man as much as a hereditary
trait. One comes to us by social inheritance,
the other by organic. These two processes,
the one depending upon the nervous system,
the other upon the reproductive mechanism,
though treated more or less separately in these
lectures, are in reality inextricably interwoven
in our natures. For a right understanding and
control of our social acts, it is necessary to
know the extent to which each factor underlies
them. This determined, the organic constitu-
ent may be modified, improved, or otherwise
controlled through the principles of genetics
as applied to the reproductive processes, and
the social constituent may similarly be dealt
with through environmental changes, train-
ing, and education in their broadest sense.
These two factors thus mutually interrelated
are the fundamental biological elements that
underlie our social structure.

In dealing with these elements in the present

128 BIOLOGY AND SOCIAL PROBLEMS

lectures, I have repeatedly taken occasion to
point out their relation to the materials of the
body. Organic inheritance is dependent upon
the minute amount of these materials in the
fertilized egg, perhaps even upon those in the
chromosomes. By means of these substances
and in no other way are the organically herit-
able traits handed on from parent to child.
Social inheritance is dependent upon the ap-
proximate cubic inch of nervous protoplasm
contained in our cerebral cortex and serving
as a means for our conscious operations. When
this is removed, diseased, or temporarily dis-
turbed, as by poisons and the like, the whole
personality is shaken to the core or even van-
ishes. From a variety of directions, we have
as strong reasons for believing that that whole
aggregate of nervous states that we recognize
as our inmost selves is as essentially associated
with the cortical protoplasm as organic inher-
itance is with the materials of the egg. In
neither case do we understand much of the
process. That is a subject for future investi-
gation, but research has gone far enough to
show that these two classes of operations, the
most wonderful, perhaps, that go on in the
body, are bound up indissolubly with their

EVOLUTION 129

several kinds of protoplasm and occur under
no other circumstances.

As we know that the materials of the egg
cells and of the cortex are undergoing contin-
ual disintegration and that the loss that they
thus suffer is regularly made good by the ap-
propriation of new material which comes di-
rectly or indirectly from the inorganic sur-
roundings, the inference is that our most
profound activities are of a purely materialis-
tic nature. And this conclusion seems to me
to be entirely correct. But when we think of
material, we are prone to regard only its inor-
ganic aspects and we often forget of what it
is capable when organized into living sub-
stance; in doing this we miss completely its
most profound characteristics. In this respect
the side of approach is most important. It
would be an interesting speculation to inquire
what would be our present outlook on nature
had science made its first fundamental discov-
eries in the organic instead of in the inorganic.
I am sure that that outlook would have been
different from what it is now, but I am also
equally sure that that difference, large as it
might seem to some of us at present, would
prove in the end to be temporary and illusory,

130 BIOLOGY AND SOCIAL PROBLEMS

for, from whichever side of the problem we
make the approach, there is but one goal.

Of the nature of living substance we are
only just beginning to get a dim appreciation,
but when this appreciation grows to some-
thing of an understanding, we shall feel, I be-
lieve, no more hesitancy in abandoning our old
view of the separateness of self and body and
accepting that of their common nature than in
the past our race had in giving up Dante's para-
dise and its ten heavens for the depths of blue
above us. Organized living material, as we
meet it in the cerebral cortex, is so strictly a
part of the universe and yet so strikingly dif-
ferent from any other aggregate of material
known to us that we can look upon it at pres-
ent only with vague bewilderment and yet with
a hope, justified by the past progress of sci-
ence, that in time its secrets will be gradually
disclosed to us. With such a view of the poten-
tialities of material, it is not surprising that
the biologist finds in the study of organisms
a subject of intense interest whose applica-
tion to the problems of human welfare comes
to be day by day more apparent and intimate.

THE END

CAMBRIDGE . MASSACHUSETTS
U . S . A