Biology and social problems

Front matter

9 2

=. .

REFERENCE LIBRARY OF HOUGHTON MIFFLIN COMPANY

Foreword

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 displaces 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 considered settled. This state of the world renders the practical problems of personal conduct 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 individual.

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 foundation of these lectures. Such light may come through a recent discovery in natural or applied science, through a new tendency in art, literature, or music; it may be the result of some painstaking research in history or anthropology; 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 William Brewster Clark, M.D., who graduated from Amherst in the class of 1876. We believe 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.

New York Ciry, 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,” it would make for a loss of coherence and continuity in the lectures as a whole. Accordingly, 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 conscious direction of that progress is yet in its infancy. Few indeed there are who do not still consider human characteristics, institutions, and environment to be as immutably fixed as the hills and the ocean. The merest scattering of human beings realizes that with knowledge and codperative 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 Control 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 naturally, the basis of positive knowledge and experience. Social Control to-day is more prophecy than science.

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

With this limitation of their scope the lectures will be continued along the lines originally planned.

Introduction

I. Tar Nervous SYSTEM .

II. Hormones .

III. Repropucrion

MEEEIVOLUTION . . . .

ILLUSTRATIONS

OvaRIAN TRANSPLANTATION (Plate IV) Se eg 8.) Brontispiece

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

FEMINIZED GUINEA-Pics (PlateT) . . . 52 By courtesy of Professor FE. Steinach.

MENDELIAN INHERITANCE (Plate IT). . . 86

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

Reemudagsoters (PlatelIT): . ... . 92

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

y i '

| PAY

INTRODUCTION

In our endeavor to better the conditions of man, probably no facts are more worthy of consideration than those included in his natural 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 showers descended upon the expanse of earth beneath, fertilizing it and rendering it a fit abode for man. Here he built habitations, cultivated the soil, and peopled the earth with his offspring. T’o him the earth seemed the center of the universe, and he believed that its creation 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 provoked by it as to the condition of the antipodes 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 astronomy 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 located habitation. In fact it may be said that the Copernican theory removed the last physical vestige of the support for the anthropocentric 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 constituted, though its diameter is between five and six thousand millions of miles, is small compared 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 thousand 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 diameter 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 measurements were probably never imagined by even the astronomers of olden times and certainly 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 realization 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 replied that man is the product of his immediate environment. And it therefore behooves those who have his welfare at heart to acquaint themselves with this environment as well as with man regarded as one of its products. It is the object of these lectures to attempt to sketch in outline something of man’s nature from this standpoint.

Viewed near at hand and asa part of his immediate surroundings, man has a twofold interest. 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.

eis

te iM m we" ’ otis

. af

I THE NERVOUS SYSTEM

Or the sixteen hundred millions of human beings that populate the earth to-day experience 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 individual whom we have learned to know, we are less inclined to dwell on physical traits than on the innumerable characteristic movements 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.

These traits seem to us to indicate the real individual more truly than such obvious physical peculiarities as stature, color of hair, and the like, for the reason probably that experience has taught us that, though the physical 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 effective 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 airy in its lightness and transparency, and, like a shadow, it might separate itself somewhat from the body. More accustomed to think of an animal as a whole than as an assemblage of parts, they were prone to conceive of functions as more or less diffusely related to the body. Yet that a certain degree of localization 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 engendered 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 becameso well grounded through the investigations of the physicians of that time, particularly Haller, as to assume the form of permanency. This growth of knowledge led directly to the modern view that 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 profoundly 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, thriftiness, 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 effective 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 personality, 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 conditions 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 aggregation 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 Waldeyer 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 processes, which for a long time were not recognized as belonging to the nerve cell, are the most characteristic parts of its structure. Extending 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 processes 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 contains 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 histological 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 simplicity itself compared with the real complexity in such a nervous system as that of any of the higher animals, not to mention man.

Yet, notwithstanding the enormous complexity in the arrangement of the neurones in such animals, these elements are capable of a relatively simple classification. A large number of them extend from the skin and the organs of special sense, such as the nose, the tongue, the ear, and the like, to the central nervous organs. These neurones become active 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 neurones. Another set of neurones transmit impulses 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 matter of fact there is a host of other neurones ‘which never reach beyond the limits of the central nervous system and which are concerned with bringing one part of this system into communication with another. As a rule these neurones cannot be designated appropriately as either afferent or efferent. They have, therefore, been termed internuncial. In the higher animals they certainly far outnumber the afferent and the efferent elements collectively and constitute the bulk of the central nervous system in these forms. Thus, notwithstanding the enormous numbers of neurones in the higher animals and the intricacy 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 usually responds almost immediately by a movement. 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 mentioned, namely, the afferent and the efferent, but probably in the great majority of actual occurrences internuncial neuronesare included, and these strictly central elements mediate between the central ends of the efferent and of the afferent neurones. The reflex is thus a physiological unit, so to speak, in the action 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 operations. | Many of the elemental movements which the body of man is continually exhibiting partake of the nature of reflexes, and if we extend this term to include operations which involve 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 instinctive 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 recognize 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 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 concerned 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 regularity 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 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 itself. Henceit is clear that the sympathetic and vagus nerves are not related to the heart muscle 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 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 established, and that is that in the embryo of such a vertebrate as the chick, the heart begins to beat before any nervous tissue whatever 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 embryonic heart suggests that in primitive animals muscle may have preceded nerve in its evolution, 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 apparently dependent entirely upon the direct stimulation 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 pupille by means of which the pupil of the eye is constricted. This muscle is ordinarily under the control of the oculomotor nerve, and it responds reflexly by contracting when the retina 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 ordinary 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 neuromuscular activity.

If the embryonic vertebrate heart illustrates 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 pressure follows, demonstrating that this nerve is an afferent nerve whose activity induces through the central nervous system an enlargement 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 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, perhaps, the most primitive class of reflex movements with which we are acquainted. Although they may be absolutely unassociated with consciousness, they exhibit a nicety of adjustment that is most baffling when explanation is attempted, for they show every appearance of intelligent control. They, therefore, afford evidence for that conception of the organism 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 astatement can beat 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 simple nervous acts like the one just described than that these animals have any real conscious existence. 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 repeatedly strike a dog on one side of the middle of the back, he will begin scratching movements 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 operation of the lachrymal glands whereby tears flow. In addition to muscles and glands, elec: tric organs and luminous organs, found among fishes and other lower animals, are apparently also reflexly excitable.

Reflexes of the kind just mentioned are almost invariably congenital. The animal is born into the world with the particular reflex mechanism 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 working hive, make perfect comb. Many female insects, mostly in response to odors, lay their egos 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, insects, and so forth, are probably made up almost exclusively of this kind of activity. That these responses in the lower animals are always associated with conscious states even of a simple 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, involuntary operations, but with the stirrings of consciousness on the sensory side.