An Introduction to Social Psychology
Chapter 7: The Inherited and Acquired Equipment of Man
Luther Lee Bernard
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HEREDITY— The Somatic Cells— The inherited equipment of the organism is usually spoken of as its heredity in contradistinction to its acquired nature, which is regarded as the more immediate and direct result of environmental pressures. Biologists are now generally accustomed to think of the inheritance as determined in the chromosomes of the reproductive cells. Any trait or quality which is added to the organism from any other source or through any other channel may be regarded as acquired. This viewpoint represents the Mendelian theory of inheritance, which is dominant among the biological theories of heredity. This process of inheritance through the chromosome content of the reproductive cells may be illustrated by the diagram on the following page.
The diagram is, of course, merely symbolic, and represents the union of the two parental reproductive cells (M and F) to form the offspring cell (O). Each human, like any other, individual begins life as a single cell. This initial cell multiplies through fission into a vast number of cells. These derivative cells are o f two general kinds, somatic and reproductive. The somatic cells differentiate into the various organs and tissues of the body, totaling approximately 26,500,000,000,000 in the human adult. The development of the individual somatic organism parallels very largely the development of the type in the race. Thus the digestive and circulatory tissues are followed by the growth of a skeletal system, muscles and glands, and a nervous apparatus. The nervous system, like the other parts of the body, is not matured until several years after the birth of the organism, and perhaps it is still immature at the point of natural death.
The reproductive cells are differentiated from the somatic
(91) cells during the first two or three days after the formation of the new cell body or offspring. These
also multiply by fission. Unlike the somatic cells, which have their greatest period of
EXPLANATION OF THE DIAGRAM : M and F represent symbolically the male and female reproductive cells respectively combining to produce a new or offspring cell; they include both cytoplasm and nucleus with chromosome content, as indicated. O represents the offspring cells, O', O", etc., being successive generations. S, S', S" represent the somatic organisms which develop by fission and integration from the original offspring cell. R, R', R" represent the production of reproductive cells from the maturing offspring. These are used for the production of new offspring. The letters ss, s' s', s" s" represent the cytoplasmic determination of the somatic organization of new organisms, while sr, s'r', s"r" represent the chromosome determination of these same organisms. Note that lines of chromosome determination are indicated by direct extension to the nucleus while lines of cytoplasmic determination are indicated by extension to the cytoplasm only. No attempt is made here to represent diagrammatically determination by external environmental factors.
(92) normal multiplication during the first twenty years of life or less, with only minor divisions or multiplications thereafter, the male reproductive cells do not reach a very active stage of multiplication until the age of puberty is reached in the early or middle 'teens. They probably have their most prolific period of multiplication in the late 'teens and early twenties and gradually decline in activity thereafter, but in most cases in the male they do not cease to multiply until advanced old age. The number of male reproductive cells generated (approximately 340000,000,000) vastly exceeds that of the female for obvious reasons. It is said that the new-born female contains from 36,000 to 200,000 ova, which number has been reduced to 30,000 or fewer at puberty, and of which not more than 400 become mature and capable of fertilization by the male reproductive cells. The relative rates of multiplication of the male reproductive cells at different age periods doubtless has much to do with the organization of the emotional and other behavior patterns of the male at different stages of his development.
DETERMINATION OF THE INHERITANCE— If the inheritance of the new organism is determined by the union of the chromosomes of the parent reproductive cells, there must be some point at which this inheritance determination is completed. Obviously this is the point of fertilization. Parts of the chromosomes and of the cytoplasm of the parent cells enter into the structure of the new offspring cell and determine its initial character. This in turn is modified within limits by environmental pressures. After the point of fertilization the offspring cell has no further contact with the parental reproductive cells. Consequently it is not able to receive further chromosome determination. The subsequent contacts which it has with the somatic organization of the mother during the nine months before birth and with the organisms, directly and indirectly, of both parents after birth are in the nature of environmental pressures rather than of inheritance determiners.
The inheritance of the organism is, therefore, completed at the point of fertilization, with the result that any traits developed subsequent to this point, unless predetermined in the heredity, are of environmental origin. This is a fact which
(93) it is very important to remember, because there is still much confusion about the nature and extent of the individual inheritance. The old, pre-Mendelian view of inheritance was that any traits which the child possessed at the period of birth had been received through the inheritance mechanism. It is not surprising that many persons, including not a few with biological training— usually acquired before the Mendelian theory became well known after 1900 — still do their thinking about inheritance from this untenable viewpoint. They have not yet adjusted themselves to the newer facts of biological science. Much, therefore, which formerly has been called inheritance is in reality only the product of the pre-natal environment.
THE METHOD OF ENVIRONMENTAL MENTAL DETERMINATION — Child, who has made recent contributions in biology of great significance to social psychology, rejects the preformistic conception of the organism which holds that heredity presents it fully formed and ready for action like a machine especially constructed to do its work. Such a viewpoint fails to take account of the facts either of physiology or of sociology, that is, of the relationship of the organism to either its internal or its external environments. "Actually the organism is not at any stage a closed system . . . . Reaction to environment is occurring at all stages of development, though of course the kinds and complexity of reaction differ at different stages according to the mechanisms present. Moreover, such behavior or reaction is itself a factor in development and therefore in the construction of the behavior mechanisms of later stages. The behavior of the various developmental stages as well as the specific hereditary constitution of the protoplasm is a factor in determining the behavior of the fully developed organism." [1] And this modification of behavior patterns by the behavior of the new organism in response to environment begins as soon as the new organism itself enters upon the life process. It is the failure to appreciate this fact which has prevented the biologists and psychologists of the predeterministic or preformistic type from appreciating adequately the importance of environment in determining human traits.
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The character of the behavior of the organism is determined by the character of the organism itself. The organism is a complex integration of functioning protoplasms of varying constitution and rates of metabolism. These protoplasms are fundamentally fixed in type by inheritance, although their physiology, and consequently their internal functioning, may be modified to some extent by internal chemical environment. Heredity in the protoplasms determines the general characteristics of the organism. "The organismic mechanisms arise on the basis of the hereditary substratum and . . . this determines that the organism shall be a certain species or variety of fern, elm, snail, fish, or ape. From this viewpoint the problem of behavior involves the whole problem of evolution as well as that of inheritance." The organism is a physicochemical unity, and its primary physiological pattern is the action system which is the basis of its unity. This pattern, as before said, is constantly undergoing reformation as a result of reaction to the environment. "The organism may, in fact, be defined as a pattern of relation to environment appearing in protoplasm . . . . Organismic pattern then appears to be a behavior pattern in a protoplasm," while life itself, the greatest of the complexes of behavior, "is the behavior of protoplasmic systems in relation to an external world." The potentialities of the pattern, inherited and acquired, can be realized only through the action of external or environmental factors. Consequently, we may say that inheritance initiates the behavior process, but only in its simplest and most general terms; while environment gives formation and determination increasingly to the specific content of behavior, both in the individual and in the human race.
As the functional relationships between organisms and environments become more highly differentiated and the necessity for rapid changes in these relationships becomes greater in the higher types, less of behavior is determined by heredity and more by environment. The lower animals, especially the insects, which have a short life period and live throughout this period in relatively uniform environments, require but little flexibility in their behavior. They can make their adjustments to a relatively constant environment on the basis of instinctive
(95) mechanisms or inherited organizations of behavior patterns in neural protoplasms. But in the higher animals, especially in man, whose life period covers all the seasons, hence a wide range of temperatures, and whose great motility brings him in contact with numerous diverse environments in rapid succession, instinct or fixed inherited organizations of protoplasm are no longer adequate to guide behavior, and a vast range of habits or acquired integrations of protoplasmic patterns has been developed. Man has, in fact, created for himself inventions, he has domesticated plant and animal types, and he has objectified behavior meanings in the form of symbol complexes, all of which constitute new environments to direct and organize his behavior. The flexibility and incompleteness of the neural organization of the cerebral cortex make possible adjustment to these new environments on the basis of habit in the higher mammals and man.
MODIFICATION OF BEHAVIOR PATTERNS— This modification of behavior and the formation of acquired behavior patterns to replace and to elaborate the inherited or previously acquired patterns occur in two ways. In the first instance the internal organization of the protoplasms is itself modified as a result of functional contact with the environment. This is particularly true in the higher organisms, and preëminently so in the case of man, where so large a portion of the neurons are incompletely developed and unconnected synaptically until many months or even years after the initial development of the organism. This fact of cortical flexibility in the higher organisms makes it possible to reorganize patterns in the neural protoplasm with great ease and to an extent of complexity not appreciated before the rise of modern neurology and physiology. These changing neural patterns also produce modifications of overt behavior through their neuro-muscular and neuro-glandular or efferent responses. The net result of such modifiability is that the countless number of new things we learn— mental or psychic skills— and of the new things we learn to do— neuro-muscular skills— are added as acquired characteristics to the accomplishments (themselves partly acquired) characteristic of the lower animals. In our modern civilized world, and perhaps among all peoples, however low
(96) in the cultural scale they may be, the acquired characteristics, mental and neuro-muscular, far outnumber and outrank in importance for adjustment purposes those which are inherited or instinctive.
The second way in which this modification of behavior patterns occurs is more indirect. The reaction of the changing organism upon the environment constantly modifies the environment itself. This fact was earlier illustrated in pointing out how the social environments are created out of the natural physical and biological external environments and out of the internal physiological and neural processes through their modification. As Child aptly remarks, "Most organisms would cease to exist in a very short time if it were impossible for them to alter their environment by mechanical action upon it." The modified environment reacts back upon the behavior organization and integration of the organism and produces further changes in it. The result is that the organism changes coordinately and more or less in conformity with the changes in the environment. This interaction between the organism and its behavior and the environment goes on indefinitely, augmented by independent changes in the individual (such as mutations, metabolism, etc.) and the environment (such as population growth, changes in climate and soil resources, which are not wholly independent of organismic influences). The resulting changes in environment and in the behavior of individual organisms are practically unlimited in extent and complexity.
WHERE THE CHANGES OCCUR— The final result in man is that behavior is completely transformed, although the general and original protoplasmic structures largely keep their form. The structure of the non-neural protoplasms remains much the same throughout life, except for a progressive physico-chemical integration which excludes to a large degree variational adjustment and therefore leads ultimately to fixity and death of the organism. Even the organization of the nervous protoplasms tends in this general direction, but only after the higher centers have undergone countless changes in organization and reorganization of behavior .patterns. At first there is a lack of organization of behavior patterns in the neural protoplasm of the higher levels. Under the influence of changing environ-
( 97) mental pressures this organization is effected in great complexity and in a multiplicity of forms. The higher life is developed as habits and these are modified endlessly and quite freely to suit the demands of a constantly changing environment, until the old age of the non-neural tissues, and even to some extent of the neural tissues themselves, narrows the limits and effectiveness of these variations in behavior.
We have spoken in this section primarily of the modification of behavior patterns rather than of the modification of organs and tissues of non-neural protoplasms, for the social psychologist is interested in behavior. Non-neural protoplasms are not so easily modified by environmental pressures as are the neural protoplasms, because the former react in a primarily mechanical and direct manner to environmental pressures, while the latter respond primarily in an indirect and excitatory manner to environmental stimuli. In this second type of reaction, the excitatory, "the energy transfer between the external world and protoplasm serves merely as the initiating factor in bringing about energy changes which themselves depend upon the configuration of the system acted upon." The stimulus or initiating factor merely liberates energy from the system. It is in this excitation-response system of neural protoplasm that we find the greatest flexibility of behavior patterns. It is here that conscious memory and intelligence function as the highest forms of organismic control. Of course the higher and cortical centers of neural organizations illustrate the principles of the excitation-response system better than the lower centers, for it is in the former that we find the greatest degree of complexity and flexibility of response.
THE ACQUIRED TRAITS— It is not easy to distinguish acquired and inherited characteristics. The general formulas that the inherited traits are determined by the union of the chromosomes of the parental reproductive cells to form the new offspring cell, and that the acquired traits are determined by environmental pressures, do not reveal to us the actual mechanisms by which the two types of traits appear iii the processes of growth. The process of fertilization and the genesis of the inheritance traits in the new individual have been frequently described by the geneticists and the reader is
(98) referred to that source for such information, if he does not already possess it. But the building up of the acquired traits, especially in the prenatal stage of development, has not been so well described. The recent work of Child (1924) already quoted and of Herrick (1924) also referred to, and of their collaborators, has done most to open up this process of the growth of the organism in its initial stages under environmental pressures. Also the recent investigations of the embryologists have given us many data on the determination of specific traits in the prenatal stage.
STAGES of DEVELOPMENT— Postnatal— The best results from the standpoint of an estimate of the contribution of environmental pressures to individual traits may be obtained if we divide the developmental process into three stages. These stages may be outlined as follows:
[1. Preconceptual stage]2. Prenatal stage
3. Postnatal stage
The first is bracketed, because it is not an actual stage of individual development but is preliminary to the other two stages, which are actual. Some writers add a natal stage to take account of those events which occur during the birth process. Practically all types of traits, except those which come to the child directly from the mother through the blood stream, may be acquired in the postnatal stage of development. Some of these even may be acquired during the nursing period through her milk. Thus the various germ diseases, the organic and functional diseases, the neuroses and psychoses, the results of nutrition in its various normal and abnormal aspects, modifications of the organism due to direct impact with the environment, such as wounds, distortions, and malformations, the effects of temperature and of chemical substances, and the various skills, physiological and psychical, which come to us as the result of the pressures of our psycho-social, bio-social and physico-social environments, are acquired by us in this postnatal stage of development. The traits are too numerous to specify individually and we must content ourselves at this point with a mere enumeration of their general classes or types.
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In the prenatal stage of development the number of characteristics which may be acquired is much more limited because the volume and kinds of the environment which operate in this stage are much less outstanding. The classes of traits which may be acquired in this stage may be outlined as follows
1. Traumatisms and malformations or deformities due to injury to the offspring in utero. This category also includes injuries due to abortions resulting from physical violence.
2. Infections. The most important of these is syphilis, from which it is said approximately fifty percent of the stillbirths result. Other infections, such as typhoid and typhus fever, tuberculosis and various other skin and blood diseases, affect the child either through the mother's blood stream or at parturition.3. Toxic conditions due to such chemical poisons as lead, phosphorus and alcohol and the poisonous ethers reaching the child through the mother. Such poisons often are induced as the result of the occupation of the mother. These may cause aborted or generally and specifically defective offspring.
4. Toxic conditions arising within the metabolism of the mother from such causes as infections, undernutrition or malnutrition, excessive fatigue or strain, and affecting the child through some modification of its metabolism, causing it to be born weak or defective or even dead, or to be aborted.
5. The hormones developed in the ductless glands of the mother often affect the tissues of the unborn child through the blood stream from the mother. Normal endocrines probably predispose the child towards normal development, while abnormal endocrines produce defective development and capacities in the child. For example, an endocrine disease in the mother, such as goiter, may appear in the child at birth through this means of transmission. Possibly also the vitamins from foods consumed by the mother may in some way affect the development of the child.
It is very provable that much disease formerly regarded as inherited and many of the physiological and anatomical conditions which predispose to feeble-mindedness and other forms of mental and emotional defect in childhood originate by ac-
(100) -quisition through the prenatal environmental channels here indicated. If this is true it will necessitate a change of viewpoint among the educational sociologists and psychopathologists regarding the origin and social treatment of mental defectiveness.
PRECONCEPTUAL INFLUENCES— Obviously the offspring organism cannot acquire traits in the preconceptual stage of development, because the organism does not yet exist. But anything which can happen to the cytoplasm of the parental reproductive cells may produce an effect upon the new organism at or after the point of fertilization. Anything occurring to the chromosomes in the nucleus of the parent cells would probably affect the heredity or prevent fertilization altogether through destruction of the chromosome content. But the cytoplasm of the parent reproductive cells is environment for the new offspring cells because parts of the cytoplasm of the parent cells enter into the somatic organization of the offspring organism. The cytoplasm of reproductive cells has been known to be infected or to develop toxic conditions or to undergo tissue modification under the influence of the environing somatic structure or body of the parents who carried the reproductive cells. In this way environmental pressures even from a preconceptual environment are able to reach the offspring. Apparently such environmental influences are comparatively limited and the effects upon the offspring are primarily of the nature of lesions, infections and toxic conditions due to specific germs or to poisons. Also, anything of appropriate character which can be carried to the point of fertilization along with or in the environment of the reproductive cell has a chance of influencing the development of the offspring body in the same manner.
CULTURE THE PRODUCT OF THE POSTNATAL STAGE— It Will be clear from the preceding analysis of the types of acquired traits receivable from environmental pressures in the various stages of development that from neither the prenatal nor the preconceptual sources chi we acquire thus specific mental traits and intellectual skills which collectively we call culture. No ideas or other complex mental, moral, and social traits are acquired in these stages of development. Such characteristics are
(101) the product of the postnatal environments. They are initiated primarily by the pressures of the psycho-social environment. The other social environments also play some part more or less directly in this connection, and the natural environments condition man in such ways that they influence the acquisition of culture indirectly. Especially is this true where the climate, the supply of fauna and flora, and of natural resources influence the degree and kinds of culture through the effects they have upon human behavior and the accumulation of a surplus of wealth over the bare necessities of existence which enables the culture development to be financed or promoted.
The reason why the specific mental, moral, and social traits cannot be acquired under preconceptual and prenatal conditions is that such acquisitions must come through the use of the higher exteroceptive senses, which, as was pointed out in a previous chapter, are the foundations of all intellectual development. These senses are not operative in preconceptual and prenatal stages. Certain physiological and neurological conditions, however, can be brought about through the operation of the prenatal and preconceptual environmental pressures outlined above which will predispose indirectly toward or against the acquisition of various intellectual skills and moral and social attitudes and values.
ENVIRONMENTAL VERSUS HEREDITARY TRANSMISSION OF TRAITS— There is considerable controversy regarding the relative importance of heredity and environment in the determination of behavior patterns of individual organisms. The extremists on both sides appear to be loath to grant any considerable weight to the contentions of the opposing view. It is not the purpose of this volume to enter into this controversy, but to state the facts on both sides when they are pertinent to the discussion of the mechanisms of behavior as they function in organisms and are determined or modified by environments. It is axiomatic that both heredity and environment play their parts in determining behavior. The one serves as the initial basis, while the other determines for the must part the differential development of behavior.
Heredity is racial. That is, it generally occurs in successive generations of individual organisms in direct line of biological
( 102) descent. So likewise do acquired characteristics occur. The essential distinction, therefore, between the inherited and the acquired traits is not in the occurrence of the characteristics in successive generations but in the method of their transmission. As we have already seen, the transmission of inherited traits is commonly accounted for as by means of the chromosomes. Transmission of acquired traits, however, occurs through some more external process, such as through the cytoplasm of the reproductive cells, through the environing mother during the prenatal development of the child, or through the organisms and behavior of parents, playfellows, teachers, or any other persons or "carriers" of infections, toxins, ideas, behavior symbols, or what not, with which one comes in physiological or sensory contact in his postnatal development. The psycho-social environment is perhaps the most potent and voluminous carrier through which acquired characteristics are transmitted in our modern world. Traits carried by this environment are of course not physical or biological directly, but are mental, moral, and social characteristics or attitudes which are capable of being transmitted by the intangible symbolic structures of the psycho-social environment. The composite or derivative control environments, which organize the psycho-social and other social as well as the underived environments around some process of social organization and construction, and which appear to us ordinarily as institutions, can of course carry all classes and kinds of characteristics, not merely the mental, moral, and social.
THEORY OF THE INHERITANCE OF ACQUIRED CHARACTERISTICS— The importance of environment as a source of structure and of behavior has been observed even in the midst of those periods when the theory of inheritance had most vogue. This fact gave rise to attempts to assimilate the two viewpoints. The most important of these attempts is to be found in the theory of the inheritance of acquired characters, which was approved by Lamarck and Darwin and their followers and Was later questioned by the school of Weismann. In its history it has invented many ingenious theories of the method of the transmission of acquired characters, including Darwin's doctrine of pangenesis and Semon's theory of the Mneme.
( 103) It still has its adherents, some of the most noted of whom are Dr. Paul Kammerer of Vienna and Professor Guyer of the University of Wisconsin.
The evidence however seems scarcely convincing. Dr. Kammerer finds his best illustrations among very low and simple organisms where it is doubtful if inheritance through gametes is established and where apparently the transmission which he calls hereditary takes place through external tissues and therefore comes under the category of environmental. The same criticism in general may be made of other work in support of the inheritance of acquired characteristics. Transmission of acquired traits seems to be carried from one generation to another through the blood or the endocrines or some other tissue rather than through the chromosomes, hence is not inheritance in the Mendelian sense. If it does take place through the chromosomes it is probably in those cases where the physico-chemical content of the matured tissue or characteristic is identical in kind with the substance which enters into the chromosome segments.
Certainly there is no evidence that mental, moral, and social traits can be carried through the chromosomes and thus become a part of true inheritance. True inheritance is always of structures or of organization of structures. It is inheritance of biological materials; there can be no inheritance of ideas or of moral and social attitudes and values which have no constant relation to structure, but vary freely according to time and place and value to the organism concerned. As far as the psychologist and the social psychologist are concerned the theory of the inheritance of acquired characteristics appears to have little or nothing to offer as an explanation of the appearance and modification of behavior patterns. These sciences, as well as sociology, must look rather to Child's theory of the integration of the organism through the functioning of its behavior patterns in relation to environmental pressures and to other similar theories of environmental determination.
THE SOURCE OF INHERITED TRAITS— There has also been considerable discussion as to the source of inherited traits in the first instance, if they were not induced in the heredity
( 104) through use. What causes variations and mutations in the inheritance? It is fairly easy to account for variations in structure and behavior which are obviously the product of environment and persist only a single generation or are carried from one generation to the next by means of the same external mechanisms by which they can be transferred from one individual to another in the same generation. The transmission here is environmental. But unquestionably changes or variations also occur in the chromosomes which persist through successive generations, and appear in the somatic organization as inherited traits. These often appear in the type suddenly as mutations. From what source do they come? There are various theories as to their origin which cannot be elaborated here, such as that they are the result of conditions of temperature, of nutrition, of forced development, of the penetration of hormones and even of toxins and of formative substances into the nucleus where the chromosomes are segregated as far as possible from somatic interference. All of these theories, it will be seen, trace the variation or mutation in heredity back to an environmental source or cause. It should also be noted that in no case, unless in that of the last hypothesis mentioned, would the inherited trait produced by a change in the chromosomes be the same as the environing factor or condition (which may or may not be an acquired somatic characteristic) which produced the modification of the chromosomes. These theories of the origin of true inheritance traits, even if correct, can not offer much in support of the doctrine of the inheritance of acquired characteristics.
ENVIRONMENTAL SELECTION OF TRAITS— The most commonly accepted theory of environmental determination of inherited traits is that of natural and artificial selection. This theory holds that many biological characteristics appear "spontaneously" in the chromosomes— although the true explanation of the apparent spontaneity may be that suggested in the preceding paragraph— and that those traits which aid the organism in making effective adjustments to its environment are the ones which survive and reproduce themselves, because the carrier organism survives and reproduces. This is essen-
( 105) -tially the old doctrine of the survival of the fittest, which was formulated by Darwin to explain why certain types survived the struggle for existence in nature.
To this process of natural selection we have added artificial selection, which consciously or unconsciously throws the weight of advantage, through social aid, upon the side of the socially favored. This artificial selection may result in great improvements of types, and also in degeneration, according as the selection is wisely or unwisely directed from a social standpoint. Artificial selection, especially in the form of eugenic control, is one of the great social problems of our age.
Such selection of traits for inheritance is obviously the product primarily of environmental pressures and when artificial it is the result mainly of the pressure of the psycho-social environment. The characteristics selected in the inheritance are, of course, biological. They occur apparently for the most part in the non-neural protoplasms and affect the organization of the higher or cortical neurons indirectly rather than directly.
The behavior patterns which concern the social psychologist most intimately are rarely produced as the result of natural or artificial selection of inheritance, although the acquired behavior patterns organized under the direct or indirect pressures of the environments may be significantly conditioned by selected inheritance traits or structures. The social psychologist is interested not so much in structural traits as in the neuro-psychic and neuro-muscular mechanisms resulting and the social significance of behavior which proceeds from the structural conditions.
MATERIALS FOR SUPPLEMENTARY READING- Baldwin, J. M., Social and Ethical Interpretations, Ch. II
- Bernard, L. L., "The Significance of Environment as a Social Factor," Pub. Amer. Sociological Soc., XVI:84-112
- — , Instinct: A Study in Social Psychology, Chs. XI, XII
- Boas, F., "Growth and Development, Bodily and Mental, as Determined by Heredity and by Social Environment," in The Child, the Clinic and the Court, pp. 178-88
- Bogardus, E. S., Fundamentals of Social Psychology, Ch. I
- Burnham, W., The Normal Mind, Ch. XVIII
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- Child, C. M., "The Individual and Environment from a Physiological Viewpoint," in The Child, the Clinic and the Court, pp. 126-55
- —— ,Physiological Foundations of Environment
- Conklin, E. G., Heredity and Environment
- Davies, G. R., Social Environment, Ch. IV
- Dunlap, K., Social Psychology, Ch. VI
- Feldman, W. M., The Principles of Anti-natal and Post-natal Child Physiology, Pure and Applied
- Gault, R. H., Social Psychology, Ch. IV
- Ward, L. F., Applied Sociology, pp. 95-110 and Part II
