Taboo and Genetics
by Melvin Moses Knight, Iva Lowther Peters, and Phyllis Mary Blanchard
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Transcriber's note: The irregular footnote markers in this text [numbers] refer to the reference book the author used, and not always to the specific page numbers. These reference books are listed numerically at the end of each chapter. The footnotes are marked with [letters] and the referenced footnotes are contained within the text, near to the footnote marker. Therefore, occasionally the numerical footnote markers are out of sequence. Words that were italicized are now marked by an underscore (_).


A Study of the Biological, Sociological and Psychological Foundation of the Family





Author of The Adolescent Girl

London: Kegan Paul, Trench, Trubner & Co., Ltd. New York: Moffat, Yard & Co.




Scientific discovery, especially in biology, during the past two decades has made necessary an entire restatement of the sociological problem of sex. Ward's so-called "gynaecocentric" theory, as sketched in Chapter 14 of his Pure Sociology, has been almost a bible on the sex problem to sociologists, in spite of the fact that modern laboratory experimentation has disproved it in almost every detail. While a comparatively small number of people read this theory from the original source, it is still being scattered far and wide in the form of quotations, paraphrases, and interpretations by more popular writers. It is therefore necessary to gather together the biological data which are available from technical experimentation and medical research, in order that its social implications may be utilized to show the obsoleteness of this older and unscientific statement of the sex problem in society.

In order to have a thoroughly comprehensive survey of the institutions connected with sexual relationships and the family and their entire significance for human life, it is also necessary to approach them from the ethnological and psychological points of view. The influence of the primitive sex taboos on the evolution of the social mores and family life has received too little attention in the whole literature of sexual ethics and the sociology of sex. That these old customs have had an inestimable influence upon the members of the group, modern psychology has recently come to recognize. It therefore seems advantageous to include these psychological findings in the same book with the discussion of the sex taboos and other material with which it must so largely deal.

These fields—biology, ethnology, and psychology—are so complicated and so far apart technically, although their social implications are so closely interwoven, that it has seemed best to divide the treatment between three different writers, each of whom has devoted much study to his special phase of the subject. This leads to a very simple arrangement of the material. The first part deals with the physical or biological basis of the sex problem, which all societies from the most primitive to the most advanced have had and still have to build upon. The second part deals with the various ideas man has developed in his quest for a satisfactory adaptation of this physical basis to his own requirements. Part three attempts to analyze the effect of this long history of social experimentation upon the human psyche in its modern social milieu.

In the social evolution of the human mind, the deepest desires of the individual have been often necessarily sacrificed to the needs of the group. Sometimes they have been unnecessarily sacrificed, since human intelligence is, unfortunately, not omniscient. Nevertheless, the sum total of human knowledge has now become great enough so that it is at least well to pause and take account of its bearing on the age-old problem of family life, in order that our evolution henceforth may be guarded by rational control rather than trial and error in so far as is possible. Such a summarization of our actual knowledge of the biology, sociology and psychology of the foundations of the family institution this book aims to present, and if it can at the same time suggest a starting point for a more rationalized system of social control in this field, its purpose will have been accomplished.








What is sex? A sexual and mixed reproduction. Origin of sexual reproduction. Advantage of sex in chance of survival. Germ and body cells. Limitations of biology in social problems. Sex always present in higher animals. Sex in mammals—the problem in the human species. Application of the laboratory method.


Continuity of germ plasm. The sex chromosome. The internal secretions and the sex complex. The male and the female type of body. How removal of sex glands affects body type. Sex determination. Share of the egg and sperm in inheritance. The nature of sex—sexual selection of little importance. The four main types of secretory systems. Sex and sex instincts of rats modified by surgery. Dual basis for sex. Opposite sex basis in every individual. The Free-Martin cattle. Partial reversal of sex in human species.


Intersexes in moths. Bird intersexes. Higher metabolism of males. Quantitative difference between sex factors. Old ideas of intersexuality. Modern surgery and human intersexes. Quantitative theory a Mendelian explanation. Peculiar complication in the case of man. Chemical life-cycles of the sexes. Functional-reproductive period and the sex problem. Relative significance of physiological sex differences.


Adaptation and specialization. Reproduction a group—not an individual problem. Conflict between specialization and adaptation. Intelligence makes for economy in adjustment to environment. Reproduction, not production, the chief factor in the sex problem.


Racial decay in modern society. Purely "moral" control dysgenic in civilized society. New machinery for social control. Mistaken notion that reproduction is an individual problem. Economic and other factors in the group problem of reproduction.





Primitive social control. Its rigidity. Its necessity. The universality of this control in the form of taboos. Connection between the universal attitude of primitive peoples toward woman as shown in the Institutionalized Sex Taboo and the magico-religious belief in Mana. Relation of Mana to Taboo. Discussion of Sympathetic Magic and the associated idea of danger from contact. Difficulties in the way of an inclusive definition of Taboo. Its dual nature. Comparison of concepts of Crawley, Frazer, Marett, and others. Conclusion that Taboo is Negative Mana. Contribution of modern psychology to the study of Taboo. Freud's analogy between the dualistic attitude toward the tabooed object and the ambivalence of the emotions. The understanding of this dualism together with the primitive belief in Mana and Sympathetic Magic explains much in the attitude of man toward woman. The vast amount of evidence in the taboos of many peoples of dualism in the attitude toward woman. Possible physiological explanation of this dualistic attitude of man toward woman found in a period before self-control had in some measure replaced social control, in the reaction of weakness and disgust following sex festivals.


Taboos of first chapter indicate that in the early ages the fear of contamination by woman predominated. Later emphasis fell on her mystic and uncanny power. Ancient fertility cults. Temple prostitution, dedication of virgins, etc. Ancient priestesses and prophetesses. Medicine early developed by woman added to belief in her power. Woman's psychic quality of intuition: its origin—theories—conclusion that this quality is probably physiological in origin, but aggravated by taboo repressions. Transformation in attitude toward woman in the early Christian period. Psychological reasons for the persistence in religion of a Mother Goddess. Development of the Christian concept. Preservation of ancient woman cults as demonology. Early Christian attitude toward woman as unclean and in league with demons. Culmination of belief in demonic power of woman in witchcraft persecutions. All women affected by the belief in witches and in the uncleanness of woman. Gradual development on the basis of the beliefs outlined of an ideally pure and immaculate Model Woman.


The Taboo and modern institutions. Survival of ideas of the uncleanness of woman. Taboo and the family. The "good" woman. The "bad" woman. Increase in the number of women who do not fit into the ancient classifications.


Taboo survivals act dysgenically within the family under present conditions. Conventional education of girls a dysgenic influence. Prostitution and the family. Influence of ancient standards of "good" and "bad." The illegitimate child. Effect of fear, anger, etc., on posterity. The attitude of economically independent women toward marriage.





Bearing of modern psychology on the sex problem. Conditioning of the sexual impulse. Vicarious expression of the sexual impulse. Unconscious factors of the sex life. Taboo control has conditioned the natural biological tendencies of individuals to conform to arbitrary standards of masculinity and femininity. Conflict between individual desires and social standards.


Social institutions controlling sex activities based on the assumption that all women are adapted to as well as specialized for reproduction. Neurotic tendencies which unfit women for marriage—the desire for domination. Sexual anaesthesia another neurotic trait which interferes with marital harmony. The conditioning of the sexual impulse to the parent ideal and the erotic fetish as factors which determine mating. Homosexual tendencies and their part in the sex problem. The conflict between the desire for marriage and egoistic ambitions. The social regulations from the viewpoint of individual psychology.


Mating determined by unconscious psychological motives instead of eugenic considerations. Some of the best male and female stock refusing marriage and parenthood. The race is reproduced largely by the inferior and average stocks and very little by the superior stock. As a therapeutic measure, society should utilize psychological knowledge as a new method of control. Romantic love and conjugal love—a new ideal of love. The solution of the conflict between individual and group interests.







What is sex? Asexual and mixed reproduction; Origin of sexual reproduction; Advantage of sex in chance of survival; Germ and body cells; Limitations of biology in social problems; Sex always present in higher animals; Sex in mammals; The sex problem in the human species; Application of laboratory method.

Sex, like all complicated phenomena, defies being crowded into a simple definition. In an animal or plant individual it is expressed by and linked with the ability to produce egg- or sperm-cells (ova or spermatozoa). Sexual reproduction is simply the chain of events following the union of the egg and sperm to produce a new individual. Looked at from another angle, it is that sort of reproduction which requires two differentiated individuals: the male, which produces spermatoza, and the female, which produces ova. In the case of very simple forms, it would be simply the union or conjugation of a male and a female individual and the reproductive process involved. Where there is no differentiation into male and female there is no sex.

An individual which produces both sperm-and egg-cells within its body is termed an hermaphrodite. Very few hermaphrodites exist among the vertebrates, although they may be found in one or two species (e.g., the hagfish). There are no truly hermaphroditic mammals, i.e., individuals in which both the male and the female germ cells function, except perhaps in rare instances.

Sexless or asexual reproduction assumes various forms. What is usually considered the most primitive of these is fission or simple division, in which the cell divides into two equal, identical parts. There is of course no suggestion of sex here. It is fairly safe to assume that life began thus in the world, as neuter or sexless—i.e., with no suggestion of either maleness or femaleness.[A]

[Footnote A: This asexual type of reproduction has been misinterpreted by a whole school of non-biological writers, who have followed the lead of Lester F. Ward, in his classification of these neuter-organisms as females. Ward says ("Pure Sociology," Ch. 14): "It does no violence to language or science to say that life begins with the female organism and is carried on a long distance by means of females alone. In all the different forms of asexual reproduction from fission to parthenogenesis, the female may in this sense be said to exist alone and perform all the functions of life including reproduction. In a word, life begins as female" (p. 313). Adding to this statement the assertion that the male developed at first as a mere parasite, in the actual, physical sense, Ward proceeds to build up his famous Gynaecocentric Theory, which is familiar to all students of social science, and need not be elaborated here. It is obvious that a thorough biological knowledge destroys the fundamental concept on which this theory is founded, for there is no doubt that life begins as neuter or sexless, and not as female.]

There are a number of other forms of asexual reproduction, or the "vegetative type" (Abbott's term, which includes fission, budding, polysporogonia and simple spore formation). Budding (as in yeast) and spore formation are familiar to us in plants. Such forms are too distant from man, in structure and function, for profitable direct comparison. Especially is this true with respect to sex, which they do not possess.

Parthenogenesis includes very diverse and anomalous cases. The term signifies the ability of females to reproduce in such species for one or a number of generations without males. Many forms of this class (or more strictly, these classes) have apparently become specialized or degenerated, having once been more truly sexual. Parthenogenesis (division and development of an egg without the agency of male sperm) has been brought about artificially by Jacques Loeb in species as complicated as frogs.[1,2] All the frogs produced were males, so that the race (of frogs) could not even be theoretically carried on by that method.

The origin of sexual reproduction in animals must have been something as follows: The first method of reproduction was by a simple division of the unicellular organism to form two new individuals. At times, a fusion of two independent individuals occurred. This was known as conjugation, and is seen among Paramecia and some other species to-day. Its value is probably a reinvigoration of the vitality of the individual. Next there was probably a tendency for the organism to break up into many parts which subsequently united with each other. Gradually some of these uniting cells came to contain more food material than the others. As a result of their increased size, they possessed less power of motion than the others, and in time lost their cilia (or flagella) entirely and were brought into contact with the smaller cells only by the motion of the latter. Finally, in colonial forms, most of the cells in the colony ceased to have any share in reproduction, that function being relegated to the activities of a few cells which broke away and united with others similarly adrift. These cells functioning for reproduction continued to differentiate more and more, until large ova and small, motile spermtozoa were definitely developed.

The clearest evidences as to the stages in the evolution of sexual reproduction is found in the plant world among the green algae.[3] In the lower orders of one-celled algae, reproduction takes place by simple cell division. In some families, this simple division results in the production of several new individuals instead of only two from each parent cell. A slightly different condition is found in those orders where the numerous cells thus produced by simple division of the parent organism unite in pairs to produce new individuals after a brief independent existence of their own. These free-swimming cells, which apparently are formed only to reunite with each other, are called zooespores, while the organism which results from their fusion is known as a zygospore. The zygospore thus formed slowly increases in size, until it in its turn develops a new generation of zooespores. In still other forms, in place of the zooespores, more highly differentiated cells, known as eggs and sperms, are developed, and these unite to produce the new individuals. Both eggs and sperms are believed to have been derived from simpler ancestral types of ciliated cells which were similar in structure and closely resembled zooespores.[A]

[Footnote A: This evidence, which points to the conclusion that in the early origin of sexual reproduction the males and females were differentiated and developed from a uniform type of ancestral cell, quite controverts Ward's point that the male originated as a kind of parasite.]

Having once originated, the sexual type of reproduction possessed a definite survival value which assured its continuation. Sex makes possible a crossing of strains, which evidently possesses some great advantage, since the few simple forms which have no such division of reproductive functions have undergone no great development and all the higher, more complicated animals are sexual. This crossing of strains may make possible greater variety, it may help in crossing out or weakening variations which are too far from the average, or both.

Schaefer[4] thinks that an exchange of nuclear substance probably gives a sort of chemical rejuvenation and very likely stimulates division. At any rate, the groups in which the reproductive process became thus partitioned between two kinds of individuals, male and female, not only survived, but they underwent an amazing development compared with those which remained sexless.

There came a time in the evolution of the groups possessing sexual reproduction, when increasing specialization necessitated the division into reproductive and non-reproductive cells. When a simple cell reproduces by dividing into two similar parts, each developing into a new individual like the parent, this parent no longer exists as a cell, but the material which composed it still exists in the new ones. The old cell did not "die"—no body was left behind. Since this nuclear substance exists in the new cells, and since these generations go on indefinitely, the cells are in a sense "immortal" or deathless. In a one-celled individual, there is no distinction between germinal and bodily functions. In the more complicated organisms, however, there are innumerable kinds of cells, a few (the germ cells) specialized for reproduction, the others forming the body which eats, moves, sees, feels, and in the case of man, thinks. But the germ-cells or germplasm continue to be immortal or deathless in the same sense as in the simplest organisms. The body, in a historical sense, grew up around the germ-cells, taking over functions a little at a time, until in the higher animals nutrition and other activities and a large part even of the reproductive process itself is carried on by body-cells.

When we think of a man or woman, we think of an individual only one of whose innumerable activities—reproduction—is carried on by germ-cells, and this one only at the very beginning of the life of a new individual. Human societies, needless to remark, are not organized by germplasms, but by brains and hands—composed of body cells. If these brains and hands—if human bodies—did not wear out or become destroyed, we should not need to trouble ourselves so much about the germplasm, whose sole function in human society is to replace them.

Since the individual human bodies and minds which seek after the things to which we mortals attach value—moral worth, esthetic and other pleasure, achievement and the like—do have to be replaced every few years, the germplasms from which new individuals must come have always been and always will be of fundamental importance. It is always the product of the germplasm which concerns us, and we are interested in the germ-cells themselves only in relation to their capacity to produce individuals of value to society.

So let us not go erring about in the philosophical ether, imagining that because the amoeba may not be specialized for anything over and above nutrition and reproduction that these are necessarily the "main business" or "chief ends" of human societies. Better say that although we have become developed and specialized for a million other activities we are still bound by those fundamental necessities. As to "Nature's purposes" about which the older sex literature has had so much to say, the idea is essentially religious rather than scientific. If such "purposes" indeed exist in the universe, man evidently does not feel particularly bound by them. We do not hesitate to put a cornfield where "Nature" had a forest, or to replace a barren hillside by the sea with a city.

Necessities and possibilities, not "purposes" in nature, claim our attention—reproduction being one of those embarrassing necessities, viewed through the eyes of man, the one evaluating animal in the world. Thus in reasoning from biology to social problems, it is fundamental to remember that man as an animal is tremendously differentiated in functions, and that most of the activities we look upon as distinctively human depend upon the body rather than the germ-cells.

It follows that biology is the foundation rather than the house, if we may use so crude a figure. The solidity of the foundation is very important, but it does not dictate the details as to how the superstructure shall be arranged.

Civilization would not be civilization if we had to spend most of our time thinking about the biological basis. If we wish to think of "Nature's" proscriptions or plans as controlling animal life, the anthropomorphism is substantially harmless. But man keeps out of the way of most of such proscriptions, has plans of his own, and has acquired considerable skill in varying his projects without running foul of such biological prohibitions.

It is time to abandon the notion that biology prescribes in detail how we shall run society. True, this foundation has never received a surplus of intelligent consideration. Sometimes human societies have built so foolishly upon it that the result has been collapse. Somebody is always digging around it in quest of evidence of some vanished idyllic state of things which, having had and discarded, we should return to. This little excursion into biology is made in the full consciousness that social mandates are not to be found there. Human projects are the primary material of social science. It is indispensable to check these against biological fact, in order to ascertain which are feasible and which are not. The biological basis may help in explaining old social structures or in planning new ones; but much wild social theory has been born of a failure to appreciate the limitations of such material.

All the so-called higher animals, mammals and others, are divided into two sexes, male and female. Besides the differentiation of germ-cells there are rather obvious differences in the bodies of the two sexes. In common with many other mammals, the human male has a larger and stronger body, on an average, than has the human female. This is true also of the anthropoid apes, the species which most resemble man physically and are commonly supposed to be his nearest blood relatives in the animal kingdom. It has been true of man himself as far back as we have any records.

Such differences are only superficial—the real ones go deeper. We are not so much interested in how they originated in the world as in how they do come about in the individual. At least, we can come a good deal nearer ascertaining the latter than the former. In either case, our real purpose is to determine as nearly as possible what the unlikeness really consists of and so help people to sensibly make up their minds what can be done about it.

To define sex with rigid accuracy as the term applies to human beings, it is necessary to tell what it is in mammals, since man is a mammal. The presence of distinct body-cells is not peculiar to mammals, but there is one respect in which these latter are quite different from non-mammals: A mammalian individual, beginning like a non-mammal with a fertilized egg, has a period of intra-maternal development which a non-mammal has not. That is, a non-mammalian is a fertilized egg plus its parental (or extra-parental) environment; but a mammalian individual is a fertilized egg, plus its intra-maternal environment, plus its non-parental environment.

Here in a nutshell is the biological basis of sex problem in human society. Human individuals do wear out and have to be replaced by reproduction. In the reproductive process, the female, as in mammals generally, is specialized to provide an intra-maternal environment (approximately nine months in the human species) for each new individual, and lactation or suckling afterward. The biological phase of the sex problem in society consists in studying the nature of that specialization. From the purely sociological standpoint, the sex problem concerns the customs and institutions which have grown up or may grow up to meet the need of society for reproduction.

The point which most concerns us is in how far biological data can be applied to the sex problem in society. Systematic dissections or breeding experiments upon human beings, thought out in advance and under control in a laboratory, are subject to obvious limitations. Surgical operations, where careful data are kept, often answer the same purpose as concerns some details; but these alone would give us a fragmentary record of how a fertilized egg becomes a conscious human being of one sex or the other. The practice of medicine often throws light on important points. Observation of abnormal cases plays its part in adding to our knowledge. Carefully compiled records of what does occur in inheritance, while lacking many of the checks of planned and controlled experiments, to some extent take the place of the systematic breeding possible with animals. At best, however, the limitations in experimentation with human subjects would give us a rather disconnected record were it not for the data of experimental biology.

How may such biological material be safely used? Indiscriminately employed, it is worse than useless—it can be confusing or actually misleading. It is probably never safe to say, or even to infer directly, that because of this or that animal structure or behaviour we should do thus and so in human society. On this point sociology—especially the sociology of sex—must frankly admit its mistakes and break with much of its cherished past.

The social problem of sex consists of fitting the best possible institutions on to the biological foundation as we find it in the human species. Hence all our reasoning about which institution or custom is preferable must refer directly to the human bodies which compose society. We can use laboratory evidence about the bodies of other animals to help us in understanding the physical structure and functions of the human body; but we must stop trying to apply the sex-ways of birds, spiders or even cows (which are at least mammals) to human society, which is not made up of any of these.

It is possible to be quite sure that some facts carefully observed about mammals in a biological laboratory apply to similar structures in man, also a mammal. Because of this relationship, the data from medicine and surgery are priceless. Thus we are enabled to check up our systematic experimental knowledge of animals by an ascertained fact here and there in the human material, and to get a fairly exact idea of how great the correspondence actually is. Gaps thus filled in are narrow enough, and our certainty of the ground on either side sufficiently great, to give a good deal of justifiable assurance.

If we use our general biological evidence in this way, merely to help in clearing up points about human biology, we need not be entirely limited to mammals. Some sex phenomena are quite general, and may be drawn from the sexual species most convenient to study and control in experiments. When we get away from mammalian forms, however, we must be very sure that the cases used for illustrations are of general application, are similar in respect to the points compared, or that any vital differences are understood and conscientiously pointed out.

Too much stress cannot be laid upon the point that such animal data, carefully checked up with the human material, cannot safely be used for any other purpose than to discover what the facts are about the human body. When the discussion of human social institutions is taken up in Part II, the obvious assumption will always be that these rest upon human biology, and that we must not let our minds wander into vague analogies concerning birds, spiders or crustacea.


1. Loeb, Jacques. Artificial Parthenogenesis and Fertilization. Chicago, 1913.

2. Loeb, Jacques. The Organism as a Whole. N.Y., 1916, p. 125—brief summary of results of [1].

3. Bower, Kerr & Agar. Sex and Heredity. N.Y., 1919, 119 pp.

4. Schaefer, E.A. Nature, Origin and Maintenance of Life. Science, n.s., Vol. 36, pp. 306 f., 1912.

5. Guyer, M.F. Being Well-Born. Indianapolis, 1916; p. 123.



Continuity of germplasm; The sex chromosome; The internal secretions and the sex complex; The male and the female type of body; How removal of sex glands affects body type; Sex determination; Share of egg and sperm in heredity; Nature of sex—sexual selection of little importance; The four main types of secretory systems; Sex and sex-instincts of rats modified by surgery; Dual basis for sex; Opposite-sex basis in every individual; The Free-Martin cattle; Partial reversal of sex in man.

In Chapter I, the "immortality" of the protoplasm in the germ cells of higher animals, as well as in simpler forms without distinct bodies, was mentioned. In these higher animals this protoplasm is known as germplasm, that in body cells as somatoplasm.

All that is really meant by "immortality" in a germplasm is continuity. That is, while an individual may consist of a colony of millions of cells, all of these spring from one cell and it a germ cell—the fertilized ovum. This first divides to form a new group of germ cells, which are within the embryo or new body when it begins to develop, and so on through indefinite generations. Thus the germ cells in an individual living to-day are the lineal descendants, by simple division, of the germ cells in his ancestors as many generations, or thousands of generations, ago as we care to imagine. All the complicated body specializations and sex phenomena may be regarded as super-imposed upon or grouped around this succession of germ cells, continuous by simple division.

The type of body in each generation depends upon this germplasm, but the germplasm is not supposed to be in any way modified by the body (except, of course, that severe enough accidents might damage it). Thus we resemble our parents only because the germplasm which directs our development is a split-off portion of the same continuous line of germ cells which directed their development, that of their fathers, and so on back. This now universally accepted theory is called the "continuity of the germplasm."

It will be seen at once that this seems to preclude any possibility of a child's inheriting from its parents anything which these did not themselves inherit. The bodies of each generation are, so to speak, mere "buds" from the continuous lines of germplasm. If we develop our muscles or our musical talent, this development is of the body and dies with it, though the physical basis or capacity we ourselves inherited is still in the germplasm and is therefore passed along to our children. We may also furnish our children an environment which will stimulate their desire and lend opportunity for similar or greater advancement than our own. This is social inheritance, or the product of environment—easy to confuse with that of heredity and very difficult to separate, especially in the case of mental traits.

It will likewise become clear as we proceed that there is no mechanism or relationship known to biology which could account for what is popularly termed "pre-natal influence." A developing embryo has its own circulation, so insulated from that of the mother that only a few of the most virulent and insidious disease germs can ever pass the barrier. The general health of the mother is of utmost importance to the vitality, chances of life, constitution and immunity from disease of the unborn child. Especially must she be free from diseases which may be communicated to the child either before or at the time of birth. This applies particularly to gonorrhoea, one of the most widely prevalent as well as most ancient of maladies, and syphilis, another disastrous and very common plague which is directly communicable. As to "birthmarks" and the like being directly caused by things the mother has seen or thought about, such beliefs seem to be founded on a few remarkable pure coincidences and a great deal of folk-lore.

Reproduction in its simplest form is, then, simply the division of one cell into two parts, each of which develops into a replica of the original. Division is also the first stage in reproduction in the most complicated animal bodies. To get an idea of what takes place in such a division we must remember that a cell consists of three distinct parts: (a) the protoplasm or cytoplasm, (b) the nucleus, and (c) a small body known as the centrosome which need not be discussed here.

When a cell division takes place, the nucleus breaks up into a number of thread-like portions which are known as chromosomes. There are supposed to be 24 pairs, or 48, in the human cell. All the evidence indicates that these chromosomes carry the "factors" in inheritance which produces the characters or characteristics of the individual body.

In mitosis or ordinary cell division, these chromosomes split lengthwise, so that the new cells always have the same number as the original one. When the germ-cells of the male and female make the division which marks the first step in reproduction, however, the process is different. Half the chromatin material passes into each of the two cells formed. This is called maturation, or the maturation division, and the new cells have only half the original number of chromosomes. Each of these divides again by mitosis (the chromosomes splitting lengthwise), the half or haploid number remaining. The result is the gametes (literally "marrying cells"—from the Greek game, signifying marriage). Those from the male are called sperms or spermatozoa and those from the female eggs or ova. (The divisions to form ova present certain complications which need not be taken up in detail here.) Of the 24 chromosomes in each sperm or egg we are here concerned with only one, known as the sex chromosome because, in addition to transmitting other characteristics, it determines the sex of the new individual.

Neither the ovum nor the spermatozoon (the human race is referred to) is capable alone of developing into a new individual. They must join in the process known as fertilization. The sperm penetrates the egg (within the body of the female) and the 24 chromosomes from each source, male and female, are re-grouped in a new nucleus with 48 chromosomes—the full number.

The chances are half and half that the new individual thus begun will be of a given sex, for the following reason: There is a structural difference, supposed to be fundamentally chemical, between the cells of a female body and those of a male. The result is that the gametes (sperm and eggs) they respectively produce in maturation are not exactly alike as to chromosome composition. All the eggs contain what is known as the "X" type of sex chromosome. But only half the male sperm have this type—in the other half is found one of somewhat different type, known as "Y." (This, again, is for the human species—in some animals the mechanism and arrangement is somewhat different.) If a sperm and egg both carrying the X-type of chromosome unite in fertilization, the resulting embryo is a female. If an X unites with a Y, the result is a male. Since each combination happens in about half the cases, the race is about half male and half female.

Thus sex is inherited, like other characters, by the action of the chromatin material of the cell nucleus. As Goldschmidt[1] remarks, this theory of the visible mechanism of sex distribution "is to-day so far proven that the demonstration stands on the level of an experimental proof in physics or chemistry." But why and how does this nuclear material determine sex? In other words, what is the nature of the process of differentiation into male and female which it sets in motion?

To begin with, we must give some account of the difference between the cells of male and female origin, an unlikeness capable of producing the two distinct types of gametes, not only in external appearance, but in chromosome makeup as well. It is due to the presence in the bodies of higher animals of a considerable number of glands, such as the thyroid in the throat and the suprarenals just over the kidneys. These pour secretions into the blood stream, determining its chemical quality and hence how it will influence the growth or, when grown, the stable structure of other organs and cells. They are called endocrine glands or organs, and their chemical contributions to the blood are known as hormones.

Sometimes those which do nothing but furnish these secretions are spoken of as "ductless glands," from their structure. The hormones (endocrine or internal secretions) do not come from the ductless glands alone—but the liver and other glands contribute hormones to the blood stream, in addition to their other functions. Some authorities think that "every cell in the body is an organ of internal secretion",[2] and that thus each influences all the others. The sex glands are especially important as endocrine organs; in fact the somatic cells are organized around the germ cells, as pointed out above. Hence the sex glands may be considered as the keys or central factors in the two chemical systems, the male and the female type.

These various hormones or chemical controllers in the blood interact in a nicely balanced chemical system. Taken as a whole this is often called the "secretory balance" or "internal secretory balance." This balance is literally the key to the sex differences we see, because it lies back of them; i.e., there are two general types of secretory balance, one for males and one for females. Not only are the secretions from the male and the female sex glands themselves quite unlike, but the whole chemical system, balance or "complex" involved is different. Because of this dual basis for metabolism or body chemistry, centering in the sex glands, no organ or cell in a male body can be exactly like the corresponding one in a female body.

In highly organized forms like the mammals (including man), sex is linked up with all the internal secretions, and hence is of the whole body.[3] As Bell [2, p.5] states it: "We must focus at one and the same time the two essential processes of life—the individual metabolism and the reproductive metabolism. They are interdependent. Indeed, the individual metabolism is the reproductive metabolism."

Here, then, is the reason men have larger, differently formed bodies than women—why they have heavier bones, tend to grow beards, and so on. The sex glands are only part of what we may call a well-organized chemical laboratory, delivering various products to the blood, but always in the same general proportions for a given sex. The ingredients which come from the sex glands are also qualitatively different, as has been repeatedly proved by injections and otherwise.

Each of these sex types, male and female, varies somewhat within itself, as is true of everything living. The two are not so far apart but that they may overlap occasionally in some details. For instance, some women are larger than are some men—have lower pitched voices, etc. The whole bodily metabolism, resting as it does upon a chemical complex, is obviously more like the male average in some women than it is in others, and vice versa. But the average physical make-up which we find associated with the male and female sex glands, respectively, is distinctive in each case, and a vast majority of individuals of each sex conform nearly enough to the average so that classification presents no difficulty.

The extreme as well as the average body types existing in the presence of the respective types of sex-glands are different. For example, we find an occasional hen with male spurs, comb or wattles, though she is a normal female in every other respect, and lays eggs.[4] But we never find a functional female (which lays eggs) with all the typical characteristics of the male body. Body variation can go only so far in the presence of each type of primary sexuality (i.e., sex-glands).

The bodily peculiarities of each sex, as distinguished from the sex-glands or gonads themselves, are known as secondary sex characters. To put our statement in the paragraph above in another form, the primary and secondary sex do not always correspond in all details. We shall find as we proceed that our original tentative definition of sex as the ability to produce in the one case sperm, in the other eggs, is sometimes difficult to apply. What shall we say of a sterile individual, which produces neither? The problem is especially embarrassing when the primary and secondary sex do not correspond, as is sometimes the case.

Even in a fully grown animal, to remove or exchange the sex glands (by surgery) modifies the bodily type. One of the most familiar cases of removal is the gelding or desexed horse. His appearance and disposition are different from the stallion, especially if the operation takes place while he is very young. The reason he resembles a normal male in many respects is simply that sexuality in such highly-organized mammals is of the whole body, not of the sex-glands or organs alone.

Suppose this horse was desexed at two years old. Nearly three years had elapsed since he was a fertilized egg. During the eleven months or so he spent within his mother, he developed a very complicated body. Beginning as a male, with a male-type metabolism (that is, as the result of a union between an X and a Y chromosome, not two X's), all his glands, as well as the body structures they control, developed in its presence. Not only the sex glands, but the liver, suprarenals, thyroid—the whole body in fact—became adjusted to the male type. He had long before birth what we call a male sex complex. Complex it is, but it is, nevertheless, easy enough to imagine its nature for illustrative purposes. It is simply all the endocrine or hormone-producing organs organized into a balanced chemical system—adjusted to each other.

When the horse had had this body and this gland system for nearly three years (eleven months within his mother's body and twenty-four outside), it had become pretty well organised and fixed. When a single chemical element (the hormones from the sex-glands) was withdrawn, the system (thus stereotyped in a developed body and glands) was modified but not entirely upset. The sex complex remained male in many respects. It had come to depend upon the other chemical plants, so to speak, quite as much as upon the sex glands. The later the castration is performed—the more fixed the body and gland type has become—the closer the horse will resemble a normal male. Much laboratory experimentation now goes to show that some accident while this horse was still a fertilized egg or a very small embryo might have upset this male type of body chemistry—perhaps even caused him to develop into a female instead, if it took place early enough. This is well illustrated by the so-called "Free-Martin" cattle, to be described later.

For a long time a controversy raged as to whether sex is determined at the time of fertilization, before or after. Biologists now generally prefer to say that a fertilized egg is "predisposed" to maleness or femaleness, instead of "determined." The word "determined" suggests finality, whereas the embryo appears to have in the beginning only a strong tendency or predisposition toward one sex type or the other. It is now quite commonly believed that this predisposition arises from the quantity rather than the quality or kind of factors in the chemical impetus in the nuclei of the conjugating gametes. A later chapter will be devoted to explaining the quantitative theory of sex.

Hence the modern theory of "sex determination" has become:

1. That the chemical factors which give rise to one sex or the other are present in the sperm and ovum before fertilization;

2. That a tendency or predisposition toward maleness or femaleness arises at the time of fertilization, depending upon which type of sperm unites with the uniform type of egg (in some species the sperm is uniform while the egg varies);

3. That this predisposition is:

a. Weaker at first, before it builds up much of a body and gland system to fix it;

b. Increasingly stronger as the new body becomes organized and developed;

c. Liable to partial or complete upset in the very early stages;

d. Probably quantitative—stronger in some cases than in others.

The new definition is, then, really a combination and amplification of the three older points of view.

The term "sex determination" does not mean to the biologist the changing or determining of the sex at will on the part of the experimenter. This might be done by what is known as "selective fertilization" artificially with only the kind of sperm (X or Y as to chromosomes) which would produce the desired result. There is as yet no way to thus select the sperm of higher animals. It has been authoritatively claimed that feeding with certain chemicals, and other methods to be discussed later, has affected the sex of offspring. These experiments (and controversies) need not detain us, since they are not applicable to the human species.

Let us consider this fertilized egg—the contributions of the father and the mother. The total length of the spermatozoon is only about 1/300 of an inch, and 4/5 of this is the tail. This tail does not enter the egg, and has no other known function than that of a propeller. Its movement has been studied and found to be about 1/8 of an inch per minute. Only the head and neck enter the egg. This head consists almost entirely of the nuclear material which is supposed to determine the characters of the future individual.

The ovum or egg contributed by the mother is much larger—nearly round in shape and about 1/120 of an inch in diameter. Besides its nucleus, it contains a considerable amount of what used to be considered as "stored nutritive material" for the early development of the individual.

In ancient times the female was quite commonly supposed to be a mere medium of development for the male seed. Thus the Laws of Manu stated that woman was the soil in which the male seed was planted. In the Greek Eumenides, Orestes' mother did not generate him, but only received and nursed the germ. These quaint ideas of course originated merely from observation of the fact that the woman carries the young until birth, and must not lead us to imagine that the ancients actually separated the germ and somatic cells in their thinking.

A modern version of this old belief was the idea advanced by Harvey that the ovum consisted of fluid in which the embryo appeared by spontaneous generation. Loeuwenhoek's development of the microscope in the 17th century led immediately to the discovery of the spermatozoon by one of his students. At the time, the "preformation theory" was probably the most widely accepted—i.e., that the adult form exists in miniature in the egg or germ, development being merely an unfolding of these preformed parts. With the discovery of the spermatozoon the preformationists were divided into two schools, one (the ovists) holding that the ovum was the container of the miniature individual, the other (animalculists) according this function to the spermatozoon. According to the ovists, the ovum needed merely the stimulation of the spermatozoon to cause its contained individual to undergo development, while the animalculists looked upon the spermatozoon as the essential embryo container, the ovum serving merely as a suitable food supply or growing place.

This nine-lived notion of male supremacy in inheritance was rather reinforced than removed by the breeding of domestic animals in the still more recent past. Attention has been focused on a few great males. For example, the breed of American trotting horses all goes back to one sire—Hambletonian 10. The great Orloff Stud Book, registering over a million individuals, is in the beginning founded on a single horse—a male. It is not strange that we still find among some breeders vestiges of the ancient belief that the male predominates in inheritance. A superior male can impress his characters in a single year upon 100 times as many colts as a female of equal quality could produce in her lifetime. So slight an incident in his life is this reproductive process for each individual that he could if he devoted his life solely to reproduction stamp his characters upon a thousand times as many colts as could a female. Thus under artificial breeding conditions, the good males do have a tremendously disproportionate share in improving the whole breed of horses, though each single horse gets his qualities equally from his male and female parents.

Though Mendel knew an astonishing amount about inheritance a half-century ago, it is worth noting that the foundation upon which rests our present knowledge of sex has been discovered less than twenty years before—the reference is, of course, to the chromosomes as the carriers of inheritance. While from the standpoint of biology the opinions of two decades ago about sex literally belong to a different age, some of them have been so persistent in sociological thought and writings that they must be briefly reviewed in order that the reader may be on his guard against them. Books which still have a wide circulation deal with the sex problem in terms of a biology now no more tenable than the flatness of the earth.

On the one hand were the ancient traditions of male predominance in inheritance, reinforced by the peculiar emphasis which animal breeding places upon males. On the other hand, biologists like Andrew Wilson[5] had argued as early as the seventies of the past century for female predominance, from the general evidence of spiders, birds, etc. Lester F. Ward crystallized the arguments for this view in an article entitled "Our Better Halves" in The Forum in 1888. This philosophy of sex, which he christened the "Gynaecocentric Theory," is best known as expanded into the fourteenth chapter of his "Pure Sociology," published fifteen years later. Its publication at this late date gave it an unfortunate vitality long after its main tenets had been disproved in the biological laboratory. Germ-cell and body-cell functions were not separated. Arguments from social structures, from cosmic, natural and human history, much of it deduced by analogy, were jumbled together in a fashion which seems amazing to us now, though common enough thirty years ago. It was not a wild hypothesis in 1888, its real date, but its repeated republication (in the original and in the works of other writers who accepted it as authoritative) since 1903 has done much to discredit sociology with biologists and, what is more serious, to muddle ideas about sex and society.

In 1903, Weismann's theory of the continuity of the germplasm was ten years old. De Vries' experiments in variation and Mendel's rediscovered work on plant hybridization had hopelessly undermined the older notion that the evolution or progress of species has taken place through the inheritance of acquired characters—that is, that the individuals developed or adapted themselves to suit their surroundings and that these body-modifications were inherited by their offspring. As pointed out in Chapter I, biologists have accepted Weismann's theory of a continuous germplasm, and that this germplasm, not the body, is the carrier of inheritance. Nobody has so far produced evidence of any trace of any biological mechanism whereby development of part of the body—say the biceps of the brain—of the individual could possibly produce such a specific modification of the germplasm he carries as to result in the inheritance of a similar development by his offspring.

Mendel's experiments had shown that the characters we inherit are units or combinations of units, very difficult to permanently change or modify. They combine with each other in all sorts of complicated ways. Sometimes one will "dominate" another, causing it to disappear for a generation or more; but it is not broken up. These characters have a remarkable way of becoming "segregated" once more—that is, of appearing intact later on.

While it follows from Weismann's theory that an adaptation acquired by an individual during his lifetime cannot be transmitted to his offspring, it remained for De Vries to show authoritatively that evolution can, and does, take place without this. Once this was established, biologists cheerfully abandoned the earlier notion. Lester Ward and the biologists of his day in general not only believed in the transmission of acquired characters, but they filled the obvious gaps which occurred in trying to apply this theory to the observed facts by placing a fantastic emphasis upon sexual selection. That is, much progress was accounted for through the selection by the females of the superior males. This, as a prime factor in evolution, has since been almost "wholly discredited" (Kellogg's phrase) by the careful experiments of Mayer, Soule, Douglass, Duerigen, Morgan and others. The belief in sexual selection involved a long string of corollaries, of which biology has about purged itself, but they hang on tenaciously in sociological and popular literature. For instance, Ward believed in the tendency of opposites to mate (tall men with short women, blonds with brunettes, etc.), although Karl Pearson had published a statistical refutation in his Grammar of Science, which had run through two editions when the Pure Sociology appeared. The greater variability of males than females, another gynaecocentric dogma had also been attacked by Pearson on statistical evidence in 1897 (in the well-known essay on Variation in Man and Woman, in Chances of Death) and has become increasingly unacceptable through the researches of Mrs. Hollingworth[6,7,8]. The idea of a vanished age of mother-rule in human society, so essential to the complete theory, has long since been modified by anthropologists.

De Vries' experiments showed that a moderately simple fact practically makes all these complicated theories unnecessary. No two living things are exactly alike—that is, all living matter is more or less variable. Some variations are more fortunate than others, and these variants are the ones which survive—the ones best adapted to their environment. Given this fact of the constant variation of living matter, natural selection (i.e., survival of the fittest and elimination of the unfit) is the mechanism of evolution or progress which best accounts for the observed facts. Such variation is called "chance variation," not because it takes place by "chance" in the properly accepted sense of the term, but because it is so tremendously varied—is evidently due to such complicated and little-understood circumstances—that it can best be studied mathematically, using statistical applications of the "theory of probabilities."

The fine-spun, elaborate theories about sex, so current twenty years ago, have fallen into almost complete desuetude among scientists. With the discovery of the place of the chromosomes in inheritance, biologists began to give their almost undivided attention to a rigid laboratory examination of the cell. This has included sex phenomena since McClung and Sutton pointed out the function of the sex chromosome in 1902 and 1903. Present-day "theories" are little more than working hypotheses, developed, not in a library or study, but with one eye glued to a high-power microscope.

Besides its faulty foundation as to facts, the old gynaecocentric theory involved a method of treatment by historical analogy which biologists have almost entirely discarded. Anyone interested in the relative value of different kinds of biological data for social problems would do well to read the opening chapter of Prof. Morgan's "Critique of the Theory of Evolution"[9], for even a summary of which space is lacking here. College reference shelves are still stocked with books on sex sociology which are totally oblivious of present-day biology. For example, Mrs Gilman (Man-Made World), Mrs Hartley (Truth About Woman) and the Nearings (Woman and Social Progress) adhere to Ward's theory in substantially its primitive form, and not even sociologists like Professor Thomas (Sex and Society) have been able to entirely break away from it.

The old question of male and female predominance in inheritance has been to a considerable extent cleared up, to the discomfiture of both sides to the controversy. Most exhaustive experiments failed to trace any characters to any other part of either sperm or egg than the nucleus. Transmission of characteristics seemed to be absolutely equal by the two parents. The male nucleus enters the egg practically naked. Hence if the characters are transmitted equally, there is certainly ground for supposing that only the nucleus of the egg has such functions, and that the remainder merely provides material for early development. Yet this does not seem to be strictly true.

Parthenogenesis (development of eggs without agency of male sperm) proves that in many simple forms the female nucleus alone possesses all the essential determiners for a new individual. Boveri's classic experiment[10] proved the same thing for the male nucleus. He removed the nuclei from sea-urchin eggs and replaced them with male nuclei. Normal individuals developed. To make things still more certain, he replaced the female nucleus with a male one from a different variety of sea-urchin. The resulting individual exhibited the characteristics of the male nucleus only—none of those of the species represented by the egg. Here, then, was inheritance definitely traced to the nucleus. If this nucleus is a male the characters are those of the male line; if a female those of the female line, and in sexual reproduction where the two are fused, half and half.

Yet the fact remained that all efforts to develop the spermatozoon alone (without the agency of any egg material at all) into an individual had signally failed. Conklin[11] had found out in 1904 and 1905 that the egg cytoplasm in Ascidians is not only composed of different materials, but that these give rise to definite structures in the embryo later on. So a good many biologists believed, and still believe[12,13,14] that the egg is, before fertilization, a sort of "rough preformation of the future embryo" and that the Mendelian factors in the nuclei "only impress the individual (and variety) characters upon this rough block."

If we look at these views from one angle, the apparent conflict disappears, as Professor Conklin[15] points out. We can still presume that all the factors of inheritance are carried in the nucleus. But instead of commencing the life history of the individual at fertilization, we must date it back to the beginning of the development of the egg in the ovary. Whatever rude characters the egg possesses at the time of fertilization were developed under the influence of the nucleus, which in turn got them half and half from its male and female parents. These characters carried by the female across one generation are so rudimentary that they are completely covered up, in the developing embryo, by those of the new nucleus formed by the union of the sperm with the egg in fertilization.

In case fertilization does not take place, this rude beginning in the egg is lost. Since no characteristic sex is assumed until after fertilization, we may say that life begins as neuter in the individual, as it is presumed to have done in the world. It will occur to those inclined to speculation or philosophic analysis that by the word "neuter" we may mean any one or all of three things: (a) neither male nor female; (b) both male and female, as yet undifferentiated, or (c) potentially either male or female. Clearly, the above explanation assumes a certain germinal specialization of the female to reproduction, in addition to the body specialization for the intra-parental environment (in mammals).

A tremendous amount of laboratory experimentation upon animals has been done in late years to determine the nature of sex. For example, Goodale[16] castrated a brown leghorn cockerel twenty-three days old and dropped pieces of the ovary of a female bird of the same brood and strain into the abdominal cavity. These adhered and built up circulatory systems, as an autopsy later showed. This cockerel, whose male sex glands had been exchanged for female ones, developed the female body, and colouration so completely that expert breeders of the strain pronounced it a female. He found that simply removing the female sex glands invariably led to the development of spurs and male plumage. But simple removal of the male sex glands did not alter plumage. To make sure, he replaced the male sex glands with female, and found that the former male developed female plumage.

This obviously signifies that in birds the female is an inhibited male.[4, p.49.] Either sex when castrated has male feathers—the male has them either with or without testes, unless they are inhibited by the presence of (transplanted) ovaries. It will be remembered that the sociological theory of sex held by Ward, Mrs. Hartley and a host of others was founded on the supposition that evolution or development of a species is chiefly due to selection by the females of the better males, a conclusion based almost entirely on bird evidence. Ward[17] states that "the change or progress, as it may be called, has been wholly in the male, the female remaining unchanged"; also that "the male side of nature shot up and blossomed out in an unnatural, fantastic way...." Speaking of the highly-coloured males, especially among birds, the same writer states that "the normal colour (italics ours) is that of the young and the female, and the colour of the male is the result of his excessive variability." Goodale's results completely refute this idea, and should bury for ever the well-known sociological notion of "male afflorescence."

The general doctrine of a stable, "race-type" female and a highly variable male has been widely circulated. In tracing it back through voluminous literature, it appears to have been founded on an article published by W.I. Brooks in the Popular Science Monthly for June, 1879, fourteen years before Weissmann's enunciation of the theory of continuity of the germ-plasm. Like Wallace, Brooks continued to study and experiment till the last, and finally withdrew from his earlier position on sexual selection. However, this has not prevented others from continuing to quote his discarded views—innocently, of course.

Havelock Ellis[18] and G. Stanley Hall[19] have applied the idea of a "race-type" female with peculiar insistence to the human race. Goodale has finally killed the bird evidence upon which earlier workers so largely founded this doctrine, by showing that the "race type" toward which birds tend unless inhibited by the female ovarian secretion is the male type, not the female. There is a great difference in the way the internal secretions act in birds and in man, as will be pointed out later. It is so important that such a major point as general variability must be supported and corroborated by mammalian evidence to prove anything positively for man. As already noted, the statistical studies of Pearson and Mrs. Hollingworth et al. have yielded uniformly negative results.

In the utilization of data gathered from non-human species, certain differences in the systems of internal secretion must be taken into account. Birds differ from the human species as to internal secretory action in two vital particulars: (a) In the higher mammals, sex depends upon a "complex" of all the glands interacting, instead of upon the sex glands alone as in birds; (b) The male bird instead of the female is homogametic for sex—i.e., the sperm instead of the eggs is uniform as to the sex chromosome.

Insects are (in some cases at least) like birds as to the odd chromosome—the opposite of man. But as to secondary sex-characters they differ from both. These characters do not depend upon any condition of the sex organs, but are determined directly by the chemical factors which determine sex itself.[20]

In crustacea, the male is an inhibited female (the exact opposite of birds), as shown by the experiments of Giard and Geoffrey Smith on crabs. A parasite, Sacculina neglecta, sometimes drives root-like growths into the spider crab, causing slow castration. The females thus desexed do not assume the male type of body, but castrated males vary so far toward the female type that some lay eggs[3, p.143; 20]. It is the discovery of such distinctions which makes it necessary to re-examine all the older biological evidence on the sex problem, and to discard most of it as insufficiently exact.

The work of Steinach[12, pp.225f.] on rats is another well-known example of changing sex characters by surgery. Steinach found that an ovary transplanted into a male body changed its characteristics and instincts into the female type. The growth of the male sex organs he found to be definitely inhibited by the ovaries. He went so far as to transplant the whole uterus and tube into the male body, where it developed normally. One of the most interesting of his results is the observation of how the instincts were changed along with the type of body. The feminized males behaved like normal females toward the other males and toward females. Likewise they were treated as normal females by the males.

It would be impossible to give here any just idea of the vast amount of rigid scientific experimentation which has been carried on in this field, or the certainty of many of the results. Sex is really known, about as well as anything can be known, to arise from the chemical causes discussed above. That is, the endocrine explanation is the correct one.

One of the most significant results of the transplantation experiments is the evidence that each individual carries the fundamental bases for both sexes. When Goodale changed a male bird into a female as to secondary characters and instincts by replacing one secretion with another, he was faced with the following problem: How can a single secretion be responsible for innumerable changes as to feather length, form and colouring, as to spurs, comb and almost an endless array of other details? To suppose that a secretion could be so complicated in its action as to determine each one of a thousand different items of structure, colour and behaviour would be preposterous. Besides, we know that some of these internal secretions are not excessively complicated—for instance adrenalin (the suprarenal secretion) can be compounded in the laboratory. We may say that it cannot possibly be that the ovarian or testicular secretion is composed of enough different chemical substances to produce each different effect.

There remains only the supposition that the female already possesses the genetic basis for becoming a male, and vice versa. This is in accord with the observed facts. In countless experiments it is shown that the transformed female becomes like the male of her own strain and brood—to state it simply, like the male she would have been if she had not been a female. If we think of this basis as single, then it must exhibit itself in one way in the presence of the male secretions, in another way under the influence of the female secretions. In this way a very simple chemical agent in the secretion might account for the whole difference—merely causing a genetic basis already present to express itself in the one or the other manner.

This may be illustrated by the familiar case of the crustacea Artemia salina and Artemia Milhausenii. These are so unlike that they were long supposed to be different species; but it was later discovered that the genetic basis is exactly the same. One lives in 4 to 8% salt water, the other in 25% or over. If, however, the fresh-water variety is put in the saltier water with the salt-water variety, all develop exactly alike, into the salt-water kind. Likewise, if the salt-water variety is developed in fresh water, it assumes all the characteristics of the fresh-water kind. Thus the addition or subtraction of a single chemical agent—common salt—makes all the difference.

If this basis for sex is single, it is represented by the male plumage in domestic birds, the secretions from the sex-glands acting as modifiers. But a great deal of evidence has been produced to show that the genetic basis, in man and some other forms at least, is double. That is, we must think of two genetic bases existing in each individual—each representing one of the two types of secondary sex characters. The primary sex (i.e., the sex glands) would then determine which is to express itself. In the domestic birds described above, the male type of body appears in the absence of the ovarian secretion, and the female type in its presence. In man and the more highly organized mammals, we must use "secretions" in the plural, since a number of them, from different glands, act together in a "complex." Goodale, experimenting with birds, was unable to definitely decide whether the basis for sex was single or double in that material, though he favoured the latter explanation.

Dr Bell, the English gynecologist, using human surgical cases as a basis, commits himself strongly to the dual basis.[2, p.13.] "Every fertilized ovum," he says, "is potentially bisexual," but has "a predominating tendency ... toward masculinity or femininity." But "at the same time," he remarks, "it is equally obvious that latent traits of the opposite sex are always present." After discussing mental traits observed in each sex which normally belong to the other, he concludes as follows: "If further evidence of this bisexuality, which exists in everyone, were required, it is to be found in the embryological remains of the latent sex, which always exist in the genital ducts."

In some lower forms, dual sexuality is apparent until the animal is fairly well developed. In frogs, for example, the sex glands of both sexes contain eggs in early life, and it is not possible to tell them apart with certainty, until they are about four months old.[12, p.125.] Then the eggs gradually disappear in the male.

However, we need not depend upon non-mammalian evidence for either the secretory explanation or the dual basis. An ideal case would be to observe the effects of circulating the blood of one sex in a developing embryo of the other. This blood-transfusion occurs in nature in the "Free-Martin" cattle.[21]

Two embryos (twins) begin to develop in separate membranes or chorions. At an early stage in this development, however, the arteries and veins of the two become connected, so that the blood of each may circulate through the body of the other. "If both are males or both are females no harm results from this...," since the chemical balance which determines the bodily form in each case is of the same type. But if one is a male and the other a female, the male secretory balance dominates the female in a very peculiar fashion. The female reproductive system is largely suppressed. She even develops certain male organs, and her general bodily appearance is so decidedly masculine that until Dr Lillie worked out the case she had always been supposed to be a non-functional male. She is sterile. The blood transfusion not only alters the sex-type of her body, but it actually modifies the sex glands themselves, so that the ovary resembles a testicle, though dissection proves the contrary.

Why does not the female become a true, functional male? Perhaps she does in some cases. Such a one would not be investigated, since there would be no visible peculiarity. In all the cases examined, the embryo had begun its female development and specialization under the influence of a predisposition of the female type in the fertilized egg, before the transfusion began. There is no absolutely convincing mammalian evidence of the complete upset of this predisposition, so all one can say is that it is theoretically possible. Cases of partial reversal, sometimes called "intersexes," are common enough. In birds and insects, where the material is less expensive and experimentation simpler, males have been produced from female-predisposed fertilized eggs and vice versa, as we shall see in the next chapter.

Dr Bell[2, pp.133f.] points out that the so-called human "hermaphrodites" are simply partial reversals of the sex type from that originally fixed in the fertilized egg. As has been remarked earlier in these pages, there is rarely if ever true hermaphroditism in higher animals—i.e., cases of two functional sexes in the same individual. In fact, the pathological cases in the human species called by that name are probably not capable of reproduction at all.[A]

[Footnote A: Note on human hermaphroditism: This subject has been treated in a considerable medical literature. See, for example, Alienist and Neurologist for August, 1916, and New York Medical Journal for Oct. 23, 1915. It has been claimed that both human and higher mammalian "hermaphrodites" have actually functioned for both sexes. Obviously, absolute certainty about cause and effect in such cases, where human beings are concerned, is next to impossible, because of lack of scientific, laboratory control. If a case of complete functional hermaphroditism in the human species could be established beyond question, it would indicate that the male secretory balance in man does not inhibit the female organs to the same extent that it apparently does in the Free-Martin cattle. If established, the idea of "male dominance" in the human species would be undermined in a new place. Such cases, if they occur at all, are exceedingly rare, but are of theoretical interest. We must not rush to conclusions, as the earlier sociologists used to do. Such a case would require careful analysis. Its very uniqueness would suggest that it may not be due to the ordinary causes of hermaphroditism, but might arise from some obscure and unusual cause such as the fusion of two embryos at a very early stage. The biochemistry involved is so intricate and so little understood that any deduction from the known facts would be purely speculative.]

Like the Free-Martin cattle, some accident has resulted in a mixture of male and female characteristics. This accident occurs after a certain amount of embryonic development has taken place under the influence of the original predisposition of the fertilized egg. The delicate secretory balance, so complex in man, is upset. With partially developed organs of one type and with a blood-chemistry of the opposite one, some curious results follow, as the illustrative plates in Dr Bell's book show.

It should be remembered that sex in higher mammals is of the whole body, and depends upon all the secretions. Hence an accident to one of the other glands may upset the balance as well as one to the sex glands themselves. For example, 15% of Neugebauer's[22] cases of female tubular partial hermaphroditism had abnormal growths in the suprarenals.

Thus in the human species, it is possible for one type of sex glands to exist in the opposite type of body, as we saw it to be in cattle—though it apparently could not occur unless compensated for in some way by the other secretions. This is a very great departure from birds, rats and guinea pigs, whose bodies change over their sex type when the gonads are transplanted. Birds take on the male appearance when the sex glands are removed (or retain it, if they are males). This is not true of man. The chemical life processes of the two sexes after puberty in the human species are quite characteristic. The male and female types are both very different from the infantile. When it becomes necessary to desex men, the resulting condition is infantile, not female.[23]

The desexed man is of course the eunuch of ancient literature. If desexed near maturity, he might look like a normal man in many respects; but if the operation were performed before puberty, his development is simply arrested and remains infantile—incomplete. Only in 1878 was the practice of desexing boys to get the famous adult male soprano voices for the Sistine Choir discontinued.

Removal of the ovaries in women likewise produces an infantile condition, which is pronounced only in case the operation takes place very young. [24] From his clinical experience, Dr Bell [2, p.160] concludes that no very definite modifications can be produced in an adult woman by withdrawal of the ovarian secretion alone. "There must be," he says, "some gross change in those parts of the endocritic system, especially apart from the genital glands, which normally produce masculinity—potentiality that appears to be concentrated in the suprarenals, the pituitary and probably in the pineal."

What, then, do we mean by "male" and "female" in man? Take Dr Russell Andrews' patient: photographs[2, plate opposite p.243] show a rounded bodily outline, hairless face, well-developed mammae—the female sex characteristics in every respect which the ordinary person could detect. Yet an operation proved that the sex glands themselves were male.

Presumably extreme cases like the above are rare. Obviously operations cannot be performed on all those with female-type bodies who do not bear children, to determine the primary sex, and conversely with men. This does, however, point the obvious question: Are not some we classify as men more male or masculine than others—some we classify as women more feminine than others? Bearing in mind the fact that the genetic basis for both sexes exists in each individual, are not some women more masculine than others, some men more feminine than others? However much we may object to stating it just that way, the biological fact remains thus. The Greeks called these intermediate types urnings—modern biology knows them as "intersexes."

Only within the past few years have the general phenomena of intersexuality been cleared up to any considerable extent—naturally on the basis of the secretory explanation of sex. This secretory or endocrine idea has also given us an entirely new view of sex differences. These are best discussed as functional rather than as structural. To correlate this material, we must next give a rude sketch of the quantitative theory of sex.


1. Goldschmidt, R. Intersexuality and the Endocrine Aspect of Sex. Endocrinology, Vol. I, p. 434, 1917.

2. Bell, Dr Blair. The Sex Complex. London, 1916, p. 98.

3. Paton, D. Noel. Regulators of Metabolism. London, 1913, p. 146.

4. Goodale, H.D. Gonadectomy...Carnegie Pub. 243, 1916, pp. 43f.

5. Wilson, Andrew. Polity of a Pond (essay). Humboldt Lib. of Sc., No. 88—reprint, dated 1888.

6. Hollingworth, L.S. Variability as Related to Sex Differences in Achievement. Am. Jour, of Sociol., XIX., 1914, pp. 510-530.

7. Lowie, R.H. & Hollingworth, L.S. Science and Feminism. Sci. Mthly., Sept., 1916, pp. 277-284.

8. Montague, Helen & Hollingworth, L.S. Comparative Variability of the Sexes at Birth. Am. J. of Sociol. XX, 335-70. 1915.

9. Morgan, T.H. A Critique of the Theory of Evolution. N.Y., 1916, pp. 1-27.

10. Loeb, Jacques. Artificial Parthenogenesis and Fertilization. Chicago, 1913, pp. 3, 51f., 240f, 303.

11. Conklin, E.G. Organ-Forming Substances in the Eggs of Ascidians. U. of Pa. Contrib. from the Zool. Lab. Vol. 12. 1905, pp. 205-230.

12. Loeb, J. The Organism as a Whole. N.Y., 1916, pp. 138f, 151-2.

13. Guyer, M.F. Being Well-Born. Indianapolis, 1916, p. 51.

14. Tower, W.L. (et al.). Heredity and Eugenics. Chicago, 1912, pp. 164, 254-5.

15. Conklin, E.G. Share of Egg and Sperm in Heredity. Proc. Nat. Acad. of Sc., Feb., 1917.

16. Goodale, H.D. A Feminized Cockerel. Jour. Exp. Zool. Vol. 20, pp. 421-8.

17. Ward, Lester F. Pure Sociology. N.Y., 1903, pp. 322f.

18. Ellis, Havelock. Man and Woman, 4th Ed. London, 1904. Ch. XVI.

19. Hall, G. Stanley. Adolescence. N.Y., 1907. Vol. II, pp. 561-2.

20. Morgan, T.H. Heredity and Sex. N.Y., 1913, pp. 155f.

21. Lillie, F.R. Theory of the Free Martin. Science, n.s., Vol. XLIII, pp. 611-13.

22. Neugebauer, F.L. Hermaphrodismus, Leipzig, 1908.

23. Vincent, S. Internal Secretions and the Ductless Glands. London, 1912, p. 69.

24. Marshall, F.H. Physiology of Reproduction. London, 1910, p. 314.



Intersexes in moths; Bird intersexes; Higher metabolism of males; Quantitative difference between sex factors; Old ideas of intersexuality; Modern surgery and human intersexes; Quantitative theory a Mendelian explanation; Peculiar complication in the case of man; Chemical life cycles of the sexes; Functional-reproductive period and the sex problem; Relative significance of physiological sex differences.

Crossing European and Japanese gypsy moths, Goldschmidt [1,2,3,4] noticed that the sex types secured were not pure—i.e., that certain crosses produced females which bore a distinctly greater resemblance to the male type than others, and vice versa. One of these hybrids of "intersexes," as he calls them, would always possess some female and some male sexual characters. He found that he could separate the males and females, respectively, into seven distinct grades with respect to their modification toward the opposite-sex type, and could produce any one of these grades at will by breeding.

For example, the seven grades of females were roughly as follows: (1) Pure females; (2) Females with feathered antennae like males and producing fewer than the normal number of eggs; (3) Appearance of the brown (male) patches on the white female wings; ripe eggs in abdomen, but only hairs in the egg-sponge laid; instincts still female; (4) Instincts less female; whole sections of wings with male colouration, interspersed with cuneiform female sectors; abdomen smaller, males less attracted; reproduction impossible; (5) Male colouration over almost the entire wing; abdomen almost male, with few ripe eggs; instincts intermediate between male and female; (6) Like males, but with rudimentary ovaries and show female traits in some other organs; (7) Males with a few traces of female origin, notably wing-shape.

The males showed the same graded approach to the female type. Their instincts likewise became more and more female as the type was modified in that direction. That is, a moth would be 12% or 35% female, and so on.

Goldschmidt watched the crosses which produced seven different grades of maleness in his females. The moth material, like the birds and mammals, suggested a dual basis for sex in each individual. The grades of maleness and femaleness made it seem probable that the factor which determines sex must be stronger in some instances than in others, i.e., that the difference between two of these grades of female is originally quantitative, not qualitative—in amount rather than in kind.

Mating European moths with European, or Japanese with Japanese, produced pure, uniform sex-types, male and female. But a cross of European with Japanese strains resulted in intersexes. Goldschmidt concluded that (1) all individuals carried the genetic basis for both sexes; and (2) that these basic factors were two chemicals of enzyme nature. One of these he called Andrase, enzyme producing maleness, the other Gynase, enzyme producing femaleness. Further, (3) since each chemical sex determiner is present in both individuals in every cross, there must be two chemical "doses" of maleness and two of femaleness struggling for mastery in each fertilized egg. (4) If the total dose of maleness exceeds the total dose of femaleness, the sex will be male, and vice versa. (5) These quantities get fixed by natural selection in a single race which always lives in the same environment, i.e., the doses of maleness and femaleness in a given sex always bear practically the same relation to each other. Hence the types are fixed and uniform. (6) But different races are likely to have a different strength of chemical sex-doses, so that when they are crossed, the ratios of maleness to femaleness are upset. Often they are almost exactly equal, which produces a type half male and half female—or 2/3, or 1/3, etc. The proof of this theory is that it solved the problems. Goldschmidt was able to work out the strengths of the doses of each sex in his various individuals, and thereby to predict the exact grade of intersexuality which would result from a given cross.

Riddle's work on pigeons [5,6] brings us much nearer to man, and suggests the results noted by both Goldschmidt and Lillie. As in the Free-Martin cattle, there is an apparent reversal of the sex predisposition of the fertilized egg. As in the gypsy moths, different grades of intersexes were observed. In the pigeons, it was found that more yolk material tended to produce a larger proportion of females. The most minute quantitative measurements were made of this factor, to eliminate any possibility of error.

The chromosome mechanisms practically force us to suppose that about half the eggs are originally predisposed to maleness, half to femaleness. A pigeon's clutch normally consists of two eggs, one with a large yolk and one with a small yolk. But the half-and-half numerical relation of males to females varies considerably—i.e., not all the large-yolked eggs produce females or all the small-yolked ones males.

Wild pigeons begin the season by throwing a predominance of males, and the first eggs of the clutches also tend to produce males all along. In both cases, the male-producing eggs were found to be the ones with the smaller yolks. Family crosses also produce small yolks, which hatch out nearly all males. Some pairs of birds, however, have nearly all female offspring. Riddle investigated a large number of these cases and found the amount of yolk material to be large. In other words, there seems to be a definite relation between the amount of yolk and sex.

A great number of clever experiments were carried out to find out if eggs originally predisposed to one sex were actually used to produce the other. Selective fertilization with different kinds of sperm was impossible, since in these birds there is only one type of sperm—two of eggs—as to the sex chromosome. For instance, by overworking females at egg-production, the same birds which had been producing more males than females were made to reverse that relation.

One of the interesting results of the experiments was the production of a number of intersexual types of various grades. This was easily verifiable by colour and other characteristics. To make sure that the instincts were correspondingly modified, behaviour was registered on moving-picture films. Where the first egg of a clutch (the one with a small, normally male-producing yolk) produces a female, she is usually found to be more masculine than her sister from the second egg with the larger yolk. This is true both as to appearance and as to behaviour. Some of these were quite nearly males in appearance and behaviour, though they laid eggs.

Testicular and ovarian extracts were injected. The more feminine birds were often killed by the testicular extract, the more masculine by the ovarian extract. Finally, to make assurance doubly sure, some females which should theoretically have been the most feminine were dissected and shown to be so. That is, out-crosses which produced a predominance of females in the fall were mated with females which had been overworked at egg production until they threw nearly all females. Dissecting the females thus produced, they were shown to have right ovaries, which means double femaleness, since normally the pigeon is functional only in the left ovary, like other birds. The right one usually degenerates before or at hatching and is wholly absent in the week-old squab.

In pigeons, Riddle thinks the "developmental energy" of the eggs is in an inverse ratio to their size. The last and largest eggs of the season develop least and produce most females. The second egg of a clutch is larger than the first, but develops less and the bird produced is shorter-lived. Overworking and other conditions tending to produce large eggs and females also throw white mutants and show other signs of weakness. Old females lay larger eggs than do young ones. These eggs produce more females. They store more material, have a lower metabolism and less oxidizing capacity than do the earlier male-producing eggs.

It would be unsafe to draw specific conclusions about mammals from these bird and insect experiments. Both the secretory action and the chromosome mechanisms are different. The quantitative nature of sex, and also the existence of intersexual types, between males and females, would seem to be general phenomena, requiring rather slight corroboration from the mammals themselves. We have such mammalian cases as the Free-Martin cattle, and some convincing evidence of intersexuality in the human species itself, which will be reviewed presently.

The notion of more "developmental energy" or a higher metabolism in males is borne out in the human species. Benedict and Emmes[7] have shown by very careful measurements that the basal metabolism of men is about 6% higher than that of women. Riddle cites the work of Thury and Russell on cattle to show that a higher water value (as he found in the pigeon eggs), associated with increased metabolism, helps to produce males.

In males, the secretion of the sex glands alone seems to be of particular importance, again suggesting this idea of "strength" which comes up over and over again. Removal of these glands modifies the male body much more profoundly than it does the female.[8] It is quite generally supposed that the action of this one secretion may have much to do with the superior size and vigour of males. For example, Paton says[9]: "The evidence thus seems conclusive that in the male the gonad, by producing an internal secretion, exercises a direct and specific influence upon the whole soma, increasing the activity of growth, moulding the whole course of development, and so modifying the metabolism of nerve and muscle that the whole character of the animal is altered." It used to be said that the male was more "katabolic," the female more "anabolic." These expressions are objectionable, inasmuch as they hint that in a mature organism, with metabolism rather stable, tearing down, or katabolism, could go on faster than building up, or anabolism, or that one of two phases of the same process might go on faster than the other. It seems safer to say merely that a lower metabolism in the female is accompanied by a tendency to store materials.

A long time will doubtless be required to work out the details of differences in metabolism in the two sexes. Some of the main facts are known, however, and the general effects of the two diverse chemical systems upon the life cycles of the sexes are quite obvious. What we call the "quantitative theory of sex" has, besides a place in exact science, an interesting relation to the history of biological thought, especially as applied to society. It is thus in order to state as clearly as possible what it now is; then, so that no one may confuse it with what it is not, to run over some of the old ideas which resemble it.

Experiments with transplanted sex glands, with sex-gland extracts (testicular and ovarian) and the observation of infusions of a male-type blood-stream into a female body, as occurs in nature in some cattle and in the so-called human "hermaphrodites," indicate a gross chemical difference between the respective determiners for femaleness and for maleness. So the chemicals involved, though not yet isolated, must be presumed to be qualitatively different, since they produce such different results.

But such experiments also indicate that both determiners must be present in some proportions in every individual of either sex. The basis for both sexes being present, the one which shall predominate or be expressed in the individual must depend upon the quantitative relation between the determiners which come together at fertilization. The quantitative theory merely means that this predominance of one factor or the other (maleness or femaleness—Gynase or Andrase) is more pronounced in some cases than in others.

In brief, then, the quantitative theory of sex is merely the most reasonable explanation of the known fact that intersexes exist—that is, females with some male characteristics, or with all their characters more like the female type than the average, and vice versa. Laboratory biology has established the phenomena of intersexuality beyond question, and the word "inter-sex" has become a scientific term. But the fact that this word and the idea it represents are new to exact science does not mean that it is new in the world.

Intersexes in the human species—not only the extreme pathological cases represented by the so-called "hermaphrodites," but also merely masculine women and effeminate men—have been the subject of serious remarks as well as literary gibes from the earliest times. The Greeks called these people urnings. Schopenhauer was interested in the vast ancient literature and philosophy on this subject. The 19th century produced a copious psychological treatment of warped or reversed sexual impulses by such men as Moll, Krafft-Ebing and Havelock Ellis. Otto Weiniger[10] collected a mass of this philosophy, literature, psychology, folklore and gossip, tied it together with such biological facts as were then known (1901) and wove around it a theory of sex attraction.[A] The same material was popularized by Leland[11], Carpenter[12] and W.L. George[13] to support quite different views.

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