Ellis has collected the results of investigations on almost every tissue of the body, which serve to show the universal presence of sexual differences. It is plain that there is a striking difference in the coloration of the typical male and female. This fact establishes the existence of sexual differences in the skin (cutis) and in the blood-vessels, and also in the bulk of the colouring-matter in the blood and in the number of red corpuscles to the cubic centimetre of the blood fluid. Bischoff and Rudinger have proved the existence of sexual differences in brain weight, and more recently Justus and Alice Gaule have obtained a similar result with regard to such vegetative organs as the liver, lungs and spleen. In fact, all parts of a woman, although in different degrees in different zones, have a sexual stimulus for the male organism, and similarly all parts of the male have their effect on the female.

The direct logical inference may be drawn, and is supported by abundant facts, that every cell in the body is sexually characteristic and has its definite sexual significance. I may now add to the principle already laid down in this book, of the universal presence of sexually intermediate conditions, that these conditions may present different degrees of development. Such a conception of the existence of different degrees of development in sexuality makes it easy to understand cases of false hermaphroditism or even of the true hermaphroditism, which, since the time of Steenstrup, has been established for so many plants and animals, although not certainly in the case of man. Steenstrup wrote: “If the sex of an animal has its seat only in the genital organs, then one might think it possible for an animal really to be bisexual, if it had at the same time two sets of sexual organs. But sex is not limited to one region, it manifests itself not merely by the presence of certain organs; it pervades the whole being and shows itself in every point. In a male body, everything down to the smallest part is male, however much it may resemble the corresponding female part, and so also in the female the smallest part is female. The presence of male and female sexual organs in the same body would make the body bisexual only if both sexes ruled the whole body and made themselves manifest in every point, and such a condition, as the manifestations of the sexes are opposing forces, would result simply in the negation of sex in the body in question.” If, however, the principle of the existence of innumerable sexually transitional conditions be extended to all the cells of the body, and empirical knowledge supports such a view, Steenstrup’s difficulty is resolved, and hermaphroditism no longer appears to be unnatural. There may be conceived for every cell all conditions, from complete masculinity through all stages of diminishing masculinity to its complete absence and the consequent presence of complete femininity. Whether we are to think of these gradations in the scale of sexual differentiation as depending on two real substances united in different proportions, or as a single kind of protoplasm modified in different ways (as, for instance, by different spatial dispositions of its molecules), it were wiser not to guess. The first conception is difficult to apply physiologically; it is extremely difficult to imagine that two sets of conditions should be able to produce the essential physiological similarities of two bodies, one with a male and the other a female diathesis. The second view recalls too vividly certain unfortunate speculations on heredity. Perhaps both views are equally far from the truth. At present empirical knowledge does not enable us to say wherein the masculinity or the femininity of a cell really lies, or to define the histological, molecular or chemical differences which distinguish every cell of a male from every cell of a female. Without anticipating any discovery of the future (it is plain already, however, that the specific phenomena of living matter are not going to be referred to chemistry and physics), it may be taken for granted that individual cells possess sexuality in different degrees quite apart from the sexuality of the whole body. Womanish men usually have the skin softer, and in them the cells of the male organs have a lessened power of division upon which depends directly the poorer development of the male macroscopic characters.

The distribution of sexual characters affords an important proof of the appearance of sexuality in different degrees. Such characters (at least in the animal kingdom) may be arranged according to the strength of their exciting influence on the opposite sex. To avoid confusion, I shall make use of John Hunter’s terms for classifying sexual characters. The primordial sexual characters are the male and female genital glands (testes and epididymis, ovaries and epoophoron); the primary sexual characters are the internal appendages of the sexual glands (vasa deferentia vesiculæ seminales, oviducts and uterus), which may have sexual characters quite distinct from those of the glands and the external sexual organs, according to which alone the sex of human beings is reckoned at birth (sometimes quite erroneously, as I shall show) and their consequent fate in life decided. After the primary, come all those sexual characters not directly necessary to reproduction. Such secondary sexual characters are best defined as those which begin to appear at puberty, and which cannot be developed except under the influence on the system of the internal secretions of the genital glands. Examples of these are the beards in men, the luxuriant growth of hair in women, the development of the mammary glands, the character of the voice. As a convenient mode of treatment, and for practical rather than theoretical reasons, certain inherited characters, such as the development of muscular strength or of mental obstinacy may be reckoned as tertiary sexual characters. Under the designation “quaternary sexual characters” may be placed such accessories as relative social position, difference in habit, mode of livelihood, the smoking and drinking habit in man, and the domestic duties of women. All these characters possess a potent and direct sexual influence, and in my opinion often may be reckoned with the tertiary characters or even with the secondary. This classification of sexual characters must not be taken as implying a definite chain of sequence, nor must it be assumed that the mental sexual characters either determine the bodily characters or are determined by them in some causal nexus. The classification relates only to the strength of the exciting influence on the other sex, to the order in time in which this influence is exerted, and to the degree of certainty with which the extent of the influence may be predicted.

Study of secondary sexual characters is bound up with consideration of the effect of internal secretions of the genital glands on general metabolism. The relation of this influence or its absence (as in the case of artificially castrated animals) has been traced out in the degree of development of the secondary characters. The internal secretions, however, undoubtedly have an influence on all the cells of the body. This is clearly shown by the changes which occur at puberty in all parts of the body, and not only in the seats of the secondary sexual characters. As a matter of fact, the internal secretions of all the glands must be regarded as affecting all the tissues.

The internal secretions of the genital glands must be regarded as completing the sexuality of the individual. Every cell must be considered as possessing an original sexuality, to which the influence of the internal secretion in sufficient quantity is the final determining condition under the influence of which the cell acquires its final determinate character as male or female.

The genital glands are the organs in which the sex of the individual is most obvious, and in the component cells of which it is most conspicuously visible. At the same time it must be noted that the distinguishing characters of the species, race and family to which an organism belongs are also best marked in the genital cells. Just as Steenstrup, on the one hand, was right in teaching that sex extends all over the body and is not confined to the genital organs, so, on the other hand, Naegeli, de Vries, Oskar Hertwig and others have propounded the important theory, and supported it by weighty arguments, that every cell in a multi-cellular organism possesses a combination of the characters of its species and race, but that these characters are, as it were, specially condensed in the sexual cells. Probably this view of the case will come to be accepted by all investigators, since every living being owes its origin to the cleavage and multiplication of a single cell.

Many phenomena, amongst which may be noticed specially experiments on the regeneration of lost parts and investigations into the chemical differences between the corresponding tissues of nearly allied animals, have led the investigators to whom I have just referred to conceive the existence of an “Idioplasm,” which is the bearer of the specific characters, and which exists in all the cells of a multi-cellular animal, quite apart from the purposes of reproduction. In a similar fashion I have been led to the conception of an “Arrhenoplasm” (male plasm) and a “Thelyplasm” (female plasm) as the two modes in which the idioplasm of every bisexual organism may appear, and which are to be considered, because of reasons which I shall explain, as ideal conditions between which the actual conditions always lie. Actually existing protoplasm is to be thought of as moving from an ideal arrhenoplasm through a real or imaginary indifferent condition (true hermaphroditism) towards a protoplasm that approaches, but never actually reaches, an ideal thelyplasm. This conception brings to a point what I have been trying to say. I apologise for the new terms, but they are more than devices to call attention to a new idea.

The proof that every single organ, and further, that every single cell possesses a sexuality lying somewhere between arrhenoplasm and thelyplasm, and further, that every cell received an original sexual endowment definite in kind and degree, is to be found in the fact that even in the same organism the different cells do not always possess their sexuality identical in kind and degree. In fact each cell of a body neither contains the same proportion of M and W nor is at the same approximation to arrhenoplasm or thelyplasm; similar cells of the same body may indeed lie on different sides of the sexually neutral point. If, instead of writing “masculinity” and “femininity” at length, we choose signs to express these, and without any malicious intention choose the positive sign (+) for M and the negative (-) for W, then our proposition may be expressed as follows: The sexuality of the different cells of the same organism differs not only in absolute quantity but is to be expressed by a different sign. There are many men with a poor growth of beard and a weak muscular development who are otherwise typically males; and so also many women with badly developed breasts are otherwise typically womanly. There are womanish men with strong beards and masculine women with abnormally short hair who none the less possess well-developed breasts and broad pelves. I know several men who have the upper part of the thigh of a female with a normally male under part, and some with the right hip of a male and the left of a female. In most cases these local variations of the sexual character affect both sides of the body, although of course it is only in ideal bodies that there is complete symmetry about the middle line. The degree to which sexuality displays itself, however, as, for instance, in the growth of hair, is very often unsymmetrical. This want of uniformity (and the sexual manifestations never show complete uniformity) can hardly depend on differences of the internal secretion; for the blood goes to all the organs, having in it the same amount of the internal secretion; although different organs may receive different quantities of blood, in all normal cases its quality and quantity being proportioned to the needs of the part.

Were we not to assume as the cause of these variations the presence of a sexual determinant generally different in every cell but stable from its earliest embryonic development, then it would be simple to describe the sexuality of any individual by estimating how far its sexual glands conformed to the normal type of its sex, and the facts would be much simpler than they really are. Sexuality, however, cannot be regarded as occurring in an imaginary normal quantity distributed equally all over an individual so that the sexual character of any cell would be a measure of the sexual characters of any other cells. Whilst, as an exception, there may occur wide differences in the sexual characters of different cells or organs of the same body, still as a rule there is the same specific sexuality for all the cells. In fact it may be taken as certain that an approximation to a complete uniformity of sexual character over the whole body is much more common than the tendency to any considerable divergences amongst the different organs or still more amongst the different cells. How far these possible variations may go can be determined only by the investigation of individual cases.

There is a popular view, dating back to Aristotle and supported by many doctors and zoologists, that the castration of an animal is followed by the sudden appearance of the characters of the other sex; if the gelding of a male were to bring about the appearance of female characteristics then doubt would be thrown on the existence in every cell of a primordial sexuality independent of the genital glands. The most recent experimental results of Sellheim and Foges, however, have shown that the type of a gelded male is distinct from the female type, that gelding does not induce the feminine character. It is better to avoid too far-reaching and radical conclusions on this matter; it may be that a second latent gland of the other sex may awake into activity and sexually dominate the deteriorating organism after the removal or atrophy of the normal gland. There are many cases (too readily interpreted as instances of complete assumption of the male character) in which after the involution of the female sexual glands at the climacteric the secondary sexual characters of the male are acquired. Instances of this are the beard of the human grandam, the occasional appearance of short antlers in old does, or of a cock’s plumage in an old hen. But such changes are practically never seen except in association with senile decay or with operative interference.