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.
In the case of certain crustacean parasites of fish, however (the genera Cymothoa, Anilocra and Nerocila of the family Cymothoidæ), the changes I have just mentioned are part of the normal life history. These creatures are hermaphrodites of a peculiar kind; the male and female organs co-exist in them but are not functional at the same period. A sort of protandry exists; each individual exercises first the functions of a male and afterwards those of the female. During the time of their activity as males they possess ordinary male reproductive organs which are cast off when the
