Essays of a Biologist

by Julian Huxley

It is quite clear from these and other facts that in higher vertebrates there are present in every individual of either sex the nervous connections which give the possibility of either male or female behaviour; but that normally only one of these two possibilities is realized, since for the potentiality of action given by the nervous connections to become actual as behaviour it is necessary for the nervous system to be activated by the secretion of one or other of the reproductive organs. Castrated animals fail to realize either possibility of normal sex-behaviour, although their nervous machinery is untouched.

There are, further, some facts of observation which, even if they have not yet been fully analysed by experiment, still throw light on the matter. Although many of the most familiar birds—fowls, pheasant, peacock, duck, finches, and so forth—have bright-coloured males and drab females, with marked difference of behaviour between the sexes, there are, as we have seen, many others, such as herons, divers, swans, grebes, moorhens, and auks, in which the sexes are alike in plumage and furthermore show what may be called a “mutual” courtship in which both male and female play similar rôles. In this latter class it seems clear that the secretions of the male and female reproductive organs must be more alike than in the markedly dimorphic species: and this is borne out by some strange facts regarding not merely the courtship but the actions concerned with pairing itself. In the crested grebe and the little grebe, for example, close observation has shown that either member of the pair may assume the passive “female” attitude or the active “male” attitude in pairing: and in the moorhen we meet with the still more extraordinary phenomenon of double pairing, in which an act of pairing with male and female in normal position is immediately followed by a second act in which the normal position is reversed.[35] It would appear in such cases that the similarity of male and female internal secretion is so great that quite slight changes in nervous or metabolic activity can cause the nervous centres for the opposite sex’s mode of behaviour to become activated.

In human beings we are confronted with various grades of sexual organization and behaviour besides the typically feminine and the typically masculine. In the first place it is matter of common knowledge that many women, who so far as their physical reproductive capacity goes are perfectly normal, show various mental traits which are more characteristic of men, and vice versa. What is more, the “masculinoid” woman (to use the current jargon) tends physically also to be less feminine, to have the feminine secondary sexual characteristics in stature, form of skeleton, distribution of fat, breasts, etc.—less strongly developed than normal, while the “feminoid” man shows the reverse tendency.[36]

In trying to analyse these facts further, we are brought up against new depths of complication. It is becoming ever clearer that the gonads do not operate as independent organs, but in conjunction with the whole of the rest of the endocrine system—thyroid, pituitary, adrenal, and the rest. In the first place, it seems to be established that the reproductive organs must be in some way activated by other ductless glands before they become normal, just as they in their turn must activate the sexual centres in the brain. This phase of the matter is being investigated by many workers to-day; provisionally we may say that pituitary and adrenal cortex are especially concerned. In the second place the gonads, once activated and in normal working order, react upon the other ductless glands. It thus comes about that the relative proportion or relative activity of the parts of the whole ductless gland system is different in male and female. Blair Bell is the protagonist of this view. A woman is a woman, he says, not merely because of her ovaries, but because of all her internal secretions, of her endocrine balance as a whole.

It cannot be said that we have any certainty on the details of this subject. It is clear, however, that some such fundamental difference does exist, and it is therefore further probable that if a woman has a thyroid, say, or an adrenal which for some reason (and there are many possible reasons) is producing an amount of secretion abnormal for a woman but more like that which is produced by a man, she will, in spite of her ovaries, be more masculine in tendency.

I will content myself with one example. The cortex of the adrenal gland, if active beyond a certain measure, assists the development of male, prevents the development of female, characters. Women with adrenal tumours frequently develop moustache and beard and other appanages of the male. One presumes that a slight preponderance of the adrenal cortex in the normal endocrine make-up will lead to a less feminine type of woman than normal. I repeat that we are but on the verge of the matter and that premature speculation is certainly risky and probably fallacious. But all the same, there is very little doubt that we are on the right track, and that we shall have to search for the finer shades of temperamental difference between man and woman not so much in differences in the quality of the secretion of testis or ovary as in differences of balance in what the Americans call the “endocrine make-up.”[37]

There is, however, also the possibility of difference in the quality of gonad secretion, and of recent years Steinach and his followers have been claiming that this may be at the bottom of many cases of so-called “perversion of sexual instinct.” The latest claim of this school is that homosexual men may be rendered heterosexual in instinct by removal of their testes and implantation of a testis from a sexually normal person—from a man, for example, who is being operated on for cryptorchidism. It is frankly impossible as yet to say whether their conclusions are well founded: a very much larger series of cases will be necessary, and the possibility of suggestion’s action must be eliminated. It is well to remember, however, that there is no theoretical objection to the possibility. We know that in various lower animals, such as moths and flies, the balance between the male- and female-determining factors in the chromosomes may be altered in certain crosses, and that this altered balance in the constitution is reflected in some cases in a state permanently intermediate between male and female, in others by a reversal of sex at some point during development. For various reasons we should not usually expect reversal in mammals; but if such abnormal balance should exist in the constitution, as it well might, we should expect a gonad secreting an abnormal, intermediate secretion. This we might also expect as the result of certain accidents of embryonic life, as actually happens in the abnormal female cattle known to farmers as free-martins. These animals are always born co-twin to a male, and their abnormality is due to the blood-systems of the embryonic membranes of the twins having fused, so that the secretion of the developing male’s gonad acts upon the developing female.

Further light on abnormally-directed sex-instinct is thrown by recent analysis of abnormal domestic animals by Crew.[38] In both goats and swine he finds that by far the commonest form of sexual abnormality is one in which the external appearance, at least in youth, is so nearly female as to raise no question in the mind of the casual observer; about the time of maturity, however, male secondary sex characters begin to develop, including male instincts; and dissection reveals the presence of a double set of ducts—the female uterus and vagina, the male epididymis and vas deferens, but only a single uniform reproductive organ, and that always a testis. The simplest explanation (although it is admittedly tentative) appears to be that the testis has not been activated during embryonic and juvenile life, and that therefore until puberty the animal, though really male, has been physiologically in a neutral state, which permits the growth of the internal apparatus proper to both sexes. Externally, the “neutral” condition approximates more closely to the female type, and the animal is thus first classed as a female. Some other gland is then responsible for the second activation at puberty, and this occurs in a normal manner.

This is of considerable interest, since it appears that in man too the largest class of sexually abnormal individuals are those whose external appearance is almost or quite feminine, but who possess male instincts. It is at least probable that examination will show that they, too, or many of them, will be of the type described above—males with delayed activation of testis, a consequent classification as female at birth, and a girl’s upbringing, with male instincts arising in the unhappy creature at puberty.

It is the fashion nowadays to write down abnormal sexual psychology wholly to the account of the mind, to an abnormal development with causes entirely psychological. It is clear, however, that if some abnormal individuals can be cured by implantation, and others are abnormal owing to an early failure of activation, this conception falls to the ground, and the Freudian is robbed of some of his most cherished examples.