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]