The masculinoid woman, as a functional hermaphrodite, exists first as a congenital entity, with an inborn distribution of endocrine predominances that make for masculinity. There are also numerous acquired forms. The infections of childhood, measles, scarlet fever, diphtheria, and above all mumps, may so damage the hormone system that an inversion of sex type follows. However, the stimulative and depressive effects of environment are even more significant. The effects of environment in producing changes in an organism, the changes the biologist sums up as adaptation, can be tracked in many instances to responsive reactions of the glands of internal secretion to demands made upon them by changed external conditions. So a cold climate, which necessitates a more voluminous hair covering for an animal, will evoke a hypertrophy of the adrenal cortex. Secondarily other effects appear as by-products of the adaptation. The adrenal cortex makes for pugnacity, temper, animal courage, irritability and anger reactions. So a hairy animal will, in general (unless other endocrines come in to defeat the primary effect), be more pugnacious, courageous, irritable and combative. The same applies to woman. An environment which tends to encourage the masculine traits in her, to arouse repeatedly her pugnacity and combative decisions in the more rapid give and take of the masculine world, will rouse the adrenal cortex to greater activity, and so make her face hirsute, her attitudes aggressive, and perhaps render her sterile. Concomitantly there may be a disturbance of menstruation. The presence or absence of sterility, natural or enforced, always present, or say appearing after the birth of one child, must all be donated a prominent place in studying the endocrine make-up of a woman. When there is not enough ovarian secretion, the ovum may not be able to burst through the ovary, a necessity before it may begin its travels to the uterus. Next, the propulsive action of the genital ducts may be insufficient because of defective corpus luteum. Or the uterus may not have received enough posterior pituitary or thyroid to make it fit soil for the ovum to plant itself in. Or there may be too much of these, which cause the uterus to massage itself daily by gentle contractions and so keep it well-toned. Excessive massage will throw the ovum out. All these are factors in the sterility problem, with its psychic resonances affecting the maternal instinct. THE MATERNAL INSTINCT