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. In any case, the work on animals definitely shows that, unless the mechanism of activation of instinct by gonad secretion has altered between animal and man more than we have any right to postulate a priori, the quality of gonad secretion and the balance of all the endocrines has to be taken into account far more than is done by the average psycho-analyst.