These doctrines, as a basis for the breeding of animals, Hencke had discovered by castrating swine, dogs, and rabbits. Thus it happened that a boar, who, after castration, had only the left testicle, twice running bred with a sow female young only. Similar phenomena occurred with other animals, so that this method was recommended by the author to the breeders of his time. But it happened, also, that a surgeon upon opening the body of a woman who had had sons only and never a single daughter, found the left ovary very thin and withered, so that it was hardly possible that it could serve for the development of a new individual. On the contrary, the right ovary was in a normal condition. It now remained only to discover some device for man, by which he might be able, during the act of generation, to avail himself of the discoveries thus made, so as to obtain the result of an absolute choice of the sex of the offspring. The ligation of one of the testicles was Hencke’s infallible remedy. When this severe proceeding proved impracticable, in its place was substituted an elevation of the testicle by means of its suspending muscle (the cremaster). Under certain conditions this takes place of itself in particular positions, and was accordingly recommended as an established proceeding for men. One other conclusion of Hencke’s deserves particular mention. He was bold enough not only to assert that the right and left sexual glands served exclusively for the generation of male and female individuals, respectively, but also asserted that the generative matter from the right or left gland of one parent was productive only when united with that of the same gland of the other parent. His counsels were not for such persons as are too heated, too ardent. “For young, hot, hasty men,” he says, “who are altogether without consideration, I am not writing; but for chaste married people, and especially for those to whom the production of a child of one or the other sex is a matter of importance.” * * * * *