Most important of all, and the chief source of human energy in man, are the sex glands, which distribute energy to all the sixty trillion cells of the body, making each carry out the function assigned it. Voronoff made personal studies of eunuchs in the East and among the many traits so often mentioned he finds them not only arrested along various lines of bodily and psychic growth but short-lived and perhaps old before they are forty. They are often selfish and crafty. Sex glands stimulate not merely amorousness but all kinds of cerebral and muscular energy, pouring into the blood a species of vital fluid, and give a sense of vigor and well-being and plenitude of life, which later vanish when their source begins to run dry in age. Can this wonderful source of human energy be placed, in any sense, in man’s control? It has already been proven that trituration of the sex glands does not produce its entire product and particularly lacks the active element. Moreover, all preparations of this liquid change very rapidly and may even become toxic. This method has passed beyond the stage of ingestion in the stomach or subcutaneous ingestions. Voronoff undertook to graft young sex glands themselves into bodies older than those from which they came and if they lived and throve in the body of the host, the product they secreted would be complete and also vital. He says of the testes: “To graft this gland is to participate at first hand in the work of creation, to imitate nature in the procedures which she has elaborated in order to secure the harmonious functioning of our body”[190] (p. 65). He published his first results in 1912. He then showed a lamb born of an ewe whose ovaries he had removed, replacing them with the ovaries of her younger sister. His most important paper was read in October, 1919, on “Testicular Grafts.” He had been experimenting on flocks of sheep and goats, grafting the whole gland in twenty-five, large fragments in fifty-eight, and small ones in thirty-seven individuals. Transplantation was effected subcutaneously sixty-five times, in the scrotum itself thirty-two times, and twenty-three times in the peritoneum. Anastomosis did not follow; nor was it necessary. Testicular tissue, he thinks, has remarkable aptitude for transplantation and a microscopist, M. Retterer, shows us with abundant illustrations just what takes place. The nutrition of the small fragments was more easily assured than that of the large fragments or the whole. Sometimes where sex power is restored in old animals so that they bear young, the parental instinct seems weakened, but the rejuvenation effects of this process, as his many photographs show, are marked. The old and debilitated animals become well, lively, vigorous, and belligerent.