Case 1. Man of 44, lean, weak, wrinkled, incapable of physical work by reason of easy fatigue. Libido failing for years and almost extinct, testicular pains, and double-sided hydrocele. With local anesthesia the typical Winkelmann operation was performed. On both sides there was ligature of the vas deferens between the testicle and the epididymis. The cure took a week and the patient was soon discharged. A few weeks witnessed a striking change. He increased in weight, the wrinkles almost vanished, and in five months he had won back muscular power and become a hard worker, carrying heavy burdens. “Libido and potence returned with great intensity.” The upper part of the thigh grew hairy and both hair and beard increased so that he had to shave more often. Improvement continued during the year and a half in which he was under observation and he seemed in every way a vigorous and young man. Case 2. Man of 71, of large business, who came to the hospital with an abscess in the left testicle with septic signs--chills, high temperature, etc.--so that it was necessary to remove the source of maturation _in toto_. At the same time the right, sound testicle was subjected to ligature of the passage from the epididymis to the vas deferens. In twenty-four hours the patient lost his fever and in three weeks left the hospital. Quite apart from the acute symptoms, this patient had for years suffered marked signs of age, especially calcification phenomena--dizziness, shortness of breath, weakness of heart, great fatigue, tremors, etc., with libido extinct for eight years. Within a few months a marked change occurred. A feeling of masculinity returned and in nine months the patient described his own condition in a letter in which he says in substance that, to his great surprise, certain nocturnal phenomena had recurred, his appetite was so great that for a long time it was difficult for him to satisfy it, instead of previous depression he found himself again full of the joy of life and considered himself very elastic for his age, while his friends often remarked the great change that had taken place and could not believe he was seventy-one. He suffers little from fatigue, calcification and dizziness have ceased, he can think clearly, had to go to the barber more often, and all his functions have greatly improved.