THE PROBLEM OF REJUVENATION 485 



the relation between sex hormones and senility. The question 

 seemed to have been lost sight of for about thirty years after 

 the first experiments of Brown-Sequard in 1889. But Harms 

 in 19 14 described an experiment in which a senile male 

 guinea pig had implanted into it the testicle of its six weeks 

 old son. Renewal of sexual activity was noticed subse- 

 quently for several weeks or somewhat longer. Harms (1922) 

 performed similar experiments on old dogs, both male and 

 female. Hairless places on the skin became covered with 

 hair again after testicular transplantation, and the hair was 

 thick and shiny. The teeth which had been loose became firm 

 again. In one case a senile cataract disappeared almost 

 entirely. Voronoff (1923) transplanted testicles of young 

 animals into senile rams ten or twelve years of age. Various 

 indications of senility, such as thin wool, cachexia, apathy, 

 tremor in the legs, and incontinentia urinae, partly disappeared. 

 The animals became more lively about two months after the 

 operation; the wool became shiny, sexual activity reappeared, 

 and one animal which was said to be sterile for two years once 

 more bred. Voronoff says that the animals looked so well 

 that one would suppose them to be 6 to 8 years of age if the 

 horns and teeth had not indicated an age of 12 to 14. He 

 observed his animals for more than four years. Removal of 

 the graft causes reappearance of the signs of senility, which 

 disappear again when a second transplantation is made. 

 Voronoff fixed the testicular fragments on the testicle in situ 

 with catgut. Spermatozoa could be detected fourteen months 

 after transplantation; they were present even when the graft 

 did not originally contain ripe spermatozoa. 



Great interest has been aroused by Steinach's experiments 

 (1920) in which, to bring about rejuvenation, another method 

 was used. Since Bouin and Ancel performed their original 

 experiments it has been known that ligature of the vasa defer entia 

 causes profound changes in the testicle. Several investigators 

 some time after the operation have observed an increased 

 sexual activity which has been ascribed to greater hormonic 

 activity on the part of the testicle. Now Steinach conceived 

 the idea of using this method to increase the hormonic activity 

 of the testicle in animals with symptoms of senility. In the 

 experiments which Steinach performed on rats, there were 

 unmistakable signs of improvement. The hairless spots on 



