486 



INTERNAL SECRETIONS 



the skin disappeared and the hair of the whole body became 

 thick; it was the same with the scrotal skin. The bent position 

 of the aged animal changed to that characteristic of a vigorous 

 youthful one. The weight increased. The seminal vesicles 

 and the prostate, which were in a state of atrophy, regenerated. 

 The animals which were hitherto apathetic became more 

 active, and they took an interest in individuals of the other sex 



Fig. 139. — "Rejuvenation" oj senile dog, 18 years old. Before operation, 

 after having been seven months under observation. Weight 33 kgr. ; 

 onl}^ small changes in weight during the whole time of observation not- 

 withstanding best alimentation. — ^From Wilhelm. 



and generally regained sexual activity. These results could be 

 attained even if only one vas deferens was ligatured. To 

 bring about this effect it is necessary to avoid injury to the 

 blood vessels accompanying the vas deferens. Since it is not 

 always possible to do this, Steinach, in his later experiments, 

 effected a ligature of the efferent ducts between the testicle 

 and the cauda epididymidis. He observed operated senile 

 animals for about eight months after the operation. In regard 



