STUDIES ON THE DURATION OF LIFE 217 



suits are far too meager, and, statistically, too unrepre- 

 sentative to warrant any attempt at generalization from 

 the present point of view. 



As in so many other cases the experimental method is 

 likely to shed far more critical light on this problem than 

 is the purely statistical method dealing with human data. 

 There are too many factors in the latter material that 

 cannot be controlled. 



GONADS AND DURATION" OF LIFE 



There is another and quite different line of experi- 

 mental work on the duration of life which may be touched 

 upon briefly. The daily press has lately had a great deal 

 to say about rejuvenation, accomplished by means of 

 various surgical procedures undertaken upon the primary 

 sex organs, particularly in the male. This newspaper 

 notoriety has especially centered about the work of 

 Voronoff and Steinach. The only experiments which, at 

 the present time, probably deserve serious consideration 

 are those of Steinach. He has worked chiefly with white 

 rats. His theory is that, by causing through appropriate 

 operative procedure, an extensive regeneration, in a sen- 

 ile animal about to die, of certain glandular elements of 

 the testis, senility and natural death will for a time be 

 postponed because of the internal secretion poured into 

 the blood by the regenerated "puberty glands" as he calls 

 them. The operation which he finds to be most effective 

 is to ligate firmly the efferent duct of the testis, through 

 which the sperm normally pass, close up to the testis 

 itself, and before the coiled portion of the duct is reached. 

 The result of this, according to Steinach 's account, is to 

 bring about in highly senile animals a great enlargement 

 of all the sex organs, a return of sexual activity, previously 



