286 CARL RICHARD MOORE. 



testis graft is due to the removal of the retarding influence of the 

 ovary and not to an influence of the testis graft as claimed by 

 Steinach. Sufficient data were presented in the second paper of 

 this series 1 to show that Steinach's femininized and masculinized 

 rats can not be so adjudged on the basis of differences in weight. 



Since Steinach has applied the same principles to the guinea pig 

 to detect changes in its sexual condition after operative procedures, 

 the writer in 1921 criticized again such indiscriminate uses of 

 weight records and mentioned an experiment under way to deter- 

 mine the fundamental reactions in weight upon removal of the 

 gonads. The present paper embodies the results obtained from 

 this investigation. 



The growth of a series of guinea pigs, consisting of normal 

 males and females, as well as totally castrated males and totally 

 spayed females, was followed from birth to maturity (for one 

 year). And in addition to determining the growth curves for the 

 four classes of animals it appeared not only desirable to examine 

 the glands of internal secretion for possible changes correlated 

 with sex glands, but to examine as well the effect of castration and 

 spaying on the growth of the long bones of the leg. 



II. MATERIAL AND METHODS. 



The animals for this experiment were selected from young born 

 from our own laboratory stock at a time when the stock was able 

 to supply a quantity within a relatively short period of time. 

 Comparisons in weight were then made at approximately the same 

 time of the year, as all the animals of this experiment were born 

 between April 20 and August 27, 1920. The forty-six animals 

 with which the experiment was begun were grouped in the follow- 

 ing manner: 12 normal males, n castrated males, 12 normal 

 females, and n spayed females. These were so caged as to be 

 recognizable at any moment, and in such a manner that pregnancy 

 was eliminated in the normal females in all but two cases.- 



The animals were kept in the same room, in ordinary wire cages 



1 Moore, '19. 



2 Minot, 1891, has shown that pregnancy does not cause a permanent 

 change in the weight of a female animal ; a correction for the weight of the 

 unborn young was made in these two cases of pregnancy. 



