460 CARL R. MOORE 



to 30 per cent above that of normal females;^ he has proved also 

 that the removal of the testis from young males does not in- 

 fluence the subsequent growth curve as compared with normal 

 males. 



As the presence of the gonads, at least in case of the female 

 rat, is a modifying element of the growth curve, it is highly 

 desirable to know whether there is a difference in the growth 

 of the two sexes aside from any influence exerted by the gonads. 

 Is there a latent, potential, sex difference between the male and 

 female growth aside from any modification brought about by 

 the presence or absence of the sex glands? Stotsenburg's data 

 as presented are not adequate for giving an answer to this 

 question. 



This paper contains the results of a comparison of the growth 

 of completely castrated males and spayed females of the same 

 litters and shows conclusively that there is constantly a differ- 

 ence in weight in the two gonadectomized sexes. The spayed 

 females do increase in weight relative to the normal females and 

 approach more nearly the weight of the males, but in every case 

 the males are heavier than the females. 



MATERIAL 



Seven litters of the common white rat (Mus norvegicus 

 albinus), composed of fifty-four rats, forty of which were 

 castrated or spayed, the remaining fourteen serving as controls, 

 constitutes the material used. Each litter was kept in a sepa- 

 rate cage, but in the same room during their growth, and the 

 entire experiment was confined to the period from November 29, 

 1917, the birth of the oldest Utter used, to September 1, 1918, 

 when the last weighing was made; and since the weight of each 

 litter was recorded for 180 days, it will be realized that corre- 

 sponding weights for each litter were made at comparatively the 

 same time of year. 



The diet used was a constant one and consisted of milk and 

 bread daily, a small amount of meat twice each week mixed 



* Stotsenburg ('13). 



