306 CARL RICHARD MOORE. 



the femur and 4 mm. for the tibia in castrated animals ; the total 

 lengths were not given, consequently the relative growths of bone 

 in the two cases are unknown. In capons he found an increase of 

 8 mm. for the femur and I cm. for the tibia. Delay in the ossifi- 

 cation of the epiphyses following castration is considered the 

 causal factor for increase in length. Sellheim ('99) found de- 

 layed ossification in castrated vertebrates (pig, dog, and bull) and 

 a consequent increase in size and length of bones. Hatai ('15) 

 found a very slight increase in the ratio of body length to bone 

 length in castrated rats. He mentions, however, that this differ- 

 ence appears only upon close computation, and is in doubt whether 

 any significance should be attached to his findings. 



X. DISCUSSION. 



The primary object in conducting the experiment reported 

 herein was to study the reactions in weight of guinea pigs, from 

 birth to maturity, as this may be influenced by the sex glands. 

 Certainly secretions of the sex glands do modify somatic structures 

 in many vertebrates and it has been assumed that weight of labo- 

 ratory animals such as the rat and the guinea pig reflect, to some 

 degree, their sexual nature ; the differences are supposedly detect- 

 able if comparisons are made between the weights of normal ani- 

 mals and those having undergone operations at a previous date. 

 However much one may be inclined to doubt the advocacy of 

 utilizing weight as a criterion of sex-gland conditions, an intimate 

 understanding of the reactions are necessary before the doubt can 

 be expressed in definite form. 



In the guinea pig (speaking of averages of groups of animals 

 of the same age, same conditions as concerns sex glands, and 

 reared under identical conditions) normal males are constantly 

 heavier than normal females up to the end of the first year; at 

 thi.s time the weights between the two groups are almost identical 

 and, according to Minot, the females subsequently become slightly 

 heavier than the males. But does this mean that the testis pro- 

 motes, and the ovary retards, growth and increase in weight? 

 Elimination of the gonads of each sex should afford a basis for a 

 partial answer to the question by comparing the growth curves of 

 each group with that of the normal group. Referring to Fig. I, 



