EFFECT OF CASTEATION ON THE WHITE RAT 311 



at all, in the case of guinea pigs and rabbits, so far as we are 

 able to determine from existing data furnished by the several 

 investigators. 



What this sex difference in the albino rats actually means, I 

 cannot say. 



One point is clear from the preceding, namely, that the hypoph- 

 ysis reacts differently according to the sex after the removal 

 of the sex glands. Thus we noticed that spaying in the female 

 does not produce the enlargement of the hypophysis, but on the 

 other hand, overgrowth and obesity invariably follow this opera- 

 tion. 



Castration produces in the male a striking enlargement of the 

 hypophysis while overgrowth and obesity are entirely absent. This 

 peculiar relation between the response of the hypophysis on the 

 one hand and overgrowth and obesity on the other, is worthy of 

 further consideration. 



Clinical as well as experimental evidence (Cushing '09, and for a 

 general account on the subject, see Vincent '12) shows with a 

 high degree of probability that 'hypo-secretion' of the pituitary 

 gland produces abnormal accumulation of fat possibly due to 

 lowered oxidation. Thus if a compensatory growth of the hypoph- 

 ysis does not follow, as is the case after spaying, the product 

 of the unaltered gland must be employed for two purposes; one, 

 to replace the ovarian hormone and two, for the normal uses, 

 whatever these may be. Spaying thus appears to overtax the 

 normal secretion coming from the unmodified gland and con- 

 sequently to produce phenomena similar to those following hypo- 

 secretion. On the other hand, the compensatory hypertrophy of 

 the hypophysis in the male albino rat after castration appears 

 to prevent the phenomena of hypo-secretion, and consequently 

 the body changes, overgrowth and obesity, are prevented. The 

 value of this view must be tested. Nevertheless it seems to offer 

 a reasonable explanation for the true growth and the accumula- 

 tion of fat following spaying on the one hand, and the absence of 

 these reactions after castration, on the other. 



The result of semi-spaying in the albino rats gives still further 

 evidence in support of the view just presented. 



