EFFECT OF CASTRATION ON THE WHITE RAT 299 



variability is greater when individuals of different litters are 

 compared (Jackson '13). This method was followed also in the 

 other two series, that is, the spayed and the semi-spayed. The 

 results of the observations are given in table 1 . 



BODY WEIGHT 



Stotsenburg ('09) has shown that in the albino rat castration 

 does not modify the growth of the body in weight. This conclu- 

 sion is fully supported by the present series. We notice in table 

 1 that the observed body weight of the castrates is nearly iden- 

 tical with that of the controls, the average body weight of cas- 

 trates being 122.1 grams contrasted with 123.5 grams for the 

 controls at the same age. 



We notice further from the table that not only the growth of 

 the body in weight remains unmodified, but the relation between 

 body length and body weight characteristic for this series is un- 

 affected by castration. 



The difference in body weight between the castrated and control 

 rats when body length is taken as the basis for the computation 

 is 3.63 per cent in favor of the controls. This difference can cer- 

 tainly not be regarded as significant when we also consider the 

 normal fluctuations in this character. 



In those species which respond to castration by an overgrowth 

 several investigators have noted a definite effect on the develop- 

 ment of the skeleton. Poncet ('97) noted that the bones, partic- 

 ularly the femur, the tibia and fibula, of the castrated rabbits 

 were longer. Fichera ('05) and Lannois, and Roy ('02) noted an 

 elongation of the leg bones in castrated guinea pigs, in oxen, in 

 capons and in some other animals. Numerous other confirmatory 

 observations can be found in the literature (see Vincent '12 and 

 Marshall '10). 



Since however in the rats not only the growth of the body as 

 a whole remains unaltered, but a perfect normality is shown in 

 the relation between length and weight of the body, it seems 

 improbable that alterations in the length of the leg bones should 

 occur. Observations on this point however are now being made. 



