304 SHINKISHI HATAI 



SPAYING EXPERIMENTS 



The present series contains 15 litters comprising 27 spayed 

 and 27 control rats. The series is divided into five groups each 

 containing three litters, according to the method described. 

 The results of the observations are shown in table 2. 



Body weight. At the time of maximum body weight, that is, 

 at 271 days in age, Stotsenburg ('13) records an average body 

 weight of 226 grams for spayed rats in this series and 176 grams 

 for the corresponding controls. This gives a difference of 28.4 

 per cent in favor of the spayed animals. 



At the time of killing however, some of the rats had lost weight 

 through lung infection or had died, and consequently the body 

 weights given by Stotsenburg and those given by the present 

 writer are not the same. 



Nevertheless we see clearly that the spayed rats made a better 

 growth not only in length, but in entire body weight as can be 

 shown by the following differences. 



At the same age, the body length of the spayed is 2.8 per cent 

 longer, and when body length is equated, the body weight of the 

 spayed is 3.07 per cent heavier than that of the controls. 



We further notice that at the time of examination, the body 

 weight of the spayed was on the average 158.9 grams against 141 

 grams of the control. This gives a difference of 12.7 per cent in 

 favor of the spayed against 28.3 per cent, at the time of the maxi- 

 mum weight. This means that during the interval the spayed 

 rats lost more than the controls. This loss was mainly in fat. 



Tail length. Unlike castration, spaying does not modify the 

 length of the tail. The difference of 0.61 per cent or one milli- 

 meter in absolute measurement in favor of the spayed, seems to 

 be too slight to insist on. 



Brain weight. Similarly, as in the case of the castrates, the 

 spayed rats show a slight reduction in brain weight (—0.39 per 

 cent) when compared with that of the controls. To determine how 

 far we can rely on this difference, additional data are necessary. 



Spinal cord weight. Like the brain, the spinal cord of the spayed 

 shows the figure below ( — 1.57 per cent) that of the controls. 



