PHYSIOLOGICAL PROPERTIES OF THE GONADS. 2Q7 



Sexual Differences. Comparing the average weight of the 

 twelve normal male hypophyses (.0140 gram) with the average of 

 nine normal female glands (.0150 gram), we see that the female 

 hypophysis is 7.1 per cent, heavier than that of the male. And 

 comparing the average body weights of the same two groups, one 

 sees a difference of but one gram ; in other words, the average 

 body weights of the two groups are almost identical. There 

 appears, therefore, to be a slight sexual difference in the weight 

 of the male and female guinea pig hypophysis at the end of one 

 year's growth, the female hypophysis being slightly heavier than 

 the male. 



Castration. Comparing the average weights of the twelve nor- 

 mal male hypophyses (.0140 gram) with the average of the six 

 castrated male hypophyses (.0122 gram), we find that the normal 

 male hypophysis is 14 per cent, heavier than the hypophysis of 

 castrated males. Comparing the body weights of these two 

 groups, the normal males are 7.6 per cent, heavier than the cas- 

 trated males, or, in other words, the relationship of the hypophysis 

 of the normal male to that of the castrated male is proportionally 

 greater than the relationship of the body weights. Thus we con- 

 clude that castration causes a relative decrease in the hypophysis 

 as well as an actual one, as shown by the figures in the table. 



Spaying. If one compares the average weight of the hypophy- 

 ses of the nine normal females (.0150 gram) with the average 

 weight of the same gland of the eight totally spayed females 

 (.0134 gram), it will be seen that the normal female hypophysis 

 is 12 per cent, heavier than the hypophysis of the spayed females. 

 And looking at the ratio of body weights of the two groups, it 

 will be seen that the spayed females are approximately i per cent, 

 heavier than the normal females. Thus at the end of one year the 

 normal female hypophysis is both relatively and actually heavier 

 than that of the spayed females, or, in other words, total spaying 

 causes a decrease in weight of the hypophysis. 



Discussion. It has been impossible to find in the literature more 

 than one or two observations wherein the weight relations between 

 the hypophysis of the normal male and female of any group of 

 animals have been determined. It would appear that a knowledge 

 of sexual differences would be of great value in attempting to 



