304 



CARL RICHARD MOORE. 



normal male spleen is 14 per cent, heavier than the castrated male 

 spleen, but the body weight of the normal male is 7.6 per cent, 

 greater than that of the castrated male ; the relative difference is 

 therefore not so great. Apparently castration slightly inhibits 

 growth of the spleen. 



Spaying. Comparing the normal female spleen with that of the 

 spayed female spleen, we note that the spayed female possesses on 

 the average a spleen 14 per cent, less in weight than the normal ; 

 since the body weights are but slightly different, we may conclude 

 that spaying results in a decrease in the spleen growth. 



IX. BONE LENGTHS. 



Reported increases in the length of bones following gonadec- 

 tomy indicate that the sex glands control to some degree the lengths 

 acquired. In order to determine possible differences referable to 

 a sex-gland disturbance, the bones of the hind leg of each animal 

 of the series were measured at the time they were killed. These 

 measurements are given in Table II. and are expressed in average 

 lengths of the two similar bones from each animal. Thus the 

 given femur length for each animal is the average between the 

 lengths of the two femurs, etc., and it has been found that differ- 

 ences between the two bones are often greater than could be 

 anticipated. 



Se.vual Differences. When a comparison was made between 

 average lengths of the hind-leg bones of the normal male group 

 and an average of similar bones from the normal female group, it 

 was found that the bones of the normal males were but slightly 

 greater in length than those of the females. The difference was 

 as follows : femur, 3.6 per cent, longer ; tibia, 3.4 per cent, longer ; 

 fibula, 1.9 per cent, longer. 



The sexual difference in bone lengths of normal guinea pigs is 

 therefore one of slight degree, the males being favored as to 

 growth in length. 



Castration. When the average lengths of the bones of the nor- 

 mal males were compared with similar ones of the castrated ani- 

 mals, the actual lengths were greater in the normal animals than 

 in castrated ones; the femur was 2.5 per ce.nt. greater in length, 

 the tibia 1.7 per cent., and the fibula considerably less than i per 



