36 CM. JACKSON 



the female the relative weight increases from 0.037 per cent of 

 the body at 5 grams to a maximum of about 0.042 per cent at 

 10 grams, decreasing to 0.038 per cent at 20 grams, 0.032 per 

 cent at 50 grams, 0.029 per cent at 100 grams, 0.027 per cent at 

 160 grams, and 0.026 at 300 grams. Thus the suprarenal bodies 

 appear relatively much larger in the female, especially for a body 

 weight above 100 grams. 



■ Grouped according to age periods, my own data (table 13, 

 fig. 4) likewise show the relative growth of the suprarenals to be 

 quite different in the two sexes. In the male, the maximum rela- 

 tive size, 0.038 per cent of tlie body weight, apparently occurs 

 in the newborn, decreasing to 0.023 per cent at seven days, but 

 increasing again to 0.036 per cent at twenty days, which is nearly 

 as large as the maximum. Thereafter the relative weight de- 

 creases to 0.027 per cent at six weeks, 0.018 per cent at ten weeks, 

 and 0.016 per cent at five months and one year. The course of 

 relative growth is somewhat similar in the female, but the maxi- 

 mum (0.043 per cent) occurs at twenty days instead of at birth 

 (0.041 per cent) . After six weeks, the relative size is much greater 

 in the female, being 0.026 per cent to 0.028 per cent of the body 

 weight. Even the absolute weight of the suprarenals (after six 

 weeks) is considerably greater in the female, although the body 

 weight is much less. 



When compared with the theoretical curve of growth, a marked 

 discrepancy may be noted in the present data (table 13) at seven 

 days. For some unaccountable reason, the suprarenals in my 

 series appear to lag behind during the first week, increasing in 

 weight only about 20 per cent, while the body weight is doubled. 

 There is also a corresponding irregularity in correlation with the 

 body weight at seven days, which is very low, especially in the 

 male. 



The coefficient of variation in absolute weight is somewhat 

 high and irregular (20.4 to 38.7) with variations showing no 

 definite relation to age or sex. The coefficient of variation in 

 percentage weight is usually but little, if any, lower. The coeffi- 

 cient of correlation between suprarenals and body weight is cor- 



