332 E. R. HOSKINS 



my rats have a slightly higher percentage in the females and 

 lower in the males, than in Jackson's older rats of corresponding 

 body weight. The sexual difference in the weight of the supra- 

 renals discovered independently by Jackson ('13) and by Hatai 

 ('13) occurs likewise in my rats. 



b. Thyroid groups. As shown in tables 6 to 10, the thyroid- 

 fed animals show a distinct increase in the relative size of the 

 suprarenals in all groups. According to Donaldson's method 

 of comparison, the younger females show an overgrowth in 

 the absolute weight of the suprarenals of 14.5 per cent, the 

 older females of 16.1 per cent, the younger males of 36.4 per cent, 

 and the older males of 38.1 per cent (table 10). This indicates 

 that the reaction of the suprarenals to thyroid treatment is 

 relatively greater in males, in which sex the gland is normally 

 relatively lighter in weight than it is in the females. 



c. Thymus, hypophysis, and pineal groups. In all these groups 

 the suprarenal glands do not appear to differ from the controls 

 more than might be expected from the normal variability (tables 

 6 to 9). In the younger pineal-fed female rats, however, the 

 suprarenals average about 9 per cent lighter in weight than in 

 the corresponding controls. 



16. Kidneys (tables 4 lo 10) 



a. Controls. As compared with Donaldson's tables, the 

 kidneys in my rats (tables 4 and 5) were somewhat heavier 

 in the younger groups and lighter in the older groups. The 

 differences are not great, however, and may possibly be due to 

 age. My younger rats are larger than is usual at that age. 

 The relative size of the kidney tends to decrease with the less 

 active metabolism of adult life. 



In relative (percentage) weight (tables 8 and 9), all the groups 

 are in fairly close agreement with the results obtained by Jack- 

 son ('13) for rats of the same age. In two rats of the same sex 

 and same size but of different age, the younger usually has larger 

 kidneys. 



