30 CHESTER A. STEWART. 



spending body weight. In the females refed four weeks the 

 ratio (.84) was practically identical with that in the controls 

 (.85). For the male rat of this group the value was exceptionally 

 low (.76), as was also true of the male refed two weeks. In the 

 adult rats the average tail-ratio was practically normal in the 

 test males and females, as compared with the controls of the 

 same sex. 



In general, therefore, it appears that the tail and body assume 

 the normal proportions (for corresponding body weight) in the 

 test rats during the first week of refeeding, and remain normal at 

 all subsequent periods. The exceptional cases are probably due 

 to normal variability. 



3. Head (Table IV.}. 



According to Jackson ('15), the head normally forms an average 

 of 22.5 per cent, of the body, the average net body weight being 

 21.2 grams. In the female rat killed after being kept at constant 

 body weight (24.3 grams net) from three to twelve weeks of age, 

 the head (Table IV.) formed 22.2 per cent, of the net body 

 weight. In the male rat of this group the relative weight of the 

 head (17.7 per cent.) was unusually low, which was due to the 

 body weight being unusually high. It is probable that the weight 

 of the head remained practically unchanged during maintenance, 

 as noted by Jackson ('15). 



On refeeding (as also during normal growth) the relative weight 

 of the head gradually decreases, reaching an average of 15.1 

 per cent, in the females refed one week, whose net body weight 

 averaged 51.5 grams. This is nearly identical with the relative 

 weight (15.2 per cent.) of the head observed by Jackson ('13) 

 for normal rats of practically the same body weight (50 grams). 

 The relative weight of the head in the rats refed four weeks was 

 practically the same as in the 'controls of the same age (Table 

 IV.). In the adult rats the head was normal in the test animals 

 as compared with the controls. On the whole, then, the head 

 appears to have remained practically normal in relative weight 

 throughout the period of refeeding. 



