42 CHESTER A. STEWART. 



the test females, which were slightly larger. The differences 

 are probably due to individual variation. 



The results therefore indicate that the lungs, which lose weight 

 during maintenance, completely recovered within two weeks of 

 ref ceding. There is possibly an over-compensatory growth 

 before the end of four weeks, but no indication of such in the 

 animals refed to the adult stage. 



1 6. Liver (Table V.}. 



The weight of the liver in the two rats killed at the end of nine 

 weeks of maintenance was 37.5 and 59.4 per cent, below Donald- 

 son's norm for the male and female respectively. (However, 

 Jackson ('13) found the normal liver weight, especially in young 

 rats, considerably below the curve derived from Hatai's formula, 

 upon which Donaldson's norm is based.) Jackson ('15) found 

 the liver to increase in weight in rats held at maintenance from 

 three to six and ten weeks of age, but it decreased in those held 

 for longer periods (from six to thirty-two weeks of age). The 

 low weight of the liver for my rats at the end of the maintenance 

 period was probably due in part to the length of their maintenance 

 period. 



During the first four weeks of refeeding the weight of the liver 

 was below Donaldson's norm, except in the male refed one half 

 week. In most instances, however, especially after the first week, 

 the deviations are within the limits of normal variation. In the 

 controls at sixteen weeks, however, the weight of the liver was 

 23.3 per cent, below the norm, while in the test females of the 

 same age it was but 5.3 per cent, below. Thus when compared 

 with Donaldson's norm, the liver is about normal in the test rats 

 refed four weeks, but when compared with the controls it is 

 relatively heavy. 



In the adult test rats the weight of the liver was very close to 

 Donaldson's norm, but very low ( 18.3 to 21.0 per cent.) in 

 the controls. 



Therefore in comparison with the Wistar norm the liver 

 appears practically normal after the first week of refeeding. As 

 compared with the controls, however, there is some indication of 

 hypertrophy in the liver of the rats refed four weeks, and also in 



