GROWTH AFTER INANITION FOR VARIOUS PERIODS. 39 



11. Eyeballs (Table V.}. 



As compared with Donaldson's ('15) norm, the eyeballs were 

 excessively heavy (plus 42.8 and 45.5 per cent.) in the two rats 

 killed at the end of nine weeks of maintenance. The persistent 

 growth of the eyeballs in young rats held at constant body weight 

 was discovered by Jackson ('15). In the rats refed one half, 

 one, and two weeks the eyeballs are still relatively heavy as 

 compared with Donaldson's norm, although the difference has 

 decreased somewhat during these periods. Even in the rats 

 refed four weeks the eyeballs are still somewhat above Donald- 

 son's norm, but are practically normal as compared with my 

 controls. 



Likewise in the adult refed rats, as compared with the controls, 

 the eyeballs appear to be normal in weight, although in the females 

 they somewhat exceed the Wistar norm in weight. 



The evidence therefore indicates that the eyeballs, which were 

 relatively heavy at the end of the maintenance period, returned 

 to the normal proportion by the end of the fourth week of 

 refeeding, and were normal in the adult test rats. 



12. Thyroid (Table V.}. 



At the end of the maintenance period the weight of the thyroid 

 in the male rat was 35.2 per cent, below the Wistar norm, while 

 in the female it was 25.7 per cent, above. Jackson ('15) noted 

 that the thyroid suffered a marked loss during maintenance. 

 The exceptionally large weight for the female above noted may 

 be due to experimental error or normal variation. On refeeding, 

 the thyroid remains below Donaldson's Wistar norm, although 

 by the fourth week it is only 18.7 to 20.1 per cent, below. In the 

 controls for this group the weight of the thyroid is also below 

 Donaldson's norm by 13.9 per cent., which deducted from the 

 minus 20.1 per cent, for the test females leaves 6.2 per cent, loss 

 apparently produced by the fasting experiment. In view of the 

 known variability of the thyroid, this difference is too small to 

 be considered significant. We may therefore conclude that the 

 thyroid gland has probably recovered its normal weight during 

 the four weeks of refeeding. In the adult rats the fluctuations 

 in the weight of the thyroid gland are likewise well within the 



