GROWTH AFTER INANITION FOR VARIOUS PERIODS. 43 



the adult test animals. It is more probable that this apparent 

 increase is due merely to normal variability, which is quite large 

 in the liver. 



17. Spleen (Table V.). 



Jackson ('15) noted a considerable decrease in the weight of the 

 spleen in rats held at maintenance from three to eight and ten 

 weeks of age. My data (Table V.) likewise indicate that the 

 spleen is low in weight at the end of nine weeks of underfeeding 

 (minus 10.7 and 44.9 per cent.) when compared with Donaldson's 

 norm. 



On refeeding, at all periods the weight of the spleen was much 

 higher than Donaldson's norm, the excess appearing greater at 

 one and two weeks of refeeding, than at later periods. In the 

 controls the spleen likewise exceeded the Wistar norm, 82.8 

 per cent, at sixteen weeks, and 23.5 and 36.6 per cent, in the adult 

 control males and females respectively. As compared with the 

 controls the spleen was practically normal in the adult test rats. 



In this connection it may be noted that, as was pointed out by 

 Jackson ('13), Ratal's formula for the growth of the spleen 

 (upon which Donaldson's norm is based) gives a curve which in 

 general is too low (excepting the earlier stages), because he 

 excluded all "enlarged" spleens from the series, without apparent 

 justification. In most cases, however, the spleens of my refed 

 rats appear considerably heavier even than Jackson's curve. 

 The fact that the weight of the spleen is normally exceedingly 

 variable, as shown by Jackson ('13) must also be kept in mind. 



In general therefore the results indicate that upon refeeding 

 the spleen rapidly (within ^ week) recovered the loss suffered 

 during fasting. There is apparently an excessive (over-com- 

 pensatory) growth of the spleen during the first two weeks of 

 refeeding. At the end of the fourth week, however, and in the 

 adult rats the spleen in the test animals is not above that of the 

 controls. 



1 8. Stomach and Intestines (Table V.). 



The weight of the empty alimentary tract at the end of main- 

 tenance was much below the Wistar norm (minus 36.7 to 48.8 

 per cent.). My data, however, are somewhat above the weights 



