WEIGHTS OF ORGANS IN UNDERFED YOUNG RATS 145 



In the rats held at constant body-weight from the age of three 

 weeks the suprarenal glands appear to increase slightly in weight 

 at six and eight weeks; and especially at ten weeks, where the 

 characteristic sexual difference has distinctly appeared. In 

 absolute weight, the suprarenal glands have increased from 

 0.0090 gram (0.0088 gram, plus correction for difference in body- 

 weight; or 0.037 per cent of the body-weight) at three weeks to 

 0.0101 gram (0.042 per cent of the body-weight) in the male at 

 ten weeks, an increase of about 12 per cent in absolute weight. 

 In the female, the corresponding increase is from 0.0084 gram 

 (0.0088 gram, less correction for difference in body-weight) 

 (or 0.037 per cent, of the bodj^-weight) to 0.0117 gram (0.051 per 

 cent of the body-weight), an increase of 39 per cent in absolute 

 weight. Normally the suprarenals during this period are de- 

 creasing in relative (percentage) weight. In the experiments 

 at later and longer periods (six to thirty-two weeks and ten to 

 thirty-five weeks), the changes are apparently not great, but a 

 larger number of observations is necessary before definite con- 

 clusions can be reached. 



In adult rats during inanition there is little or no loss in the 

 absolute weight of the suprarenal glands, which therefore in- 

 crease markedly in relative (percentage) weight (Jackson '15 a, 

 '15 c). 



KIDNEYS 



The kidneys (table 21) in rats held at constant body-weight 

 from the age of three weeks show a tendency to increase which 

 is more marked at six and eight than at ten weeks. Between 

 three and ten weeks of age the increase is from an average of 

 0.388 gram (0.393 gram, less correction on account of differ- 

 ence in body-weight; or 1.62 per cent of the body-weight) to 

 0.404 gram (1.69 per cent of the body-weight), an inci*fease of 

 only about 4.1 per cent in absolute weight. At later and longer 

 periods (six to thirty-two weeks and ten to thirty-five weeks) 

 there is apparently but little change in the weight of the kidneys. 

 The slight differences shown in the table are probabl}' not 

 significant. On the whole, it appears that in young rats held at 



