AVEIGHTS OF ORGANS IN UNDERFED YOUNG RATS 143 



following the normal growth tendency, there appears to be in 

 these retarded rats an early increase in the weight of the ali- 

 mentary canal, reaching a maximum at about the age of six 

 weeks, after which there is a decline in weight. It may be that 

 the early increase in these organs is diminished later on account 

 of the exhaustion of the stored food-supplies available else- 

 where in the body at the beginning of the experiment. Individ- 

 ual organs and tissues differ greatly from each other in their 

 relative susceptibility to attack and absorption at different times 

 during the course of inanition. 



The behavior of the stomach and intestines weighed with 

 contents (table 19 a) is very similar to that of the empty canal. 

 Contrary to what might be expected, during constant body- 

 weight, with a restricted food-supply (water ad libitum), the 

 canal does not decrease in contents. On the contrary there is 

 an increase in contents (watery or mucous in character) which 

 may even exceed in relative weight the normal contents in full- 

 fed aminals. The maximum occurred in animals held at con- 

 stant body-weight from the age of three to eight weeks, when 

 the canal with contents formed 20.2 per cent of the body-weight! 

 In experiments beginning at later ages and extending over longer 

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

 the canal with contents appears to remain more nearly uniform 

 in weight, with some tendency to decrease. 



During both acute and chronic inanition in adult albino rats, 

 there is a very marked decrease in the weight of the stomach and 

 intestines, both with and without contents (Jackson '15 a, '15 c). 



SUPRARENAL GLANDS 



The suprarenal glands (table 20) from the age of about six 

 weeks must be considered separately in the sexes, on account 

 of a distinct sexual difference in their weight, as discovered 

 independently by Hatai ('13) and myself (Jackson '13). In the 

 earlier ages, however, there is no apparent sexual difference, 

 hence the sexes are combined. 



