WEIGHTS OF ORGANS IN UNDERFED YOUNG RATS 119 



In the rats experimented upon at later and longer periods 

 (ages of six to thirty-two weeks and ten to thirty-five weeks) 

 there is also a marked loss in the weight of the skin, though 

 apparently not so great as at the earlier periods. 



This loss in the weight of the integument is in striking contrast 

 with the results of inanition in adult rats (Jackson '15 a, '15 c). 

 Here the loss is very nearly proportional to that of the whole 

 body, so the integument nearly maintains its relative (per- 

 centage) weight. 



From his experiments upon young dogs held at constant body- 

 weight, Aron ('11, p. 29) states that: "The skin shows a slightly 

 higher percentage of the body-weight in those animals kept at a 

 constant weight than in the normal, control dogs. These figures 

 indicate that, while the (body) weight was constant, the skin 

 increased very slightly in weight." The figures cited show the 

 skin in animals held at nearly constant body-weight to form (in 

 four cases) 12.2 to 14.6 per cent of the body-weight, whereas in 

 three corresponding full-fed controls the skin formed 11.2 to 

 13.0 per cent. Aron, however, overlooks the fact that he is 

 making his comparison with controls at the end of the experi- 

 ment. In order to judge what changes have taken placed during 

 the experiment, the comparison must be with normal control 

 animals killed at the beginning of the experiment. Aron records 

 but one case which can be used for this purpose. His Dog D 

 (table 13, Experiment IV) killed at the age of 40 days, the begin- 

 ning of the experiment, with body- weight of 1985 grams shows a 

 skin- weight of 320 grams, or about 16.1 per cent of the body- 

 weight. From Aron's own data, therefore, I would reach the 

 opposite conclusion, viz., that in young dogs held at constant 

 body-weight, the skin suffers a marked loss in weight. This 

 would agree with my results on rats. 



SKELETON 



The skeleton (table 7; fig. 4) was prepared in three ways. 

 The bones, together with the cartilages, periosteum and liga- 

 ments, constitute the 'ligamentous skeleton' (table 7 a). The 

 bones and cartilages, after removal of the periosteum and liga- 



