WEIGHTS OF ORGANS IN UNDERFED YOUNG RATS 115 



integument; although, as will be shown later, the average loss 

 in the integument of the entire body is relatively slightly greater 

 than the corresponding skeletal increase (fig. 4). 



In both acute and chronic inanition in adult rats (Jackson 

 '15 a, '15 c) the head increases very markedly in relative weight, 

 the loss in absolute weight being but very slight in comparison 

 with the loss in weight of the entire body. 



EXTREMITIES AND TRUNK 



The extremities (table 5 ; fig. 3) were separated at the shoulder- 

 joint and hip-joint, respectively. There is apparently a slight 

 decrease in the relative weight of the fore-limbs in the young 

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

 six, eight, ten, thirteen and sixteen weeks of age. In the case of 

 the rats held constant from three to ten weeks, the apparent 

 decrease is from an average of 9.6 per cent to 8.5 per cent. On 

 account of the small number of observations, however, and the 

 difficulty in separating the limbs (especially the integument) 

 in an absolutely uniform manner, the slight apparent decrease 

 is of doubtful significance. 



In the case of the hind-limbs, there is likewise an apparent 

 indication of a slight decrease, but even less marked than in the 

 fore-limbs. The apparent average decrease from 15.7 per cent 

 to 15.4 per cent of the body-weight in the largest group (three to 

 ten weeks, is well within the lunits of experimental error. 



On the whole, therefore, it is doubtful whether there is any 

 distinct and significant change in the weights of the extremities 

 in young rats held at constant body-weight for considerable 

 periods. A slight loss, however, might be accounted for by the 

 slightly greater loss in the integument (as compared with the 

 gain by the skeleton); especially since the integument of the 

 limbs probably forms a relatively larger part of the limbs than 

 the whole integument does of the whole body. 



The trunk was not weighed directly, but its weight was cal- 

 culated by subtracting from the net body-weight the weight 

 of the head and extremities. From what has been said con- 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 19, NO. 2 



