WEIGHTS OF ORGANS IN UNDERFED YOUNG RATS 153 



SUMMARY 



The principal results of the present paper may be summarized 

 briefly as follows : 



Young albino rats may be held at constant body-weight for 

 considerable periods by underfeeding. The amount of . food 

 required for this purpose decreases as the experiment proceeds. 



As to the body-proportions, the relative weights of the head, 

 trunk and extremities remain practically unchanged during the 

 experiment. There is apparently a slight increase in the head, 

 counterbalanced by a corresponding decrease in the trunk and 

 extremities, but the change is so slight as to seem of doubtful 

 significance. 



Of the systems — integument, skeleton, musculature, viscera 

 and 'remainder' — there is but little change in the weights of the 

 musculature, visceral group (as a whole) and 'remainder.' There 

 is, however, a marked decrease in the weight of the integument, 

 counterbalanced by a marked increase in the skeleton. Thus on 

 the low plane of nutrition in the young body maintained at con- 

 stant weight, the growth capacity appears weakest in the skin 

 and strongest in the skeletal system. This is in striking Contrast 

 with the normal growth process of corresponding ages, during 

 which the musculature increases with relatively great rapidity 

 and the skeleton lags behind relatively. 



The increase in the skeleton during constant body-weight 

 appears to involve the ligaments as well as the cartilages and 

 bones. The skeletal growth tends to proceed along the lines of 

 normal development, as indicated by decrease in the water- 

 content, and by formation and union of various epiphyses. 

 Another evidence of the tendency to normal development of the 

 skeleton is seen in the increased relative length of the tail as 

 compared with the body-length. The teeth also continue to 

 develop normally (formation and eruption of the third molars). 



The individual viscera may be classified in three groups: 



(1) There is during the maintenance of constant body-weight 

 in young rats a well-marked increase in the weights of the eye- 



