EFFECTS OF THIRST ALBINO RATS 447 



inanition likewise occurs in the young of other species (calves, 

 puppies, human infants) . Jackson and Stewart have shown that 

 the growth of the skeleton in underfed rats appears less intensive 

 in very young (newborn) rats and in older rats (approaching 

 maturity) . 



MUSCULATURE 



As shown in table 2, the various groups of tests rat show appar- 

 ent slight decreases (4.7 to 7 per cent) in weight, excepting the 

 third group, which is nearly constant. These differences are 

 insignificant, especially when the slight differences in body weight 

 between controls and test rats are taken into account, but there 

 is perhaps a slight tendency to decrease in the later periods. 



In young rats held at constant body weight by inanition (simple 

 underfeeding) the musculature, as in thirst, also remains nearly 

 constant, but with a very slight tendency to increase in weight 

 (Jackson, '15 a). 



During thirst in adult rats the musculature loses approximately 

 in proportion to the entire body (Kudo, '21). 



VISCERA AND 'REMAINDER' 



The visceral group includes the brain, spinal cord, hypophysis, 

 and eyeballs, as well as thoracic and abdominal viscera. In the 

 animals held at constant body weight (table 2) the visceral group 

 shows a progressive increase in weight of 3.1 to 20.6 per cent in 

 the five test series. 



The weight of the visceral group depends essentially upon that 

 of the larger organs. As will be seen later, however the individ- 

 ual viscera differ greatly in their changes in weight during the 

 thirst experiments. 



In the maintenance of the body weight by simple inanition, 

 Jackson ('15 a), in young albino rats, and Aron ('11), in young 

 dogs, found that the visceral group undergoes but little change in 

 weight. 



The 4'emainder' is that part of the body which remains after 

 removing the skin, skeleton, musculature, and visceral group. 

 It includes the adipose and interstitial connective tissue, mesen- 



