458 TOKUYASU KUDO 



upon the exact accuracy of the figures shown in table 2, it is evi- 

 dent that, with respect to the changes in weight during the thirst 

 experiments, the organs may be divided into three groups. In 

 the first group, which includes hypophysis, eyeballs, kidneys, 

 suprarenals, spinal cord, skeleton, sciatic nerves, pancreas, alimen- 

 tary canal, liver, humerus and femur, visceral group and uterus, 

 there is a well-marked increase in w^eight during the maintenance 

 of constant body weight by thirst in young rats. As shown in 

 table 2, the rate of increase in the weight of the organs, in general, 

 is progressively greater in the longer periods. 



In the second group, which includes heart, brain, musculature, 

 and lungs, the organs remain nearly constant in weight. 



In the third group, including the thymus, ovaries, parotid and 

 submaxillary glands, 'remainder,' spleen, testes, epididymides, 

 thyroid, and integument, there is a marked loss in weight. This 

 loss appears in most of the organs already in the earlier test 

 periods and in some cases (thymus, thyroid) appears more or 

 less progressive in character. 



If we compare the changes in weight, as a measure of their rela- 

 tive resistance to thirst, in young growing rats with those observed 

 in adult rats during acute and chronic thirst (Kudo, '21), 

 it is found that in general there is in many cases a considerable 

 degree of correspondence. The hypophysis, eyeballs, skeleton, 

 and spinal cord increase in weight in the young rats and also show 

 marked resistance (slight loss in weight) in adults during acute 

 and chronic thirst. The brain in all cases remains nearly con- 

 stant in weight. 



The heart weight is nearly constant in the young rats and loses 

 nearly in proportion to the body during adult thirst. The thy- 

 mus, 'remainder,' salivary glands, spleen, testes, and epididy- 

 mides lose weight markedly during thirst in both young and 

 adult rats. 



In many other cases, however, the changes in organ weight in 

 the young differ materially in tendency from those in adult. 

 Thus the pancreas and liver have a marked growth tendency in 

 the young test rats, but lose heavily during adult thirst. Lesser 

 degrees of difference are observed in many other organs. 



