436 TOKUYASU KUDO 



It has been shown by various investigators that if young ani- 

 mals are underfed so as to prevent an increase in body weight, 

 changes nevertheless occur in various parts of the body. Some 

 organs remain nearly constant in weight, others lose, and still 

 others show a remarkably persistent growth in spite of the under- 

 feeding. Since for growth water is no less essential than food 

 (as demonstrated for the human infant by Meyer, '13), it is of 

 interest to determine whether similar changes occur in the organs 

 of young animals in which growth is prevented by a restriction of 

 the water in the diet. The present investigation was undertaken 

 for this purpose. 



The work was done in the Institute of Anatomy of the Uni- 

 versity of Minnesota. This opportunity is taken to express my 

 indebtedness to Dr. C. M. Jackson, Director of the Department, 

 for valuable aid and direction. 



MATERIAL AND METHODS 



The albino rat (Mus norvegicus albinus) was chosen as the most 

 convenient form for experiment. Postnatal growth norms for the 

 body and various organs are available for comparison (Donaldson, 

 '15). The changes in the weights of the organs have also been 

 studied in young rats during underfeeding (Jackson, '15 a; Stew- 

 art, '18, '19) and in adult rats on a dry diet (Kudo, '21). 



The material used in the present experiment included fifty-six 

 individuals in all. The forty-one survivors (from eight litters) 

 are listed in table 1. In the first column the letter (K) indicates 

 the series, the number preceding the decimal point designates the 

 the litter, and the number following is for the individual rat. 

 The letter "m" signifies male; "f" female. Litters K5, K7, K8, K9, 

 KIO, Kll, K12, K13, and K14 include, respectively, 4, 1, 5, 2, 

 8, 3, 5, 2, and 11 individuals. These include 17 males and 24 

 females, a total of 41. In addition 15 rats died during the test. 

 They are excluded from the tables because the coagulated blood 

 due to postmortem congestion might affect the weights of the 

 organs. 



In most cases the experiment began when the rats were about 

 four weeks of age. Some of the experiments began at the age of 

 three weeks (time of weaning), but most of these rats died. 



