440 TOKUYASU KUDO 



While no exact chemical determinations were made, it is evident 

 that the amounts of food consumed by the rats in these thirst 

 experiments are more than sufficient for maintenanance when 

 water is allowed at libitum. Under these circumstances, Jackson 

 ('15) found that rats of about 24 grams in body weight require for 

 maintenance only about 5 grams daily of Graham bread soaked 

 in whole milk; decreasing to about 3 grams later. Since a greater 

 amount of food was consumed by my rats on the thirst experi- 

 ments, it is evident that the prevention of growth is due to the 

 lack of water rather than to inanition from inadequate food- 

 intake. 



In the inanition experiments with water (Jackson, '15 a) the 

 amount of food required for maintenance of body weight in young 

 rats was found to decrease as the experiment proceeds. Simi- 

 larly in the present tests (as above shown) a decreasing amount 

 of liquid (milk) is required for maintenance with dry food ad 

 libitum, although the amount of dry food taken remains fairly 

 constant. 



The difference in the amount of milk required for maintenance 

 of body weight with the different kinds of food probably depends 

 (at least in part) upon the amount of water contained in the food. 

 In all cases, however, there is a decrease in the milk required as 

 the experiment proceeds. Jackson ('15 a) thought that in young 

 rats held at maintenance by underfeeding the amount of living 

 protoplasm is greatly decreased, thereby decreasing the basal rate 

 of metabolism, with a corresponding decrease in the necessary 

 food-intake. Possibly a similar explanation may hold in. the 

 case of the present thirst experiments. The metabohsm maybe 

 altered in some way so as to require less water for maintenance of 

 constant body weight. 



Both test rats and controls were killed by chloroform and dis- 

 sected according to the technique described by Donaldson ('15), 

 with a few modifications. The submaxillary gland and thyroid 

 gland were removed first. The parts and organs upon removal 

 were placed in a closed jar upon glass plates resting on moist 

 filter-paper. After weighing, the organs were dried to constant 

 weight in an oven at about 95°C. in order to determine their 

 water content (not included in this paper) . 



