400 TOKUYASU KUDO 



MATERIAL AND METHODS 



The albino rat (]Mus norvegicus albinus) was chosen for use in 

 this experiment. As the rat normally requires but little water 

 in its diet, it seems (like the pigeon) to be especially suitable for 

 thirst experiments. 



The material used in the present experiments included twenty- 

 five adult albino rats from the colony in the Institute of Anatomy. 

 Three died during the tests, and are excluded because the coagu- 

 lated blood from postmortem congestion might affect the weights 

 of the organs. Two additional females (one pregnant) are also 

 excluded from the tables for lack of adequate controls. The re- 

 maining twenty rats (table 1), which were killed and autopsied, 

 are all males except one. Twelve of these were from six litters of 

 known age (167 to 259 days). The other eight were stock rats 

 of unknown age. Four of the rats were used for normal controls. 

 They include the one female, which, however, is excluded in the 

 case of organs (suprarenals, hypophysis, and gonads) that show 

 a sex difference in weight. 



The rats had all been fed chiefly upon maize, and Graham 

 bread soaked with whole milk, with occasional fresh vegetables. 

 They were usually placed upon a maintenance diet of whole milk 

 and dry biscuit for some days before beginning the experiment. 

 The biscuit used in the experiments was the 'Old Grist Mill' 

 brand ('dog-bread') manufactured by Potter and Wrightington, 

 Charlestown, Massachusetts, according to Castle's formula, and 

 having approximately the following composition: 



per cent 



Moisture at 100°C 4.63 



Phosphates as tricalcium 6 . 73 



Crude fiber 0.58 



Proteids 15.40 



Carbohydrates, starch, sugar, etc 65.57 



Ether extract (fat, etc.) 7. 10 



Estimated calories per gram 4.6 



The test rats were weighed daily and individual records kept. 

 The temperature of the animal room was fairly constant at about 

 77° F. (range 65° to 80°). 



