EFFECTS OF THIRST — ALBINO RATS 405 



Chronic thirst. In the chronic-thirst experiments, seven rats 

 were used. Six (table 1) were fed upon dry biscuit ad Hbitum 

 with milk gradually decreased in amount, so as to reduce the 

 body weight about 1 per cent (of the initial weight) daily. They 

 were killed after an average of 50.6 (range 47 to 55) days (table 

 1) . These rats daily ate an average of 6.9 grams of dry biscuit and 

 9 grams of milk. The feces averaged 1.1 grams daily. One rat 

 (Sr. 3) ate a daily average of 6.7 grams of maize and 6.5 grams of 

 whole milk. Another rat (Si. 4) was fed with dry biscuit and 6 

 grams of milk daily. This rat took an average of 6.3 grams of 

 biscuit and passed an average of 1 gram of feces daily. In the 

 rats of the acute-thirst series, it was observed that those getting 

 5 grams of milk a day (that is, only a little less than in the chronic 

 series above) weakened rapidly and could live only about ten 

 days. It therefore appears that, under the conditions stated, 

 the water contained in about 6 grams of milk represents a critical 

 limit, below which the rats can live but a few days. 



In order to determine the amount of dry biscuit or corn re- 

 quired for maintenance, when water is allowed ad libitum, sup- 

 plementary experiments were made upon adult rats. It was 

 found that under these conditions about 13 to 15 grams of dry 

 biscuit or maize are required to maintain approximately constant 

 body weight for short periods. Jackson ('15) found that in adult 

 rats with water ad libitum a diet of Graham bread soaked in 

 whole milk and amounting to 10 per cent of the body weight 

 daily is not quite sufficient for maintenance. It is therefore evi- 

 dent that in the present experiments the food-intake was not 

 sufficient for maintenance, so that to some extent the effects of 

 general inanition are added to those of thirst. 



At the end of both acute and chronic thirst experiments, the 

 rats were killed by chloroform and the various organs and parts 

 carefully dissected and weighed. The technique followed is that 

 described by Donaldson ('15), with a few modifications. The 

 submaxillary glands and thyroid gland were removed first. The 

 blood is so thick during thirst that slight pressure upon the body 

 is necessary to obtain any appreciable flow even from the larger 

 vessels. The organs and parts upon removal were placed in a 

 closed jar upon glass plates resting on moist filter-paper. 



