the groups and the concentrations were of the same order of magnitude as the con- 

 centrations found in other rodents, showing that there is no storage of waste pro- 

 ducts during water deprivation. 



Figure L 

 Desert rodents from different parts of the world. 



1. Gerbil from East Africa (From Buxton, 1923) 



2. Jerboa from Egypt (From Buxton, 1923) 



3. Kangaroo mouse, Nolomys. from Australia (From le Souef & Burrell, 1926) 



4. Kangaroo rat, Dipodomys from North America (From Scientific Monthly, 69: 180, 1949.) 



The third question was: Do the animals have a water storage that is gradually 

 spent during low water intake? To determine this the water content was determined 

 in animals that had lived on dry barley diet for varying periods of time. From Fig. 2 

 it is seen that the animals that had lived without water for 52 days had the same 

 average body water percentage as the animals that had been kept without water for 

 14 days only. There was no difference in percentage of body water between groups 

 of Heteromyids (kangaroo rats and pocket mice) on dry diet (barley alone) or wet 

 diet (barley and watermelon) while white rats and Neotoma (wood rat, family Crice- 

 tidae) had lower percentage of body water on dry diet than on wet diet. 



Since the kangaroo rats maintained on dry barley without water (1) show no 

 weight loss, (2) excrete all of their metabolic waste products and, (3) do not get a 

 decreased percentage of body water, we can conclude that the animals simply 



174 



