VARIABILITIES OF WATER RELATIONS 



83 



Departing from conditions that I chose to regard as standard 

 ones, I may measure variations in water content when the total 

 exchange, (turnover) of water is enhanced, as in physical exercise 

 (fig. 48). It appears that water is not only more liberally ingested, 

 but more exactly restores the body weight, in a hot climate than in a 

 cool one. In other words, a high turnover now maintains more uni- 

 form contents than a lower turnover. In a like manner a variety 



6 



Water Load 



Fig. 48. Simultaneous fluctuations in rates of water drinking and in water load 

 (or body weight, in % of Bo) in a dog (16.0 to 18.9 kg.) walking on leash in two 

 tests in different climates and drinking ad libitum after each 1.5 hours. In the hot 

 desert the dog made up 96 per cent of the total weight losses by concurrent drinking; 

 in the cool climate 63 per cent. Data of Dill et al. ('33). 



of conditions might be studied; in each one the constancy with 

 which water content is maintained would be ascertained quantita- 

 tively. It is still unknown whether the variability of water ex- 

 changes increases with the variability of the environment. Similar- 

 ities and differences among individuals in any one set of conditions 

 also remain to be found. 



In rating the accuracies (fidelities) of maintenance no assump- 

 tion is implied as to whether the dog functions ''better" by having 



