Chapter V 

 WATER RELATIONS OF MAN 



§ 26. As the physiological pattern of the dog with respect to 

 water exchanges has been described, so it is possible to character- 

 ize quantitatively the water exchanges of man. In early crude 

 studies it was implicitly supposed that all mammals are alike and 

 that approximate facts about one species would hold for all. Now, 

 it is easily demonstrated that the similarities, extensive though 

 they be, do not extend to all characteristics of water relations. In 

 fact, it becomes apparent that precision of description differen- 

 tiates species and individuals physiologically with respect to these 

 very characteristics. One description, even when thorough, can- 

 not suffice for two descriptions. Descriptions of two or more 

 species allow the identification of uniformities as distinct from 

 diversities. 



Does a man compensate for disturbances of water content just 

 like a large-sized dog? Does identity of organs of exchange mean 

 that functions are quantitatively alike? If not, are the rates of 

 water exchange correlated with other differences between the 

 species? 



Proceeding with the investigation in somewhat the same man- 

 ner for man as for dog, I analyze analogous data on water ex- 

 changes. At first the data are restricted to the same four kinds 

 of variables (water content AW, water exchange SW/At, time t, 

 and velocity quotient 1/At). The responses are described follow- 

 ing single ingestions by mouth, repeated ingestions by mouth, and 

 desiccations by privation. From these, an equilibration diagram 

 is obtained. 



§ 27. Single ingestions by mouth 



Tolerance curves (fig. 49) for excesses cover longer times than 

 in the dog. Or, in the larger species the half -life of the water load 

 is greater. The curves are little modified when alimentation and 

 absorption (see fig. 62) are taken into account. 



The coefficient of difference in rates of total water loss between 

 successive control periods of 1.0 hour each is ± 13 per cent of the 

 mean rate or ±: 0.020% of Bo/hour, and in rates of urinary excre- 



88 



