274 



PHYSIOLOGICAL. EEGULATIONS 



ation is apparently as large in one species as among species. In 

 small species nearly all water turned over is therefore expended in 

 evaporation. Most of the diversity with body size is in the urinary 

 fraction. Fecal outputs become large only in large species ; these 

 species are ruminants, and all ruminants are large. Conversely, 

 few species not ruminants are eventually available for further 

 comparison within that range of body sizes. Man happens (accord- 

 ing to fig. 142) to put out the largest fraction of water loss as uri- 

 nary, being at a size between the energy evaporators and the 

 roughage eliminators. 



1.2 



■08- 



^04 



E 







-H 







Fig. 141. 



2 4 6 



Log Gm. Body Weii^h-t (B) 



Total quantity of water ingested and formed for each Calorie of food 

 ingested (and a suggested partition of it) in relation to body weight among diverse 

 species of mammals. The line corresponds to the empirical equation, gm./Cal. = 0.17 + 

 0.173 log B. The data are from table 20. The elephant consumes about 2.3 gm./Cal. 

 according to Benedict ( '36) ; this point (not shown) would be far above the line. 



Figure 138 relates rate of water exchange to body weight alone. 

 These are species that have turnovers ; it is only an inference that 

 species not yet measured will fit, within the present range of vari- 

 ations. Figure 141 includes rate of energy exchange, as well as 

 rate of water exchange and body weight. This is a mutual relation 

 among three quantities ; there is no evidence that one of the three 

 sets the pace for other one or two. It would be possible to add 

 further correlatives and in the end to build up an inclusive descrip- 

 tion of many relations to water exchanges among mammals, and 

 among some other restricted groups of animals. 



In this brief fashion I have tried to present certain materials 



