Chapter X 



SOME OTHER CORRELATIVES OF WATER CONTENT 



(IN DOG) 



§ 77. The maintenance of water content has now been examined 

 in relation to water exchanges. Ordinarily a gradual turnover of 

 the body's water is occurring; extraordinarily one exchange (in 

 deficit the gain) augments while the other exchange (in deficit the 

 loss) often diminishes. Where separate exchanges are not ob- 

 served, net exchanges are still of the same character as where 

 simultaneous gain and loss were separately examined ; from which 

 I infer that the pattern is the same in both cases but is incompletely 

 visible in one. 



Perhaps the limitation of the study to water exchanges nar- 

 rowed the view as much as it intensified it. Are exchanges the 

 only processes that vary with water content? They seemed to 

 explain how content is maintained and restored; but many other 

 variables may or may not be equally concerned in water regulation. 

 The possibilities can be tested only by broadening the horizon. 



Beyond the intensive investigation of the relations among the 

 four sorts of variables within the water-time system, the inquiry 

 might be pushed out in any of a large number of directions. A few 

 topics that will be followed are : 



(1) Diverse correlatives of water content or load (chapters 

 X-XII) ; 



(2) Equilibration and variability of diverse components (chap- 

 ters XIV-XV) ; 



(5) Interrelations among components in balances and equili- 

 brations (chapter XVII). 

 These directions depend upon arbitrary choices, and there is at 

 present no evidence that thorough study of any other combinations 

 of variables would be less fruitful. The purposes in mind are to 

 see how precisely water balance and its regulation can be defined ; 

 and then to compare many regulations with that of water in order 

 to find how general the features of equilibration, regulatory be- 

 havior, and variability may be. 



Water content, which has been scrutinized particularly in rela- 

 tion to water exchanges and to time, is equally related to many 



206 



