WATER BALANCES AND EXCHANGES 291 



(7) Time relations and rates of recovery may be similar even 

 though paths and structures employed are diverse (fig. 111). 



(8) Rates of water exchange are faster with larger increments 

 than with moderate ones. But the total times occupied in recovery 

 (and the velocity quotients) are nearly independent of increment. 



(9) The amounts of water returned before the control rates of 

 exchange again prevail, do not exceed the water loads administered 

 (figs. 1 and 49), when compared with equally timed control 

 individuals. 



(10) Recovery is faster, and often more prompt, in negative 

 increments of water than in positive (fig. 106). 



(11) Species or units that eliminate excesses rapidly, also pro- 

 vide for restoring deficits rapidly. Though diverse organs be con- 

 cerned in gain and in loss, the two are proportioned to each other. 



(12) Tolerance curves are usually such that net exchanges are 

 most rapid in the early portions of recovery, diminishing as loads 

 are discharged. Most loads are therefore exponential with time. 



(13) High rates of turnover accompany high variabilities of 

 water content at successive times (table 12). 



(14) Intake by mammals is usually more variable in periods of 

 hours than in periods of days. Output, however, is equally variable 

 in periods of diverse durations (table 12). 



(15) No one kind of change other than augmentation of water 

 exchanges, is known to occur in all organisms studied, in invariable 

 correlation with increments of water content. 



(16) But in vertebrates, for instance, certain changes of com- 

 position, rates of other exchanges, activities and behaviors are 

 found to accompany water increments under specified conditions 

 (table 29). 



(17) Maximal rates of urinary output are nearly proportional 

 to body weight, among the species of vertebrates studies (table 13). 



(18) Evaporative loss is a larger fraction of total loss in small 

 mammals than in large ones. Oxidative gain is a larger fraction of 

 total gain in small mammals than in large ones. 



(19) Rates of exchange of water are among many animals pro- 

 portional to the 0.6 to 1.0 power of body weight (figs. 133 to 140). 



(20) In mammals in which turnovers in water balance have been 

 measured, the maximal rates of intake or of output observed (fig. 

 138) are 20 to 30 times the rates of turnover in the respective 

 individuals. 



