118 PHYSIOLOGICAL REGULATIONS 



Hence, maintenance of water content may be regarded as the 

 resultant of fluctuations in two paths of exchange, imbibitory gain 

 and urinary loss. Within periods of one hour no adjustment of 

 rate of gain to rate of loss is evident, but in successive hours rates 

 of gain compensate one another. In 24 hours, variation of body 

 weight is only thrice as great as in one hour, indicating that adjust- 

 ments of rates of one exchange to those of the other have intervened 

 to limit the variation found. 



§ 39. Some other types of water load 



Frogs have been subjected to water loads in several diverse 

 ways. What is the course of recovery in those other physiological 

 states and environmental conditions? 



(1) Frogs that are pronounced dead, if the criterion of sur- 

 vival be a subsequent muscular activity, gain water at the same 

 rates as living ones. This is the case both near water balance 

 (Brugsch et al., '28) and at extreme water deficits (fig. 66). Yet 

 the rates at those two water contents differ by a factor of 8, as 

 though the machinery of intake is modified in spite of the concur- 

 rent failure of some other activities. Sudden stoppage of the cir- 

 culation without other immediate injury (Adolph, '31b) likewise 

 indicates that movement of the blood is not necessary in ordinary 

 water exchanges. 



(2) Frogs that are kept out of water while provided with vari- 

 ous water contents may also be compared (Adolph, '39b). From 

 deficit no recovery occurs even in air saturated with moisture; 

 instead a very slow loss by evaporation continues (which is inde- 

 pendent of water load), the frog being slightly warmer than the air 

 (Adolph, '32). Urinary loss is almost zero after the frog has been 

 out of water for two hours. Since gain by oxidation is smaller 

 than the slight continued loss of water, even in deficits water bal- 

 ance is never precisely maintained. 



From water excess recovery is by diuresis only (fig. 71). The 

 excess, administered by sudden intraperitoneal injection of distilled 

 water, is to the inside of the frog seemingly the same as in the stand- 

 ard (immersed) conditions ; yet the diuresis is much smaller. Urine 

 forms at less than half the rates that prevail in frogs immersed in 

 water that have similar loads (fig. QQ) ; but due to the fact that 

 water also enters the immersed frogs, the net recovery by the frogs 

 in air is slightly more than half as fast. Hence with the stoppage 



