246 



PHYSIOLOGICAL, REGULATIONS 



(not whole blood), are demonstrable as averages, while any single 

 individual or determination may fail to register any. Every incre- 

 ment involves one measurement in a control state and a second 

 measurement in a loaded state. The ideal diagnostic procedure is 

 one that does not need the first, for rarely is the diseased individual 

 available then. Hence a great variability must be recognized in 

 control states, and a greater one is loaded states; and only the 

 coarsest increments of water content can be recognized with high 

 probability from the specific gravity or refractive index of plasma. 

 More reliance can be placed in simultaneous determination of a 

 volume, a plasma concentration, a rate of salivary flow, a metabo- 

 lism, a clearance, and a rate of water exchange. Then the role of 

 variability in each is mutually minimized; the characterization of 

 a state of water load is laborious yet certain. 



§89. Frog 



Frogs differ from mammals in containing higher proportions by 

 weight of water, and probably much larger and more variable vol- 

 umes of interstitial fluid. The distributions of excesses and defi- 

 cits of water may therefore prove to be very different in them. For 

 present purposes all species of Rana are treated together ; nearly 

 all the measurements at hand were made upon frogs suddenly 

 killed and sampled. 



Volumes of tissues are compared in control and in partially 

 desiccated individuals, each being measured as a fraction of the 

 original body weight (table 26). That the losses represent deple- 

 tion of water alone was ascertained in a third group of frogs that 



TABLE 26 



Distribution of water losses among tissues of 10 frogs (mean Bg, 4S.S7 gm.) desiccated 



by - 42.1 per cent of Bg and separately analyzed. Data of Smith 



and Jackson {'31) 



Tissue 



%of 

 body in 

 controls 



%of 



tissue 



weight 



lost, AV 



%of 

 whole 

 body's 



loss 



% water found by 

 analysis, 100 E/F 



Control 



Desic- 

 cated 



% water 

 lost, 

 A/D 



Whole body 



Muscles 



Skin 



Skeleton 



Liver 



Stomach + intestine 



Blood 



"Lymph spaces" ... 



-43.5 

 -30.0 

 -35.0 

 - 0.4 

 -14.4 

 -39.6 

 -51.3 



