224 



PHYSIOLOGICAL. EEGTJLATIONS 



On the whole, correlations between blood dilution and body load 

 of water become apparent when large loads are provided. They 

 are clearest for dilution of total substance in plasma {e.g., refrac- 

 tive index). Many dilutions are colligative, but with slightly 

 diverse ratios. The ratios here recorded indicate volumes of dis- 

 tribution of the water increment amounting to about half the body 

 weight. Further, dilutions are correlated with rates of urinary 

 output of water. Accordingly, blood serves as a distributor, 

 putting all other tissues in an equilibrium of water partition with 

 it, and also furnishes in its dilution a possible stimulus to kidneys, 

 mouth, and other organs, informing them what water content pre- 

 vails in the body. 



§ 81. CONCENTKATIONS OF URINE 



Urinary concentrations are closely related to the body's water 

 load (fig. 128). Since these relations are widely recognized, they 



1.06 



4- 

 O 



X 



1 1.04 h 

 o 



QJ 

 Q_ 



[00 



-4 +4 +8 



Total Water Load 

 Fig. 128. Specific gravity of urine in relation to total water load (% of Bo). 

 Dog, on constant diet. Each dot represents a separate day; in negative loads 3 individ- 

 uals deprived of water, in positive loads 2 other individuals given repeatedly water by 

 stomach. Each cross represents a mean sp. gr. for a one per cent interval of load. 

 Further data of Adolph ( '39a) and of Kingsley. 



are likely to be thought of as only qualitative. Actually a single 

 measurement of urinary specific gravity may do more to identify 

 the existence of a water increment than any other one measure- 

 ment, particularly if other measures are not already controlled by 

 a series of like data on the same individual. Quantitatively the 

 correlation is blurred by the fact that in all positive loads the 



