106 PHYSIOLOGICAL REGULATIONS 



one liter of water to drink and the urine excreted is measured in 

 hourly periods for 4 or 5 hours (fig. 51). Quite often no precau- 

 tions are observed as to whether the subject had opportunity to 

 be in water balance at the start. Hence if little of the water drunk 

 is returned, the individual may be either (a) in initial water deficit, 

 or (b) deficient in elimination. A deficiency of diuretic response 

 to the water drunk is usually presumed to indicate (bl) deficiency 

 of renal function. But it may indicate {h2) deficiencies in any 

 other parts of the metabolizing and mobilizing tissues. Hence 

 further tests are desirable to differentiate these states, such as the 

 duration of the same diuresis ; but here I am not concerned with 

 allocating the shortcomings between (hi) and (b5). State (b) can 

 be distinguished from (a) by repeating the test 3 hours after the 

 diuresis that results from the first administration of water. 



(2) The maximal rate of urine production after large inges- 

 tions of water appears to be a useful characterization of individ- 

 uals. This establishes either a single point or an equilibration 

 diagram, or a tolerance curve that can be compared with the ranges 

 occupied by other tolerance curves established after the same ini- 

 tial water loads. For instance, in individuals having an admin- 

 istered load of 4.4% of Bq, the fastest urinary output is found to 

 be 0.53% of Bo/hour, while other individuals excrete 1.10% of 

 Bo/hour (A, fig. 50). To eliminate that load, diuresis lasts about 

 12 hours instead of the usual 4 or 5 hours. 



(3) Further features of water recoveries may be compared by 

 coefficients that have already been defined, such as economy 

 quotient, ratio of modification, velocity quotient, and increment 

 returned. 



Future investigation will undoubtedly lend meaning to several 

 other quantitative characterizations within the four variables 

 studied. Tests are lacking especially in water deficits. This state 

 occurs unintentionally where there is some interference with volun- 

 tary water intake ; in which case the most sensitive test, ingestion 

 itself, cannot be used. Diminished urinary and evaporative losses 

 are hardly significant without controls in the same individual. 

 Additional indicators from outside the four variables then need to 

 be employed. 



For use, each quantity to be compared requires measurement 

 of variabilities. If the variability of one rate of exchange is as 



