90 PHYSIOLOGICAL KEGULATIONS 



rate exceeds the control by double this deviation. The latency 

 varies from 0.3 to 0.7 hour (fig. 50). 



The maximal rate of water loss is regularly attained later with 

 large administered loads than with small (fig. 50). 



Completion of diuresis may be said to occur either (a) when the 

 rate of urinary water loss once more comes within ± 42 per cent 

 of the rates characteristic of control periods at the same hour, or 

 (b) when the rate decreases by less than it fluctuates in successive 

 periods of measurement. The times in hours required to complete 

 the diuretic response are related to the volumes administered 

 (AWc) by the equation tc = 1.3 + 1.0 AWe. Similar rules hold for 

 diverse fractions of unloading, such as, for the half-life of the 

 sensible water load. 



The volumes of water finally eliminated (returned) differ from 

 the volumes ingested by a constant positive amount, and not by a 

 uniform fraction of the initial load. Part of this volume of reten- 

 tion vanishes when a preparatory water administration just pre- 

 cedes the test. Three manners of computing the volumes elimi- 

 nated yield nearly similar returns : (a) total water loss, (b) urinary 

 water loss, (c) total or urinary water loss in excess of that elimi- 

 nated in equal control periods, either at some arbitrary time or at 

 completion of diuresis. If one must know how large a drink of 

 water can be disposed of in 3 hours, the first comparison is used. 

 If, however, the body is allowed unlimited time in which to adjust 

 its water content, the second or third might be preferred. Losses 

 by the several paths are found not to increase significantly with 

 water load. 



It has been previously concluded that all the water ingested by 

 a man in water balance is returned as excess urine by the time the 

 diuresis ends (Adolph, '21). The evidence now available is more 

 extensive and precise; from it (fig. 49) the conclusion appears to 

 be that in man as well as dog the urine that issues at rates above 

 control ones is significantly less than the water administered. 

 This may mean that some of the water drunk takes the place of 

 that which is being ''catabolized" or made available for excretion 

 from other sources. It may be supposed that the man or dog is 

 never '' saturated" but at best maintains himself in slight deficit, 

 and so retains small absolute amounts of the water ingested. 

 Other data (A, fig. 51) indicate returns in urine alone that equal 



