24 PHYSIOLOGICAL REGULATIONS 



tional to body weight, being about 62 per cent of it, in the intact 

 dog (see table 18). A 1.0 per cent load or increment (± AW) as 

 based on body weight, is therefore a 1.6 per cent increment in body 

 water. 



Loads of water may be classified (fig. 5) into: 



(1) Total Load = Excess body weight, CDD' 



(2) Sensible Load = Excess administered, minus urine ex- 



creted, CEE' 



(3) Administered Load = Excess administered, C 



(4) Absorbed Load = Excess administered and not in the ali- 



mentary tract, AA' 



(5) Absorbed Total Load = Excess absorbed, minus amount 



lost judged by body weight, BD' 



(6) Absorbed Sensible Load = Excess absorbed, minus urine. 



excreted, BE' 



It might be considered poor technique to employ a large number 

 of types of water load. In reality the number studied is the small- 

 est number suitable for the purposes in hand. In the course of 

 study it is poignantly observed that several confused variables are 

 easily and usually thrown into a single category by virtue of 

 having the same dimensions or names. The distinction of varie- 

 ties of water contents may be a step toward clarity and precision 

 in the study of the physiology of water. 



The tolerance curves shown above are approximately confirmed 

 in unanesthetized dogs by less complete data of other investigators 

 (Falck, 1872; Molitor, '26a; Rioch, '30; Abe, '31a; Hatafuku, '33a; 

 Theobald, '34; Pickford, '36; Rydin and Verney, '38). 



Now I have described what happens to loads and rates of ex- 

 change in the course of time. By correlating the ordinates of 

 figure 2 with the simultaneous ordinates of figure 1, I compare 

 rates of water elimination at diverse contents of water in the body. 

 The course of each test or set of tests may be followed on the new 

 coordinates (figs. 6 and 7). If corrected for absorption (fig. 8), 

 only the early portion is modified. At any one time after the 

 initial 0.5 hour (fig. 2) the rates of water loss increase with the 

 excesses present. During a chosen interval of total elapsed time 

 this is also true (fig. 9). After a while a maximal rate of excre- 

 tion is attained, and thereafter at any one load (fig. 6) the rate of 

 excretion is roughly independent of time. I believe it is signifi- 



