WATER EXCHANGES OF DOG 



33 



gram." It explicitly embodies a description of what takes place 

 to correct the organism's water content. All the processes simul- 

 taneously occurring may be collectively termed equilibration. 



Some features of the dog's equilibration diagram for water 

 are: (1) The curves have but one crossing, at which gains equal 

 losses. (2) After any departure from the water content at which 

 this crossing occurs, water contents tend to be restored to it. (5) 

 The slope of each curve represents an equilibrating increment, or 

 velocity quotient, of recovery either by gain or by loss of water. 

 (4) High net rates of exchange mean rapid recovery. (5) Com- 

 parisons of maximal and minimal rates for gain and for loss can be 



A lA 



^ ^ 



2 ■ 







O *2 



Total Water Load 



Fig. 14. Partitions or rates of water exchanges (% of Bo/hour) at various water 

 loads (% of Bo). Losses are taken from figures 7 and 12; gains are from figure 11 and 

 from the data of Straub (1899), Heilner ('07) and Lusk ('12), which indicate that rate 

 and R.Q. of oxidation, and hence the production of water by oxidation, all are approxi- 

 mately independent of water content both in negative and in positive loads. 



made. (6") The relative role of diverse paths at each water load 

 may be investigated (fig. 14). 



The partition of losses and gains among paths (fig. 14) is, of 

 course, provisional. At present, outputs by three paths have been 

 measured: urinary (sensible), evaporative (insensible), and fecal. 

 The output by the last is too small to be shown graphically. It is 

 noteworthy that in the dog evaporative exchange exceeds urinary 

 at negative loads. While evaporative loss diminishes slightly 

 where water conservation is greater, according to figure 12, this 

 fact fails to be properly represented in figure 14 because the values 

 recorded in figures 6 and 7 were transferred, instead of scaling the 

 evaporative losses to their proper controls at zero load. It may 

 be said with excellent approximation that the urinary fraction only 



