WATER EXCHANGES OF DOG 



27 



cally greater than usual. At each time, after a latency which is 

 related to absorption of the water from the alimentary tract, the 

 rate is proportional to the load. A family of curves of water 

 tolerance is thus described. Recovery of water content ensues 

 within a few hours ; it takes but little longer after large excesses 

 than after small. The urinary route is the only path of output 







-6 



+1 +^ +3 +4 +5 



To-tal Walter Load 



Fig. 9. Eate of total water output (% of Bo/hr.) within the first 1.0 hour after a 

 single administration of water by stomach, in relation to administered water load. Each 

 point represents one of the tests of figures 1 and 2. Data of Kingsley and Adolph. 



in which rates of loss are significantly modified during this recov- 

 ery, and through it nearly all of the excess is eliminated. All this 

 is what the dog does to compensate for having more water than 

 usual. 



§ 8. Deficits of water 



It seems natural to expect the dog to deal with water deficits 

 just as effectively as it deals with excesses. Initial states of water 

 shortage are established in the body by administering food which 

 is constant both in composition and in amount, but allowing with 

 it insufficient water for maintenance. After one to five days of 

 partial privation, with loss of body weight and of water content, 

 water is offered to the dog (Adolph, '39a). 



Promptly the dog drinks (fig. 10) amounts of water which on 

 the average slightly exceed the amounts of water shortage in the 

 body as judged from deficits of body weight. The weight is more 

 than restored for the time being, within 1 to 4 minutes from the 

 time water was first offered. Thus the dog closely matches its 

 deficit by its intake, without waiting for absorption of the water 

 drunk to ascertain whether it has enough. The mean rate of inges- 

 tion (SW/At) is initially enormous, and just as promptly falls to 



