86 physiological regulations 



§ 25. Summary 



Variations of water content and of rate of water exchange in 

 the dog are indications of the latitude permitted in the regulations 

 of these quantities. Fluctuations outside the usual are opposed by 

 activities or processes that tend to restore water balance or flow. 

 Often the fluctuations found are not random in their sequences. 



Differences among successive values are influenced by durations 

 of period of measurement, numbers of individuals, conditions of ob- 

 servation, and other factors. From any one set of measurements, 

 however, accurate characterizations of regulatory activities, with 

 respect to water content or to rates of water exchange, are obtain- 

 able in terms of statistics of distribution. 



Variabilities of water content or exchange may be correlated 

 with variations in the environing conditions, and in states of the dog 

 both present and previous. Evidence exists especially in water 

 ingestion, as part of turnover, of long-time oscillations. The fluctu- 

 ations permitted characterize, equally with the mean position of 

 each content and rate of exchange, the ''normal" or balanced state. 



There is no evidence that during turnover water intake sets the 

 pace for water output or vice versa, or that one path of output 

 compensates for irregularities in another path of output. During 

 recoveries, rates of ingestive gain in water deficits are about equal 

 in variability to rates of total loss in water excesses. The variabili- 

 ties in usual individuals being known, unusual features of compen- 

 sations of water content in other individuals may be detected. 



This marks the end of the formal account of the water-time re- 

 lations of the dog. Even within the limited selections of variables 

 and of types of water loads the account is far from exhaustive. 



The dog's recoveries from sudden excesses of water and re- 

 coveries from deficits of water were studied in relation to amounts 

 of water load (± AW). Total exchanges, net exchanges, and par- 

 titioned exchanges were each covariates of load, their regressions 

 forming equilibration diagrams. The responses were evaluated in 

 terms of modification ratio, velocity quotient, tolerance, promptness 

 of modification, maximal rates, and completion of recovery. Sta- 

 tionary states of water load were similarly investigated. It was 

 found that excesses of water in the body were eliminated, almost 

 exclusively through the kidneys, at rates proportional to the load. 

 Deficits of water were dispelled by ingestion of amounts that were 



