82 PHYSIOLOGICAL KEGULATIONS 



first correlation, output is modified after intake has changed ; in the 

 second, intake is modified after output has changed. Separation in 

 time is also no guarantee that one determines the other. 



The variation found in any one individual that is maintaining 

 water balance is to be related to the form of the equilibration dia- 

 gram (fig. 29). Any departure of water content from the usual 

 involves a load, and a load inevitably means a rate of intake unequal 

 to rate of output. The variability found is an expression of the 

 occurrence of each load ; some minimal departure from balance ap- 

 pears before measurable steps for its correction go into effect (fig. 

 47). Thereafter the rate of the correction (recovery) depends upon 

 the difference between rate of intake and rate of output. If a large 

 difference of rates (large net rate) occurs at a small load, it pro- 

 vides a rapid means of recovery, a deterrent to variations of con- 

 tent. Quantitatively, the standard difference at hourly intervals of 

 time (fig. 45) is 0.098% of Bq. At loads of ± 0.098% of Bo the 

 economy quotients (rate of intake/rate of output) are 1.4 and 0.7 

 (compared with 1.0 at balance) as inferred by interpolation upon 

 the diagram (fig. 47, C) for the physiological maintenance of water 

 relations of a dog under the conditions specified. Variation of con- 

 tent and equilibration of content are two aspects of maintenance, 

 showing what does not happen and what does happen, respectively, 

 when the water content is near balance. 



The avoidance of extreme rates of exchange has been studied 

 with respect to certain other components and species by Gasnier 

 and Mayer ('39). They defined several useful measures of con- 

 stancy in turnover, (l) Precision is the ratio of gain to loss in a 

 chosen period of time. Here this ratio is termed economy quotient. 

 (2) Fidelity is the difference (latitude) between largest and small- 

 est precision, or presumably any other measure of distribution of 

 precisions. (5) Sensibility is the percentage of successive observa- 

 tions of rate between which the sign of the difference has changed 

 (inversions have occurred). (4) Rapidity is the shortest interval 

 of time at which the gain most usually equals the loss, or over which 

 the precision is near to 1. These are ready methods other than first 

 differences of working with data upon variability of exchanges in 

 dogs that are maintaining water balance. Each of the four might 

 be illustrated from the data of figures 44 and 45. Each term has 

 here a specific definition that may not be confused with some other 

 definition or connotation of the same word. 



