78 



PHYSIOLOGICAL EEGULATIONS 



In order that the variations found shall be clearly of physio- 

 logical significance, the deviations among control measurements of 

 each quantity recorded are appreciably less than the deviations to 

 be evaluated. This stipulation probably rules out all analytical 

 methods (2, above). The method of measurement is preferably 

 such as not to modify the general physiological state of the animal 

 without cognizance being taken of that fact ; this reduces the utility, 

 for instance, of method 5. 



Successive variations of water content and their statistical 

 parameters indicate in part what sort of ^'governor" controls the 

 diverse processes by which certain departures in content do not 

 persist. Each serves to characterize the maintenance of the dog's 

 water content as a whole, treating it as a specific project in hy- 

 draulic engineering. Some of the particular characterizations 

 suggested are : the coefficient of difference between successive body 

 weights at a series of time intervals ; and frequency of inversion in 

 the direction of change of water content, or reciprocally the mean 

 time that intervenes before each inversion or compensation ap- 

 pears. Additional numerical factors may easily be devised, each 

 adding to the completeness with which performance is evaluated. 



§ 23. Vaeiations of turnovers 



Rates of exchange that prevail in those states and conditions 

 selected as control ones likewise vary. The data to be mentioned 



-5 -4 -3 -2 



+1 '2 +3 



Water Con+en-fc 

 Fig. 44. Simultaneous variations of rates of water drinking and of body weight 

 (or water content). Water content is in % of Bq, zero of its scale being the mean of 

 the 27 values of body weight. Measurements were made in 24-hour periods on 27 con- 

 secutive days during which uniform food, containing additional 3.05% of Bq of actual 

 plus potential water, was consumed daily. Dog B', 18.0 kg. New data. 



