Chapter IV 

 VARIABILITIES OF WATER RELATIONS (DOG) 



§ 21. Physiological regulation concerns the preservation of reg- 

 ularity in some property that might otherwise show larger changes. 

 It seems to me that a way to measure how much preservation occurs 

 is to ascertain how much regularity prevails. That task is accom- 

 plished by finding the natural distribution of physiological states, 

 or, more specifically, of diverse water contents. Any maintenance 

 of content or exchange may be regarded as the systematic preven- 

 tion of unusual states or contents. 



It may be realized that such a measure of regulation fails to 

 distinguish between what the organism does to preserve itself and 

 what the environment contributes. This realization is a part of 

 the discovery that the organism and its environment are insepa- 

 rable. The presence of water instead of liquid ammonia in the 

 animal body is a tacit recognition of the fact that the environment 

 lavishly aids in supplying water and does not abound in ammonia. 

 It seems to me quite inadequate to consider the anatomical bound- 

 aries of the organism as the boundaries of a physiological system ; 

 for the initiation of isolation is the end of the stationary state. 

 Even an excretory organ works in continuous reference to atmos- 

 phere and hydrosphere, whether or not the correlation between 

 them be one that is explicit in the reports of experiment. 



Suitable methods of characterizing whatever irregularities oc- 

 cur in the dog's water content are first required. Preferably the 

 distribution of contents is observed in a single individual at suc- 

 cessive equal intervals of time. Is the distribution random? What 

 parameters lend themselves to expressing it? 



<§> 22. Variations of water content 



The fluctuations of water content in the individual dog may be 

 analyzed like any other characteristic. Most methods of study 

 ask the blunt question, are the fluctuations random? And in what 

 respects are the fluctuations non-random? 



According to one definition, regulation is that portion of the 

 change in content of water that is non-random. It will shortly be 

 evident, however, that in many series of data on water content no 



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