410 PHYSIOLOGICAX, REGULATIONS 



empirical until the mechanisms of regulation are understood" 

 (Adolph, '33, p. 349). Evidently a non-statistical kind of signifi- 

 cance is referred to in the statement of C. Y. Cannon et al. ('32) 

 that "If these results could be explained or predicted, reasoning 

 from a physiological basis, they would be highly significant. Since 

 no good physiological explanation can be made, the level of sig- 

 nificance secured is only great enough to warrant further test." 

 Wishing to find in what manner the activities of the organism are 

 knit together, I do not think it desirable to suppress knowledge of 

 any relation that comes to light. 



Were no other connections visible, body size alone would require 

 that water content, water turnover, heat exchange, total substance, 

 heart frequency, and many other quantities are related in the way 

 they have been ascertained to be. They need no common organ of 

 exchange or common physical characteristic to fix them at those 

 particular rates. In attempting to ''explain" those observed cor- 

 relations, one theory suggests one connection where a hundred 

 probably exist. Experience teaches, I think, that biological rela- 

 tions usually have too many factors to allow identification of pre- 

 dominant or causal ones even if such exist. 



Having decided that any two kinds of measurement made simul- 

 taneously upon one living unit may be usefully correlated, I might 

 now analyze any of a semi-infinite variety of investigations. It 

 seems appropriate to mention several that concern the component 

 water, with which the present work started. Each will illustrate a 

 system of variables manifesting an interrelation among compo- 

 nents that are being simultaneously handled by a living unit. 



(1) In the dog, the continuous infusion of 1.1 M solution of glu- 

 cose induced marked losses of water (experiments of Wierzuchow- 

 ski, '36). The urinary outputs of water and of glucose were mea- 

 sured during 6 hours of infusion, when for each gram of glucose 

 retained about 24 grams of water were depleted. At the same time 

 exchanges of oxygen, carbon dioxide and some others were ascer- 

 tained, allowing interrelations to be established among 18 com- 

 ponents. 



(2) In the dog in water loads, measurements of concentrations 

 of diverse variables in blood have been presented (figures 126 and 

 117). Each variable may be designated as a distinct component, 

 and in reality the data already used in other connections are now 

 available for comparisons among components. Indeed, table 24 



