CHOOSING PHYSIOLOGICAL VAEIABLES 433 



what controls the rainfall. The doctrine of anatomical, biochemi- 

 cal and mechanical controls is an ancient one, at least as old as the 

 location of emotion in the heart or thinking in the liver. Four 

 humours have been succeeded by sixteen endocrines ; the heart and 

 the liver by the adrenals and the brain. The present generation 

 laughs at only the humours. But the supposition is the same in all, 

 and has scarcely faded with what I believe are successive disappoint- 

 ments. For many physiologists, concrete thinking may be difficult 

 without, and may profitably employ, pictures of machinery. But 

 to suppose that the distribution of blood in a man is dictated hy a 

 head office seems to me as unlikely a view as to suppose that a school 

 of fishes has an appointed leader. 



"Many will discover in themselves a longing for mechanical 

 explanation which has all the tenacity of original sin. ... It is 

 easy to see how the demand for this sort of explanation has its 

 origin in the enormous preponderance of the mechanical in our 

 physical experience. But nevertheless just as the old monk strug- 

 gled on to subdue the flesh, so must the physicist struggle to subdue 

 this sometimes irresistible, but perfectly unjustifiable desire" 

 (Bridgman, '27, p. 47). "A law of science, however wide its scope, 

 does not go beyond a statement of the relationship or of the cause 

 of these facts. Now that mind of man is so constituted that this 

 ignorance of causes is to it a constant source of irritation ; we are 

 almost resistlessly tempted to pass beyond the mere statement of 

 law to erecting a theory of the reality that underlies the law" 

 (More, '13, p. 194). 



Of purpose there is no clear evidence in the study of regulations. 

 Many will insist that a pattern of equilibration bears the same evi- 

 dence of intention as a watch. Others will equally feel no such 

 inference. For, though equilibration may represent how an animal 

 recovers its content, it tells nothing of why it does so. 



Of origin of an innate pattern of regulations there is no informa- 

 tion, of course. Such a pattern may be coeval with the first animal, 

 and those who require to know where the first physiological regula- 

 tion arose can do nothing to retrieve a situation of which there 

 is no record. In the individual the development of constancy, of 

 equilibration, and of appropriate behavior has been described for 

 particular components. There is evidence that specific regulations 

 are acquired. 



Scientists wish to generalize before sufficient data have been 



