432 PHYSIOLOGICAL. REGULATIONS 



phenomenon to others, the investigator entertains various senti- 

 ments, hunches, and hypotheses. Emphatically there are many 

 ways of consciously (as well as unconsciously) visualizing nexuses 

 between a first observed fact and a second. Investigators are not 

 limited to tracing origins, or to imagining causes, or to seeking 

 analogies or to following communication lines ; many paths of 

 progression exist other than those postulated. Visualizations of 

 nexuses are important chiefly in moving the mind along, in inducing 

 the investigator to look for something ; seldom are they indispens- 

 able in the final contribution. 



Of mechanisms in the restricted sense, just as much information 

 appears to be given by descriptive physiology as by other hy- 

 potheses of relation. For, mechanically minded physiologists em- 

 phasize, it appears, the chemical intermediaries, the anatomical ele- 

 ments, and the physical categories that are correlatives in each 

 body of relations. In the broader sense, all correlations indicate 

 mechanisms (categories), and are equally explanatory. 



Of causes there is regularly more hope than realization. One 

 relation is exalted while the rest are ignored. An engineer does 

 not designate any one part or one process of a machine as the 

 cause of its functioning; he regards most or all of its parts and 

 arrangements as indispensable. Physiologists say they regard 

 a living machine similarly, and behave quite otherwise. When one 

 part of a machine is missing or damaged, its replacement, if leading 

 to restoration, may be spoken of as the cause of the dysfunction. So 

 there may be causes of failure but hardly causes of success. ''Our 

 grand foible turns out to be . . . the facile and hasty reference 

 of natural phenomena to mystical bogus entities, or to emotionally 

 associated and whimsically selected 'causes' (Wheeler, '28b, p. 

 xxiv). 



' ' In studying the interaction between oxygen and carbonic acid, 

 it is of the first importance not to regard the change in one sub- 

 stance as cause and the change in the other as effect. If we think of 

 our terms mathematically as variables and functions, the difiiculty 

 does not arise. This error is an example of one of the most fam- 

 iliar and one of the most natural of fallacies and it was responsible 

 for the long delay in reaching an understanding of carbonic acid 

 transport" (Henderson, '28, p. 82). 



To suppose that a physiological regulation is managed by a 

 director or a lever is probably in the same category as to decide 



