CHOOSING PHTSIOLOGICAL VAKIABLES 431 



be a hypothesis, it is the minimum, others being added thereto when 

 the data are given any "interpretation," or designated as having 

 some particular kind of connection with one another. I believe 

 descriptive methods make it easier to distinguish hypotheses from 

 facts. It even seems possible that "Description is the method of 

 most use in biology" (Just, '39, p. 10). Certainly "description 

 by no means opposes experiment, it calls for it. ' ' 



Occasionally it is said that descriptive propositions have no 

 human interests. Actually, however, men {e.g., Galileo) suffered 

 martyrdom for them; whether the earth or the sun was the 

 spatial center of rotation of the other, was ascertained by quanti- 

 tative description. The fact, when demonstrated, precipitated 

 great conflicts of men 's sentiments and concepts, for plain equations 

 of relations aroused intense feelings. 



I have tried to make clear that an explanation of physiological 

 regulations consists in the rules according to which organisms 

 maintain constancies. Some scientists think explanations can only 

 come from imagining hidden "mechanisms"; others find abstrac- 

 tions from relations among data more illuminating. It is impor- 

 tant not to suppose that either procedure has a monopoly; and 

 important not to expect the first kind to be used in a work devoted 

 to the second. No one has, I believe, really found mechanisms of 

 regulations of a causal nature such as are often subsumed. Until 

 they are found, explanations of regulations rest upon those concrete 

 forms of physiological relations in organism which have been here 

 described. 



§ 155. Other modes of procedure 



An understanding of the place of quantitative description may 

 be furthered by comparison of how physiologists behave with de- 

 scription in view and of how they behave with other kinds of think- 

 ing in its place. 



Hypotheses are intellectual means of avoiding randomness in 

 inquiries, of building up interest, and possibly of increasing the 

 chances of finding correlations other than zero. Some of the com- 

 mon hypotheses of relation among biological data may be classified 

 as follows : mechanism, cause, purpose, origin, analogy, intermedi- 

 aries, interaction. These terms overlap, and are diversely under- 

 stood among physiologists that use them. 



In choosing the direction in which he shall progress from one 



