396 PHYSIOLOGY 



have something in common in their methods of investigation; they 

 must employ the inductive method, and must strive to reach in their 

 results that degree of certainty which the nature of each individual 

 science permits it to attain. But the four divisions differ greatly from 

 one another; each one has its own subjects and laws and its own 

 problems, which have to be solved by methods peculiarly adapted 

 for each division. It is certainly clear to every one that it cannot be 

 the essential task of animal morphology to reduce itself to mineralogy 

 because it can be demonstrated that some anatomical objects con- 

 tain lime and other mineral substances. It seems to me it ought to be 

 also clear to every one that it cannot be the sole task, and not even 

 the essential task, of physiology to reduce itself to physics and chem- 

 istry because some or many of the living phenomena are governed 

 to some extent by known laws of physics and chemistry. Physiology 

 has to study the functional side of life, and in the attempts to eluci- 

 date its complex phenomena it certainly has to employ also the known 

 facts of physics and chemistry. But if we would confine the domain 

 of physiology to such parts only which can be interpreted by the laws 

 of physics and chemistry of to-day, we should have to give up nine 

 hundred and ninety-nine out of a thousand of the phenomena of life 

 as still inappropriate for physiological study. The four divisions of 

 the natural sciences are closely interwoven, and each one can, of course, 

 profit by the experience of the others. Boyle, Mayow, Priestley, 

 Lavoisier, and others attempted to unravel the nature of oxygen, 

 nitrogen, and carbon dioxide gas by the aid of experimental studies of 

 the physiology of respiration. The physicist or the chemist employs 

 any method which would help him to shed light upon his subject, but 

 physics and chemistry have methods peculiar to themselves, and that 

 is the secret of their great success. And so it should be with physi- 

 ology. However, when physiology broke away from medicine, it ran 

 into the arms of physics and chemistry, and is still largely there. The 

 early successes which have attended the new venture, which, by the 

 way, is the case with every new venture, led to the conception that 

 this is the most desirable, the most natural union. An analysis, how- 

 ever, of the work in animal physiology in the last few decades will 

 show the fact that the too great gravitation towards physics and 

 chemistry prevented the development in many directions of a purely 

 physiological character. 



I contend that physiology is an independent science with a clear 

 outline of its domain, but it ought to direct its declaration of inde- 

 pendence not only towards medicine, but also towards such exact 

 sciences as physics and chemistry. 



As to the standard of precision and exactness to be required of 

 physiology, let me say this. Certainly no physiological problem can 

 be solved with that exactness, with that absolute reliability which is 



