308 THE AMERICAN MONTHLY. [Oct. 



out and free the body, but they themselves perish. They 

 sacrifice themselves for the rest of the body as surely as 

 ever did soldier or philanthropist for the betterment or 

 preservation of the state. 



Thus I have tried to sketch in briefest outline some of 

 the phenomena or processes of life revealed by the mi- 

 croscope. Most of those discussed have come under my 

 own personal observation and are therefore to me par- 

 ticularly real and instructive. But to every one long 

 familiar with the microscope and with the literature of 

 biology, many other examples will occur, some of them 

 even more striking. This discussion has been confined 

 to the above also because it seems to me to show with 

 great clearness the way in which we can justifiably hope 

 to do fruitful work in "the future. This sure way it 

 seems to me is the study of structure and function to- 

 gether ; the function or activity serving as a clew and 

 stimulus to the investigator for finding the mechanism 

 through which function is manifested and thus give due 

 significance to structural details which, without the hint 

 from the function, might passed unnoticed. 



This kind of microscopical study, it seem to me, may 

 be well designated as Physiological Histology. It is in 

 sharp contrast with ordinary histology, in which too 

 often the investigator knows nothing of the age, state of 

 digestion or of fasting, nervous activity, rest or exhaus- 

 tion. Indeed, in many cases it is a source of congratu- 

 lation if he knows even the name of the animal from 

 which the tissue is derived. Such haphazard observa- 

 tion has not in the past, and is not likely in the future, 

 to lead to splendid results. If structure, as I most firmly 

 believe, is the material expression of function, and the 

 sole purpose of the structure is to form the vehicle of 

 some physiological action, then the structure can be 

 truly understood only when, studied in action or fixed 

 and studied in the various phases of action. 



