PROCESSES OF LIFE REVEALED BY THE MICROSCOPE. 391 



but they themselves perish. They sacrifice themselves for the rest of 

 the body as surely as ever did soldier or philanthropist for the better- 

 ment or the preservation of the state. 



Thus I have tried to sketch in briefest outline some of the phe- 

 nomena or processes of life revealed by the microscope. Most of those 

 discussed have come under my own personal observation, and are there- 

 fore to me particularly 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. The dis- 

 cussion 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 together; the function or activity serv- 

 ing as a clue 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 

 pass unnoticed. 



This kind of microscopical study may be well designated as physiolog- 

 ical 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 exhaustion. Indeed, in many 

 cases it is a source of congratulation if he knows even the name of the 

 animal from which the tissue is derived. Such haphazard observation 

 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 expres- 

 sion 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. 



Indeed, if one looks only for form or morphology in the study of his- 

 tology the very pith and marrow is more than likely to be lost. 1 



For example, if one wished to study the comparative histology of the 

 pancreas, and were to take pieces from various animals to be compared 

 without regard to their condition of fasting or digestion, he might find 

 the coarser anatomical peculiarities in each. In all probability he 

 would also find two dictinct structural types. One type with clearly- 



1 Although in a different field, the words of Osborn in discussing the unknown fac- 

 tors of evolution tire so pertinent that tbey may well be quoted: "My last word is, 

 that we are entering the threshold of the evolution problem, instead of standing 

 within the portals. The hardest task lies before us, not behind us. We are far 

 from finally testing or dismissing these old factors [of evolution], but the reaction 

 from speculation upon them is in itself a silent admission that we must reach out 

 for some unknown quantity. If such does exist there is little hope that we shall 

 discover it except by the most laborious research; and while we may predict that 

 conclusive evidence of its existence will he found in morphology, it is safe to add 

 that the fortunate discoverer will be a physiologist" [armed with a microscope]. 

 I would like to add the last four words. S. H. G. Am. Nat., May, 1895. 



