218 



SCIENCE. 



[N. S. Vol. II. No. 34. 



the nervous system were to be studied 

 comparativeljr, and the tissue taken from 

 one animal after refreshing sleep and rest, 

 from another after exhausting labor, an- 

 other in infancy, and another from an ani- 

 mal decrepit with years, the difference in 

 general appearance and in structural de- 

 tails would be striking enough to satisfy 

 any morphologist that, as with the struc- 

 ture of the pancreatic cells, there were two 

 or more distinct types ; but the physiological 

 histologist would recognize at once that the 

 differences so much insisted upon repre- 

 sented different phases of activity, and, as 

 with the pancreatic cells, might be all rep- 

 resented in the same animal at different 

 times. 



I would be far from saying that there are 

 no structural differences in the different 

 animals independent of any particular 

 phase of functional activity; but if these 

 only are sought and the others neglected, 

 the physiological appearances will often ob- 

 trude and confuse, if they do not utterly 

 confound. 



I have therefore for the last ten years 

 urged my students, and mean to go on ad- 

 vocating with all the earnestness of which 

 I am am capable, that, in studying an or- 

 ganism or its tissues, the investigator, to 

 gain certain knowledge, must know all that 

 it is possible to learn concerning the age, 

 health, state of nervous, muscular and di- 

 gestive activity ; in fact, all that it is possi- 

 ble to find out about the processes of life 

 that are going on and have gone on when 

 the study is made. 



Fortunatelj% there are some microscopic 

 forms in which the entire study can be 

 made while the creature is alive. With 

 the higher organisms also some of the liv- 

 ing elements, as the white corpuscles, can 

 be studied and their various actions and 

 structural changes observed for a consider- 

 able time. Most of the tissues of the higher 

 forms, however, cannot be thus studied. 



and the best that can be done is to fix the 

 different phases of action, as by a series of 

 instantaneous photographs, then with a 

 kind of mental kinetoscope put these to- 

 gether and try to comprehend the whole 

 cj'cle. 



Fortimately for the histologist the inces- 

 sant experimentation of the last twenty-five 

 years has brought to knowledge chemical 

 substances which do for the tissues the won- 

 der that was ascribed to the mythical Gor- 

 gon's head — to kill instantly and to harden 

 into changeless permanence all that gazed, 

 upon it. So the tissues maj' be fixed at any 

 phase, and then studied at length. If then 

 the investigator observes and keeps record 

 of every point that may have an influence 

 on the structural appearances, whether 

 shown by experience or suggested by in- 

 sight, and this record alwaj's accompanies 

 the specimen, thus and thus only, it seems 

 to me, can he feel confident that he is lia- 

 ble to gain real knowledge from the study, 

 knowledge that represents actuality and 

 which will serve as the basis for a newer 

 and more complete uni-aveling of the intri- 

 cacies of structure, an approximate insight 

 into the mechanism through which the life 

 energj' manifests itself 



And so, with all the light that physics 

 and chemistry can give, commencing with 

 the simplest problems and being careful 

 that everj' factor that can influence the re- 

 sult is being dulj' considered, the microsco- 

 pist can go forward with enthusiasm and 

 with hope, not with the hope that the great 

 central question can be answered in one 

 generation, perhaps not in a thousand, but 

 confident that if each one adds his little to 

 the certain knowledge of the world, then in 

 the fullness of time the knowledge of living 

 substance and the life processes will be so 

 full and deep that what life is, though unan- 

 swered, may cease to be the supreme ques- 

 tion. Simon Heney Gage. 



CoENKLL University. 



