70 



accepting generalizations along this line, no matter how brilliant. 

 The amount of empirical information in this field is already be- 

 coming unwieldy, and nowhere else is the necessity of unifying 

 principles so plainly shown. Here it is that more definite chemi- 

 cal knowledge may in one stroke clear up the whole situation. 



If it is not possible to ascertain the chemical structure of a 

 single enzyme, how much more difficult then must it be to deter- 

 mine that of the living protoplasm ? It goes without saying, that if 

 we try to analyze the living protoplasm, in the ordinary chemical 

 sense, we kill it. This being the case, the student who is trying 

 to penetrate these difficult problems must have recourse to other 

 modes of attack. Therefore does he experiment with the effect 

 of agents which do not kill but merely stimulate the organism 

 or partially inhibit its functions and, by studying the nature and 

 products of the reactions produced, obtain in an indirect manner 

 clues to the real nature of life processes. The fascination of 

 these plunges into the unknown is perhaps hardly comprehensible 

 to those who are not engaged in the work, but all must admit 

 the importance of the end they have in view, namely to penetrate 

 a little further into the mystery of life. The advance in all these 

 fields is of necessity along the line of the mechanistic conception 

 of vital manifestations, that is, the reference of them to chemical 

 and physical laws. To appeal to a " Vital Force " is, as my 

 predecessors in these lectures have said, to appeal to an empty 

 name, a mere " question-begging epithet." It is obvious that if 

 we are to make any progress at all, we must admit of the possi- 

 bility of some solution that our senses can perceive, even though 

 we are perfectly willing to admit that the final answer may never 

 be reached. The reference of vital phenonema to a vague " Vital 

 Force" would mean the extinction of inquiry by robbing the in- 

 vestigator of any sense of responsibility for adequate explanations 

 of the results of his researches. 



( 7o be continued. ) 



