106 Decomposition of Glucose and Mannitol &?/B. coli communis.. 



l^evertheless, the independent existence within the cell of enzymes (if ^by 

 definition such enzymes act independently of the hfe of the cell) has been, in' 

 the case of bacteria at least, rather a matter of speculation. 



It may be suggested here, however, that it is not necessary to isolate 

 from cells an unorganised material capable of bringing about a fermentation 

 in order to demonstrate that such a fermentation is brought about by 

 enzymes (unless such substances were defined as enzymes only provided 

 they could be isolated by the present means at our disposal). If an 

 enzyme is regarded as a substance capable of inducing fermentation inde- 

 pendently of the life of the cell, then there are two methods of demonstration 

 which serve to establish the existence of enzymes in any particular case- 

 without the necessity of separating them from the cell. The first method 

 consists in carrying out the fermentation under conditions which do not 

 support the life of the organism. The first part of the experiment described 

 in this communication very closely approaches such conditions. Here it 

 was shown that the amount of sugar decomposed during the rapid diminu- 

 tion in the number of living cells was as great as during that period where 

 the number of living cells was both at the start and the finish enormously 

 greater. 



The second method, it is suggested, of demonstrating without actual 

 destruction of the cell that the fermentation is brought about by enzymes, 

 depends upon the proof that the several fermentation phenomena are- 

 independent of one another. For if a series of functions of a cell are 

 absolutely independent of one another, some of them, at least, cannot be- 

 essential to the life of the cell. 



Both methods here referred to have found application in the experiments' 

 described in this communication, and, although the separation of the phases 

 of the fermentation was not absolute, either as regards complete absence 

 of living cells at any one time, or complete transformation of glucose in 

 one direction only, nevertheless taken in conjunction with the earlier work 

 of Harden and Penfold, and later of the writer, the present results leave- 

 little room for doubt that the several fermentation processes by means of 

 which B. coli communis brings about the decomposition of glucose and allied 

 substances are true enzyme actions, and are capable of acting independently 

 of one another, and thus breaking down the sugar in various ways. 



This conclusion is probably applicable to other cases of fermentation. 



In conclusion I would express my thanks to Prof. Auguste Fernbach for 

 his kind hospitality and for valuable criticism. 



