GENERAL DEFINITION OF FERMENTATION. 23 



merit special mention in this place, because they brought our 

 ideas into closer harmony with the ferment theory, at least so far 

 as regards the ammoniacal fermentation of urine. Moreover, they 

 have greatly strengthened the position of the ferment theorists 

 by proving that this urase cannot be placed amongst inorganic 

 chemical substances, in the ordinary sense of the term, but is 

 really an intermediate stage between these and living protoplasm. 

 Miquel goes so far as to say that his urase is actually protoplasm, 

 chiefly differing from that of the cell contents in that it dispenses 

 with the protection of the cell- wall, and remains and works on 

 the outside. 



The reader desiring fuller information on the properties of the 

 enzymes than can be obtained from the present work is referred to 

 the comprehensive treatise published by E. BOURQUELOT (I.) in 1896. 



19. General Definition of Fermentation. 



We will now pass in review all the preceding explanations, 

 and attempt to extract from each of them whatever can possibly 

 afford us assistance in finally arriving at a satisfactory definition 

 of the term fermentation. In the first place, Liebig's explanation 

 certainly does not call for further consideration in this connection. 

 In the results of the remaining researches we find one factor 

 common to all, and that is the certainty that, for the inception 

 and continuance of the process, which in harmony with the 

 limitation expressed in i we have hitherto entitled "fermenta- 

 tion," the presence and active collaboration of low types of living 

 organisms is a prime essential. Concerning the nature of the 

 influence, whether direct or indirect, of these organisms, opinions 

 are, however, divided. 



If, now, the instigators of fermentation be examined seriatim 

 according to the method outlined later on, it will be found that 

 not only are they vegetable, but also that all belong to the same 

 class, and that, too, the lowest in the vegetable kingdom, namely, 

 the fungi. The power of inciting fermentation is, however, re- 

 stricted to comparatively few of the genera of. this class. Never- 

 theless, these latter are so intimately connected with the others, 

 from a botanico-morphological point of view, that it is impossible 

 to classify the fungi into two sub-groups, characterised by the 

 presence or absence of this faculty, without introducing serious 

 systematic anomalies. 



The limitation that can be given to the definition of fermenta- 

 tion may be thus expressed: "Fermentation is a decomposition 

 effected by the vital activity of fungi." Nevertheless, as is evident 

 from what has already been intimated, no greater precision can at 

 present be imparted to such part of this definition as refers to the 

 nature or mode of action of the ferment. On the other hand, 

 as will soon be apparent, the word " decomposition " must give 



