OBJECTIONS TO THE GERM THEORY. 89 



contact-substances, and also by dilute sulphuric acid 

 and various other agents ; the amount of the chemical 

 ferments remains the same or becomes diminished during 

 the process ; the best temperature for their action is 

 about 60 C., and they are not affected by powerful 

 physiological poisons. In fermentation and putrefaction, 

 on the other hand, there is always a complex alteration 

 in the grouping of the atoms, a separation of carbonic 

 acid, and often of other atomic groups ; the number of 

 the causal organisms increases in proportion to the 

 intensity of the fermentation ; they are most active at 

 a temperature between 25 and 40 C., and their action 

 ceases under the influence of physiological poisons. 

 Thus the nature and action of the chemical ferments, 

 and of the fermentative organisms, are sharply separated 

 from one another, and a relation between them only 

 exists in so far as in the more complex fermentative 

 processes, and especially in putrefaction, both agents 

 are often at work in such a manner that chemical fer- 

 ments which are in part produced by the micro-organisms 

 lead to the solution of the fermentescible substance, and 

 so prepare the soil for its subsequent profound alteration 

 under the influence of the specific organised ferments. 



If, however, we assume with Liebig that in the latter 

 instance the transposition of the atoms in fermentation 

 and putrefaction occurs as the result of the action of a 

 ferment-like group of atoms which can only be produced 

 by living micro-organisms, and are practically bound up 

 with the life of the cells, we cannot regard this view as 

 an essential objection to the vitalistic theory; it is, on 

 the contrary, a recognition of it. This view corresponds Recognition o 

 entirely with the vitalistic theory in the immediate de- te Y r y talistic 

 pendence of the fermentative process on the life of the 

 yeast cells ; it only seeks to define more precisely the 

 mode in which the living cells occasion the decomposition 

 of the fermenting or putrefying substance. But the exist- 

 ence of such a ferment is a pure hypothesis, as is evident 

 from the fact that it has as yet been found impossible to 

 isolate the supposed ferment from the yeast cells ; this 

 failure being excused on the idea that the ferment is at 



