88 FERMENTS AND MICRO-PARASITES. 



according to this view are not the primary and immediate 

 cause of the decompositions of organic substances occur- 

 ring in fermentation and putrefaction ; on the contrary, 

 it was assumed that a transformation of the fermentescible 

 materials usually occurs at first from causes present in 

 the substances themselves by soluble chemical ferments, 

 and that it is only when the material has undergone a 

 certain amount of alteration that multiplication of those 

 organisms occurs, which on account of the wide distri- 

 bution of their germs always of course gain access to 

 these substances ; the nature and constitution of the 

 fermentescible substrata, and especially the first changes 

 that occur in it, determine what particular species of 

 organism chiefly develop and flourish. From that point 

 these organisms aid as a rule in the decomposition of the 

 substance ; but they are not absolutely necessary even for 

 its further splitting up, and the decomposition does not 

 go on by any means parallel with their development. 



On this view accordingly by far the most important 

 role is ascribed to the unorganised soluble ferments. 

 Lately we have become acquainted with a large number 

 of such ferments, and in accordance with this knowledge 

 the probability of their great activity in the ordinary 

 processes of fermentation and putrefaction seems to 

 increase. The action of diastase, of emulsine, of 

 myrosine, of the inverting ferment of yeast, of ptyalin 

 and pepsin, the energetic action of the pancreas, and of 

 the trypsin isolated from it, offered the most important 

 analogies, and the support of the " chemical" theory of 

 Differences fermentation. As a matter of fact the supporters of the 

 action 6 of th< germ theory have never disputed the influence and the 



ac ^ on ^ chemical ferments, but an exact analysis of the 

 the organised decomposition caused by chemical ferments on the one 

 ageiits^f hand, and of the marked alterations in fermentation 

 fermentation. and p U t re faction on the other, lead us of necessity to 

 the conviction that it is quite inadmissible to designate 

 these two processes as sufficiently analogous and similar 

 to warrant the inference that both are due to a similar 

 cause. The chemical ferments only set up hydrolytic 

 decompositions ; their place can be taken by so-called 



