CHEMICAL FERMENTS. 585 



and rennet, for example, do not interfere with each 

 other at all. 



As to the mode in which the soluble ferments act, we Attempts to 

 can make no definite hypothesis. We may perhaps actionof the 

 suppose that the ferment acts as a carrier of the water ferments. 

 to be taken up ; that it, in the first place, takes up the 

 water itself, and then hands it on to the molecules which 

 are breaking up. Or, according to Bunsen-Hiifner we 

 may picture the contact and fermentative action by 

 supposing that the ferment, like sulphuric acid in the 

 formation of ether, has a greater affinity for certain 

 atoms or groups of atoms of the molecule which is being 

 broken up than the remainder has, and thus brings 

 about a new grouping of the atoms, after the com- 

 pletion of which it is again regenerated. Both these 

 hypotheses want the support of any actual demon- 

 stration that water is taken up, or that any such 

 combinations of the ferment occur. A third view, 

 put forward by Nageli, is closely allied to that last 

 mentioned, but also harmonises with the hypothesis 

 put forward by Nageli as to the process of fermenta- 

 tion, which will be referred to below; according to 

 this view the ferments do not themselves enter into 

 combinations, but only act on definite groups of atoms 

 by the condition of movement of their molecule s, and 

 thus cause a transformation and new grouping of the 

 elements. 



In whatever way the action of ferments may be Distinction 

 ultimately explained, it is clear that we have here to ac tion of 

 do with another kind of process than that which occurs 

 in the true fermentations. The ferments are soluble 

 chemical bodies, not necessarily united with living 

 organisms which are only able to set up hydrolytic 

 decompositions, while in the true fermentation com- 

 plex alterations of groups of atoms occur which 

 require the constant presence and the immediate action 

 of living organisms. The great difference in both 

 these processes is most clearly evident from a com- 

 parison of the external conditions which favour or 

 injure them ; the soluble ferments act best at a 



