FERMENTS. 469 



are identical. Even the application of the definition of catalysis to 

 fermentation requires reflection. The ferment in such a case would 

 merely serve to accelerate reactions which were already in progress. We 

 would have to assume, for example, that albumin would be decomposed 

 hydrolytically at 37 degrees in an aqueous solution or suspension, although 

 the hydrolysis proceeds so slowly that we are unable to detect its progress. 

 The addition of pepsin-hydrochloric acid, or of trypsin, accelerates the 

 reaction to such an extent that we are able to recognize the hydrolysis in a 

 short time, on account of the appearance of cleavage-products. We can- 

 not deny that such an explanation is hardly satisfactory. It is not sus- 

 ceptible to direct proof, and leads to a forced assumption. It is not at 

 all clear why pepsin-hydrochloric acid should hydrolyze the albumin 

 molecule so much less and possibly in an entirely different manner than 

 trypsin does, or why the latter should split off definite amino acids so 

 much quicker than others, and furthermore leave certain complexes en- 

 tirely unaltered. We know, furthermore, that grape-sugar may be decom- 

 posed in various ways, which must be regarded as fermentation processes. 

 In butyric acid fermentation, it yields butyric acid, carbon dioxide, and 

 hydrogen : 



C 6 Hi 2 O 6 = C 4 H 8 O 2 + 2 CO 2 + 2 H 2 . 

 In lactic acid fermentation, it is decomposed as follows: 



O = 2 CHO. 



Finally, we know, that zymase splits it into ethyl alcohol and carbon 

 dioxide: 



C 6 H 12 6 = 2 C 2 H 5 OH + 2 CO 2 . 



The two latter processes are unquestionably pure fermentations. In these 

 cases, the ferment not only accelerates reaction already existing, but it 

 also determines the direction and progress of the same. The fact that the 

 ferments act in such a specific manner, i.e., only attack substances of 

 definite configuration, leaving other closely related compounds entirely 

 untouched, indicates very clearly that we cannot be satisfied with the 

 definition of Ostwald, at least as far as fermentation processes are con- 

 cerned. We cannot expect to understand perfectly the action of fer- 

 ments until we have become better acquainted with their chemical 

 composition. As long as we deal with them only as conceptions, we can 

 hardly expect to make any progress regarding the nature of their action. 

 We do not wish to underestimate the value of physical chemistry in this 

 direction; we merely wish to differentiate between those facts which we 

 can consider as proved, out of the numerous investigations of recent years, 

 and those results which are only based upon hypotheses. 



