ENZYMES AND OTHER FERMENTS DIGESTION. IIQ 



logical explanation was of no value in accounting for the 

 changes produced by the active agents described as diastase, 

 pepsin, emulsin, etc. These, it was pointed out, are as truly 

 " ferments " as are yeast and the mother of vinegar. To 

 avoid confusion it became customary to speak of the organised 

 and unorganized ferments, or the insoluble and soluble fer- 

 ments. The term enzyme was later applied to these soluble 

 unorganized agents of change, but this new expression did 

 nothing toward explaining the difficulty or toward relating 

 the two classes of ferments. 



Certain scientists from the start, however, refused to admit 

 any fundamental difference between the work of the yeast 

 ferment on the one hand and that of bodies like diastase on 

 the other. Even after the biological theory of Pasteur had 

 become current Berthelot, Hoppe-Seyler and other chemists 

 of prominence maintained that the living cell ferments are 

 active because they secrete soluble or enzymic bodies. In the 

 one case the actual " fermentation " takes place within the 

 cell, as appeared to be the fact with yeast; in other cases en- 

 zymes are produced by cells and thrown off to do their work 

 elsewhere. This is true, for example, in the stomach where 

 certain groups of cells produce the active ferment pepsin which, 

 however, does its work of dissolving coagulated protein, or 

 digesting it, outside the cells themselves. In germinating 

 barley the living cells secrete diastase which may be leached 

 out and used to digest starch of other grains. If not leached 

 out the diastase gradually digests the starch of the barley ker- 

 nel itself, unless the action be checked by heat or other means. 



The Work of Buchner. In principle, therefore, the two 

 kinds of ferment action were held to be alike, but although 

 many attempts were made no chemist succeeded in isolating 

 the assumed enzyme from the active cells. Repeated failure 

 in this direction only served to strengthen the belief of the 

 advocates of the vital theory according to which alcoholic and 

 similar fermentations by fungi are processes which cannot be 

 thought of dissociated from the function of life itself. But 



