SOLUBLE FERMENTS OR ENZYMES. 497 



THE SOLUBLE FEEMENTS OK ENZYMES.* 



By Professor EDWIN O. JORDAN, 



UNIVERSITY OF CHICAGO. 



IT has been said somewhat sententiously that the advance of science 

 consists simply in a change of problems; we achieve progress 

 when we substitute for one problem another at once more delicate and 

 more precise. The recent history of the theory of alcoholic fermenta- 

 tion furnishes a conspicuous illustration of this aphorism. Liebig's 

 ingenious conception concerning the breaking-down of the sugar mole- 

 cule by the decomposing albuminous compounds in dead and dying 

 yeast cells — his notion being that the sugar is toppled over, so to speak, 

 by the mechanical shock of other falling molecules — was forced to 

 yield to Pasteur's apparently clear demonstration of the part played 

 under natural conditions by the living yeast cell. More recently the 

 conception of the living cell as the essential feature of the process has 

 been dethroned in its turn, and alcoholic fermentation is now shown to 

 rest on the action of an ^unorganized,' 'lifeless,' or 'soluble' ferment or 

 enzyme, secreted by the yeast plant. Further, the action of this enzyme 

 and of other and more familiar 'unorganized' ferments has been 

 brought into line with some of the most characteristic activities of the 

 living cell, and many general life phenomena have been shown to be in 

 reality phenomena of fermentation. 



The consequent focusing of attention upon the enz}Tnes, their 

 nature, mode of action and chemical relations, has already been prolific 

 in results of great biological interest. The science of experimental 

 medicine, in particular, is discovering that many of the problems 

 relating to immunity, to toxins, antitoxins and agglutinating sub- 

 stances are closely connected with the problems of fermentation and 

 the enzymes. 



So far as is known, the peculiar substances called enzymes are pro- 

 duced only by the living cells of animals and plants, although there 

 are certain inorganic substances that so closely reproduce the essential 

 qualities of enzyme action that they might almost be termed 'inorganic 

 enzymes.' The enzymes obtained from the animal or plant cell have 



* The Soluile Ferments and Fermentation. J. Reynolds Green. Cambridge 

 University Press, 1899. 

 Masson, Paris, 1899. 



Trait4 de microiiologie, II., diastases, toxines et venins. E. Duclaux. 



Les enzymes et leurs applications. J. Effront. Carre et Naud, Paris, 1899. 



VOL. Lix. — 35 



