74 ENZYMES OR SOLUBLE FERMENTS. 



account, and was based simply upon the supposed properties of 

 the changing cell-substance, might obviously therefore be applied 

 to any ordinary soluble enzyme. There is however no evidence to 

 show that the enzymes are in the state of change or decomposi- 

 tion which Liebig supposed ; on the contrary they are observed to 

 be on the whole remarkably stable substances, from the point of 

 view that a minute trace can produce a profound decomposition in 

 a relatively enormous mass of material, during an almost indefi- 

 nitely long time, without itself undergoing any proportionate altera- 

 tion or destruction. 1 The theory of v. Nageli previously quoted 

 was applied by its author to explain the fermentative power of 

 the living cell, and is thus not directly applicable to the non-living 

 enzymes. Mayer, it is true, has put forward a view which is essen- 

 tially a development of v. Nageli's and is applicable to the en- 

 zymes. These substances are in all cases produced solely and 

 entirely by the activity of living cells or organisms, and Mayer 

 regards them as retaining in themselves a portion of that molecu- 

 lar motion which is supposedly so characteristic of the living 

 parent cell from which they have been separated. 2 It cannot how- 

 ever be said that these theories afford any real insight into the 

 probable mode of action of an enzyme, and we must look for it in 

 some other direction. 



Attention has been already drawn (p. 53) to the existence of a 

 large and increasing class of chemical reactions whose occurrence 

 is determined by mere traces of some substance which does not 

 itself at the same time undergo any change during the decomposi- 

 tions which it initiates, and the enzymes have been compared to 

 these substances. Now in the case of the reactions of which we 

 are now speaking it is known in some and probable in all that the 

 process which takes place is in general terms the following. The 

 determinant substance interacts with one of the reagents to form 

 a compound which can now enter into combination with the other , 

 the result is the formation of a more complex compound which at 

 once decomposes, giving rise to products of which one is the origi- 

 nal determinant substance in an unaltered form, the others the 

 product characteristic of the reaction. 3 This suggests at once that 

 the enzymes may play their part in a manner similar to that of 

 the determinant in the above reactions, a view which has been put 

 forward but scarcely receives the attention that it deserves. 4 



1 Berzelius explained fermentation as the outcome of a mysterious 'catalytic ac- 

 tion,' or 'action by presence ' or ' contact.' He thus compared ferments to platinum- 

 black, which is able, in minute quantity, to cause a liberation of oxygen from peroxide 

 of hydrogen without itself undergoing any recognisable change. This is however no 

 explanation, for it does not amount to more than saying that given the contact of 

 two substances capable of reacting on each other, a certain reaction takes place. 



2 Die Lehre von den chem. Fermenten, Heidelb 1882. 



3 Vide the reactions in the continuous etherification process and the manufacture 

 of sulphuric acid. See also Traube (Ber. d. deutsch. chem. Gesell. 1885, S. 1890), on 

 the part played by water in determining the explosion of O and CO. 



4 Kiihne, Lehrb. d. physiol. Chem. 1868, S. 39. Hoppe-Seyler, Med.-chem. Unters. 



