1913.] Processes Operative in Solutions and Enzyme Action. 565 



The distinction between the view promulgated by Ostwald and that which 

 we advocate lies in the fact that we do not admit that action is either 

 possible or ever takes place between two non-electrolytes — such as hydrogen 

 and oxygen, for example— but hold that action sets in only when a suitable 

 electrolyte is present together with the frwo substances thought of as inter- 

 acting directly, though in reality they interact only indirectly. Thus — 



H HO H o H0H HO....H H0 



• + + •• = + + • 



H HO H HOH HO....H HO 



(Electrolyte) (Electrolyte 



-2 H.OH) 



In such a case, the electrolyte is the catalyst, the occurrence of change 

 being determined by and dependent on its presence : it does not merely 

 accelerate the change but gives rise to it by making it possible. The change 

 may be and is promoted, however, by the inclusion in the circuit of a sub- 

 stance such as platinum, which, by condensing or combining with the gases, 

 promotes their association with the electrolyte. Therefore, if the term 

 catalyst be restricted to materials which act merely by increasing the extent 

 to which substances are brought into interaction and only as intermediaries, 

 the definition given by the Ostwald school may be accepted as satisfactory : 

 whereas, if the electrolyte be regarded as the effective catalyst, this is not the 

 case, as the catalyst not only determines the occurrence of interaction but 

 contributes, ex hypothesi, of its own substance to the change and is only 

 recovered unchanged, i.e. undiminished in amount, because it is constantly 

 being changed reversibly. 



The Nature of Enzymes. — The enzymes are peculiar as catalysts not only 

 because they are agents derived from natural organic sources which determine 

 the resolution of a variety of compounds by hydrolysis but, more particularly, 

 on account of their specific and limited activity : it is in this respect that 

 they differ from most other catalysts. Each particular enzyme corresponds, 

 if not to a single hydrolyte, at most to a series of compounds of one particular 

 type. But until their specific nature be deciphered, it will be difficult to 

 arrive at any final definition of enzymes. 



The view that we have gradually been led to form of an enzyme involves 

 the assumption that it has a double function — that of attracting or holding 

 the hydrolyte and that of determining its hydrolysis : in other words, that 

 the enzyme retains the hydrolyte in circuit while hydrolysis is being effected 

 through the agency of an electrolyte itself formed from an active radicle 

 present in the enzyme. 



This twofold action we attribute to the presence in the enzynie of an 



