THE SO-CALLED INORGANIC ENZYMES 119 



agency as in the case of enzymes. In fact, their action is con- 

 fined to simple reactions upon inorganic bodies, such as the 

 catalysis of hydrogen-peroxide into water and oxygen, or of 

 hydrogen and oxygen to form water. Such reactions are shown 

 by the metals concerned in finely divided form apart from 

 solution, and the increased activity is merely due to finer division, 

 and is removed by anything which interferes with the action of 

 the large surface. Accordingly, it appears to the writer that the 

 term " inorganic enzyme " is not a very appropriate name for a 

 colloidal solution of platinum, since it indicates that we possess 

 more knowledge of the mode of action of enzymes than we really 

 do. 1 The same applies to the term " poisoning " as applied to 

 the action of hydrocyanic acid and sulphuretted hydrogen in 

 stopping the action of such metal-sols when added in minute 

 traces, for this term is one which has hitherto been applied to 

 the destruction of life by reagents, and until we know that the 

 stopping of the action of colloidal platinum by hydrocyanic acid 

 arises from the same causes as the poisoning of a living cell by 

 that reagent, it is dangerous to apply the same tsrm to both pro- 

 cesses. By a strange process of reasoning this same " poisoning " 

 of the colloidal platinum by hydrocyanic acid has been put forward 

 as supporting the view that the platin-sol is an " inorganic 

 enzyme." Now, if the process of " poisoning " proves anything 

 at all, it proves that the colloidal platinum is a living cell, for it 

 is living cells and not enzymes that are destroyed by the action 

 of hydrocyanic acid, by which in such minute concentrations 

 most enzymes are entirely unaffected. The only action related 

 to enzymes which is stopped in the same degree by hydrocyanic 

 acid is the identical one to that stopped in the case of colloidal 

 platinum, namely, the action upon hydrogen-peroxide, which is 

 found not only in practically every enzyme but in nearly all tissue 

 extracts. This action is ascribed usually to enzymes called 

 " oxydases " or " perox : dases," occurring generally in all tissues 

 where oxidative processes occur ; but our knowledge of the subject 

 is scarcely sufficient to state whether it is to be ascribed to any 



1 The suggestion of Oppenheimer (Die Fermente, p. 46), that it would be 

 better to call the enzymes "organic catalysts," is much better if any change 

 must be made. For it is much better to retain the name catalyst as a general 

 class name, including both inorganic and organic, and the enzymes now form 

 a well-defined group of organic catalysts for which the name ought to be 

 retained. 



