ANTIC ATALYSTS, ANTIFERMENTS 215 



and preventing or retarding its action. Bredig places these sub- 

 stances in analogy with the antitoxins. Strictly speaking, all those 

 substances ought to be placed in this group, which have already 

 been described above as affecting enzyme action, such as acids 

 and alkalies, neutral salts, anesthetics and antiseptics; but it 

 is better to reserve the term, if it is to be used at all, for substances 

 which act after the fashion of catalysts of a second order, so to speak, 

 in quantities small compared to the amount of the primary catalyst. 



An example of such an action is the " paralysis " of the action 

 of solutions of colloidal platinum upon hydrogen peroxide, by 

 the addition of traces of hydrocyanic acid. Thus, Bredig, Muller 

 von Berneck, and Ikeda found that the addition of 0-000,000,001 

 grm. hydrocyanic acid per cubic centimetre to a colloidal platinum 

 solution containing 0-000,006 grm. platinum per cubic centimetre 

 reduced the intense action of the platinsol upon hydrogen per- 

 oxide to half its original value. Here it is to be noted that 

 although the quantities of both platinum and hydrocyanic acid are 

 small, that of the platinum is 6000 times as large as the hydro- 

 cyanic acid; hence there is no stoichiometric relationship, and the 

 action cannot be ascribed to any chemical combination in definite 

 molecular relationship between the colloidal platinum and the 

 hydrocyanic acid. The paralysing effect of the hydrocyanic acid 

 can be removed by passing a stream of air through the solution 

 and so removing the hydrocyanic acid. The " recovery " shows 

 that the catalyst is not destroyed by the " poison " of the anti- 

 catalyst but only inhibited during its presence. 



The catalytic action of platinum upon hydrogen peroxide or 

 water gas is also anticatalysed by traces of many substances, of 

 which the following list is given by Bredig: Iodine, mercuric 

 chloride, hydrogen sulphide, sodium thiosulphate, carbon mon- 

 oxide, phosphorus, hydrogen phosphide, hydrogen arsenide, mer- 

 curic cyanide, carbon bisulphide. 



In this group must also be placed the antiferments or anti- 

 enzymes which have been shown to exist in the case of the majority 

 of the enzymes. These have usually been obtained by the process 

 of injection into an animal of solutions containing the enzyme 

 in question for a period, and then separating the animal's serum 

 and demonstrating that it contains a substance capable of stopping 

 the action of the enzyme. 



The first anti- enzyme was shown to exist by Morgenroth in. 



