226 PROTOPLASMIC ACTION AND NERVOUS ACTION 



of the solidity of the adsorbing phase and the remoteness 

 of the internal molecules from the sphere of reaction. 



SPECIAL FACTORS IN THE CATALYTIC ACTION OF 



PROTOPLASM 



Since surface-relations are all-important in hetero- 

 geneous catalysis, all conditions modifying the composi- 

 tion, electrical polarization, or other characters of the 

 active surfaces influence the catalytic activity of the 

 system. Hence surface-active substances as a class 

 have a marked effect on such catalyses, and their influ- 

 ence on the chemical activity of Hving matter is un- 

 doubtedly in large part referable to this effect. A brief 

 review of the action of these substances on the catalytic 

 and other properties of heterogeneous systems will 

 indicate the nature of the factors. 



One of the most complete recent studies of the anti- 

 catalytic action of surface-active substances on enzyme 

 action is that of Warburg and WieseP on the zymase- 

 containing ''press- juice" of yeast. All substances of 

 the anaesthetic class retard the alcohoHc fermentation 

 caused by this enzyme, although the non-hving enzyme 

 requires higher concentrations than the hving cell for 

 the same proportional degree of retardation. In homolo- 

 gous series the concentration necessary for a given retar- 

 dation decreases in the usual manner with increase of 

 molecular weight. The following orders of relative 

 action were found for different compounds. Alcohols: 

 methyl < ethyl < propyl <isobutyl; urethanes: ethyl < 

 propyl <isobutyl; nitriles: aceto<propio<isovalero; 

 ketones : acetone < methyl-propyl < methyl-phenyl. It 



* Warburg and Wiesel, loc. cit. 



