CATALYSIS AND BIOCHEMICAL PROCESSES 229 



propionate, and nitrate), ethyl ether, KtCl, i:tHr, 

 chloretone, paraldehyde,, CCI4, hydrocarbons like benzol, 

 toluol, and xylol, but not by urethanes and lower 

 alcohols.^ In a lecithin-containing system such as 

 protoplasm this influence might act anticaUilytically 

 by slowing diffusion- velocities ; any chemical process 

 whose rate depended on the rate of diffusion would thus 

 be retarded. Increased hindrance to the movement of 

 ions would be shown in decreased electrical conductivity. 

 Loewe^ has in fact found that artificial membranes 

 impregnated with lecithin exhibit an increased electrical 

 resistance in the presence of anaesthetics; in a system 

 Hke living protoplasm such an effect would retard 

 chemical reactions dependent on electrochemical con- 

 ditions. The increase in viscosity is probably to be 

 referred in part to the formation of adsorption-films at 

 the surface between the lecithin particles and the water.^ 

 It is possible also that changes in the relative volumes 

 occupied by the colloidal particles and the aqueous 

 phase may play some part; presumably the lipoid-soluble 

 compound concentrates in the lecithin in accordance 



. . . lipoid-solubility, . 



with its partition-ratio, — : , , ...^ and in so 



^ ' water- solubihty 



doing enlarges the particles; this may explain why the 



higher alcohols are more effective in causing gelation than 



the lower alcohols, which are highly water-soluble. 



As the emulsion particles enlarge, their freedom of 



movement becomes less, contacts are more frequent, 



and coherence to a gel is favored. 



^ Cf. my review, The Theory of Anesthesia, op. cit., p. 362. 

 * Loewe, loc. cit. ^ Cf . Ibid. 



