1915] 



CZAPEK PROTOPLASM AND ITS COLLOIDAL PROPERTIES 251 



cent. When concentrations higher than this were used then 

 the emulsion, examined capillarimetrically, did not differ 

 from a mixture of pure alcohol and water of the same concen- 

 tration (but without oil). Then we added to the emulsion 

 Van't Hoff's solution 0.1 mol instead of water. The decompo- 

 sition of the emulsion by ethyl alcohol was now observed at 

 2 mols, i. e., about 10-11 per cent. This is just the concentra- 

 tion of alcohol which kills cells of the higher plants. The 

 addition of sodium chloride 0.1 mol instead of Van't Hoff's 

 liquid showed the critical concentration of alcohol to be 3 mols, 

 about the same concentration as in the absence of mineral 

 salts. On the other hand, the addition of magnesium chloride 

 induced the fatal effect of alcohol at 1 mol, much lower than 

 in living cells. Magnesium sulphate showed the same effect 

 as magnesium chloride, and the sulphate of sodium the same 

 as the chloride. Therefore, it does not seem probable that 

 the differing solubility in alcohol is responsible for the various 

 effects of the salts. One may endeavor to explain these 

 phenomena in the following way: Emulsions are only stable 

 when the droplets of the emulsified fat remain suspended in 

 a soap solution of approximate concentration. Substances 

 which alter the limiting surface between the soap solution and 

 the suspended oil must prove fatal as soon as their capillary 

 activity surpasses the capillary effect of the soap solution. 

 Bivalent cations, such as Mg and Ca, which form insoluble 

 salts with fatty acids, lower the concentration of soap, so that 

 alcohol must exhibit a decomposing action on the emulsion, 

 even in lower concentrations. 



From such experiments it seems as if the critical concen- 

 tration of alcohol for living cells would not be so sharply 

 determined by proteins contained in protoplasm as by the 

 mineral salt and the lipoid constituents of the protoplasm. 

 Since we suppose that the various mineral salts in protoplasm 

 are present in about the same concentration as they are found 

 in sea water, or as they are mixed together in Van't Hoff's 

 solution, we have to face the question whether the destructive 

 effect of alcohol on living cell plasma consists in some decom- 

 position of colloidal fat emulsoids in protoplasm. 



