THE ELECTRICAL CHARGES OF MICELLA 167 



centration effects on the P.D. When the P.D. between solid 

 gels of gelatin and of coagulated egg albumin and water was 

 investigated, no potential differences were observed, to the great 

 surprise and disappointment of the writer, who had hoped that 

 the investigations of the P.D. might lead to an explanation of the 

 antagonistic ion effects in which he was then interested. It is 

 possible that the negative results with protein were due to the 

 fact that the measurements were accidentally made near the 

 isoelectric point. On the other hand, it was found that there 

 existed a P.D. at the boundary of lipoids (lecithin dissolved in 

 guaiacol) which was depressed by the addition of salts and the 

 more the higher the concentration of the salt. 1 



This analogy between lipoids and living cells gave us the im- 

 pression that the proteins had no share in the potential differ- 

 ences observed between living tissues or living cells and watery 

 solutions. The experiments recorded in this chapter leave no 

 doubt that this conclusion was wrong; any ion in a cell or on its 

 surface which cannot diffuse into the surrounding watery solu- 

 tion (no matter whether the ion is a protein or a fatty acid or some 

 complicated lipoid or a complicated carbohydrate or even a 

 crystalloid) can or must give rise to a P.D. which is depressed 

 when a diffusible salt is added to the surrounding watery solution. 



The idea that lipoids are the substances responsible for the 

 P.D. of tissues led Beutner to an extensive and most interesting 

 investigation of the P.D. at the boundary of water-immiscible 

 substances and water. 2 He found always a depressing effect 

 of the addition of salt. Beutner tried to explain this on the 

 basis of differences in the electrolytic dissociation in the watery 

 and the water-immiscible (oily) phase. Such an explanation 

 cannot be applied to the experiments with protein solutions and 

 yet these latter solutions also show the depressing effect of the 

 addition of salt on the P.D. in a most striking way. In this 

 latter case the depressing effect of the salt on the P.D. is due to 

 the Donnan equilibrium, and there is no reason why the theory 

 of membrane equilibria should not apply to the P.D. between 



, J. and BEUTNER, R., Biochem.-Z., vol. 51, p. 288, 1913; vol. 59, 

 p. 195, 1914. 



2 BEUTNER, R., "Die Entstehung elektrischer Strome in lebenden Gewe- 

 ben," Stuttgart, 1920. 



