BIOELECTRIC PHENOMENA 305 



with respect to the cations of the solution. Results 

 similar to the foregoing were obtained also with NaCl and 

 HCl. 



More recently Loeb and Beutner/ in an extended and 

 important series of researches, have shown that the 

 characteristic logarithmic relation between the concentra- 

 tion of the ions in the solution and the potential difference 

 holds for organic membranes of a variety of kinds and 

 also for solutions of lipoids in organic solvents. The 

 organic membranes act as if they were reversible to 

 cations as a class. This result is highly significant, for 

 it seems to imply that reversible combinations between 

 these ions and components of the membrane (e.g., pro- 

 teins or lipoids) occur, and that the formation of these 

 combinations is the essential factor determining the 

 potential equilibria observed in a given solution. Just as 

 a metallic electrode, like Zn in contact with a solution of 

 ZnS04, may be regarded as '^dissociating off" zinc ions 

 until an equilibrium (to which corresponds a definite 

 potential difference) exists between the ions tending to 

 pass into solution from the metal and those already in 

 solution, so in the case of a salt solution in contact 

 with an organic membrane a certain potential difference 

 corresponds to the equilibrium existing between the 

 ions in solution and the ion-membrane compounds 

 formed by the combination of these ions and the mem- 

 brane components (proteins, etc.). Any increase of the 

 ions in solution decreases the potential difference in 

 logarithmic ratio. 



» Loeb and Beutner, Science, XXXIV (191 1), 884; XXXVII (1913), 

 672; Biochem. Zeitschrift, XLI (1912), i, and XLIV, 303; LI (1913), 288, 

 301; LIX (1914), 195. Cf. also Beutner, ibid., XL VII (191 2), 73. 



