BIOELECTRIC PHENOMENA 305 



with respect to the cations of the solution. Results 

 similar to the foregoing were obtained also with XaCl 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 hpoids) 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, ^2,y be regarded as ''dissociating off" zinc ions 

 until an equihbrium (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 dilYerence in 

 logarithmic ratio. 



» Loeb and Beutner, Science, XXXIV (191 1), 884; XXXVII (19 13), 

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

 301; LIX (1914), 195. Cf. also Beutner, ibid., XLVII (1912), 73. 



