3o8 PROTOPLASMIC ACTION AND NERVOUS ACTION 



while with the intact skin the reversibihty relates to 



cations alone. In other words, the two regions exhibit 



different electromotor properties. 



Further experiments^ showed that the behavior of 



the organic membrane could be closely imitated by an 



arrangement in which a solution of a weak organic 



acid in a water-immiscible solvent is in contact with the 



salt solutions. In the arrangement already described : 



calomel concentrated membrane- dilute calomel 



electrode salt inclosed salt electrode 



solution system solution 



(e.g., apple) 



the dilute solution is positive and becomes more positive 



with increasing dilution; such a chain is comparable to 



one containing a metal in contact with solutions of its 



salt; e.g.: 



calomel concentrated metallic dilute calomel 



electrode AgNOa Ag AgNOj electrode 



in which also the side containing the dilute solution is 

 positive; AgCl may be substituted for metalhc silver 

 with the same result. Similarly the arrangement: 



gave potential differences of a similar order to those 

 found with the organic structure, and varying similarly 

 with the concentration of the dilute salt solution. In 

 other words, the surface of the non-aqueous phase acts 



* Cf . Beutner, Trans. Amer. Electrochem. Soc, XXI (1912), 219; 

 XXIII (1913), 401; American Journal oj Physiology, XXXI (1913), 343. 



