382 PROTOPLASMIC ACTION AND NERVOUS ACTION 



a chemical change in the substance of the membrane; 

 the theory further assumes that this change is of such a 

 kind as to be readily induced by the passage of a current. 



The analogy between this hypothetical type of 

 process and the phenomenon known as "local action" at 

 metallic surfaces is a close one, to which I have recently 

 called attention.^ An example is the spread of corrosion 

 in metals like iron in contact with electrolyte solutions; 

 this spread is the result of local chemical action under the 

 influence of local electrical circuits between the altered 

 and the unaltered areas of the metal. The possibility 

 is thus suggested that in the irritable protoplasmic 

 element the primary change in electrical excitation is 

 also of the nature of an electrolysis. Through the 

 chemical change thus induced the properties of the 

 surface-film are altered in such a manner as to render it 

 ''negative" to unaltered areas; a local circuit then 

 arises at the boundary between altered and unaltered 

 areas and causes electrolysis in the latter, in the same 

 manner as the original current; and by a repetition of 

 this effect the chemical and electromotor change spreads. 

 Evidently a wavelike transmission without decrement 

 is theoretically possible under these conditions. The 

 chief requirement is the presence of a uniform and 

 chemically unstable film forming the boundary layer 

 of the irritable element. 



Conditions of essentially this kind are in fact realized 

 in the passive iron wire in nitric acid solution; and in 

 this simple inorganic system the phenomena of activation 

 and transmission exhibit a surprisingly detailed resem- 



^ " Electrolytic Local Action as the Basis of Propagation of the 

 Excitation-Wave," American Journal of Physiology, XLI (1916), 126. 



