282 PROTOPLASMIC ACTION AND NERVOUS ACTION 



We are thus led to consider the kinds of effect which 

 changes in the electrical polarization across the cell 

 surface may have upon chemical processes occurring in 

 this region. 



It should first be noted that various phenomena 

 occurring at metallic surfaces and involving electrolysis 

 have been shown to follow the same '' square root law" 

 as the stimulation process. Bredig and Kerb found this 

 to be true for the influence of alternating currents in 

 initiating the characteristic rhythmical action in the 

 mercury hydrogen peroxide system, which, as we have 

 seen, resembles closely the passive iron model in its 

 mode of activity; the same was found by Wilke and 

 Meyerhof in the electrolytic oxidation and reduction of 

 chromic salts and chromates at platinum electrodes.' 



Whenever a sufficient uncompensated potential 

 difference is established between an electrode and a 

 solution, as in any battery with closed circuit, the 

 conditions for chemical change are present; there is a 

 transfer of electricity associated with a chemical decom- 

 position or other reaction (oxidation, synthesis, etc.) at 

 the interface. It is well known that a certain critical 

 decomposition-voltage must be exceeded in order to 

 carry out any definite electrolysis, e.g., of a metallic 

 salt; and if the cell surface possesses the general proper- 

 ties of an electrode, the chemical reactions there occurring 

 must be subject to similar conditions. The need for 

 a certain minimal or ''threshold" current-intensity in 

 stimulation is thus explained ; it is evident that if the fore- 

 going theory of transmission is well founded the potential 



* Bredig and Kerb, loc. cit.; Wilke and Meyerhof, Arch. ges. Physiol., 

 CXXXVII (1910), I. 



