BIOELECTRIC PHENOMENA 311 



VARIATIONS OF BIOELECTRIC POTENTIALS 



The sudden fluctuations of potential accompanying 

 normal vital processes like stimulation evidently require 

 a different type of explanation. In such cases rai)id and 

 reversible alterations of the electromotor properties of 

 the protoplasmic surfaces are apparently involved ; these 

 effects can only be referred to the chemical or metabolic 

 processes characteristic of living matter. The external 

 surface layer of the living cell consists of a thin film of 

 chemically alterable material in immediate contact with 

 the surrounding medium on the one side, and with the 

 internal protoplasm on the other; it is, therefore, subject 

 not only to purely physical changes, such as local thin- 

 ning or interruption, but also to changes of chemical com- 

 position, resulting from variations in oxidati\'e or other 

 metabolism. Along with such alterations must go 

 alterations in physical properties, thickness, permeability 

 to electrolytes, acid or basic character, etc.; and these 

 must alter correspondingly the electromotor properties 

 of the cell surface. It has already been pointed out 

 that the reversible variations of potential seen in the 

 action-currents of tissues like muscle and nerve have a 

 range closely similar to that of the demarcation-currents 

 {ca. 0.05 volt); and this fact receives a consistent 



by Adams favors the idea that the difference between the internal and 

 external H-ion concentrations is an important factor in the bioelectric 

 potentials {Journal oj Physical Chemistry, XXVI [1922], 639). 



Recently Rohonyi has opposed Beutner's conception of the impor- 

 tance of an oil-like phase in the determination of the bioelectric poten- 

 tials; cf. his critique: Biochcm. Zcilschrift, CXXX (1922), 68. He 

 regards semi-permeability (permeability to water, but not to electrolytes) 

 as the essential property. 



