BIOELECTRIC PHENOMENA 301 



significant fact is that the demarcation potentials 

 (shown in the injury-currents of muscle and similar 

 phenomena) vary with the condition of the protoplasmic 

 surface layer. The loss of semi-permeability accompany- 

 ing death is always associated with a decline or dis- 

 appearance of the demarcation potential, a fact indicating 

 that the latter depends on the presence of a semi- 

 permeable partition between the internal protoplasm 

 and the surrounding medium. Such a partition allows 

 the existence of permanent differences of electrolyte- 

 content between the solutions adjoining the outer and 

 inner faces of the plasma membrane, and so provides 

 the asymmetric conditions necessary for a potential- 

 difference. Just why this potential-difference should 

 have the observed orientation (positive externally) and 

 range (of the order of 0.05 to o.i volt) is not entirely 

 clear; possibly these conditions are referable to a higher 

 total electrolyte content of the cell interior as. compared 

 with the surroundings, or to a preponderance of certain 

 ions (e.g., H ions) in the cell interior. The chemical 

 relations between the ions present in solution and the 

 materials composing the surface-film are undoubtedly an 

 important factor, and it seems probable that oxidation- 

 reduction potentials and adsorption potentials (in the 

 Freundlich sense) are also concerned. The total poten- 

 tial as observed thus represents an additive effect. 



It is evident, however, that the demarcation potential 

 depends primarily on the special physical and chemical 

 properties of the cell surface, since whatever modifies 

 the structure or chemical character of the protoplasmic 

 surface layer also alters the potential. This is shown by 

 the conditions under which the so-called currents of 



