302 PROTOPLASMIC ACTION AND NERVOUS ACTION 



injury arise. Mechanical or other injury and the 

 application of cytolytic substances, which demonstrably 

 increase permeability, always lower the potential; i.e., the 

 altered region becomes negative relatively to unaltered 

 regions. This effect is often reversible if the tissue is not 

 exposed too long; thus potassium salts render a voluntary 

 muscle locally negative, in accordance with their 

 permeabihty-increasing action; and if the tissue is soon 

 afterward bathed in Ringer's solution, the original 

 isoelectric condition returns. Any local alteration which 

 impairs semi-permeability thus induces local negativity; 

 i.e., decreases the potential-difference between the 

 protoplasm and the surroundings. The fact that the 

 variation of potential is always in a negative direction 

 is consistent with the theory that the normal negative 

 variation accompanying stimulation is also the effect 

 of an alteration of the cell surface, involving a temporary 

 and rapidly reversed increase of permeability. We may 

 thus understand why the bioelectric variation of stimula- 

 tion is similar in its direction and range to that accom- 

 panying loss of semi-permeability, while differing in 

 being reversible or evanescent. 



It has long been recognized that variations in the 

 permeability of a semi-permeable partition separating 

 two electrolyte solutions must involve variations in the 

 potential difference across the partition, and the chief 

 modern attempts to explain the bioelectric potentials 

 have been based on this ground (''membrane theory" 

 of Ostwald, 1890,^ followed by Cybulsky, Bernstein,^ 



^ Ostwald, Z. physik. Chem., VI (1890), 71. 



2 Cybulsky, Bull. Acad. Sci. de Cracovie (1898), p. 231; Bern- 

 stein, Arch. ges. Physiol., XCIT (1902), 521. For other references cf. 

 Hober's textbook, op. cit., p. 579. 



