PHYSICO-CHEMICAL BASIS OF TRANSMISSION 381 



view has more recently been emphasized by Cremer in an 

 important series of studies on the ''Kernleiter" theory, 

 pubhshed at intervals since 1899. He assumes in nerve, 

 in addition to the physical polarization which this tissue 

 exhibits in common with artificial systems of the core- 

 conductor type, the presence of a special '^ physiological 

 polarization,"^ by which termi he means some active 

 process (in the nature of a response or reaction) exhibited 

 at the regions of entrance and exit of the current; this 

 process he conceives as based on a chemical change of 

 some kind, which secondarily may alter polarization and 

 hence serve as the source of a current. In this manner 

 the polarization effect may be renewed at successive 

 areas of a nerve, and transmission to an indefinite 

 distance becomes possible.^ 



In the foregoing form the Kernleiter theory requires 

 only slight modification in order to make it entirely 

 consistent with the present form of the ''membrane" 

 theory. Both theories agree that a change of polariza- 

 tion is the critical or primary event in the local stimula- 

 tion process. Evidently if the polarization is confined 

 to the surface of the protoplasmic element (as also of the 

 metal in a core-conductor), this critical change is a 

 surface change. According to the membrane theory, the 

 variation of polarization in stimulation is the result 

 of a sudden change in those features of structure, compo- 

 sition, or permeabiHty which determine the normal 

 electromotor properties of the protoplasmic surface-film 

 or plasma membrane. Such a change may result from 



^ SUzungsber. Ges. Morph. u. Physiol., Munchen (1899-1900), 

 Hefte I and 2. 



2 See Cremer's exposition in his article in Nagel's Handhuch, pp. 

 930 flf. 



