380 PROTOPLASMIC ACTION AND NERVOUS ACTION 



itself a strong argument in its favor. It is surprising 

 that until recently it has received relatively little serious 

 consideration from physiologists, most of whom have 

 been apparently content to regard the bioelectric phe- 

 nomena as inessential by-products of protoplasmic action. 

 The importance of the electrical factor in the phe- 

 nomena of protoplasmic transmission is, however, 

 clearly recognized in the ''core-conductor" (Kernleiter) 

 theory or theories of nervous action/ This conception 

 has as its basis the presence of characteristic polarization 

 effects in a nerve through which a current is led (by 

 non-polarizable electrodes) ; these effects closely resemble 

 those exhibited by a system consisting of a simple metallic 

 wire surrounded by a sheath or layer of electrolyte 

 solution. The resemblance is so detailed, as regards 

 the distribution, rate of development, and subsidence 

 of the polarization potentials, that there can be little 

 doubt of the essential identity of the physical conditions 

 underlying these phenomena in the two systems. In 

 nerve the surface of the axone has usually been regarded 

 as the chief seat of the polarization, and Hermann 

 especially has called attention to the intimate relations 

 existing between polarization and stimulation. Neither 

 he nor his successors, however, could explain satis- 

 factorily, on the basis of the phenomena shown by simple 

 polarization models of this type, the characteristic wave- 

 like transmission of the electrical variation in the excited 

 nerve. Apparently the presence of special physiological 

 factors must be assumed, whose effects are superposed 

 on those of the purely physical factors. This point of 



^ Cf. Cremer's [article, op. ciL, p. 904, for historical account and 

 discussion. 



