THE ELECTROMOTIVE PHENOMENA 327 



of saturated solution of sulphate of zinc, there 

 will be no polarization, and the current will not 

 spread to any Extent beyond the electrodes. If, 

 however, the wire is platinum instead of zinc, 

 polarization will take place where the current 

 passes from the electrodes through the electrolyte 

 into and out of the wire, and the polarization 

 may be recognized by connecting the extrapolar 

 region with the electrometer as in the foregoing 

 experiment. The resistance to the spread of the 

 electrotonic current in a longitudinal direction is 

 relatively slight, so that it passes almost instantly 

 along the core. 



In nerve, also, the greater resistance in the 

 transverse direction (five-fold greater than the 

 resistance in the longitudinal direction) would 

 favor the spread of electrotonic currents length- 

 wise along the nerve. 



Certain observations of Biedermann make it 

 difficult to accept without reservation the simple 

 physical explanation just offered. For example, 

 the narcotization of a nerve with ether or chloro- 

 form causes the electrotonus to disappear a 

 short distance from the electrodes, although 

 still strongly present in their immediate neigh- 

 borhood. These experiments cannot be discussed 

 here, but they indicate that to the purely physi- 

 cal must be added a physiological electrotonus. 



