THE ELECTROMOTIVE PHENOMENA 325 



on the side of the anode, but is opposed to that 

 on the side of the cathode. It appears when 

 any two points on the longitudinal surface are 

 "led off" to the electrometer, and is entirely 

 independent of the demarcation current. 



The intensity of the electrotonic current de- 

 pends on the intensity of the polarizing current. 

 The greater the separation of the polarizing elec- 

 trodes, the less the electrotonic effect, as might be 

 expected from the great resistance of nerve. If 

 this factor be excluded by placing in the circuit 

 a much greater resistance than that of nerve, the 

 electrotonic effect will be found to increase with 

 the length of the intrapolar region. The electro- 

 tonic current is absent in dead nerves, in strongly 

 cooled nerves, and in those ligated between the 

 polarizing electrodes and the electrodes leading 

 to the electrometer. 



In muscle, the electrotonic currents are much 

 stronger than in nerve. 



Negative Variation of Electrotonic Currents ; 

 Positive Variation (Polarization Increment) of Polar- 

 ising Current. Place the polarization electrodes 

 near one end of the nerve. Connect them through 

 a short-circuiting key with a dry cell. From the 

 short-circuiting key lead to a capillary electrom- 

 eter (Fig. 56). From the middle of the nerve 

 lead off the electrotonic current through a short- 



