326 THE OUTGO OF ENEEGY 



circuiting key to a second capillary electrometer 

 Near the other end of the nerve place stimu- 

 lating electrodes connected with the secondary 

 coil of an inductorium arranged for tetanization. 

 Make the polarizing current. Open the short- 

 circuiting key leading to the electro tonic elec- 

 trometer, and note the position taken by the 

 meniscus under the influence of the electrotonic 

 current. Make the tetanizing current. 



Fig. 56. 



The strength of the electrotonic current will 

 be diminished. At the same time the strength 

 of the polarizing current will be increased (polar- 

 ization increment). 



These are in reality action currents. 



The eleetrotonic currents are absent in nerves 

 which lack a rnyelin sheath. This suggests that 

 the myelin in some way divides the nerve into a 

 core and a sheath. If a zinc wire connecting 

 two electrodes is surrounded by a layer or srjeath 



