THE ELECTRICAL CONDITIONS OF MUSCLE AND NERVE 65 



Demarcation and action currents of nerve. These are examined 

 and measured in exactly the same way as those of muscle. 



Action current of frog-heart. Non-polarisable electrodes are con- 

 nected with a beating frog-heart, which may either be removed from 

 the body and laid with the base upon one electrode and the apex on 

 the other, or left in situ, and the electrodes connected with apex and 

 base by thick threads wetted with salt solution. The electrodes are 

 joined by wires to any of the above instruments. Each contraction of 

 the heart is accompanied by movements of the respective indicators 

 (mercury column, silvered quartz thread, or magnetic needle), the 

 direction of which are recorded and the alterations in electrical 

 potential of base and apex deduced therefrom. 



