METHODS OF ELECTRICAL STIMULATION 71 



UNIPOLAR INDUCTION 



1. Arrange the inductorium for tetanizing 

 currents (posts 2 and 3). Make a nerve-muscle 

 preparation. Lay it on a clean dry glass plate. 

 Let the nerve rest on a wire connected with one 

 pole of the secondary coil. Set the inductorium 

 in action. Connect the muscle with the earth 

 by touching the muscle with the end of a wire 

 the other end of which rests on a gas or water 

 pipe. 



The muscle will show tetanic contractions, 

 provided the induced current is sufficiently 

 strong. If no tetanus is seen, move the second- 

 ary coil completely over the primary. 



Unipolar induction may be produced by the 

 electric currents in the skin. This may be 

 demonstrated with a sensitive nerve-muscle prep- 

 aration. 



2. Ligature the nerve between the electrode 

 and the muscle, and repeat the experiment. 



Stimulation will still be secured. The uni- 

 polar discharge passes through the entire length 

 of nerve and muscle to or from the point at 

 which the connection with the earth is made, and 

 thus stimulates the entire preparation. 



DuBois-Reymond, who was the first to make 

 the preceding experiments, pointed out that 



