STIMULATION OF MUSCLE AND NERVE 121 



shocks, placing in the circuit a simple key and 

 the electro-magnetic signal. Lead wires from the 

 poles of the secondary coil to the side cups of a 

 pole-changer (without cross-wires). In each of 

 the remaining two holders of the moist chamber 

 place a cork pierced by two metal electrodes. 

 One wire in each pair should be insulated from 

 its fellow by rubber 

 tubing drawn over the 

 part between the cork 

 and the end of the elec- 

 trode to be applied 

 to the nerve. Connect 

 the wire soldered to 

 the basal ends of these 

 electrodes with the re- 

 maining cups of the 

 pole-changer in the sec- 

 ondary circuit of the 

 inductorium. Arrange the signal to write on the 

 smoked drum beneath the writing point of the 

 muscle lever. 



Make a nerve-muscle preparation. Let the 

 nerve rest on the non-polarizable electrodes near 

 the cross-section. Place one pair of the metal 

 electrodes beneath the nerve near the muscle, the 

 other pair near the non-polarizable electrodes. 

 The clockwork of the drum should be fully 



Fig. 32. 



