15 



CHAPTER XXXII. 



EXPERIMENTS ON NERVES. 



Rate of nerve conduction, e.g., the velocity with which 

 a nervous impulse travels along a nerve. 



Required : Inductorium, 2 keys, 2 Leclanche cells, commutator less 

 cross wires, double electrodes, electric style, and 12 wires. Muscle 

 chamber, with fine writing point. Nerve muscle preparation, with 

 nerve most carefully dissected and with piece of spinal column attached. 

 Drum at very fast speed. 



Set up the P circuit with 2 cells and in drum contact. 

 Wire the S circuit from S key to the inleading binding 



screws of a Pohl's commutator, less cross wires. 



The two sets of outleading terminals of the Pohl are wired 



to the two sets of external terminals of the muscle-chamber. 



From the latter remove 

 the platinum and non- 

 polarisable electrodes and 

 in their stead attach the 

 double electrodes Fig. 43, 

 so that the two sets of 

 wires shall be connected 

 respectively with opposite 

 sides of the commutator. 

 When the rocker lies one 

 way it will lead the stimu- 

 lating current into wires 

 at a near the muscle, and 



when turned over it will establish connection with b farthest 



from the muscle. 



Set up the style to write 96th seconds under the muscle curve. 



FlG. 43. M Muscle. N Nerve on G, glass- 

 plate across this, a and b, pairs of wires at 

 2*5 cm interval ending in A, B, for attachment 

 to binding; screws of muscle chamber. L Lead 

 plate. 



