228 NERVE. 



Write a second abscissa through the position chosen, and 

 measure the distance between them against the time tracing 

 immediately below. 



From this calculate the rate in metres per second as 

 follows : 



The interval is estimated as lying between 1/8 to a 1/10 

 of a 1/96 of a second time interval. Assume it to be 1/9. 



The nervous impulse has therefore taken 1/864 of a second 

 to travel 2'5 cm . 



In 1 second the impulse would travel 864 x 2*5 cm = 2160 cm 

 = 21 *6 metres. A somewhat low estimate. 



16 Rate of transmission of a nervous impulse, measured 

 by means of ike pendulum myograph and the electrical method. 



Required: Electric style fastened to the side bar of the general 

 stand, muscle break, 2 commutators, inductorium, 2 keys, 4 Daiiiell 

 cells, and 16 wires. 



All the records are made in this experiment with one time 

 marker, which is so connected to the time distribution board 

 and the muscle break by means of a commutator that it 

 can be thrown into line with either of these as required. 

 The movement of the muscle consequent upon the stimulation 

 of the nerve is recorded by the break of the circuit. This 

 circuit whilst closed keeps the point of the style depressed, 

 on breaking the point flies up, making a sharply denned 

 upward stroke, which is more easily read than the muscle curve 

 in the previous experiment. 

 Set up as follows (Fig. 44) : 



1. Stimulating circuit. The board of the pendulum carries 

 a projecting arm which, in swinging past, knocks open a closed 

 key. This key is fixed to the floor of the instrument in 

 such a position that the pendulum is travelling nearly at its 

 maximum speed when it opens the key. 



