NERVE. 49 



Non-medullated fibres seem to conduct more slowly, the rate 



being as low as 8 meters per second. 



Experiment 21. Although the rate of transmission of the nerve 

 impulse is rapid, it can be determined by a high speed kymo- 

 graph. Prepare a gastrocnemius muscle with the nerve as 

 long as possible. Clamp the femur in the moist chamber, then 



FIG. 14. Tracing to show rate of conduction of the nervous impulse, (i) Contraction 

 of the gastrocnemius when the electrodes are near the muscle; (2) contraction resulting 

 from stimulation at the far position. Stimulation at X. 



lay the nerve across two sets of cork-held electrodes. One 

 pair should be close to the muscle and the other as far away as 

 possible. Avoid stretching the nerve. The electromagnetic 

 signal is placed in line with the point of the muscle lever 

 and alignment marks made on the smoke-drum. The signal 

 and kymograph are connected in the primary circuit. Adjust 



