PRACTICAL PHYSIOLOGY 



45 



along the length of nerve between the two pairs of 

 electrodes. The interval is relatively small com- 

 pared with the total latency period of the muscle- 

 nerve preparation ; it can be rendered more evident 

 if the nerve (not the muscle) be cooled. But to 

 measure it accurately a very fast rate of movement 

 and a longer nerve must be taken. This is usually 

 done by the use of the pendulum myograph, upon 



FIG. 29. EXPERIMENT TO DETERMINE THE RATE OF CONDUCTION ALONG A MOTOR 

 NERVE. THE MUSCLE AND LEVER SHOULD BE ON THE RIGHT-HAND SIDE OF THE 

 DRUM ; NOT ON THE LEFT SIDE, AS REPRESENTED IN THE DIAGRAM. 



which the contraction of the thumb muscles in man 

 is recorded, the electrodes being applied over the 

 median nerve at the elbow and over the brachial 

 plexus above the clavicle respectively ; the length of 

 nerve thus investigated may be a foot or more. The 

 muscle-contraction is recorded by means of tambours. 

 Conduction in both directions ; Kulme's ex- 

 periment. Remove the gracilis with part of its 

 entering nerve ; lay it on a glass plate, with its inner 

 surface uppermost. The nerve is seen to give 



