192 



PRACTICAL PHYSIOLOGY. 



[XXXIII 



Because it is devoid of nerve-fibres. Then cut across the muscle 

 about 4 mm. higher up and dip tlie fresh -transverse section into 

 the glycerin. Soon the muscle twitches. Why? As glycerin 

 stimulates nerve and not muscle, there is no response until the 

 glycerin is eitlier directly applied to nerve-fibres, or is diffused 

 so as to aftect them. 



Klihne used this experiment to demonstrate the independent 

 excitability of muscle and nerve. 



4. Comparative Excitability of Muscle and Nerve. 



(a.) Prepare a frog as for the curare experiment, i.e., ligature 

 one leg all except the sciatic nerve on that side, then inject curare 

 into a lymph-sac. After the curare has acted, expose both sciatic 

 nerves and both gastrocnemius muscles. 



(b.) ^N'ote the approximation of the secondary coil to the primary 

 required to obtain a mechanical response or contraction to — 

 (i.) Single make induction shocks, 

 (ii.) Single break induction shocks, 

 (iii.) Faradisation. 



"When the electrodes are applied to the sciatic nerve of the 

 ligatured limb, i.e., the protected side, tabulate the results. 



(c.) Apply the electrodes directly to the gastrocnemius muscle 

 of the opposite side, i.e., the poisoned limb, which is practically 

 nerveless, as curare paralyses the terminations of the motor nerves. 

 It will be found that a stronger shock is required to cause the 

 muscle to contract than is necessary through the intervention of 

 the nerve, i.e., muscle is less excitable than nerve. 



Faradisation. 



