224 MUSCLE. 



of waxed paper, upon this place the nerves on the hand 

 electrodes. 



Fix the knees with pins passed through the quadriceps 

 tendon, and turn the feet out so that their movements may be 

 well seen when the calf muscles contract. 



Expose the calf muscles on both sides and attach the 

 thin wires, one to each tendon. 



Carry the connection of the hand electrodes and the thin 

 wires to opposite sides of the commutator (less cross wires), 

 wire the inleading terminals to the S circuit. 



Induction shocks can now be thrown into either the muscles 

 or the nerves. 



First stimulate the nerves with minimal interrupter shocks, 

 and note that the muscle of the poisoned side does not 

 contract, whilst the other does. 



The nerve has not been paralysed, because you are stimulating 

 a portion of nerve which has been under the influence of the 

 poison. 



Next stimulate the muscles, commencing with minimal 

 shocks and note which muscle contracts first ; usually the 

 unpoisoned one does (Rosen thai effect). This is due to the 

 excitability of the nerve in the muscle. 



Both muscles respond, hence they are not paralysed. 



There remains the conclusion that the end plates of the 

 nerves are the seat of the change. 



14 Effect of Veratria upon muscle. 



Required: Recording and stimulating arrangements as for single 

 contraction with direct stimulation of muscle. 



Apply a ligature to one leg of the frog in the same manner as for 

 the curara experiment, and inject 10 drops of 1/1000 solution of 

 sulphate of veratria into tlie dorsal lymph sac. The full effect of the 

 drug will take three-quarters of an hour to develop. When stimulated 

 the poisoned limb will exhibit prolonged contractions. 



