IRRITABILITY AND CONDUCTIVITY 171 



Paralysis of Nerve Endings with Curare. 

 Make two nerve muscle preparations A and B$ 

 and fill two watch glasses with curare solution. 

 In one watch glass lay the nerve trunk of prep- 

 aration A and in the other watch glass the muscle 

 of preparation B. Cover muscle A and nerve B 

 with filter paper moistened with normal saline 

 solution, to prevent drying. At intervals of ten 

 minutes stimulate nerve B with induction 

 currents. 



When the poison has acted the stimulation of 

 nerve B will produce no contraction of the at- 

 tached muscle, which lies in the curare. Either 

 the muscle or the nerve has been poisoned. 



Stimulate muscle B directly. 



It contracts. Hence the curare has poisoned 

 the nerve ; probably the terminals of the nerve 

 within the muscle. 



Now remove nerve A from the curare and 

 stimulate the trunk of the nerve. 



The attached muscle will contract. Hence 

 the trunk of the nerve has not been poisoned 

 by the curare. 



It follows that curare poisons the endings of 

 the nerve within the muscle. Therefore, the 

 contraction of muscle B, in which the nerve end- 

 ings were paralyzed, must have been due to the 

 independent irritability of the muscle fibres. 



