Stimulation of Nerve-endings in Muscle. 89 



fibrillar character. In isotonic solutions the primary contraction 

 was lacking, but fibrillar twitches occurred, although less fre- 

 quently than in the hypertonic solutions. Hypertonic solutions 

 (2 per cent.) of sodium chloride failed to give anything more than 

 a small increase in tone. The marked primary contraction as well 

 as the isolated twitches observed in the hypertonic solutions of 

 sodium sulphocyanide were entirely lacking in the muscles of 

 curarized frogs or in frogs in which nerve degeneration had been 

 effected by cutting out a portion of the sciatic nerve. In the 

 latter experiments observations were made upon frogs at varying 

 intervals from 3 to 51 days after section of the nerve. It is 

 noteworthy that the falling out of the contraction caused by the 

 sodium sulphocyanide was observed as early as seven days after 

 section and at a time when a response could still be obtained from 

 the muscle by electrical stimulation of the peripheral end of the 

 nerve. So, also, in the case of curare it was found that the sodium 

 sulphocyanide contraction might be abolished even when the 

 curarization of the animal was incomplete. Two per cent, solu- 

 tions of sodium sulphocyanide have no stimulating action upon 

 the sciatic nerve when immersed in the solution. 



Conclusion. — The stimulating action of sodium sulphocyanide is 

 not simply a sodium effect. The fact that its action is abolished 

 by curare may be explained in accordance with Langley's hypothe- 

 sis of receptive substances, but the fact that its action is readily 

 removed by de-nervating the muscle is in contradiction to the 

 generalization made by Langley in regard to the improbability of 

 a special action of chemical substances upon the nerve endings 

 in muscle. 



Since hypertonic solutions of the sodium sulphocyanide do 

 not stimulate the motor fibers in the sciatic nerve, their action in 

 stimulating the muscle can be explained only on the assumption 

 that they stimulate the nerve endings, if one bears in mind that 

 this stimulating action falls out after the nerve fibers in the muscle 

 begin to degenerate, as well as after administration of curare. 

 It is noteworthy that the stimulating effect of this sodium sulpho- 

 cyanide upon the nerve-terminals disappears in the incipient 

 stages of the degeneration following section of the motor nerves. 



