ELECTROMOTIVE ACTION IN NERVE 239 



therefore compensates the demarcation current at a sufficient 

 intensity) according as, with previous closure of the nerve circuit, 

 the battery circuit is made, or with closed battery current the nerve 

 circuit is completed. The " apparent " closure twitch that appears 

 in the former case* alone must, properly speaking, be an opening 

 effect of the nerve current, as, on the other hand, the " false " 

 break twitch discharged after previous closure of both circuits, by 

 the opening of the key in the battery circuit, must be a closing 

 effect of the nerve current, as indicated by its absence when the 

 nerve circuit alone is opened. " If the branch current from the 

 battery is too weak to compensate the nerve current in the nerve 

 circuit, it will still have some effect in the same direction, though 

 not in the same degree. If, on the other hand, it is stronger 

 than is necessary for compensation, the current in the nerve, after 

 closure of both circuits, will actually be ascending, although it is 

 only, as it were, traversed by the remainder of the branch from 

 the battery current. If the nerve circuit therefore be closed, 

 with previous closure of the battery circuit, there will be no con- 

 traction, provided the branch current from the battery be not too 

 strong. If, on the other hand, the battery circuit be made with 

 previous closure of the nerve circuit, the opening effect of the 

 nerve current is superposed upon the weak and intrinsically 

 inadequate closing effect of the battery current, and a contraction 

 is obtained." 



" If the nerve circuit is opened with previous closure of 

 the battery circuit, there is no twitch, provided always that 

 the ascending battery current in the nerve is not so powerful 

 as to excite opening twitches notwithstanding its partial 

 compensation by the nerve current. If, on the other hand, the 

 battery circuit is opened with closed nerve circuit, the nerve 

 current simultaneously finds a new short-circuit, and contraction 

 follows, which is here still further augmented by the action of the 

 voltaic alternative" (Hering, 11). 



Accordingly, "on commencing operations with the weakest 

 outgoing branches of the battery current, as they find exit at the 

 transverse section of the nerve, the break twitch makes its first 

 appearance on opening the battery circuit, and only with much 

 stronger currents at break of the nerve circuit also. The ' make 

 twitch,' again, is first seen on closing the battery circuit, and only 

 with stronger deriving currents at closure of the nerve circuit also." 



