

ON NERVE-EXCITATION BY THE NERVE-CURRENT. 133 



new current comes into existence whether as a branch of the battery- 

 current or of the nerve-current, and consequently no electrical change 

 of the nerve. Nor can there be a contraction at opening of the 

 nerve-circuit, although such was present in the absence of the 

 battery-current. 



The preparation will act quite differently if a key is placed 

 between battery and rheochord in the ' battery-circuit ' as I shall 

 henceforth designate it for the sake of brevity. If the latter is 

 closed subsequently to closure of the nerve-circuit, this will be 

 equivalent, as regards the nerve, to opening of the nerve-current, 

 and the muscle will contract. And now what appears to be the closure 

 effect of a current derived from the battery, is, in reality, the effect of 

 breaking the nerve-current 1 . Under such conditions then a contrac- 

 tion is obtained if with previously closed nerve-circuit the battery- 

 circuit is closed; but, on the contrary, no contraction if with 

 previously closed battery-circuit the nerve-circuit is closed. 



If when both circuits are closed the key of the battery-circuit 

 is opened, the compensation of the nerve-current in the nerve- 

 circuit is removed, and the muscle contracts because the nerve- 

 current is at the same time reclosed. Thus, what now appears to 

 be an opening effect of the derived current of the battery, is, in 

 reality, a closure effect of the nerve-current, so that under the 

 conditions in question a contraction is obtained if, after previous 

 closure of both circuits, the battery-circuit is opened ; but, on the 

 contrary, no contraction if the nerve-circuit is opened. 



If the branch current from the battery is too weak to compensate 

 the nerve-current in the nerve-circuit, its effects will manifest them- 

 selves in the same direction as above, but not in the same degree. 

 If, on the other hand, it is somewhat stronger than is required for 

 compensation, the nerve will, with the closure of both circuits, be 

 traversed by an ascending current a remainder, so to speak, of 

 the branch current of the battery. And if the nerve-circuit is 

 closed after previous closure of the battery-circuit, there is no 

 contraction, provided the branch current of the battery does not 

 exceed a certain strength ; if, on the other hand, the battery-circuit 

 is closed after previous closure of the nerve-circuit, the opening 

 effect of the nerve-current adds itself to the weak, and of itself 

 inadequate, closure-effect of the branch current of the battery, and 



1 That under certain conditions the break-contraction due to the nerve-current 

 must in reality be considered as a new make-contraction by the nerve-current, has 

 already been mentioned on p. 129. 



