110 PHYSIOLOGY OF MUSCLES AND NERVES. 



inductive sliocks are applied, each separate shock pro- 

 duces a muscular pulsation, and if many separate in- 

 ductive shocks are applied to the nerve, the muscle 

 passes into a state of tetanus. These inductive shocks 

 must be applied to the nerve at some distance from 

 the muscle. Each inductive shock induces a muscu- 

 lar pulsation. On cutting the nerve with a pair of 

 scissors, between the point irritated and the muscle, 

 all influence upon the muscle ceases. It is useless to 

 place two cut surfaces together, even with the greatest 

 care; they may adhere, and the nerve, when super- 

 ficially examined, may appear uninjured, but irritants 

 applied above the point of section cannot act through 

 the nerve upon the muscle. The same thing occurs if 

 a thread, passed round the nerve, is drawn tight be- 

 tween the point irritated and the muscle. The thread 

 may be removed, but the crushed spot proves an im- 

 passable barrier to all influence on the muscle. If, 

 however, the wires are moved and the inductive cur- 

 rents are applied to another point below the cut or the 

 constriction, the action at once recommences. 



3. The conclusion to be drawn from these experi- 

 ments is, either that the nerve, even if only a small 

 portion of it is irritated, passes at once into an active 

 condition throughout its entire length as far as the 

 muscle, or that the irritant acts directly only on the 

 spot immediately irritated, and that the activity which 

 is excited in the nerve at this point propagates itself 

 alonof the fibres until it reaches the muscle in which it 

 causes a contraction. If the latter view is correct, it 

 must also be inferred that any injury to the nerve-fibre 

 prevents the propagation of the activity in the latter ; 

 and it may also be deduced from the experiments with 



