ACTION OF VOLTAIC CURRENT ON MUSCLE. 431 



fatigue, regains it at the cathode the moment a voltaic current is led 

 through it ; whence it is evident that the cathodic after-effect cannot 

 be of the nature of exhaustion. Another reason for this conclusion is 

 that the decrease of the excitability at the cathode after opening, has its 

 counterpart in increase at the anode. The preceding facts are comprised 

 in the general statement that, during closure of the voltaic current, each 

 of the polar states first brought into existence (the cathodic augmenta- 

 tion and the anodic diminution) gives way to the contrary state, and 

 the relation between these two effects can be best understood by saying 

 that the normal state of muscle is intermediate between two opposite 

 states, which contrast with each other both as regards the ability of the 

 tissue to contract and the readiness with which it responds to stimulation. 

 This being so, we may expect that the loss of the second of these 

 qualities at a pole of the voltaic current would also be attended with 

 loss of conductivity. That this is so can be easily shown experi- 

 mentally, for if a curarised sartorius is so arranged that a current is 

 led to the middle of the muscle from its pelvic end, and if on its 

 cessation the tibial end is excited by an induction current, no response 

 takes place at the pelvic end, the wave of contraction being stopped half- 

 way by the cathode of the voltaic current. If the current is strong 

 enough, the block persists for some time after opening, but after the 

 passage of the same current in the reverse direction the status quo is 

 restored. What the cathode has done the anode has annulled, so that 

 the wave of contraction passes freely once more from end to end. 1 



Polar excitation of muscle by the voltaic current. Localisa- 

 tion of the excitatory effects at the poles. When a voltaic current is led 

 for a short time through a curarised muscle in the direction of the fibres, 

 it contracts when the current is closed. This closing contraction starts 

 at the cathode. 



The first experimental indication that the closing excitation is localised at 

 the cathode, was given by Schiff about half a century ago. 2 He found that in 

 a muscle in which the mechanical response to electrical stimulation is no 

 longer propagated, in consequence of poisons or cessation of circulation, a very 

 slight " idiornuscular hump " is formed at the cathode when a battery current 

 is closed through it, which does not spread. Not many years later, v. Bezold 3 

 showed that the localisation thus indicated had no necessary connection with 

 the absence of propagation, or the peculiar conditions of Schiff' s experiment, 

 but could be demonstrated on fresh curarised muscle. His method was 

 founded on the consideration that, inasmuch as the period of latency in 

 curarised muscle increases with the distance from the seat of excitation of the 

 part where the change of form is being observed, this distance can be 

 computed from the loss of time. A sartorius was laid in a shallow groove cut 

 in a cork plate, and kept in its place by two wires which crossed it at a distance 

 of half a centimetre from each other. These served as electrodes for the battery 

 current. The tendon end of the muscle was attached to a writing lever, and 

 the muscle so arranged that the latent period could be measured graphically. 

 This was found to be longer at closure when the current was directed from 

 the tendon, than when it was in the opposite direction. This difference in the 

 period of latency in the two cases evidently indicated that the starting-point of 

 the excitation wave must in either case have been the cathode. 



1 Biedermann, loc. cit., S. 252 ; Translation, vol. i. p. 296. 



2 Schiff, see " Beitr. z. Physiol.," Bd. ii. S. 13, 14. 



3 " Untersuch. ueber die electrische Erregung der Nerven und Muskeln." Leipzig, 

 1861, S. 239-244. 



