296 ELECTRO-PHYSIOLOGY CHAP. 



wave of contraction initiated in the non-polarised section of the 

 muscle. In the first place, it is seen that the two halves of 

 the muscle do not, as before, contract eqiially, inasmuch as the 

 curves of twitch in the polarised half become smaller and smaller 

 during the passage of current, while on the directly-excited half 

 they remain unaltered. Finally, with renewed excitation of the 

 non-polarised half of the muscle, changes of form on the farther 

 side of the fixed spot fail altogether : the wave of contraction is 

 unable to get past the kathode. 



According to v. Bezold we should expect that the whole 

 intrapolar tract would by this time have become incapable of 

 conduction. This, however, is emphatically contradicted by the 

 circumstance that when the polarising current enters at the middle 

 of the muscle, i.e. when the anode is at that part, there is never, 

 even on applying very strong galvanic currents, and prolonging the 

 passage of current indefinitely, any perceptible impediment to 

 the propagation of a wave of contraction ; sometimes, as we shall 

 see, the direct contrary. There can therefore be no doubt that 

 fibre-points which have served for some time as the exit of a 

 sufficiently strong electrical current, fall into a condition in 

 which they become incapable of propagating a \vave of excitation 

 from one side to the other of the section. This impenetrability 

 of the kathode has also been established for nerve by Hermann 

 and Werigo (infra). The conditions of its development are pre- 

 cisely similar to those of muscle. 



That it is not the persistent closure contraction, localised at 

 the kathode as such, which interferes with propagation, is seen 

 (apart from the fact that both halves of the muscle frequently 

 contract equally, although at the kathode, in the centre of the 

 muscle, there is also a marked continuous contraction), in that 

 the inhibition is most pronounced when a persistent descending 

 current in the upper half of the muscle has reduced the original 

 persistent closure contraction to a minimum. It is therefore 

 legitimate to assume that the local fatigue of muscle-substance 

 produced by current at the kathode is the fundamental cause of 

 the inhibition of conductivity in that region. With regard to 

 the above observations on the rapid decrease of response at 

 kathodic points during polarisation, it might appear strange that 

 with the given experimental conditions the inhibition of con- 

 ductivity at the kathode is first exhibited at a comparatively 



