Ill 



ELECTRICAL EXCITATION OF MUSCLE 



281 



polarising current. The second twitch, like the first, is recorded 

 graphically, and thus we obtain a comparative tracing of the 

 time-relations and magnitude of twitch in the muscle traversed 

 (polarised), or not traversed, by current. If v. Bezold's pre- 

 sumption were correct, that all points of the tract through which 

 current passes are excited simultaneously and uniformly, trre 

 comparison of the height of twitch in both cases would not 

 indeed determine the changes of excitability in definite points 

 of the intrapolar area, since the different elements would of 



FIG. 05. 



course participate collectively in such changes, each according to 

 its particular state at the moment; but we should obtain the 

 sum of resulting excitability, or as v. Bezold expresses it, the 

 " total excitability," in the tract of muscle traversed. As, how- 

 ever, it has since been demonstrated that induced currents, like 

 constant currents, have only polar action, the experiments de- 

 scribed can, of course, show no more than alterations in excita- 

 bility at the physiological kathode or anode. It is therefore 

 evident that v. Bezold's method only determines the alterations 

 in excitability at the ends of the fibres in a longitudinally 



