in ELECTRICAL EXCITATION OF MUSCLE 203 



excitatory pro&css is set up l>tj the current at its commencement 

 or end, as well as iliiriny its pcissaijc. The immediate presump- 

 tion which, at least for induced currents, was for long the only ac- 

 cepted theory, is obviously that excitation occurs uniformly at every 

 point of the area traversed, so that when current passes through 

 the muscle longitudinally, each transverse section falls into simul- 

 taneous, and, in so far as the excitability everywhere is equal, 

 uniformly strong contraction. The bare consideration of a 

 striated muscle stimulated by closure or opening of a current 

 gives no certain conclusion, for there is always, even in such 

 cases, an apparently simultaneous shortening of the entire 

 muscle, which must be due to an undulatory progress of the con- 

 traction, as, e.g., in the partial excitation of a muscle with parallel 

 fibres. The question must either be decided by delicate methods 

 of time-measurement, as in the determination of rate of conduct- 

 ivity, or by experiments on muscles in which, as in smooth 

 fibre-cells, the processes of contraction and conduction are 

 uniformly slower. Both lead to the same end eventually. If 

 total longitudinal passage of current in a parallel-fibred, cross- 

 striated muscle, e.g. sartorius, produces excitation which is trans- 

 mitted in undulations from one pole to the other, it must 

 obviously be possible, by means of two levers that rise succes- 

 sively at different points of the muscle, in consequence of the 

 wave of contraction which passes under them, to obtain two 

 curves of expansion, which, when the lever points lie vertically 

 one over the other, must easily show whether the two levers rise 

 simultaneously or no ; in the second alternative, the localisation of 

 the difference enables us to see in which direction the wave was 

 travelling. Aeby (20) tried to decide the question experimentally 

 on this principle. He laid two levers on the curve of the hori- 

 zontally situated curarised muscle, at a distance of 17 mm., which 

 recorded the expansion of the muscle, in consequence of functional 

 activity, on a rapidly rotating cylinder, and found that both 

 levers were simultaneously raised from the muscle when it was 

 excited by the make or break of a constant current passing 

 through it. This would to all appearance have been impossible 

 if excitation had really started from one end of the muscle only. 

 The result of this experiment is therefore in direct contradiction 

 with the preceding theory of a polar excitation of the muscle. 

 Von Bezold (10) tried to solve the problem by a different 



