204 ELECTRO-PHYSIOLOGY CHAP. 



method from that of Aeby. He employed the ordinary myograph, 

 in which the longitudinal alteration of a muscle or fragment of 

 muscle is recorded, using the latent period of the make and break 

 twitch as his criterion. The curarised sartorius was fixed by 

 its upper end to a cork trough fitted to its size, so that two 

 copper wires crossing the muscle at right angles to the direction 

 of its fibres clamped a certain portion of its length, about 4 mm., 

 between them, to two points in this trough. The ends of these 

 two wires served to fix the muscle to the cork, and made the 

 electrodes. The portion of muscle between them was thus at the 

 same time the tract traversed by the current. If the current 

 entered the muscle by the lower electrode, nearest to the record- 

 ing end, i.e. was, as v. Bezold expresses it, an ascending current, 

 the resulting curve showed that a longer time elapsed between the 

 moment of closure and the beginning of the twitch than when the 

 current left the muscle by the lower electrode, i.e. was descending. 

 In the first case, according to Bezold, the excitatory wave arising at 

 the upper (negative) electrode, had to spread itself over the intra- 

 polar tract, which was fixed at both sides, before it could enter the 

 free portion of the muscle below and through the lower (positive) 

 electrode ; in other cases the excitation started from the lower 

 electrode (which was now negative), and passed immediately over 

 to the free part of the muscle. The difference in the two times 

 which elapse between the moment of closing the current and the 

 beginning of the twitch corresponded to the time required by 

 the excitation to traverse the intrapolar tract of 4 mm. Yon 

 Bezold showed by the same method that on opening the circuit 

 the excitation started at the positive electrode. Aeby disputed 

 the conclusions of v. Bezold's experiments, but as Hering 

 remarks (I.e. p. 248), it is impossible to account for the time 

 differences found by v. Bezold, and constantly recurring in the 

 same sense, in any other way than by the different direction of 

 the current. The marked variation in magnitude of time- 

 difference, amounting to between 0*005 and 0'025 (average 

 0'012) sees., is perhaps, according to Hering, to be explained by 

 the fact that the conductivity of the muscle is disturbed in a 

 different degree at the part clamped, according to the amount of 

 pressure put upon it. Taking for granted then that the time 

 from the moment of closure or opening to the beginning of the 

 contraction is really longer when the upper contact makes the 



