Electro-physiology (1896-98) Electro-physiology electrophysiolog01bied Year: 1896-98 376 ELECTRO-PHYSIOLOGY CHAP. excitatory wave naturally varies considerably. Bernstein observed this, and Kiihne, to whose experiments we shall return later, found that the velocity, and with it the length of the excitatory wave, varied considerably. In the most unfavourable cases the former was 25 cms. per sec., in other cases, on the contrary, more than 2 m. This recalls the striking fact that the same muscle may propagate slow and rapid waves of contraction, and we are in fact in both cases concerned with t
Electro-physiology (1896-98) Electro-physiology electrophysiolog01bied Year: 1896-98 376 ELECTRO-PHYSIOLOGY CHAP. excitatory wave naturally varies considerably. Bernstein observed this, and Kiihne, to whose experiments we shall return later, found that the velocity, and with it the length of the excitatory wave, varied considerably. In the most unfavourable cases the former was 25 cms. per sec., in other cases, on the contrary, more than 2 m. This recalls the striking fact that the same muscle may propagate slow and rapid waves of contraction, and we are in fact in both cases concerned with the same phenomenon, since there is nothing to hinder the identification of ' excitatory wave' and ' wave of excitation.' It only remains, therefore, to establish the relations between this latter and the ' wave of contraction.' The fact that muscular contraction implies a latent period, which, according to Bernstein, is absent in the ' excitatory wave,' is a priori evidence that the ' excitatory wave outruns the wave of contraction, partially at least, in an excited muscle fibre.' As early as 1854, indeed, Helmholtz stated that the negative variation, at any rate in its steepest part where the secondary twitch is excited, was the precursor of contraction. He located it at the middle, v. Bezold later on at the beginning, of the latent period. Helm- 1 holtz (22) arranged his experiment as fol- FI.;. lows:—The nerve A of a muscle (Fig. 119) tive variation. Heim- connected with the writing - point of a holtz's experiment. ....... myograph, bridged over the longitudinal and transverse sections of the muscle B, the nerve of which was excited by a break induction shock, so that the negative variation of the muscle current of B produced secondary contraction in the muscle A. The measurable interval between the moment of exciting the primary preparation and the beginning of the secondary twitch of A was the sum of the four following time- values :—(i) interval bet
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