. Electro-physiology . FIG. 33.—Curve of muscular contraction. (Helmholtz.) n, Moment of excitation. process to be examined, in magnitude, form, and duration. If the moment of stimulation is marked upon the recording surface, the rise of the lever from the abscissa does not usually coincide with the moment of stimulation, but occurs distinctly later, the muscle does not begin to shorten at the moment at which the induction shock takes effect, but a given time elapses before the charges produced by excitation bring about contraction, as ex- pressed in the movement of the lever (Fig. 33). T
. Electro-physiology . FIG. 33.—Curve of muscular contraction. (Helmholtz.) n, Moment of excitation. process to be examined, in magnitude, form, and duration. If the moment of stimulation is marked upon the recording surface, the rise of the lever from the abscissa does not usually coincide with the moment of stimulation, but occurs distinctly later, the muscle does not begin to shorten at the moment at which the induction shock takes effect, but a given time elapses before the charges produced by excitation bring about contraction, as ex- pressed in the movement of the lever (Fig. 33). The length of this time, measured between a and the begin- ning of the curve along the abscissa, was estimated by Helmholtz at about O'Ol sec. for a loaded frog's muscle directly excited by an induction shock. It is known as the period of latent stimulation (latency period), because during this time 110 visible mechanical effect is produced by the stimulus. Contraction of the muscle begins when the discharging stimulus has ceased, and is marked by the rising of the lever to the summit of the curve. From
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