Identifier: handbookofphysio00bake (find matches)
Title: Hand-book of physiology
Year: 1892 (1890s)
Authors: Baker, W. Morrant, (William Morrant), 1839-1896 Harris, Vincent Dormer Kirkes, William Senhouse, 1823-1864. Hand-book of physiology. 13th ed
Subjects: Physiology Human physiology
Publisher: London : John Murray
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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ts. A, pivot upon whichpendulum swings; B, catch on lower end of myograph opening the key, C, in itsswing; D, a spring-catch which retains myograph, as indicated by dotted lines, andon pressing down the handle of which the pendulum swings along the arc to D on theleft of figure, and is caught by its spring. CH. xi.) SINGLE MUSCLE CONTRACTIONS. 469 pendulum carries a smoked glass plate upon which the writing lever of amyograph is made to mark. The opening or breaking shock is sent intothe nerve-muscle preparation by the pendulum in its swing opening a key(rig. 313, C) in the primary circuit. Single Muscle Contractions.—The tracing (muscle curve)obtained of a single muscle contraction or tivitch is seen infig. 314, and may be thus explained. The upper line (m) represents the curve traced by the end ofthe lever in connection with a muscle after stimulation of themuscle by a single induction-shock: the middle-line (I) is thatdescribed by the marking-lever, and indicates by a sudden drop
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Fig. 314.—Muscle-curve obtained by means of the pendulum myograph, s, indicates theexact instant of the induction shock; c, commencement; and m x, the maximumelevation of lever; t, the line of a vibrating tuning-fork. (M. Foster.) the exact instant at which the induction-shock was given. Thelower wavy line (t) is traced by a vibrating tuning-fork, andserves to measure precisely the time occupied in each part of thecontraction. It will be observed that after the stimulus has been applied, asindicated by the vertical line s, there is an interval before the con-traction commences, as indicated by the line c. This interval,termed (a) the latent period, when measured by the number ofvibrations of the tuning-fork between the lines s and c, is found tobe about y^- sec. The latent period is longer in some musclesthan in others, and differs also according to the condition of themuscle, being longer in fatigued muscles, and the kind of stimulusemployed. During the latent period there is no ap

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