An American text-book of physiology . wo seconds in the frogs heart at ordinary temperatures. Coolinglengthens the period of negativity, warming diminishes it. Some observers Recently studied by Engelmann, 1895, p. 275; see also Knoll, 1894, p. 306, who observedfibrillary contraction of the auricle coincident with strong co-ordinated contractions of the ven-tricles. * Wooldridge, 1883, p. 527. Tigerstedt, 1884, p. 500; see also Krehl and Romberg, 1892, p. 54. * The isolated ventricle may, however, beat as rapidly as the auricle, although independ-ently of it (Bayliss and Starling, 1892, p. 408
An American text-book of physiology . wo seconds in the frogs heart at ordinary temperatures. Coolinglengthens the period of negativity, warming diminishes it. Some observers Recently studied by Engelmann, 1895, p. 275; see also Knoll, 1894, p. 306, who observedfibrillary contraction of the auricle coincident with strong co-ordinated contractions of the ven-tricles. * Wooldridge, 1883, p. 527. Tigerstedt, 1884, p. 500; see also Krehl and Romberg, 1892, p. 54. * The isolated ventricle may, however, beat as rapidly as the auricle, although independ-ently of it (Bayliss and Starling, 1892, p. 408). * Roy and Adami, 1892, p. 236; see also Knoll, 1884, p. 312. * Burdon-Sanderson and Page, 1884, p. 338. CIRCULA TION. 445 believe that the excitation-wave under certain conditions returns toward thebase after havinj^ reached the apex. The sjieed of the excitation-wave has beenmeasuretl by the interval between the appearance of nei^ative variation in theventricle when the auricle is stimulated first near and then as far as possible. Fig. 112.—The electrical variation in the contracting heart of the frog, recorded by acapillary electrometer, the apex being connected with the sulphuric acid and the base with the mercuryof the electrometer. The changes in electrical potential are shown by the line e, e, which is obtained bythrowing the shadow .of the mercury in the capillary on a travelling sheet of sensitized paper. The con-traction of the heart is recorded by the line h, h ; time, in jj second, by t, t. The curves read from leftto right. The electrical variation is diphasic; in the first phase the base is negative to the apex ; in thesecond, the apex is negative to the base; the negative variation passes as a wave from base to apex(Waller, 1887, p. 231). from the non-polarizable electrodes. The interval is the time which the excita-tion-wave requires to pass the distance between the two points stimulated. Theaverage rate is at least 50 millimeters per second.^
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