. Kirkes' handbook of physiology . d the causes of the several vibrations ofwhich it is really composed have been demonstrated. In the tracing, figure 162, the intervals between the vertical lines rep-resent periods of a tenth of a second. The parts on which any given verticalline falls represent simultaneous events. It will be nees that the contraction ENDOCARDIAL PRESSURE 165 of the auricle, indicated by the marked curve at A in the first tracing, causesa slight increase of pressure in the ventricle which is shown at A in the secondtracing, and produces also a slight impulse, which is indica
. Kirkes' handbook of physiology . d the causes of the several vibrations ofwhich it is really composed have been demonstrated. In the tracing, figure 162, the intervals between the vertical lines rep-resent periods of a tenth of a second. The parts on which any given verticalline falls represent simultaneous events. It will be nees that the contraction ENDOCARDIAL PRESSURE 165 of the auricle, indicated by the marked curve at A in the first tracing, causesa slight increase of pressure in the ventricle which is shown at A in the secondtracing, and produces also a slight impulse, which is indicated by A in thethird tracing. The closure of the semilunar valves causes a momentarilyincreased pressure in the ventricle at Dr, affects the pressure in the auricle D,and is also shown in the tracing of the cardiac impulse D. The large curve of the ventricular and the impulse tracings, betweenA and D, and A and D, are caused by the ventricular contraction, whilethe smaller undulations, between B and C, B and C, B and C, are caused. Fig. 163.—Apparatus for Recording the Endocardiac Pressure. (Rolleston.) by the vibrations consequent on the tightening and closure of the auriculo-ventricular valves. It seems by no means certain that Mareys curves properly representthe variations in intraventricular pressure. Objection has been taken tohis method of investigation: First, because his tambour arrangement doesnot admit of both positive and negative pressure being simultaneously re-corded; second, because the method is applicable only to large animals,such as the horse; third, because the intraventricular changes of pressureare communicated to the recording tambour by a long elastic column of air;and fourth, because the tambour arrangement has a tendency to recordinertia vibrations. H. D. Rolleston, who has pointed out the above im-perfections of Mareys method, has reinvestigated the subject with a moresuitable apparatus. Kit; THE CIRCULATION OF THE BLOOD The method adopted by Rolles
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