American journal of physiology . f the a wavecontinues throughout auricu-lar systole is apparent. Werethis statement correct, theupstroke of the a wavewould continue throughoutauricular contraction, , second; then, as the a-v Figure 1. (One half the original size.) Nor- interval is also only .1 second,mal. The second onflow wave shows well. •, 111 1 1 • . it would be prolonged intothe systolic rise (Mackenzies c wave), which occurs synchronouswith the beginning of ventricular systole. In other words, therewould be no downward stroke of the a wave. But such is not the case. In all of
American journal of physiology . f the a wavecontinues throughout auricu-lar systole is apparent. Werethis statement correct, theupstroke of the a wavewould continue throughoutauricular contraction, , second; then, as the a-v Figure 1. (One half the original size.) Nor- interval is also only .1 second,mal. The second onflow wave shows well. •, 111 1 1 • . it would be prolonged intothe systolic rise (Mackenzies c wave), which occurs synchronouswith the beginning of ventricular systole. In other words, therewould be no downward stroke of the a wave. But such is not the case. In all of the tracings to be pre-sented, both the rise and fall of the a wave have been com-pleted by the end of auricular systole, the upstroke continuing, ashas been stated, for .05 to .07 second and the downstroke havingthe same or a slightly longer duration. The presystolic fall is thenterminated by the rise occurring coincident with ventricular systole. 1/50 immrmMJ^iWMmmwmmmwh m i/wwW/wa wwimtwwwv The Venous Pulse i6i PR. INNOM. Auricular myograms usually show the systolic movement ofthe recording lever rounding off slightly and passing directly intodiastole, but in a number of the present tracings with a rapiddrum a distinct plateau, or pause, is seen occurring betweenactual shortening and relaxation of the auricular musculature(Figs. 2, 3). This plateau is necessarily of very short duration,and when it does not appear inthe tracing, it is probably due tothe fact that it is entirely ob-scured by the fling of the record-ing lever. The crest of the a wavecoincides with the beginning ofthe auricular plateau, — that is,the upstroke of the a wavecontinues throughout the periodof actual shortening of the auri-cular musculature. Then comesthe fall of the a wave, whichterminates with the end of theauricular plateau, or beginningof actual relaxation. At thispoint, or just before, also occursventricular systole and the sys-toHc rise in the venous pulse. The manner in which the c
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