. A text-book of physiology : for medical students and physicians . ation of at least two factors,—a valvularelement due to the vibration of the auriculo-ventricular valves, anda muscular element due to the vibration of the contracting muscularmass. Accepting this view, there is a further difficulty in explain-ing the origin of the muscular element. According to some, it isdue to the fact that the contraction of the muscle fibers is not 554 CIRCULATION OF BLOOD AND LYMPH. simultaneous throughout the ventricle and the friction of the inter-lacing fibers sets up vibration in the muscular mass; a
. A text-book of physiology : for medical students and physicians . ation of at least two factors,—a valvularelement due to the vibration of the auriculo-ventricular valves, anda muscular element due to the vibration of the contracting muscularmass. Accepting this view, there is a further difficulty in explain-ing the origin of the muscular element. According to some, it isdue to the fact that the contraction of the muscle fibers is not 554 CIRCULATION OF BLOOD AND LYMPH. simultaneous throughout the ventricle and the friction of the inter-lacing fibers sets up vibration in the muscular mass; according toothers, the so-called muscular element is mainly a resonance tone ofthe ear membrane of the auscultator,—the shock of the contractingheart sets the tympanic membrane to vibrating. It seems uselessto attempt a detailed discussion of these conflicting views, since noconvincing statements can be made. Practically, the time at whichthe heart sounds occur is of great importance. A number ofobservers have recorded the time upon a cardiographic tracing of. Fig. 233.—To show the time relation of the heart sounds to the ventricular beat(Marey): , Tracing of the ventricular pressure in the right ventricle of the horse. Be-low the two marks show, respectively, the time of the first and second sounds. The firstoccurs immediately after the beginning of systole, the second immediately after the begin-ning of diastole. the heart beat with results such as are shown in Fig. 233. Thefigure shows clearly the general fact that the first sound is heardvery shortly after the beginning of systole and the second oneimmediately after the end of systole. The first sound is thereforesystolic, and the second sound diastolic. A more exact and de-tailed study of the time relations of the heart sounds has been madeby Einthoven and Geluk.* These authors obtained graphic recordsof the heart sounds. The sounds received first by a microphonewere transmitted to a capillary electrometer and th
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