A text book of physiology . th greater force ; and the flow of blood is guided onthe left side by the mitral and aortic valves in the same way thatit is on the right by the tricuspid valves and those of the pulmonaryartery. The Sounds of the Heart. When the ear is applied to the chest, either directly or by meansof a stethoscope, two sounds are heard, the first a comparatively longdull booming sound, the second a short sharp sudden one. Between 152 THE SOUNDS OF THE HEART. [Book i. the first and second sounds, the interval of time is very short, too shortto be measurable, but between the secon
A text book of physiology . th greater force ; and the flow of blood is guided onthe left side by the mitral and aortic valves in the same way thatit is on the right by the tricuspid valves and those of the pulmonaryartery. The Sounds of the Heart. When the ear is applied to the chest, either directly or by meansof a stethoscope, two sounds are heard, the first a comparatively longdull booming sound, the second a short sharp sudden one. Between 152 THE SOUNDS OF THE HEART. [Book i. the first and second sounds, the interval of time is very short, too shortto be measurable, but between the second and the succeeding firstsound there is a distinct pause. The sounds have been likened to thepronunciation of the syllables, lubb, dup, so that the cardiac cycle, asfar as the sounds are concerned, might be represented by :—lubb,dup, pause. The relative duration of the sounds, and of the pause, aswell as their relations in point of time to the changes taking place inthe heart, are shewn in the following diagram. Fig. Fig. 32. Diagrammatic Kepresentation of the Movements and Sounds of theHeart during a Cardiac Period. (After Dr Sharpey.) The ventricular systole, -which is here used to denote the action of the ventricle upto the closure of the semilunar valves, is represented as occupying about 45 , andthe two sounds together as rather more than half, of the whole period; but the diagramis intended to shew merely the general relations of the various events, and not to serveas a means of measurement. The second short sharp sound presents no difficulties. It iscoincident in point of time with the closure of the semilunar valves,and is heard to the best advantage over the second right costal car-tilage close to its junction with the sternum, at the point wherethe aortic arch comes nearest to the surface. Its characters are suchas would belong to a sound generated by the sudden tension of valveslike the semilunar valves. It is obscured and altered, replaced by murmur
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Keywords: ., bookcentury1800, bookdecade1870, bookpublisherlondo, bookyear1879
