Abstract
WHILST every one knows that the action of the heart is accompanied by sounds described as the first and second sounds of the heart, it is a remarkable fact that the mechanism by which the former of these phenomena is produced remains undetermined. It may be said to be almost universally accepted that the second sound is the result of the sudden tension of the semilunar valves, caused by the resistance which they offer to reflux of blood from the great vessels into the ventricles on the cessation of the systole. The difficulties which exist are connected with the first sound, and they result mainly from the fact that a number of events occur simultaneously with the systole of the ventricles and with the sound. Two of the most striking of these events, namely, the closure of the auriculo-ventricular valves and the muscular contraction of the walls, are regarded by many authorities as the source of the first sound. Sir Richard Quain in a paper recently read before the Royal Society has given a very graphic account of certain important investigations which lead him to the conclusion that neither of these explanations is correct, and which at the same time enable him to indicate what he believes to be the real explanation of the first sound of the heart.
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The Mechanism of the First Sound of the Heart. Nature 56, 567–568 (1897). https://doi.org/10.1038/056567a0
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DOI: https://doi.org/10.1038/056567a0