Page:Popular Science Monthly Volume 25.djvu/208

198 chest-walls, render a study of the condition of the heart entirely practicable by stethoscopic auscultation. By this method its size, its location, and the state of each of its valves can be learned with much precision.

The heart-sounds are sufficiently loud and distinct to be susceptible of much exactitude of description and characterization. The contraction of the ventricles, which mainly produces the "first sound," is the exertion of a force equal to the grasp of a strong hand; it is forcible and quick, but its time as represented by its sound is measurable. This sound is composed of two elements—one of propulsion, with a "booming" quality which is the characteristic, and one of valvular, or sudden clicking sound. Its rhythm, as observed in its succession, is trochaic.

The "second sound" is principally caused by the sudden arrest by the semi-lunar valves, of the column of blood in its tendency to return to the heart under the elastic recoil of the arteries after their forcible distention. It is quick and valvular; it is higher in pitch than the first sound and its rhythm is iambic.

Each of these sounds is more or less ringing and clear and has its appropriate timbre.

After an almost imperceptible interval, the "first sound" is followed by the "second," then by a rest; the whole cycle occupying about one second of time. Its divisions may be represented as follows: first sound, ; second sound, ; rest,. Each has its exact normal place of greatest intensity and perfection, relative to the external topography of the chest, and variations from this rule will be an index of change of structure within the heart itself, or of displacement from malformations or morbid conditions of the adjacent organs.

It is convenient to designate as heart-sounds those sounds which are normal, and as heart-murmurs those sounds which are adventitious and, as a rule, indicative of organic changes.

The murmurs are of peculiar character, of great variety, and usually of important significance. They originate either within the heart (endocardial) from defective valves or obstructed orifices, or else without it (exocardial) from friction against morbid accumulations within its membranous envelope; or, finally, though exceptionally, they are found to depend upon certain conditions of the blood.

The murmurs are very numerous and variable, and difficult of description according to any rules of rhythmics, melodies, or dynamics; as will be seen from the following names applied to them—and these only a fraction of the whole list: sawing, rasping, scratching, scraping, grinding, creaking, rubbing, churning, blowing, whistling, cooing, purring. And, as if from poverty of language, fashion or necessity has led to borrowing from abroad; as frémissement cataire, bruit de souffle, bruit de scie, etc. The terms in use should through some conventionality be revised. Many of them, however, are practicably