Page:Popular Science Monthly Volume 25.djvu/200

190 This contraction causes the pulse, with its many qualities of quick or slow, soft or hard, regular or intermittent, and others which furnish to the tactus eruditus valuable indications of the physical condition not only of the heart itself, but also of the system at large.

The sounds of respiration are also heard: the inflation of healthy air-cells, producing the vesicular murmur, is audible even to the unaided ear.

This direct application of the ear to the chest (called immediate auscultation) is preferred by some as having advantages over the mediate or instrumental method. The former is, however, open to some objections which are readily apparent, both as regards the subject and the examiner; while the stethoscopic method possesses numerous advantages, without the objections.

The following is a brief description of the appliances ordinarily in use in exploring the thoracic contents:

First in importance among these is the stethoscope (Fig. 1). This instrument, in its primitive form, was exceedingly simple: at first a cylinder of paper, rolled tightly and of convenient length. A ready substitute was found in wood; and this was carved or turned to give lightness and to improve appearance. Cedar and ebony have been preferred, as being of fine quality and easily polished. Vulcanite and



various metals are also used, made in similar form—i. e., a tube of suitable length, expanded at one end into a hollow cone for application to the chest, and suited at the other end to the rim or opening of the ear. In these as in all other forms the object is to insure, when in use, a confined column of air extending from the bare walls of the chest of the person examined to the ear of the listener; and upon the completeness of the adjustment and consequent inclosure of the air depends the efficiency of the instrument, since the confined air—not the instrument—is the medium of conduction of the sounds.

The flexible tube was used later as a step in stethoscopic evolution, which gives the advantage of allowing comfortable respiration without disturbing the inclosed air of the tube by the movements of breathing, which tend to press the instrument alternately against the ear of the listener (Fig. 2).