190 



THE POPULAR SCIENCE MONTHLY. 



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 tactics 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 y is audible even to the un- 

 aided 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 sub- 

 ject and the examiner ; while the stethoscopic method possesses nu- 

 merous 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 



Fio. 1. 



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 applica- 

 tion 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 with- 

 out 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). 



