AUSCULTATION (auscultare, to listen), a term in medicine, applied to the method employed by physicians for determining, by the sense of hearing, the condition of certain internal organs. The ancient physicians appear to have practised a kind of auscultation, by which they were able to detect the presence of air or fluids in the cavities of the chest and abdomen. Still no general application of this method of investigation was resorted to, or was indeed possible, till the advance of the study of anatomy led to correct ideas regarding the locality, structure, and uses of the various organs of the body, and to the altera-tions produced in them by disease. In 1761 Auenbrugger of Vienna introduced the art of percussion in reference more especially to diseases of the chest. This consisted in tapping with the fingers the surface of the body, so as to elicit sounds by which the comparative resonance of the subjacent parts or organs might be estimated. Auen-brugger's method attracted but little attention, till Corvisart, in 1808, demonstrated its great practical importance; and then its employment in the diagnosis of affections of the chest soon became general Percussion was originally practised in the manner above mentioned (immediate per-cussion), but subsequently the method of mediate percus-sion was introduced by Piorry, and is that now largely adopted. It is accomplished by placing upon the spot to be examined some solid substance named a pleximeter (stroke-measurer), upon which the percussion strokes are made either with the fingers or with a small hammer tipped with india-rubber. The pleximeter consists of a thin oval piece of ivory; but one or more fingers of the left hand applied flat upon the part answer equally well, and this is the method which most physicians adopt. Percussion must be regarded as a necessary part of auscultation, particu-larly in relation to the examination of the chest; for the physician who has made himself acquainted with the normal condition of that part of the body in reference to percussion is thus able to recognise by the ear alterations of resonance produced by disease. But percussion alone, however important in diagnosis, could manifestly convey only limited and imperfect information, for it could never indicate the nature or extent of functional disturbance, or distinguish between different forms of disease, even in those organs which it had proved to be in an abnormal condition, while in other cases, and notably in many affec-tions of the heart, it could afford no assistance whatever.
In 1819 the distinguished French physician, Laennec. introduced the method of auscultation by means of the stethoscope (_______, the chest, and ______, to examine), with which his name stands permanently associated. For some time previously, physicians, more especially in the hospitals of Paris, had been in the habit of applying the ear over the region of the heart for the purpose of listening to the sounds of that organ, and it was in the employment of this method that Laennec conceived the idea that these sounds might be better conveyed through the medium of some solid body interposed between his ear and the patient's chest. He accordingly, by way of experiment, rolled up a quire of paper into the form of a cylinder and applied it in the manner just mentioned, when he found, as he states, that he was able to perceive the action of the heart more distinctly than he had ever been able to do by the immediate application of his ear. He thence inferred that not merely the heart's sounds, but also those of other organs of the chest might be brought within reach of the ear by some such instrument, and he, therefore, had con-structed the wooden cylinder, or stethoscope, which bears his name. This consisted of a cylindrical piece of wood, about 12 inches long, with a narrow perforation from end to end, the extremity for applying to the chest having a movable piece of conical form fitting into the cylinder, which was withdrawn by the physician while listening to the sounds of respiration, the complete instrument being used for examining the sounds of the voice and those of the heart. This instrument, though rendered portable by being made to screw into two halves, was inconveniently large and heavy, and was subsequently modified by Piorry to the form now generally used of a thin narrow cylinder of about 7 inches long, with an expansion at one end for applying to the chest, and a more or less flattened surface at the other for the ear of the listener. Having ascertained by careful observation the sounds elicited on auscultation of the healthy chest, Laennec studied the modifications of these as produced by disease; and by comparing cases with one another, and especially by investigating the state of the affected parts after death, he was able, in his cele-brated Traite de VAuscultation, mediate, to lay the founda-tion for a rational system of diagnosis of the great classes of pulmonary and heart complaints. It does not, how-ever, appear to be the case, as Laennec supposed, that mediate auscultation by the stethoscope is superior in an acoustic point of view to immediate auscultation by the unaided ear. On the contrary, sounds are heard louder by the latter than by the former method. Nevertheless, the stethoscope possesses special advantages, among the chief of which are that by its use particular areas can be ex-amined and compared with greater accuracy ; that it can be applied to all parts of the chest, and that it can be used in all cases where, from the sex or the bodily condition of the patient, the direct application of the ear is inadmissible. On the other hand, immediate auscultation is to be preferred in the examination of young children, who are readily frightened by the sight, and still more by the pressure upon them, of the stethoscope.
The whole subject of auscultation has been greatly elaborated since the time of Laennec, and while some of his opinions have been found to require modification, con-tinued investigation only serves more clearly to demonstrate the value of this method of diagnosis, and to elicit fresh and more accurate results from its employment. Although much remains to be done in the way of the correct interpretation of the phenomena observed in auscultation, yet the facts already established are among the most important

acquisitions in the whole domain of practical medicine.
The numerous diseases affecting the lungs can now be
recognised and discriminated from each other with a
precision which, but for auscultation and the stethoscope,
would have been altogether unattainable, a point which
bears most intimately upon the treatment of this great and
common class of ailments. The same holds good in the
case of the heart, whose varied and often complex forms of
disease can, by auscultation, be identified with striking
accuracy. But in addition to these its main uses, auscul-
tation is found to render great assistance in the investiga-
tion of many obscure internal affections, such as aneurisms
and certain diseases of the oesophagus and stomach. To
the accoucheur the stethoscope yields valuable aid in the
detection of «orne forms of uterine tumours, and especially
in the diagnosis of pregnancy,—the auscultatory evidence
afforded at a particular stage by the sounds of the foetal
heart being by far the most reliable of the many signs of
that condition. (J. O. A.)