In some

gives additional security against such a mistake. parts, it is true, the organs are different in the two sides; but to a considerable extent they correspond. It is also true, that the same state of disease may exist in the corresponding parts, so as to obscure the results of a comparison between them. But this is extremely rare. In general there is a marked difference in the sounds of the two sides in most cases of decided disease. To take advantage of this comparison, it is of course necessary, that the practitioner be accurate in his knowledge of the anatomy of the parts, or he may confound the flatness produced by striking upon a solid organ for that of diseased structure.

The practice of auscultation is founded upon principles of physical science equally well established. Sounds, which are caused by certain actions within the cavities of the body, are transmitted through the walls of the cavity, and are perceived when the ear is applied closely to the surface, or through the intervention of a proper instrument. These sounds are always alike under like circumstances, and are changed when the circumstances which caused them are changed. Hence the physician, if he render his ear familiar with the sounds caused by the internal actions of the body in a healthy state, will readily perceive a variation, when the part is diseased. What disease is indicated by any particular unnatural sound, he can learn only from repeated and extensive observations. But that there is a deviation from the natural state, he will perceive at once; and the accumulated observations of all the physicians, whose attention has been directed to the subject, have now gone far to explain most of the deviations which have been noticed.

These principles are chiefly available for practical purposes in reference to the actions of the lungs and the heart. The air in passing through the windpipe gives rise to a certain sound, which in health is always nearly the same. This sound is modified in the smaller tubes (the bronchia) into which the windpipe divides, and again still more decidedly in the little air vesicles in which the bronchia terminate, and which occupy every part of the lungs. These several sounds are readily perceived and easily distinguished by a practised ear, applied to the corresponding part of the chest and neck. Hence we have tracheal, bronchial, and vesicular

respiration; and if these are heard only in their appropriate places, and in a right degree of force, they indicate a healthy state of the parts.

When a portion of the lung is diseased, the current of air in that part is either obstructed or its natural force changed, and of course the sound is modified. Hence, by applying the ear extensively over the chest, we are enabled to detect the existence, and the precise seat, and generally the nature, of the disease. In inflammation of the lungs, the air cells are for the time obliterated in the part affected. As there are no vesicles for the air to enter, there is no vesicular respiration. But we have, what would not at first view be anticipated, bronchial respiration in its stead. In the healthy condition of the lungs, the porous character of the vesicular structure renders it a bad conductor of sound, so that the sound caused by the air in the bronchial tubes is not transmitted through them. But when they are consolidated by disease, they become good conductors of sound; and, at the same time, the morbid condition of the parts gives a greater degree of intensity to the sound itself.

Bronchial respiration, then, heard in the place of vesicular, always indicates -inflammation? That would be a simplicity in the art of distinguishing diseases, which nature does not tolerate. But it always indicates a consolidation of the lung from some cause, and inflammation is one of the most frequent of the causes. Another, and unhappily a frequent cause, is the deposition of tubercles, in incipient consumption. As in regard to percussion, so in reference to auscultation, there are means of distinguishing between the several morbid affections, which give rise to phenomena in many respects similar. These it is the business of the physician to study, and they often exercise his ingenuity and industry not a little. But it would lead us too far to attempt to ex

plain them here.

There are other morbid sounds in the respiration, besides those which arise from what we may call the misplacement of such as are healthy. When the membrane which lines the air passages is inflamed, as in common cold or catarrh, its surface is at first unnaturally dry; and in that state the current of air through the tubes gives rise to various sounds more or less musical, which are the different modifications of

the sonorous râle.* At a later period the membrane becomes more than naturally moist, and the passages are crowded, and more or less obstructed, by an adhesive fluid. In this state, if the ear is applied to the chest, the air is heard bubbling through the mucus, and this is the mucous rále. Inflammation of the substance of the lung, in its earlier stage, before the air vesicles are obliterated, is accompanied by a still different rále, the crepitous. In the advanced stage of consumption, a cavity, sometimes more than one, is formed in the lungs, at first filled with purulent matter, which is afterwards discharged through an opening into a bronchial tube. The air as it rushes into, and out of, this cavity in every respiration gives rise to a peculiar hollow sound, which is the cavernous rále. If the cavity is very large, and the opening into it from the bronchia small, the sound resembles that caused by blowing into the mouth of an empty bottle (amphoric resonance). The same sound is produced when air escapes into the cavity of the chest, compressing the lung; which is sometimes the result of an accidental injury, and sometimes of ulceration.

The sounds of the voice give still farther aid in detecting and distinguishing the diseases of the lungs. In the healthy state of those organs, no peculiar sensation is communicated to the ear, unless it be applied over the windpipe, or over the larger bronchia at the root of the lungs. But where a portion of the lung is condensed, whether it be by inflammation, or tubercles, or by the infiltration of a fluid into its substance, a resonance of the voice is transmitted to the ear at the corresponding part of the chest, resembling that from the bronchial tubes, and thence called bronchophony. When there is an empty cavity in the lungs, the sound is still more remarkable. The voice seems to enter the ear, as if the mouth of the speaker were applied closely to it. This speaking from the chest (pectoriloquy), when strongly

There is a good deal of difference of opinion as to the best term to designate these morbid sounds. Some writers use the English word rattle, and others the Latin rhonchus. We prefer to adopt the French rôle, used by Laennec. Where the thing to be expressed is new, it is better to adopt a new word, than to assign a new meaning to a word already in common use. As no new English word has been proposed, we can only do this by borrowing from a foreign language; and the French term was first introduced, and is more extensively used, and more agreeable to the ear than

the Latin.

marked, is a very decided characteristic of confirmed consumption, and sometimes gives evidence of a hopeless condition of that deceptive disease, long before the symptoms have led the patient to feel any apprehension. Dr. Williams says of it, "More than once has it occurred to me, that the very words, which in that delusive confidence with which this malady enshrouds its victims, ridiculed my examination of the chest, roundly saying, that nothing ailed them there, have belied their meaning, and, coming from the breast, have told a far different tale." A modification of the voice, of a different character, is observed in some states of the chest in pleurisy. The voice comes to the ear through the walls of the chest, not in its clear natural tone, but in a vibrating, thrilling, squeaking sound; like the bleating of a goat (hagophony).

Auscultation is applied to the investigation of the diseases of the heart as well as those of the lungs, although the actions of this organ are more obscure, and the phenomena which attend them are less understood. On applying the ear over the region of the heart, we perceive, in the first place, the impulse of the heart beating against the ribs; then we hear two distinct sounds, following each other at every pulsation, in regular succession. By habitual practice we learn to distinguish the natural force of the impulse, as well as its natural extent and limits, and the regular cadence or rhythm of the successive sounds, and to appreciate the difference if either is changed by disease. The diagnosis of the particular diseases of the heart and large arteries is still involved in much obscurity. Considerable progress has been made in the knowledge of them within the last few years, and much may be hoped from the investigations which are constantly going on. As it is, we are in general able to distinguish with confidence between the actual changes of structure in that organ, and the nervous, and sometimes imaginary affections, which have often, in past times, been confounded with them. And, in many cases, if not in most, we can ascertain the particular character of the morbid affection, and give a tolerably sure prognostication of its termination. There is here consolation in the fact, that some of these diseases, which were formerly classed together without any other distinction than "diseases of the heart," and regarded alike with terror,

as surely fatal, excite very little alarm, now that their true character, and the means of distinguishing them, are better

known.

Enlargements of the heart, or its envelope, are easily detected by the greater extent over which the impulse and the sounds of its action are perceived, and by the absence of the sound of respiration, in consequence of the encroachment of this organ upon the lungs, as well as by an enlargement of the corresponding part of the chest, and a change in the sound on percussion. But a knowledge of the general fact of an enlargement is not enough. We wish to know, whether it be a simple dilatation of the cavities of the heart, or the thickening of its muscular substance, or a distention of the pericardium by a fluid. And each of these has its appropriate, characteristic marks, so as to leave little cause of doubt between them. The membrane which covers the external surface of the heart, and that which lines its internal cavities, and occasionally also the muscular substance itself, are liable to inflammation; its numerous valves are exposed to various diseases; and both its cavities and its orifices are subject to unnatural dilatation or contraction. Most of these changes can be detected with a greater or less degree of confidence during life, and some of them are capable of successful treatment. We shall not trouble our readers with a description of the different sounds heard in the several diseases, as we have done in regard to the lungs; partly because these sounds are less fully understood, and partly because we are afraid of wearying them with so many details.

Let us now see how these two modes of exploration, percussion and auscultation, bear upon each other. We have thus far examined them only in their separate capacities. In their relations to each other, they do much to correct or confirm the results obtained from either separately. In all diseases of the chest, besides the knowledge obtained from the symptoms, we have two distinct modes of observation. If the inferences drawn from the sounds on percussion are confirmed by applying the ear to the chest, and, in regard to the lungs, we have both the respiration and the voice to reveal their secrets to us ;- and especially if these inferences are in accordance with the symptoms, we may feel an assured confidence, that we have come to a just knowledge of the disease.