cuniary value to their authors. The three were then published, at the expense of the same gentleman, by the Massachusetts Medical Society, and distributed gratuitously, not only to all the Fellows of that Society, but also to every other regular physician in Massachusetts. To be distinguished as the successful one among such worthy compeers, is sufficient evidence of the value of this treatise in the estimation of those most competent to judge of it.

Like the others it was written for the medical profession, and is chiefly interesting to them, rather than to our readers in general. It gives a survey of the affections in which direct exploration is applicable, the extent to which it is required in consequence of the inadequacy of other means of investigation, and of the results to be obtained from the examination. Most of our readers must have often seen, if they have happily been too much exempt from disease in the last few years to have felt, the physician tapping on the chest of his patient, and then applying his ear, and listening wistfully, as expecting some wise suggestion from within. To many of them, all this has seemed like mere trifling or quackery, while others have been ready enough to suppose that valuable information is gained by it; although few, we believe, out of the medical profession, have any very distinct notion of the nature of this information, or of the principles on which the means of obtaining it are founded.

This knowledge we propose now to supply them; and, if their curiosity has been enough excited by seeing the process of thumping and listening (percussion and auscultation) to induce them to give us a hearing, we shall hope to make it all plain to them. We might do this chiefly in the words of our author. But, as we have already intimated, in writing for physicians, he has of course made use of the technical terms by which they avoid circumlocution and gain precision. We shall strive to make ourselves intelligible to the uninitiated, even though it may be at the expense of some more words, and of some loss of professional exactness.

The language of auscultation has been more encumbered with technical phraseology than any department of medical science. The later French medical writers, from whom we have derived a large portion of our knowledge on this subject, have shown a remarkable propensity to coin new words. Sometimes they doubtless obtain by this means a term, which

better expresses the qualities of the object they wish to designate. But, in many instances, the whole idea might be fully as well or better expressed by words already in use, and too often we get only new names for old ideas. The whole matter of auscultation has been peculiarly overburdened in this manner, by the use of new terms, coined with learned etymology from the Greek or Latin language; and we have no doubt, that a knowledge of its real utility has been greatly retarded by so much erudite phraseology. We do not mean to intimate, that the author of these "Dissertations" has exhibited any of this silly affectation. It is quite otherwise. He has merely used the language as he found it; and, writing for those to whom it is familiar, he had no reason to take any special pains to avoid or to explain it.

The principal methods of direct exploration, and the only methods of which we propose to speak, are percussion and auscultation. The others, palpation, succussion, &c., are either used too unfrequently, or their mode of application is too obvious, to demand our attention at present.

The principle, on which percussion is applied to the detection of disease, is sufficiently plain. Indeed, it is often used in the common affairs of life. The carpenter strikes his hammer against the wall, to ascertain where to drive his nail "in a sure place." The spirit-dealer knocks upon the head of his cask, to learn the quantity of liquor contained in it. With precisely the same view, the physician thumps the chest of his patient, that he may judge of the state of the organs by the sound which is given forth.

The chest is an enclosed cavity, containing, and in the natural state filled by, several organs of different degrees of density. Of course, the part corresponding to each organ gives a dull or a resonant sound, according as the organ is firm and solid, or light and porous. Much the greater portion of the chest is occupied by the lungs. They are of a light and spongy texture, partly filled with blood, and partly with air. The sound they emit is intermediate between that of an empty cavity, or one filled with air only, and a collection of fluid, or a solid organ. In the neighbourhood of the lungs is the heart on one side, and the liver on the other, both solid organs; the latter, indeed, not strictly in the same cavity, but capable of pressing upon the others. If either of these is increased in size, so as to encroach upon the lungs,

the existence and the extent of the encroachment will be shown by a flat sound in the place of the natural resonance.

If the membrane which lines the cavity of the chest becomes inflamed, a fluid is gradually poured out into the cavity, compressing the lungs, and occupying their space; and then a flat sound is the consequence. Or, the same space may be filled by air, introduced either by a wound, or as the effect of disease; and then the sound on the other hand is unnaturally resonant. The structure of the lungs itself is also liable to be changed by disease. On the one hand it may be emphysematous, too much distended by air, when the sound is hollow. On the other hand, it may be rendered unnaturally solid, either by a pressure of blood, or by inflammation, or by the formation of tubercles; either of which will cause the sound to be dull or flat in proportion to the extent of the disease.

It is not our purpose to go into particulars, and show how all the several affections are distinguished from each other. Such details belong to the physician, and must be studied by him with industry and care. The distinction is made partly by other considerations, and partly by differences in the percussion itself. We may give an example by way of illustration, of the extent to which this mode of investigation may be carried. We have said, that fluid in the chest, congestion of the lungs, inflammation, and tubercles, all cause a flat sound. How shall we know one of these from the rest? The formation of tubercles is a slow process, and the disease they produce is chronic; and it is attended by circumstances quite unlike those which ordinarily accompany the others. For this reason there can generally be little question between them. But this is not all. Tubercles are almost always first deposited in the upper portions of the lungs, while inflammation as generally occupies the middle and lower portions. In any case, therefore, where the disease has not advanced so far as to leave no room for doubt, if the flatness be in the upper part of the chest, the presumption is strong in favor of the existence of tubercles; if in the lower part, it is something else. In like manner, a crowded state of blood in the lungs is ascertained, chiefly by means other than those we are now considering. Between a collection of fluid in the chest, the result of acute inflammation of the lining membrane, and inflammation of the lung itself; that is,

between pleurisy and pneumonia, the distinction is not so easy. Both are acute diseases; and both give rise to many of the same symptoms. Indeed, so much alike are they in these respects, that it was formerly said to be impossible to distinguish them. Yet the importance of their effects is widely different. The one is a grave disease and often destroys life, the other is rarely fatal. And the treatment required by each is often very unlike. Here, too, we are by no means restricted to the use of percussion. Other modes of examination serve to explain, or correct, or confirm, as the case may be, the results of this.

what this can do.

But we must show

We have seen that, in pleurisy, the flatness of sound is caused by a fluid poured out into the cavity of the chest, taking the place of a portion of the lung. The flatness is consequently complete so far as the fluid extends, and there stops abruptly. In inflammation of the lung the condensation, and the consequent flatness, are complete only at the part most highly inflamed, and diminish by a more or less gentle gradation towards the healthy portions. This flatness, too, is constantly observed in the same place, whatever may be the position of the body, whereas in pleurisy every movement of the body causes the fluid to flow to the lowest part, and consequently changes the seat of the flat sound. These different circumstances are not always enough of themselves to establish a perfect diagnosis between the two diseases. But they go far towards it; and, taken in connexion with the results of the other principal mode of exploration, they rarely leave any just cause of doubt between them.

In detecting diseases of the heart, percussion, regarded by itself alone, will do little more than to point out an enlargement, without showing its precise character, or whether it be an enlargement of the heart itself, or a distention of the pericardium by a fluid. There are other means of making these distinctions, with a greater or less degree of certainty.

The organs of the abdomen are less concealed from observation, than those of the chest. The walls of the cavity are yielding, so that any considerable change in the size, or texture, or position, may be detected by pressure; a mode of examination now learnedly called palpation. Percussion is often useful, however, in diseases of these organs. It. enables the physician to discover their precise condition with

greater accuracy, to detect with more certainty the nature and extent of any enlargement of an organ, or the existence of any morbid growth, or the accumulation of a fluid.

From the almost constant use of percussion, in a large proportion of diseases, by most intelligent physicians, at the present day, and from the obvious principles upon which its proper application is founded, it would seem strange, that it should not have always been in use. But so it is. Until within the last few years, it was very little practised. Avenbrugger is said to have first introduced it as a new invention, in 1761. But his discovery excited very little notice until Corvisart called the attention of the profession to it, in 1808; and it did not come into general use until the publication of Laennec, in 1815. Since that time much has been written upon it, and much has been done to improve the art of practising it successfully.

At first, percussion was performed by striking with the ends of the fingers directly upon the part examined. But this is liable to serious objections. Besides that it sometimes gives pain, there is an uncertainty in the resonance, in consequence of the difference of texture in the several parts struck upon. The present practice is, therefore, always to interpose something to receive the blow. A variety of substances have been used for this purpose. An ivory plate has been much commended and much used; others prefer a piece of India rubber; and many use only a finger of the left hand. "Fingers were made before forks," says the prov

The circumstance, that the finger is always at hand, while any other pleximeter adds something to the already cumbersome apparatus of the physician, is much in its favor; though in general, that will practically be the best in the hands of any practitioner, which he is most accustomed to

use.

The degree of resonance on percussion is very considerably modified in different persons by the form and bodily condition of the patient. The chest of a thin, spare person, gives a much louder and clearer sound than one which is well clothed with fat and flesh. All this is easily taken into consideration by the physician, so that he is in little danger of mistaking an accumulation without the chest for disease within. A comparison between the two sides of the chest