CHAPTER III. PERCUSSION—RATIONALE—MODE OF PERFORMING—PLEXIMETER (Part 1)

CHAPTER III. PERCUSSION—RATIONALE—MODE OF PERFORMING—PLEXIMETER —DIVISION OF CHEST INTO REGIONS—VALUE OF PERCUSSION. We now come to a highly important part of the subject—this is, percussion, or the method of estimating the density of the viscera contained within the thorax, by tapping lightly upon its surface. The rationale of this is very simple: the lungs occupy the greater part of the thoracic cavity, and are filled with air. If percussion be made upon them when removed from the body, they yield a very clear sound, especially if a solid yet clastic substance be laid upon them, so that it may receive the impul- sion of the striking body, and prevent it from sinking into the soft pulmonary tissue: this elastic body, or sounding-board, exists naturally in the thorax, and is formed by ribs and carti- lages; and a light tap upon their surface, that is, on the exterior of the chest, gives a clear, full, hollow sound. When the patient is thin, and the skin is very sensitive, he will not bear a smart tap without inconvenience; and, on the other hand, if he be very corpulent, or if the subeutancous cellular tissue be infil- trated with serum, the sound will be quite dull, and will not truly represent the condition of the internal organs. In order to prevent this chance of error to the observer, and of ineonve- nience to the patient, we placean additional elastic body between the chest and the end of our finger. This interposed body is called a pleximeter, and was invented by Dr. Piorry. Its only utility is to iner to the clastic parietes of the thorax, and to prevent the direct impression of the fingers upon the chest of the patient. Though the ribs are an excellent natural pleximeter; they are too sen- sitive at times, and at others are rendered useless for physical exploration by the softer sub-cutaneous deposits. By applying ¢ the body of sound, by giving more resonance PERCUSSION. 37 an artificial pleximeter we not only increase the resonance of the natural sounding-board, if we may so call it, but we bring it more fully into play, by compressing, and, as it were, thrusting out of the way the tissues which impede its vibrations, and then we gain the important advantage for ourselves and our patients of preventing pain, and in this way perhaps of increasing the disease. The only method of performing percussion which is now practised, is that by means of the pleximeter. It has so many advantages over immediate percussion, or the striking with the ends of the fingers directly upon the chest, that it is much better fitted for every purpose. The pleximeters used are various; that is, those that may be used; for, practically, they are reduced nearly to the most natu- ral pleximeter, that is, the forefinger of the left hand. But if we choose, we may make use of a piece of gum elastic, of ivory, or of metal. We take this in the fingers of the left hand, and hold it firmly upon the chest, afterwards percussing in the usual way with the right hand. If it be not applied firmly against the chest, a clacking sound is immediately produced by the air which is interposed between the instrument and the skin: this clack cannot be entirely obviated, for the tap upon the instrument will of course give rise to sound. If the material be very dense, the sound will be sharp and decided, and interfere a little with the pulmonary sound, that is, the resonance developed by the tissue of the lungs; for this reason there are some advantages attend- ing the use of the gum elastic pleximeter, rather than an ivory or metallic one, which is harder, and of course gives rise to more sound. The elastic instrument was, I believe, first proposed by Dr. J. B. S. Jackson, of Boston, and is the most conyenient. We can readily enough make one for ourselves, by taking a com- mon piece of gum elastic of the flat kind, about a quarter or a third of an inch thick, and about two inches square, that is of a size convenient for holding in the fingers. The density of gum elastic is more nearly similar to that of the chest, than a harder material, which is an additional reason for its employment, as it contributes to give a clear, uncomplicated sound. "The gum elastic pleximeter is easily made, but we are provided with one which is much more simple, and which I always resort 38 PERCUSSION. to—it is the forefinger of the left hand. In thin persons, the finger is even more bony and more elastic than the ribs; but in those who are fatter, or whose hand is remarkably stout and covered with a thick skin, the finger loses its elasticity, and is not so well fitted for the office of pleximeter. Still, under ordi- nary cireumstances, it is the best one which we can employ, and is superior to any of the ordinary artificial instruments, from its ready adaptation to different partsand irregularities in the chest. The finger may in this way be placed behind the clavicle or below it, and be brought very near the lung, which could not be done if the pleximeter were a broad and flat plate: any single limited spot may be examined in the same way with great ease. This natural pleximeter may be used in two ways: we may apply the dorsal or palmar surface upon the chest, and of course.tap upon the reversed side; if we apply the palmar surface upon the chest, the dorsal side upon which the percussion is made is firm, and gives a sharp clear sound; it is much better, therefore, for the accurate appreciation of slight deviations from the natural stand- ard. The palmar surface is occasionally more convenient, espe- cially when it becomes necessary to apply the finger to the de- pression behind the clavicle,—it is of course better for this pur- pose, that the finger should be curved to fit this depression ; hence, percussion must be made upon the palmar surface. Much of this nicety in the mode of applying the finger which serves as a pleximeter, will be found to be unnecessary, and may be dis- pensed with after a little practice; the shape of the hand and fingers of the observer will, however, have some influence on the position which will be found in practice most convenient. The most difficult part of percussion is not, however, the appli- cation of the hand which serves as a pleximeter ; this is very soon acquired. Much difficulty, however, is often met with as to the method of tapping or striking with the right hand upon the plexi- meter finger. We may use for this purpose either one finger or several, but you will find that for children, and for persons who are very thin, and whose chests are therefore quite sensitive, a single finger will be most convenient. Whether we use one or more fingers, the essential part of the process is to hold the hand as firm as possible, and to give the greatest possible elasticity to PERCUSSION. 39 the wrist. The motion should’ therefore be performed at the yrist, and not at the shoulder or elbow; if we strike with the whole arm, however gently it may be, we are apt to give the pa- tient pain, and we are sure to deaden the sound. “The sound depends mainly upon the elasticity of the wrist, and if the fingers be suffered to remain in contact with the pleximeter, or the thorax, a moment longer than is necessary for the percussion, the sound will be proportionately obscured. The slowness of the motion with which the tap is given is a frequent error with those who are slightly acquainted with phy- sical exploration. They are apt to pause as soon as the finger touches the surface, and allow it to remain in contact with the part; this is altogether wrong. It is at first difficult to acquire the perfect freedom of motion which is essential to elastic, clear percussion; still, it is perfectly practicable, with a little perse- verance and experience. There are some persons, however, who never acquire much readiness with percussion, however long they may attend to the subject; the difficulty is in the form of their hand, which is too stiff or the fingers too thick, to allow them to be readily bent and quickly struck upon the chest. They should therefore content themselves mainly with auscultation, trusting but very little to the signs of percussion. If we use a single finger for purposes of percussion, there is little difficulty in holding it in the proper position. Either the fore or’ the middle finger of the right hand may be selected as the percussor; we then bring it, as nearly as possible, into the form of a light mallet or hammer, and make the second and third phalanges serve as the head of the hammer; of course, they must be flexed at right angles with the first phalanx, and must be retained -firmly in that position, otherwise the form of the hammer is lost. The extremity of the finger should be as nearly at right angles with the hand as possible, otherwise the tap is not made with the extremity of the fingers, but the pulp, which is a matter of essential consequence, as the pulp of the fingers is soft, and non-elastic, and deadens the sound. If the thorax be covered with fat, or the parietes be infiltrated, it is necessary to percuss more strongly than is possible with a single 40 PERCUSSION. finger; in that case we bring the three middle fingers of the hand together, and allow them to rebound together after striking upon the pleximeter, they thus give a more forcible impulsion, and a sound nearly as clear as if a single finger were uscd. Indeed, we shall generally find this method the most convenient for the examination of the chest, although, as I have already stated, a single finger is the best pereussor in cases of children whose chests are thin and very clastic, or those in whom the thorax is very nearly in the condition of that of children, from great emaciation. Although when we use several fingers, our tap is of course stronger than if a single one be employed, we shall find in cither case that it is not the force, but the sharpness and quickness of the impulsion, which produces the sound. A hard blow causes so much clacking sound against the finger that it proves a source of error, and renders the full resonance of the chest more difficult to draw out. Plain and easy as these directions are, probably no one will at first practise them correctly ; we shall find that the elasticity of wrist, and light, clear tap, are learned but slowly, and after many efforts. There is, however, an easy method of improving our knowledge of percussion: we must repeat the operation fre- quently upon ourselves, at night, when we have removed our outer clothing, and all is quiet around us, a slight difference in sound then becomes perceptible, and the causes which render it dull are evident, and we thus learn to avoid those errors which are the more embarrassing from their apparent trifling insignifi- cance. Notwithstanding all the care we may take, we will not make equal progress in this matter; to acquire a perfect facility, a light and rather thin hand, and a correct car, are requisite; if we have not these advantages, we of course experience more difficulty, —but with increased practice and more attention, it may be overcome. An instrument has been contrived by Dr. Bigelow, of Boston, for percussion. It is a piece of whalebone or elastic wood, covered at the end with a ball of velvet or buckskin; the ball is nearly an inch in diameter: it isa very good instrument if any accident should deprive us of the full use of our fingers: the objections to it are, of course, the trouble and complexity of its use; hence PERCUSSION. 41 Dr. Bigelow himself advises it merely in hospital practice, where we have a large number of patients to examine, and our fingers sometimes suffer from constant tapping. If we use this instru- ment, we tap with the ball upon the pleximeter, which should be made of gum elastic. While i was at Paris, some years since, an ingenious friend of mine imagined an instrument for measuring the sound of percus- sion. It was to consist of a percussor somewhat similar to that of Dr. Bigelow, but enclosed in-a large stethoscope. The per- cussor was to be set in motion by a spring and wheel, as in watches, and the car to be applied to the stethoscope in the usual way during the action of the instrument: The idea was inge- nious, but the practical application of it almost impossible. Any contrivance to assist the senses in diagnosis must be extremely simple, or it will be practically useless; and, as a general rule, we do much better to trust to our hands alone for the percussion of the chest. Percussion is applicable to the study of abdominal as well as thoracic diseases; indeed, it is largely applicable to the explo- ration of many diseases of the viscera of both cavities. The abdomen contains solid viscera, such as the spleen and liver, and tubes filled with gas or liquid. - The gaseous contents are much more abundant than the liquid; hence the sound of percussion is clear over the greater part of the abdomen from the gas re- tained in the alimentary canal. If the quantity of gas be in- creased, we necessarily have an increased resonancé on percus- sion, and the converse is, of course, true; this fact enables us to estimate the effusion of liquid in the peritoneum, the enlarge- ment of the solid viscera, and the distension of the cavity of the intestine with a-large quantity of gas, which causes a tympanitic resonance. The same manual method of percussion is applicable here as in the exploration of the thorax; but,-in general, we shall find that a very light tap, with a single finger, is the best, espe- cially in those cases in which, the gas is contained in the larger intestines, and therefore approaches very near to the surface. Pereussion of the abdomen is always practised when the patient is lying upon his back, and the surface of the abdomen is there- fore placed in the situation most convenient for examination ; 42 PERCU SSIUN. but in the thorax we vary the position,—that is, we vary it in all those gases in which the patient is well enough to change his posture at pleasure : if he be too feeble for this, we must of course, examine him in any way that happens to be practicable. In ordinary percussion, our object is to place the patient in such a position that we may render the parictes of the chest as tense, and consequently as elastie as possible ; the muscles must there- fore be put upon the stretch, and the skin drawn tightly backwards. In pereussing the anterior part of the chest, the patient should sit upon a chair; or, which is still better, he may stand erect, and throw the shoulders slightly backwards, so as to render the pectoral muscles tense. For the posterior part of the chest the position should be reversed ; the patient must lean forward, and cross his arms strongly, to draw the scapule from the spine, and throw out the arch of the back. ‘I'o examine the axillary region, the arms should be raised above the head. The chest may be percussed at first in a cursory way on each side, to gain a general idea of the condition of the yiscera, and afterwards we may proceed to the details, and compare the sonorousness of different parts of the lungs and of the heart. The lungs are not equally sonorous throughout their whole extent; for as the clearness of the sound depends upon the large quantity of air contained in the vesicles, and the small quantity of solid matter, a difference in the relative proportions of these parts will give rise to various degrees of resonance ; thus, the sound is most clear wherever the vesicles are most numerous, and the larger bronchial tubes, whose walls are thick and firm, are least developed ; for the thin parietes of the vesicles present no obstruction to the vibration of the air eontained within them, but the hard walls of the bronchial tubes offer a very decided obstacle. Hence, if other things be equal, the sound may be stated to be most clear at the lower part of the chest, and along the anterior margin of the lungs, while it is comparatively dull at the summit and root; in the rest of the Where uated as to overlap the more solid portions of viscera contained in the chest, the sound is but moderately clear, becoming more dull as the thickness of the solid organ is greater than that of the lungs. This is the ease both with the liver and lungs the sound is intermediate, neither dull nor cle: the lungs are so s PERCUSSION. 43 heart, and is a fact which is analogous to the phenomena observed in adiseased state of the lungs, where alesion which renders the deeply-seated parts of the pulmonary tissue more solid, makes the percussion dull over the corresponding parts of the lung. - The dulness of sound is observed, notwithstanding the superficial portions of the chest, in which the lungs are placed, may be perfectly pervious to the air. The relative quantity of bronchial and vesicular tissue gives rise to the modifications in the clearness of the sound in per-