heavy, or dead sound will be heard: so also when that part of the parietes covering the heart-the lower sternal region and that portion of the left mammary which is covered by the cartilages of the fifth, sixth, and seventh ribs-is similarly struck, the resulting sound will be dull; and if the heart be enlarged, or its investing membrane filled with fluid or its chief vessels enlarged by aneurism, the extent of dulness will be increased in proportion to the extent of the disease. The lungs yield their normal, full, clear sound, slightly more and more distinctly from above downwards, owing to their increasing capacity; the sound being muffled, however, by the pectoral muscles, the mammæ, and the scapulae. On the right side, from the sixth rib, a dead sound is produced from the presence of the liver; the same is elicited on the left, from the junction of the fourth costal cartilage with the left border of the sternum to the point where the heart's impulse is felt, owing to the position of the heart; while below on this side, to the left, at the sixth rib, the sound will be tympanitic, owing to the stomach being subjacent.

The morbid states discovered by percussion are few in number and simple in nature, but the indications they furnish are valuable.

Diminution of Clearness.-Whenever the density of the materials underneath the part struck is increased, there will be diminution of clearness-varying from a slight degree to perfect dulness, in proportion to the increased density-with shortening in the duration of the sound. Slight pleuritic effusion, congestion and partial condensation of the lungs, and spasmodic asthma during the paroxysm, are the chief causes of a partially dull sound on percussion; while in pleurisy with great effusion, in hydrothorax, in pulmonary apoplexy, in complete condensation of the lung from pneumonia, in phthisis, in cancer of the lung or pleura, in hypertrophy with dilatation of the heart, in pericarditis with effusion, and over aneurismal tumors, there will be an absence of any reasonant sound on percussion, or, in other words, perfect dulness.

Increase of Clearness.-Increased clearness and duration of sound, with excess of elasticity, is noted, where the relative quantity of air within the chest is increased, but not carried to such extremes as to interfere, by tension of the walls, with their vibration, as-for example-in pneumothorax, and at the upper part of the chest in hydro-pneumothorax, and in atrophy, hypertrophy, and emphysema of the lung. Dr. Stokes

has suggested that extreme anæmia, by lessening the relative quantity of blood in the lung, may increase the clearness of the percussion-sound. Increase of clearness and a duration of sound, with diminished elasticity, is observed where there is a surplus of air in the subjacent part, with considerable induration of tissue between the surface and the part containing that surplus,-a combination of conditions sometimes met with in phthisis, when a superficial cavity in the lung has a thin, indurated, and adherent external wall.1

Tympanitic Sound. This sound resembles the tone obtained from a drum, and is produced on percussing the stomach, or a portion of intestine filled with air, but never on percussing the healthy chest. When therefore it occurs, we may infer that a cavity filled with air exists beneath the spot percussed; and consequently in thoracic affections we obtain the clearest tympanitic sound in pneumothorax. It may also, however, be produced less perfectly in two conditions of the lung, independently of pneumothorax, viz.: 1, in the emphysematous portions of lung which often surround lung-tissue solidified from hepatization, tubercles, &c.; and, 2, according to Skoda, when the lung is gradually recovering from the compression of fluid previously effused into the pleural sac.

Amphoric Resonance and Metallic Tinkling.-Amphoric resonance-a modification of the tympanitic tone-is similar to that occasioned by striking a wine-cask partially or entirely empty. Cavities, larger than are required for the production of the tympanitic sound, and in which air can vibrate, are essential to the production of this tone. The only diseases in which it is heard are pneumothorax, and in tubercular cavities of large size, having walls equably and generally condensed. When the cavities contain a small quantity of fluid, metallic tinkling will be frequently audible, from drops of the fluid falling from the upper part of the cavity into the liquid below.

Tubular Sound.-The tubular percussion-sound, elicited from an elastic tube, filled with air, is natural only when produced over the larynx or trachea. It is heard, however, when any condition exists which brings the larger bronchial tubes unnaturally near the surface, or when any solid, sound-conducting substance is present between the bronchi and the surface. Thus it will be elicited in dilatation of the bronchi, in chronic consolidation of the lung, in some cases of pleu

See Dr. Walshe, op. cit. p. 71.

ritic effusion, very rarely in pneumonia, in small tubercular cavities, and in cases where a cancerous mass exists around the bronchial tubes.

The Bruit de Pot Fele.-The cracked-metal sound, resembling, according to Laennec, the sound given by a cracked pot when struck, or rather that elicited by the child's trick of striking the knee with closed hands to convey the idea that they contain money, is generated in the lungs when a large cavity exists under the part struck, having thin elastic walls, and a free communication with the bronchial tubes. It seems to be produced by the sudden forcible ejection of air and fluid along the tubes communicating with the excavation. According to Dr. Stokes, it may sometimes be elicited in cases of bronchitis where the secretion is thin and has gravitated to the lower parts of the lungs.

7. AUSCULTATION.

The genius, enthusiasm, perseverance, and energy of the author of the imperishable treatise, "De l'Auscultation Médiate, ou Traité du Diagnostic des Maladies des Poumons et du Cœur," have been so frequently discoursed upon, that it may almost appear a work of supererogation again to dilate upon that discovery by which Laennec forever holds mankind his debtor. As the Highlander, however, will not pass the cairn of his former benefactor or friend without adding a pebble to the tumulus, in grateful remembrance of favors received, so it is impossible for any author to enter upon the consideration of the subject of auscultation without his thoughts reverting to those days when, at the Parisian Hospital Necker, Laennec commenced that series of observations which enabled him, as he tells us, "to deduce a set of new signs of diseases of the chest, for the most part certain, simple, and prominent, and calculated, perhaps, to render the diagnosis of the diseases of the lungs, heart, and pleura as decided and circumstantial as the indications furnished to the surgeon by the introduction of the finger or sound in the complaints wherein these are used." But although we are now, one and all, only too happy to recognize the truth of this prediction, yet it was not so when it was penned in the years 1818 and 1819. How the facts brought forward were disputed, the inferences denied, and the stethoscope laughed at, are circumstances only too well known; and there can be but little doubt that had the work from which I have quoted

been written in a manner less excellent, or had the results drawn from repeated observations been less conclusive, Laennec would have shared the same fate as Avenbrugger, and auscultation-like percussion-might have waited for a Corvisart to introduce it to general notice.

It must not be imagined, however, that Laennec removed all the impediments or solved all the difficulties that surrounded the idol he set up. His death, in 1826, in the fortyfifth year of his age, prevented his doing much more than clear the way, and indicate the right path for research. Much remained to be done, and even now there is still much to accomplish. Happily there are men in this country, in Germany, and in France, whose chief desire appears to be to remove the existing obstacles.

Auscultation-ausculto, to listen-signifies the investigation of internal diseases by the sense of hearing. It may be immediate, when the ear is placed in opposition with the surface of the body, or mediate, when some conductor of sound, as a stethoscope, is placed between the ear of the auscultator and the person of the patient. Immediate auscultation may `be employed with the best success in some cases; the patient's chest should generally be covered with a soft towel or handkerchief, smoothly spread, and tightly drawn over the surface, and the examiner should take care that none of his hair intervenes between his ear and the chest of the examined, or sounds may be produced which will be readily mistaken for those proceeding from within. In the greater number of instances, however, mediate auscultation is to be preferred, a common hollow cedar-wood stethoscope being used as a conductor between the parietes of the chest and the ear. In employing this instrument it should be applied to the naked skin firmly, and held steady, just above the trumpet-shaped extremity, by the thumb, index, and second fingers; all friction between it and the clothes should be guarded against; both sides of the chest should be thoroughly explored; and the posture of the observer should be free from constraint.

AUSCULTATION OF THE RESPIRATION.

On applying the ear to the healthy thorax, the air will be heard entering and filling the lungs, and then leaving them, in perpetual succession. The sound caused by the ingress and egress of air, or, in other words, by inspiration and expiration, has been termed the respiratory murmur; it is caused

by the vibration of the tubes through which the air rushes, according to well-known acoustic principles, and it varies in character according to the age of the subject, the sex-being louder in females than males, and the part of the chest where it is heard, being spoken of as pulmonary or vesicular, bronchial, and laryngeal.

Pulmonary or Vesicular Respiration is heard all over the chest in health, except at those parts where it is superseded by bronchial or laryngeal breathing. The murmur is a sound of a gentle, soft, breezy character, heard with the movements of inspiration and expiration, but much more intensely with the former than the latter; though in healthy respiration the inspiratory and expiratory murmurs follow each other so closely, that they may almost be said to be continuous. The vesicular murmur is much louder during childhood than in after life, just as the whole process of respiration is then more active; hence a loud vesicular murmur is said to be puerile. Now although puerile respiration is a sign of health during the early periods of life, yet at other times it is not so, being indicative either of temporary excitement or of the presence of disease in some part of the lungs. Thus when one lung is rendered powerless, from the compression of fluid effused by an inflamed pleura, or when a portion only of a lung becomes solidified, as in pneumonic hepatization, the intensity of the respiratory murmur will be increased in the healthy lung or in the unaffected parts of the diseased lung, owing to the necessarily increased functional activity of the same, the compensating powers of the healthy lung-texture being brought into play.

In place, however, of the respiratory murmur being increased, it may become diminished or suppressed, as will occur when, from any cause, air is prevented from freely entering the lungs. Thus it will be diminished in obstructive diseases of the larynx, trachea, or bronchi, in bronchitis, in partial infiltration of the lung with tubercle, in pneumonia, in pleurisy with limited effusion, and in some cases of pleurodynia or even of old age, where there is feeble respiration from diminished action. So also it may be perfectly suppressed in complete obstruction of a bronchus, in pleurisy with abundant effusion, in pulmonary apoplexy, in spasmodic asthma during an intense paroxysm, and, very rarely, in infiltration of the lung with tubercle or other morbid matters.

Bronchial Respiration is audible over the situation of the large bronchial tubes, i. e. at the upper portion of the sternum, between the scapula on a level with their spines, and less