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fore, the contiguity of the lung and of the aorta must have been very close, whence the rubbing of the pulmonary tissue at each aortic dilatation gave a granular sound, as if the air were driven successively from several pulmonary cells." This explanation of the sound heard by Dr. Woillez is the same as that which I had already given in the cases reported above. I name this fact specially, because, from a note which he has made on those cases, he seems to have misinterpreted my reading of the phenomenon, and to convey a difference of opinion between us which in reality does not exist.

DIAGNOSIS OF PULSATILE PULMONIC CREPITATION,

DIFFERENTIAL AND ABSOLUTE.

Differential Diagnosis. There are four physical signs of disease, diagnosable by the stethoscope and by percussion, with which pulsatile crepitation may be confused. These are:

PNEUMONIC CREPITATION.

TUBERCULAR CREPITATION.

MOIST FRICTIONAL CREPITATION.
MINUTE MUCOUS Râle.

Pneumonic Crepitation, at first sight, and on careless analysis of facts, may easily be confounded with pulsatile crepitation; for it usually happens, that this lastnamed specific sound is heralded by an acute inflammatory paroxysm, in which there is much thoracic and febrile disturbance. The distinction in diagnosis rests on two broad differences. 1st, the pulsatile crepitation is louder and coarser than ever occurs in pneu

monia. 2nd, The crepitation is not absolutely governed by respiration: it is not absent when the breath is held, but is then most fully developed; it is presented in alternation with inspiration and expiration, during ordinary breathing, but is always synchronous with the beat of the heart or the pulse. 3rd, It is localised to particular points; i. e., to points where a portion of lung, a pulsating organ, and an opposing thoracic wall, are all brought into one focus.

Tubercular Crepitation may be co-existent with pulsatile pulmonic crepitation, in the same case. But tubercular crepitation may be known by the ear directly as a different phenomenon. If the tubercular sound be that which indicates an early stage of tuberculosis, its fine pneumonic character is sufficiently differential. If the tubercular crepitation indicate a late stage of tuberculosis, the moist character of the crepitation is equally differential: for the pulsatile crepitation, though loud and coarse, is essentially dry. Add to this, that the tubercular crepitation is independent of any pulsation, and is governed purely by the respiratory acts, and the distinction between the two phenomena is sufficiently clear.

Moist Frictional Crepitation, occurring in cases where, with tubercular deposit situated on the outer surface of the lung, there is slight pleuritic effusion, might be mistaken for pulsatile crepitation by the unwary; for in these cases the abnormal sound is superficial. But the crepitation in these tubercular pleurisies is moist and small, and is brought out only by a respiratory act. I have seen two cases where,

with tubercle in the lower anterior margin of the left lung, there was moist pleuritic friction; and, the impulse of the heart being plainly perceptible over the same region, a certain analogy was detectible, as between the sound thus induced and the pulsatile sound. But, on careful inquiry in both patients, the fineness and moistness of the crepitation, and its occurrence independently of the cardiac rhythm, were so obvious that no doubt could remain as to the diagnosis.

Minute Mucous Rále, occurring from effusion into the finer bronchial ramifications, is the last sound with which I am conversant, as possibly mistakeable with pulsatile crepitation. But every one who can distinguish a râle from a crepitation, can distinguish the difference required for this diagnosis; not to say, further, that the râle is synchronous with respiration and independent of the circulation,-not pulsatile.

Add, lastly, to all these facts, this one: that whereas, in cases of pneumonic crepitation, acute tubercular crepitation, moist frictional crepitation, or minute mucous râle, there is dulness on percussion over the seat of the auscultatory sound, while there is resonance on percussion over the seat of pulsatile crepitation; and the differential diagnosis is as perfect as can be desired.

Absolute Diagnosis. Pulsatile pulmonic crepitation is a loud harsh crackling sound, resembling that which may be produced by inflating a piece of lung-tissue, and, during the inflation, making forcible quick compression of the lung, so as to dislodge rapidly the air from the vesicles. The

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sound is heard only at the time when a pulsating structure, near to the point where it is met with, is presenting its impulse. Even then, it is elicited only when the lungs are charged with air. Sustained inspiration gives a condition in which the crepitation is presented at every impulse of the pulsating organ. Sustained expiration removes the crepitation, leaving to be heard the simple pulsatile sound of the vascular structure, and nothing more. The sound may be met with over the heart, i.e., between the heart and the thoracic wall; or over the aorta, i. e., between the aorta and the thoracic wall. Percussion over the points where the crepitation is detected yields a resonance, more or less clear according to the state of the respiration. During inspiration the resonance is very clear, during expiration it is reduced, but is less dull than is common on percussion over the body of the heart. Lastly, the sound under the stethoscope is superficial in character, seeming as though it proceeded from a limited point immediately below the thoracic parietes.

BEARINGS OF PULSATILE PULMONIC CREPITATION ON

PRACTICAL MEDICINE.

In the matter of treatment, a knowledge of the existence of pulsatile crepitation is of no affirmative value, or at most of little. The condition of lung which disposes to the sound is in itself comparatively harmless; and were it not so, it were difficult to devise any safe remedial means for removing the condition. But negatively, a knowledge of the nature

of the sound may prevent any mistake respecting its connection with pneumonic or other acute local inflammatory states, and may also prevent the employment of useless measures, which the hypothesis of the existence of inflammation as its cause might suggest.

In respect to prognosis, the sound has in some cases a definite meaning; in cases for example, where, as in the fourth case narrated by myself, there is, with tubercular crepitation anteriorly, pulsatile crepitation over the aorta behind. In such cases the explanation of the crepitation, without the necessity of assuming a posterior deposition of tubercle, throws a favourable cast over the prognosis; while in such an instance as that recorded by Dr. Woillez, the true reading of the cause of the crepitation removes from the mind of the practitioner all apprehension of danger, and converts what might in ignorance be considered a formidable sign into an interesting and harmless phenomenon.

The main value of a knowledge of pulsatile pulmonic crepitation relates, however, to diagnosis. For my own part, well drilled and taught in the science and art of physical exploration, I was for a period of several days utterly unable to explain the new sound, after first becoming acquainted with it in the case of Mrs. K. Indeed, my first impressions led me to attach much more importance to it than it really deserved. It occurred to me, in the first place, that the sound was possibly due to the fluctuation of some fluid enclosed in a cyst attached to the pericardium or to the outer surface of the heart, and

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