THE POSTERIOR AND LATERAL REGIONS - § 1. When there is marked dulness on one side.
A. In simple serous effusion the absence of superadded sound confirms the diagnosis, proving that there is no affection of the lung : when fibrm is also effused, friction may occasionally be heard, but not always. The point at which it is most frequently detected is near the axilla, and towards the front of the chest : and this is the necessary result of the circumstance, that the lung floats upon fluid, which e,annot alter in volume during respiration ; consequently its free edge at the point furthest from its attach ments is that which will most readily partake of the movement of the fluid as it rises and-falls with the decreased and increased capacity of the chest in bre,athing.
B. When changes exist in the mterior of the lung along with the effusion of fluid.
a. We find, in certain cases, no superadded sound at all at the base; higher up, coarse crepitation; and still higher, perhaps towards the front of the chest, or under the axilla, fine crepitation, but its existence depends a good deal upon the stage of the disease.
b. In other cases there are throughout very abundant moist sounds, diminishing in intensity and in degree of coarseness to wards the upper and front parts of the chest.
These two conditions are very dissimilar, and are to be recog nized by the different character of the voice and breath-sounds; but they are still more marked by general symptoms, to which we shall subsequently refer; the one is pleuro-pneumonia, the other pulmonary cedema, with passive effusion into the pleura.
c. When the fluid begins to be absorbed after pleuritic effusion with no change in lung-structure, a crumpling sound is heard, on deep inspiration, analogous to that observed at the apex in some cases of tubercular deposit. It is an auscultatory curiosity rather than a phenomenon of any real practical value.
§ 2. With marked resonance on one side.
A. When pneumothorax is accompanied, as it very soon is, by effusion in the pleura, two sounds may be produced which are very diagnostic; the one a plash, if the patient be swayed some what quickly from side to side, technically called succussion, which exactly corresponds to the shaking of any liquid in a half empty jar; the other, a dropping of the fluid in which the shrunken lung has been bathed, while the patient remained in the horizon tal posture; it falls in successive drops from its lower border upon the surface of the fluid, when he sits up, with a peculiar ring, which is denominated metallic tinkling. These phenomena are
neither of them constant ; and it is to be noted that, by various authors, the term metallic tinkling is often applied to any inter rupted sound which has a metallic resonance.
B. In emphysema it is necessary, as already mentioned, for the production of superadded sounds, that bronchitis be present. If moist sounds be the result, they are louder and more distinct in general bronchitis on the non-resonant side, and never exist to any great extent in a very emphysematous lung: when found only in the dilated lung, they are generally also few, and coarse, heard perhaps only towards the end of expiration, and very often superseding all breath-sound whatsoever. The sonorous sounds, on the contrary, are more audible on the resonant side : a pro longed sonorous expiration, with excessive resonance, is nearly certain evidence of emphysema.
§ 3. When the difference on percussion is less marked, espe cially in regard to resistance.
A. Consolidation existing on the duller side.
a. The coincidence of fine crepitation with loud blowing or whiffing breathing, and exaggeration of voice, is very character istic of pneumonia: it is usually local, and perhaps shades off into b. When the dulness is more extensive, the blowing character of the breathing less peculiar, and the crepitation of a coarser kind, especially when this is audible over the upper part of the chest, we may suspect that the consolidation is tubercular. The hypothesis is confirmed if we find that the greatest amount of orepitation and the loudest breath-sound are heard above, and that both equally diminish as we descend, though occasionally fine crepitation may be heard at the base. Such are the indica tions of acute general tuberculosis of one lung; and though there be generally such differences, on auscultation, as are quite suffi cient to denote that it is not pneumonia, still we must chiefly look to other circumstances for correct diagnosis, because there is, in reality, often a certain degree of chronic pneumonia present at the same time. The condition of the patient is very different from what it could possibly be if there were the same extent of athenic inflammation : and the opposite lung very generally gives evidence of the development of tubtrcles at its apex. As soon as clicking or squeaking sounds at the apex take the place of crepitation, the apparent obscurity of the case is removed.