§ 2. Percussion indicates a marked difference between the two sides of the chest, one of them being unusually resonant.
A. The breathing is heard with a loud, blowing, amphoric sound; the voice has a similar character; the percussion reso nance, while tympanitic, has commonly a hard wooden tone: these are the characteristics of pneumothorax. • B. The breathing may be inaudible while the other characters remain the same. These, like the corresponding cases in the cla vicular region, are also produced by the presence of air in the pleura; and it is when the evidence obtained from the posterior and lateral regions is analogous to that of the clavicular region, that we can alone determine its existence with certainty when the amphoric breath and voice-sound are not heard.
c. Very rarely do we find the clear elastic resonance of emphy sema on one side contrasting very strikingly with the percussion stroke on the other; most commonly the affection extends to both lungs; the inspiration is generally inaudible, and the expiration characterized by one or other of the signs of bronchitis, or heard as a distant blowing sound; the voice-sound is less distinct than usual.
§ B. The dulness on percussion being less marked— A. The expiration is prolonged, and the voice-sound exagge rated where the dulness is observed, just as we have already mentioned in similar consolidation under the clavicle.
B. A slight amount of emphysema of one lung produces effects similar to those mentioned in Div. I.; louder breath and voice sound on the duller side, without auy character of harshness or alteration of rhythm; prolonged expiration is rather to be heard on the more resonant side; but, except it be accompanied by some form of superadded sound, this condition is not one of any importance.
c. In inflammation attended with pain, the motion of the ribs is interfered with, and there is slight dulness and want of breath ing, while the voice is generally exaggerated; if a forced inspi ration be taken we perhaps obtain the friction-sound of pleurisy or the crackling of pneumonia.
D. The breathing is sometimes weaker on one side below; as we ascend, it becomes more audible, but is harsh and unnatural; and above, loud blowing breath-sound is heard more distinctly at one apex than the other; the voice is always unnaturally loud.
Both lungs are, in truth, partially affected, but in one the signs of disease are much more evident: this is the usual condition in acute tuberculosis ; it is always accompanied by corresponding changes in the clavicular region.
§. 4. No difference is anywhere detected on percussion between the two sides.
A. The resonance may be natural.
a. The indications of disease derived from auscultation are limited to the apex, where they confirm the conclusions already arrived at in examining the clavicular region. A delicate ear may make out dulness in the supra-scapular fossa; but cases con tinually present themselves in which it is not possible for the majority of persons to do so.
b. On one or both sides the superadded sound of mucus in the smaller bronchi may be heard, when there is no change whatever in the density of the lung; this commonly happens in bronchitis.
B. Both sides may be unusually resonant; the chest full and rounded, the scapulce far apart, and little movement comparatively observed in breathing; the breath and voice-sounds are both weak, or almost null, perhaps some distant blowing expiration is audible; very commonly superadded sounds are detected. If similar circumstances have pointed to emphysema in the clavi cular region, the diagnosis becomes certain.
c. Both sides may be somewhat duller than natural; rarely, indeed, equally so on both sides, but still such as not to be very distinctly different. This may occur in cedema of the lungs, double pneumonia, and general tuberculosis; a difference in per cussion resonance is least perceptible in the first of these affec tions and greatest in the last, in which over the scapula and under the clavicle, it can almost always be made out; when the lungs are cedematous, the superadded sounds leave us in no kind of doubt; in pneumonia the dulness can often be determined by percussion m the axillary region when. it cannot be made out posteriorly. In any of these cases the presence of superadded sound, or a contrast between the loudness and rhythm of the breathing, suffice to prove that there is something wrong, and we must assume that they in reality belong to the next class.