The diagnosis of the cases referred to in 1 2 is much aided by the character of the superadded sounds which are commonly present. This is especially remarkable in cases of pneumothorax; and m emphysema we know that bronchitis often coexists, and gives rise to the various sounds of that disease. In the first bursting of air into the cavity of the pleura, the intense dyspnces which it suddenly produces, determines at once the interpretation we ought to give to the tympanitic percussion sound; subsequently the invariable sequence of pleurisy and effusion—hydro-pneumothorax—is attended by other very peculiar sounds technically called the sound of succession and metallic tinkling. The loudness of the breathing, anteriorly or posteriorly, depends entirely on the position of the aperture by which the air enters, and its con tinuing open or not. 0 Emphysema commonly affects both lungs, though not equally; its weak, prolonged expiratory sound can scarcely ever be mistaken for the peculiar amphoric echo of pneumothorax, and the absence of voice-sound in the one contrasts strikingly with its metallic reverberation in the other ; not less different is the clear resiliency of the percussion sound in emphysema from that wooden hollowness which the tympanitic resonance of pnenmothorat acquires from inflammation of the pleura consequent on the admission of air.
Under there is not the same liability to error that we found in the same class in the clavicular region ; the differences observed on percussion are less delicate, and the early deposits of tubercle cannot be traced in the other parts of the lung. When dulness is perceptible, we have a more advanced form of disease, and there is not the same chance of error in mistaking its seat, when that happens to be on the more resonant side ; still it must be remembered, that the character by which we recognize an emphysematous lung is the combination of deficient, altered breathing with increased percus sion resonance; all other morbid states cogniiable by percussion at the pos terior and lateral parts of the chest belonging to those in which dulness and altered breathing go together. The respiration is weak and imperfect, or loud and harsh, over the seat of dulness ; and according to the extent to which vesicular breathing, however imperfect, is heard, do we determine whether the disease affects the superficial or the deeper-seated structure of the lung, except when pain puts a stop to the ordinary movement of the on the affected side ; but this very fact is one of the elements of diagnosis, and corrects our hypothesis of the condition of disease. It is, however, worthy of notice that, as compared with indications derived from the clavi cular region, dulness on percussion, though only of slight amount, may be accompanied by changes of breath and voice-sound which correspond to marked dulness in front. The causes of consolidation are in many respects analogous to those mentioned in Div. I., but mere compression may be ex cluded, because at the lower part of the chest we have always in such cases the evidence of the presence of fluid.
One condition only is specified as being traceable by the modification of the breathing and the percussion resonance; and this not because there is any.
thing specific in the one or the other, but simply from the pathological fact, that when the deposit is so distributed as to produce general imperfect dul ness and obstruction of the vesicular breathing, while the tissue has not be come so solid as to transmit loudly the blowing sounds of the large tubes, except, perhaps, at the apex, its character will be found after death to be tubercular and not fibrinous. The discovery of a similar condition in minor degree at the apex of the other lung puts this question beyond doubt.
The absence of any perceptible difference in percussion between the two lungs, as referred to in 4, is a more constant condition in diseased states at the posterior and lateral parts of the chest than in front, but it is also less material to ascertain the more minute differences, which are indeed in great measure not to be recognized by the student. When evidence of disease at one apex has been obtained anteriorly, the breath and voice-sounds jnay differ more or less throughout the whole extent of the lung; but when in the lower lobes they are exactly equal on both sides, we feel great certainty in the diagnosis of phthisis. If the difference in percussion be not perceived, al though really existing, as, for example, in general emphysema, in dulness affecting both sides of the chest, or in the early stages either of consolidation or dilatation, a correlative difference may yet be traced in the breath and voice-sounds, sometimes with and sometimes without superadded sound; and we must endeavor to ascertain the general character of the breathing in the individual who happens to be under examination, contrasting this, as the standard, with that heard on each side where the difference has been detected; that which deviates most is sure to be the seat of disease ; the voice may then help to determine whether it tend towards consolidation or towards dilatation.
At the upper part of the chest it is important to remember the natural ten dency to loudness on the right Bide, and this is especially remarkable over the spine of the scapula; but anywhere near the bifurcation of the trachea, owing to the different direction of the bronchi on the two sides, local loudness. even when it has a blowing character, may be disregarded. At the base in chronic states, differences of breathing without superadded sounds are of minor im portance when no dulness is made out : in acute cases, the early checking of the respiratory movement in pleurisy, and the absence of almost any indica tion in deep-seated pneumonia, should not be forgotten. It sometimes happens that very distinct evidence from general symptoms is obtained of the existence of pneumonia when the only auscultatory phenomenon consists of a diffuse voice-sound, reaching the ear more loudly on the affected side ; the breathing may be equal to, or only very little weaker than that on the opposite side ; more careful auscultation may detect somewhere or other a dis tant blowing sound proceeding from the consolidated portion, which is not altogether concealed by the vesicular murmur.