c. Moist sounds may be heard very extensively in one lung, which is the seat of a certain amount of dulness, from the break ing up of tubercular deposit: when limited to the lower lobe very similar phenomena are developed by the suppurative stage of pneumonia ; the moist sounds are closely analogous, and the exaggeration of the voice and blowing breathing of tubercular cavities there do not differ from what is ordinarily heard in pneu monia. The determination must rest chiefly on the history either of long ailment or of a recent acute attack, the symptoms of which have been necessarily severe when it has terminated in suppura tion; we may obtain evidence of pytemia, with its secondary abscsses : the diseases which afford such an explanation of the condition referred to, are much more frequently acute than chronic.
d. In the commencement of pleurisy, slight dulness is often accompanied by friction before fluid is effused. Occasionally, the exudation is wholly fibrinous, and the friction sound so intense, as to resemble crepitation.
e. If the evidence of consolidation be limited to the upper part of the chest, the same rules are applicable as those already de tailed in the previous Division ; with this difference only, that partial dulness over the scapula corresponds to marked dulness in the clavicular region. When the superadded sounds are found in both places they generally tend mutually to elucidate each other.
B. When the difference in percussion is caused by excess of resonance on one side, the absence of any morbid sounds on the duller side, and their presence on the more resonant one, would decide that the case was one of emphysema.
When moist sounds are to be heard on 'both sides, they will probably be most abundant on the duller one; and then the uestion must arise whether this be not the seat of disease. .As suraing that the c,ondition be one only affecting the lower and back part of the chest, we have to consider the phenomena con nected with the breath and voice-sounds as indicating dilatation or consolidation, especially observing on which side they deviate most from those heard a little higher up ; we have also to con sider the characters of the moist sounds themselves, whether large and coarse on the duller side, as they would be in the soften ing of tubercle and in suppuration of the lung, or whether, on the contrary, while finer and more numerous on that side, they are only found as a few coarse bubbles, where the greater reso nance is observed, the air moving in the large tubes while it is stagrt in the vesicle& longed sonorous expiration, so constantly heard in emphy sema would probably decid9 at once that the resonant side was that on which the greatest amount of disease existed : 8,nd it is to be remembered that such evidence may often be obtained in the clavicular region, when the lung is emphysematous at its lower part, and the ac,companying bronchitis is of such a cha racter that nothing but moist sounds can 'be heard behind.
o. The hypothesis of the existence of a tumor deeply-seated would derive great confirmation from the absence of any super added sound.
§ 4. When no difference is perceived on percussion. A. The percussion being natural.
a. The absence of superadded sound proves the lungs to be healthy, and taken in conjunction wit,h the same evidenoe in front, leads us to look elsewhere for the cause of any cough that may be c,omplained of.
b. Both sonorous and moist sounds are to be heard in cases of bronchitis, the former usually in the early stage of asi acute at tack, or where the disease is subsiding, the latter being its more ordinary manifestation, and being usually most distinct at the lowest part of the lung. When moist sounds are very fine, and limited to one side, the affection has been often mistakein for pneumonia; we must carefully ascertain whether the localization c,an be accounted for by consolidation, of which evidence may be found in altered breath and voice-sounds. If this suspicion be negatived, we are justified in believing that the case is one of simple bronchitis. It is much more usual to find moist sounds on both sides : and it is my belief that when the percussion is really natural, healthy breathing will always be found at the -upper part of the chest: in recent cases it is often accompanied by some sonorous sounds from the scantiness of the secretion in chronic cases, it is sometimes of rather a harsh character from loss of elasticity in the air-tubes. When the breathing is otherwise altered at the upper part, some further change has taken place in the lung, and there is in reality either increased resonance or dul ness on percussion. Sonorous sounds at the commencement of the attack are more frequently limited to one side than moist sounds.