The principal fallacy in the first stage is when the healthy lung is supposedito be tubercular because the opposite one is emphy sematous • In the second, when pneumonia of the upper lobe le mistaken 'for tubercular consolidation • in the third, when a large tube is mistaken for a cavity, or a la'rge cavity is mistaken for pneumothorax. chronic pleurisy with empyema, attended by symptoms of hectic, sounds exactly resembling those produced by tubercular deposit may be heard under the clavicle ; the practitioner must be thrown much off his guard by some tmusual circumstance, who confounds these two conditions • but what has happened more than once within my own personal Imowledge, may happen again.
For the sake of the student we may point out more in detail the relations which superadded sounds present to the different modifications of breath and voicncound observed in the progress of the disease.
The voice-sound steadily mcreases in intensity from the beginning of con solidation to its ultimate termination in the largest possible. cavity. Not so the breath-sound ; this is first commonly harsh and exaggerated, or wavy and jerking; then the inspiration becomes diminished in intensity while the ex piration is prolonged ; and subsequently, when cavities begin to form, each increases in loudness, but the expiration more especially becomes remarkably blowing. With the first condition superadded sound is usually absent; some time a crumpling sound may be heard on deep inspiration, but if the presence of tubercular matter give rise to any inflammation, fine and coarse crepitation or moist and sonorous sounds are developed; the variations probably depend ing upon whether the vesicular structure or the tubes be more particularly the seat 9f the inflammatory action. Proceeding a little further, the sonorous sound is entirely replaced by moist sound, when the secretion from the tubes becomes more abundant; but in the same proportion does the air find diffi culty in entrance, and the breath-sound become partially suppressed ; this con dition is not necessarily permanent, and the lung may return to one in which the breathing is simply harsh and exaggerated. At this stage the presence of crumpling or of friction-sound or of one or two clicks is often of great ser vice in giving certainty to the diagnosis, when bronchial irritation has passed away.
In the second period the difference in resonance becomes quite distinct; but the student may feel uncertain which of the two is the diseased lung ; unless he compare the sound of the percussion stroke above and below on each side of the chest: The moist clicks now become more frequent, and are often mixed up with squeaking sounds ; coarse crepitation and sonorous sounds are more rare, or are heard only in the vicinity of where the softening has begun; moist sounds are common. There are two circumstances which tend to produce
these effects, the partial softening of small tuberculous masses, and the pre. sence of local bronchitis, and though clicks and squeaking sounds be more distinctive of the former, and moist sounds of the latter, yet they are by no means to be taken as their direct exponents, because each may be found in either circumstance. Another cause of the presence of moist sounds with deficient breathing is the recent occurrence of hiemoptysis ; dulness is com monly present, but it is slightly marked : the circumstance of hemorrhage having existed sufficiently explains the phenomenon, and, when heard only at the apex, moist sounds are pretty conclusive evidence that its cause is the previous deposition of tubercular matter, because we know of none other which can give rise to hemorrhage at the upper part of the lung only. As a necessary consequence of the presence of the fluid, whatever it may be, that produces these sounds, the entrance of air is impeded and the breathing is deficient.
Advancing still farther, the dulness becomes unmistakable ; indeed, the wooden or tympanitic sound over a cavity would always be called dull by any but an expert auscultator. The moist sounds become coarse, abundant, and mixed with larger bubbling, until a cavity of some size has formed, and then nothing but gurgling sounds are heard when the stethoscope is applied over it; in its immediate neighborhood the signs are those of less advanced dis ease. When numerous small cavities exist, the condition is marked by more general coarse or bubbling moist sounds. But besides the size of the cavity, the proportion of air and fluid which it contains greatly modifies the sounds it gives out, and we may even have no superadded sound at all. An empty cavity produces a loud blowing sound in breathing, but no gurgling ; a full cavity gives neither one nor other, but only dulness on percussion ; a cavity communicating freely with the bronchial tubes by an opening situated below the level of the fluid produces loud gurgling ; one in which a small opening is similarly situated may give rise to only one or two resonant explosions ; when the cavity is large and nearly empty, every sound produced within it has a metallic resonance ; in a small cavity or one nearly full no such effect occurs.