238 DISEASES OF THE PARENCHYMA OF THE LUNG. 



the laity as pathognomonic of phthisis. Most patients, when they 

 consult a new physician, can state precisely what the size and extent of 

 the dulness was at the last exploration. Dulness in these regions sig- 

 nifies that a large tract of the parenchyma is infiltrated or consolidated 

 by growth of connective tissue. Tuberculosis never gives rise to a 

 consolidation of sufficient magnitude to render the percussive sound 

 dull. Hence, as a general rule, it is a favorable sign when the area 

 of dulness accords with the other symptoms, and when it extends its 

 limits in proportion as the malady advances. If it be otherwise, there 

 is reason to fear the existence of tuberculosis. 



The presence of lobular infiltration and of miliary tubercles, by 

 which the lungs' capacity for air is reduced, may give rise to a percus- 

 sion-sound which is not dull, but hollow and tympanitic. Much more 

 commonly, however, the percussion is not affected by such a condition 

 of the lungs. A distinctly tympanitic sound is most frequently heard 

 over a cavity containing air. If the pitch of the ring be altered by 

 opening and shutting the mouth, it is a sure sign of a cavity. 



From the metallic, tinkling sound upon percussion, which is of very 

 rare occurrence in consumption, it may be inferred that beneath the 

 point struck upon there is a large empty cavity, with smooth, regular, 

 and baggy walls, but we must first make sure that there is no pneu- 

 mothorax. 



The cracked-pot sound is produced upon percussion, over the seat 

 of a superficial cavity with thin walls, whereby the air is expelled into 

 a neighboring cavity, or into a bronchus with a hiss, which is charac- 

 teristic of the " bruit depot file" 



Auscultation, at the commencement of the disorder, and indeed 

 often in its more advanced stages, shows no irregularity beyond the 

 signs of a catarrh at the apex of the lung. There is a feebleness of 

 respiration, at other times it is extremely harsh, or the breath may be 

 drawn in a series of jerks (saccade). But, above all, there is the 

 greatest variety of moist rdles and peculiar squeaking rhonchi. Some- 

 times, after the patient has coughed, the moist rdles and the crackling, 

 squealing sounds cease. More frequently they are only heard after 

 the first breaths which follow a cough (Seitz). It is, therefore, always 

 advisable, in ausculting a patient, to make him cough from time to 

 time. It is easy to understand why peribronchial and pneumonic 

 deposits, which have not caused much solidification, and why tubercles 

 and tubercular masses, and cavities enveloped in parenchyma, still per- 

 vious to air, do not produce other symptoms than those of catarrh ; but 

 I must most decidedly express my disapprobation of that prevalent 

 belief according to which the signs of catarrh of the summit of the 

 lung are pathognomonic of consumption, as being both false and pre 



