522 AUSCULTATION. 



ters- of the bronchial sound. In such instances, the obvious 

 source of fallacy will be at once corrected by having resort 

 to percussion. 



Bronchial respiration varies in intensity in different cases. 

 When extended over a considerable part of the thorax, it is 

 usually less powerful, and seems to come in greater part from 

 the smaller tubes. Occasionally it is more circumscribed 

 and powerful, seeming to originate in the larger bronchial 

 trunks ; in this case it is sometimes called tubal respiration. 

 It may be further modified by the existence of a cavity 

 which opens by a large orifice into a bronchial tube. The 

 sound, in this case, has a peculiar hollow character, resem- 

 bling that produced by blowing into a wide-mouthed glass 

 or porcelain vessel, and is known as cavernous respiration. 

 When preceded or accompanied by an acute, circumscribed 

 pulmonary inflammation, and a cough with a discharge hav- 

 ing the smell of decomposing animal matters, the cavity has 

 probably resulted from gangrene of the lung ; when the dis- 

 charge is white or purulent, a large abscess of the lung may 

 be diagnosed, while, in some few cases, it may be the result 

 of softened tuberculous matter. When a large cavity com- 

 municates with a bronchial tube through a small opening, the 

 resulting respiratory sound is called amphoric. It may be 

 very fairly imitated by blowing into a narrow-necked jug. 

 The usual cause of this sound is the existence of pneumo- 

 thorax, and a narrow communication between the cavity of 

 the pleura and a bronchial tube. It is very rare in the 

 lower animals, but two cases are noted by Delafond. 



The cavernous sound is in most cases to be distinguished 

 with difficulty from the bronchial or tubal breathing, while 

 the amphoric sound, when it does exist, is not to be mis- 

 taken. 



Rales. Besides the above, which are truly modifications 



