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AUSCULTATION 



the wails of a tube, obstructing it and producing at inter- 

 vals a clicking or crackling noise, which, during excited 

 breathing, is obviated, and merges into the sonorous rale. 

 The sonorous rale is best heard over the trachea at its en- 

 trance into the chest. 



The sibilant is dependent on the same cause as the sonor- 

 ous rale, but is generated in the smaller tubes, or the 

 larger, when their capacity is very much diminished. It is 

 a low, whistling sound, heard during inspiration or expiration, 

 or both, and subject to the same conditions, as regards in- 

 terruption and duration, as the deeper sound. Like the 

 latter, too, it commonly owes its origin to the onset of bronch- 

 itis, though it is likewise said to accompany some cases of 

 pulmonary emphysema. 



In certain cases, these sounds are modified, and resolve 

 themselves into a hissing noise, but this simply depends 

 on some alteration in the calibre of the tubes. When loud 

 enough to be heard without applying the ear to the chest, 

 these sounds constitute wheezing. 



The term mucous rale has been applied to a sound 

 produced in the bronchial tubes from the passage of air 

 through mucus, pus, or blood. It may be temporary or 

 permanent ; in the former case it may be removed by cough- 

 ing or even excited breathing, either of which may temporarily 

 clear the tubes in which it is generated. This rale may be 

 much modified according to the size of the air-bubbles in 

 any individual case. The size of these may be affected by 

 the kind of liquid present, by its amount, by its viscidity, 

 and by the strength of the current of air by which the tubes 

 are traversed. 



In bronchitis, with profuse secretion of viscid mucus, 

 especially when the breathing is slow, the resulting bubbles 

 are large, and the rale may be imperfectly simulated by 



