AUSCULTATION. 521 



to some extent. In such instances, the sound generated in 

 the larger bronchial tubes is conducted along the unyielding- 

 walls of the smaller tubes, and through the hepatised tissue, 

 which, from its increased density, has become a better con- 

 ductor of sound, so that it ultimately falls upon the ear with 

 nearly all its original intensity. If such a case has been 

 previously watched, a crepitant rale will be found to have 

 preceded the bronchial respiration. Extensive deposition 

 of tubercle, from its causing more or less pulmonary con- 

 densation, will give rise to symptoms of a similar kind. 

 Bronchial breathing may result from dilatation of the bron- 

 chial tubes without any pulmonary condensation ; when con- 

 joined to the latter condition, this gives the loudest variety 

 of tubal respiration. Pulmonary emphysema may likewise 

 induce this condition ; but in this case, the absence of con- 

 densation may be ascertained by percussion, while, from the 

 frequent co-existence of bronchitis, crepitant and dry sibi- 

 lant rales are common accompaniments, and the cough is 

 small, short, and feeble. In dyspnoea from section of the 

 recurrent nerves, or in paralysis of the muscles of the glottis 

 from other causes, bronchial respiration may be heard over 

 the greater part of the chest independently of pulmonary 

 condensation; this is well observed in cases of roaring. 

 Notwithstanding the frequency of this symptom with con- 

 densation of the lung, it is not invariably met with in such a 

 case. Thus, when an entire lung is hepatised, the air in the 

 corresponding organ is placed in a condition of stasis, and the 

 solid mass meanwhile transmits the vesicular murmur of the 

 opposite lung, so that the healthy normal sound is retained. 

 In other cases, though the bronchial sound is audible, yet, 

 from its having traversed a solidified lung of little density, 

 the sound has become modified, and strikes upon the ear with 

 more of the softness of the vesicular than the usual charao 



