122 CLINICAL DIAGNOSTICS. 



In vesicular pulmonary emphysema, interstitial emphy- 

 sema (which is rare), and pneumothorax the field of per- 

 cussion is somewhat enlarged posteriorly, the diaphragm suf- 

 fering permanent backward displacement. 



An abnormally loud, full sound can be 

 heard under normal conditions if the wall 

 of the chest is very thin, under such circumstances the vibra- 

 tion of the lung being unusually audible. 



Exaggerated pulmonary resonance oc- 

 curs: 



1. If the lung is much inflated with air (emphysema). 



2. If the lung is abnormally distended with air as it oc- 

 curs at the border of pleural exudate. 



3. In pneumothorax. 



If the dull or flat percussion sound is heard where 

 the sound should be resonant, it always signifies disease. It 

 occurs : 



1. If the lung tissue becomes dense 

 from 



a. Pneumonic hepatization: in contagious 

 pleuropneumonia of the horse, and in contagious pleuro- 

 pneumonia of the ox as a rule a large portion of the lung be- 

 comes solid and liver-like, and emits, on percussion, a dull or 

 flat sound. In catarrhal pneumonias the pulmonary sound is 

 not so flat, because the solidification of the lung is not com- 

 plete, the morbid process appearing in the form of more or less 

 isolated centers or foci which are not entirely void of air. In 

 hypostatic, metastatic, and ichorus pneumonias, swin plague, 

 dog distemper, verminous pneumonia and tuberculosis the 

 percussion sound is not diffusely dulled, but a dull sound is 

 emitted over the dense diseased centers only. 



. b. Chronic interstitial pneumonia com- 

 bined with atelectasis. 



2. If tumors or neoformations are pres- 



