RESPIRATORY APPARATUS. 120 



In the presence of small or large tumors which surround 

 lung containing air. 



2. If caverns containing air and large bronchiectasis are 

 present. The intensity and clearness of the sound depend 

 upon the size of the cavern and the momentary filling of the 

 same with air or exudate. 



3. In pneumothorax. 



4. In prolapse of the bowel into the thoracic cavity, 

 through a rent in the diaphragm. 



The tympanitic percussion sound has a metallic tinkling 

 tone when the walls of the air-containing cavity are smooth 

 and distended. 



The cracked-pot resonance. [This resembles the sound 

 produced by striking the hands, loosely folded across each 

 other, against the knee, the contained air being suddenly forced 

 out between the fingers — Loomis.] It occurs in the thorax 

 when a large air-containing cavern is in direct communication 

 with a bronchus. Forcible percussion causes some of the air 

 to be suddenly driven out of the cavern into the communicating 

 bronchus, thus inducing this peculiar resonance. 



The same sound may be heard, however, when a portion 

 of lung containing air is surrounded by a zone of hepatization. 

 The cracked-pot resonance, therefore, 

 does not always indicate the presence of a 

 cavern in the lung. 



If the dull or flat percussion sound is heard where the 

 sound should be resonant, it always signifies disease. It oc- 

 curs : 



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, therefore, on percussion, 

 a dull or flat sound. In catarrhal pneumonias the pulmonary 



