AUSCULTATION. 89 



or of its rapid expulsion out of the air-cells. The sibilous rale issues from 

 the bottom of the air-cells, and constitutes a shrill, dry, hissing sound, 

 more or less prolonged and permanent. This rale is heard in pulmonary 

 emphysema, both vesicular and interlobular, with dilatation of the extreme 

 bronchi ; and particularly during deep and distressful expiration. Its 

 resonance through the bronchial tubes gives it strength and duration. 

 At the entrance of the chest the rale is a grave sound ; in the larynx and 

 nasal cavities a shrill one ; and in the open air is audible enough at a 

 distance from the animal. Its intensity, doubtless, depends upon the 

 extent of enlargement the bronchial tubes undergo. Many beginners in 

 auscultation are apt, in large animals, to confound this rale with the nasal, 

 laryngeal, or bronchial sibilation : careful exploration of the chest will 

 prevent this mistake ; inasmuch as the sound will always be found to be 

 accompanied by the dry crepitous rale, bronchial respiration of a very loud 

 character, and by catching of the breath. 



Cavernous rai.e. — This rale, as is indicated by its name, can only pro- 

 ceed from some anormal cavity or cavern, within the substance of the lung, 

 communicating with the bronchial tubes, and admitting air from them : 

 this last condition being indispensable. Should the cavern contain any 

 fluid, the air passing through it occasions gurgling or more or less ebulli- 

 tion, comparable to the noise produced by a current of air through a tube 

 into a fluid in a vessel, from which it can only escape in part. 



This gurgling, which itself constitutes the cavernous rale, is the more 

 distinctly audible the more capacious the cavern is, and the nearer it is 

 situated to the ribs. It is often accompanied by mucous and sibilous 

 rales. When the fluid contained in the cavern comes to flow into the 

 bronchi, and thence to be expelled by expectoration, the air, in passing 

 into this cavity, ordinarily terminated by a cul-de-sac, should the cavity 

 be near the ribs, gives to the ear an inordinately loud sound, called 

 cavernous respiration. When the cavernous rale follows upon circum- 

 scribed absence of the respiratory murmur, it becomes the sign of distinc- 

 tion between the bronchial and parenchymatous structures under disease 

 in that situation : this indication, in combination with such as are fur- 

 nished by the discharges from the nose, and the air expired, may enable 

 us to form some idea of the disease that has occasioned the cavern. One 

 observation we would make here, to prove the importance of immediate 

 auscultation, and that is, when the expired air is impregnated with the 

 odour characteristic of gangrene, and the cavernous rale is distinct and 

 circumscribed, we may afiirm, during life, that such a lobe of the lungs 

 is, in this part, the seat of an anormal cavity resulting from mortification. 

 This rale is also one of the best indications we possess of morbid altera- 

 tions in the lungs of our domestic animals. 



Pleural sounds, — When fluid becomes effused into the pleural sacs, 

 we directly imagine that it will discover itself by a rumbling, or by undula- 



