THE RESPIRATOEY APPARATUS. 305 



auditory canal. Auscultation is resorted to in cardiac and 

 certain abdominal diseases^ but is mainly used for deter- 

 mining the states of the lungs and air-passages. These, 

 especially the former, are less accessible than in man, on 

 account of the greater bulk of surrounding substances, the 

 pectoral position of the fore extremities, and the restlessness 

 of the patient. Also the animal cannot be made to give 

 us the various phases of respiration on demand. Though 

 our diagnoses cannot, therefore, be so exact as those of 

 human practitioners, auscultation is most valuable to us. 



Nasal sounds. — The normal rushing sound of air passing 

 through the nasal chambers is interfered with in cases of 

 tumours and other obstructions of these passages; also 

 when the mucous lining membrane is diseased. The ster- 

 torous character of breathing, as seen in coma, depends 

 on the state of the posterior nares and velum palati. 



Laryngeal sounds. — The passage of air through the 

 healthy organ gives rise to a rushing sound. In cases of 

 thickening or impediment the sounds known as roaring 

 and whistling (which are familiar to us) will be distin- 

 guished. A peculiar crowing sound is considered dia- 

 gnostic of " croup.^^ The voice, of which this organ is the 

 seat, is sometimes modified ; its tones are not varied, for 

 the organ is very simple, but it is not difficult to distin- 

 guish the peculiar lowing indicative of pain. 



In the trachea and bronchial tubes we still find the rush- 

 ing sound ; in health it is prolonged, almost uniform in 

 expiration and inspiration, and with an even transition 

 through its various modulations ; under disease it may 

 become the mucous rale, when fluid exists in these tubes 

 in excess, and air bubbles through it, the cavernous rale, 

 when the air rushes from a comparatively small tube into 

 a large space containing fluid, so that there is a special 

 gurgling sound. This, of course, can only be heard in 

 connection with disease in the lungs; it is found when 

 a cavity has been formed in those organs by suppuration, 

 or by bronchial dilatation. Sibilus, when the air rushes 

 through small tubes with a dry condition of their mucous 

 lining, such as is seen in incipient inflammation. Rhonchus 



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