WHISTLING AND EOARING. 449 



respirator}' act, avg are materially assisted in forming a true 

 prognosis of the case. These disturbances or changes, upon 

 which the symptoms of roaring are chiefly dependent, may all 

 be grouped as connected with lesions occurring — (1) In the 

 nasal 'passages ; (2) In tlte ijosterior parts of the mouth and 

 pharynx ; (3) In the la.rynx ; (4) In the trachea. 



1. The Lesions which are chiefly met with in the Nasal 

 Passages, tending to the production of the unnatural sound 

 ' roaring,' are — (a) Alterations of the calibre of these chambers, 

 the result of injuries, by which the bony walls are depressed, or 

 projections of bone- structure are produced interfering- with the 

 movements of the air, and altering the character and pitch of 

 the sound resulting from the current, (h) Alterations in the 

 area of these cavities, the result of abnormal growths, either 

 directly connected with the membrane itself, or proceeding 

 from the bone-structures forming their boundary walls. 



2. In the Posterior Parts of the Mouth and Pharynx. — The 

 abnormalities of these parts connected with the production of 

 roaring are — (a) Fibrous growths, or mucous polypi of varying 

 characters and situation. Their mode of attachment is some- 

 what peculiar, being usually ver}^ movable, either from the 

 elongation of the mucous membrane to which they are attached, 

 or from the possession of a well-developed neck or pedicle. 

 From this we account for the dyspnoea and noise attendant on 

 their presence being so excessive at one time and nearly absent 

 at others, (b) Roaring will also occur from enlarged glands in 

 the pharyngeal region, and from the presence of pus or mucus, 

 either in a liquid state or when inspissated in the guttural 

 pouches. 



3. From Lesions occurring in the Larynx. — (a) Certain acute 

 diseases of the larynx proper are attended with an unnatural 

 respiratory sound, diagnostic of inflammatory action proceed- 

 ing in connection with laryngeal structures. This abnormal 

 respiratory sound will, in acute disease of the larynx, be so 

 appreciable that no disturbance of the horse is needed to 

 develop it. (h) Following the subsidence of the acute inflam- 

 matory attacks, and when it is believed that the animal is 

 perfectly recovered, unmistakable evidence may be afforded of 

 defective respiration whenever the horse is called upon to 

 perform even moderate exertion. Many of these cases will 



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