280 EOAEIN'&. 



wards remained a confirmed roarer. Amongst the principal of 

 the proximate causes I may enumerate : — 



I. — The formation of a false membrane within the 

 trachea. This is stated to have happened, and the trachea 

 to have been opened, and the false membrane removed, and 

 the animal affected to have been in consequence restored to 

 health. It is much to be regretted, however, that the parties 

 who have treated cases of this nature, have not furnished the 

 public with more ample details with regard to them. 



II. — Hypertrophy and ossification of the arytenoid 

 cartilages. The most confirmed roarer I ever saw was a case 

 which arose from the cause now stated. The animal was a 

 draught horse, the property of Messrs. Pickfords, carriers. 

 The horse roared at every inspiration when standing at rest. 



III. — Atrophy of the muscles which open one half of 

 the glottis, principally the arytenoid muscles of one cartilage. 

 "It is, however," says Mr. Spooner, "a matter of dispute 

 whether in these cases the state of the muscles is a cause or 

 a consequence of Koaring. Some contend that the Eoaring 

 arises from an affection of the nerves, by which the muscles 

 are thrown out of action, and therefore become absorbed." 



IV. — Pressure upon, or injury of, the recurrent laryn- 

 geal nerve. Anything giving rise to either active or passive 

 closure of the glottis will cause the animal to roar. In spasm 

 of the larynx a violent roaring sound is the consequence. 

 Irritation applied to the recurrent laryngeal will produce a 

 state of spasm of the organ ; while complete annihilation of 

 the nervous power of the recurrent laryngeal, either from 



