66 Roaring in Horses. 



the vagus nerve to correct or compensate for impediments 

 in the respiration, by modifications in the mode of breath- 

 ing. So it is that, if the lungs are imperfectly or with 

 difficulty filled, the inspiratory effort will be longer and 

 more energetic, as in bad cases of Roaring ; if, on the con- 

 trary, they are easily filled with air, but can only expel it 

 with difficulty, then the expiratory effort will be prolonged 

 and powerful, even spasmodic, as in " broken wind." 



When asphyxia is imminent, the mouth is in some cases 

 open (though it is only under extraordinary circumstances 

 that the horse breathes through the mouth), and the tongue, 

 congested and blue, is protruded to give more room for the 

 larynx, which is pulled spasmodically up and down by its 

 extrinsic muscles, and if seized externally by the hand can 

 be felt vibrating. The eyes are prominent and bloodshot, 

 and the whole countenance is wild and distressed-looking. 



In paralysis of both sides of the larynx (bilateral paralysis), 

 which is extremely infrequent in the horse, the stridor and 

 dyspncea are much more severe, and on the slightest exertion 

 or excitement are quickly developed; so that the animal 

 can scarcely walk without manifesting these symptoms in 

 the highest degree. 



3. The Cough. 



The cough of a horse suffering from one-sided paralysis 

 of the larynx in an advanced stage, is different to that 

 emitted when it is healthy, it being described as deep and 

 sepulchral. The air is expelled suddenly through an im- 

 perfectly closed glottis, producing a peculiar sound, due to 

 what laryngolists term " phonetic waste of air," followed at 

 once by a rapid deep inspiration, which causes the charac- 

 teristic noise, something between a scream and a grunt. It 

 must be explained, however, that some horses which are 

 not Eoarers will emit a sound resembling a grunt, and such 

 horses are designated " grunters " ; but the noise is produced 



