'20 Roaring in Horses. 



and the flanks convulsively heaving ; the head is extended 

 and lowered, the face anxious, the eyes prominent and 

 lustrous. 



In other cases the noise will only be heard during active 

 exercise, and then only during inspiration, or during inspira- 

 tion and expiration ; sometimes it varies in intensity, or is 

 altogether intermittent. Some horses, though the instances 

 are very rare, make a noise in their respiration when they 

 are at rest, and not during movement. Others emit a noise 

 during feeding and at no other time ; while those affected 

 with swelling of the lining membrane of the air-passages, or 

 in which there is any obstacle to the entrance and exit of 

 the air from these tubes, make a noise during inspiration 

 and expiration. 



All these differences, and the causes to which they are 

 due, need close investigation in the majority of instances; 

 for upon the result will depend the probability of remedial 

 measures being successful in restoring the affected animals 

 to efficacy. 



" Chronic Roaring," due to the wasting of the laryngeal 

 muscles, is that which is by far the most frequently met 

 with ; indeed, it is not, perhaps, verging on temerity to 

 assert that ninety-six or ninety-eight per cent, of the cases 

 of chronic Roaring have atrophy of these muscles as the 

 chief post-mortem appearance on examination ; and it might 

 also be affirmed that of these, ninety-nine per cent, show only 

 the muscles on the left side of the organ involved in atrophy, 

 those on the right side being usually increased in size, as if 

 to compensate for the loss of their fellows. The reason for 

 this peculiarity we will notice hereafter, when treating of 

 the pathology of this cause of chronic Roaring — the only 

 form we are now concerned with, as it is very prevalent, 

 and of all forms is the most serious. 



