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500. Young colts should never be castrated when cases of strangles 

 are prevalent, as the result of the operation may prove troublesome ; 

 for abscesses may form in the groin and neighbouring parts. 

 Strangles frequently terminates in Roaring. 



501. Roaring is a peculiar noise made by the horse during the act 

 of mspiration, when put to heavy or fast work. It may arise from 

 obstruction of various kinds in the air passages, but is very often 

 traceable to a hereditary tendency. Injuries to the throat by foreign 

 bodies, setting up irritation and inflammation of the pharynx and 

 larynx ; tight reining of carriage horses, as with bearing-reins ; 

 severe colds, &c., are all liable to produce the disease, while long 

 peacock-necked horses are more prone to it than short-necked ones. 

 The complaint is mainly due to the muscles, particularly on the left 

 side of the larynx, becoming wasted away — atrophied ; losing their 

 bright red colour, and assuming the appearance of yellow strings, so 

 that they are unable to do their work of separating the cartilages 

 during the act of breathing. Thus the left side remains stationary, 

 and the vocal cord inside the larynx hangs loose and limp, so that, on 

 inspiration, more air rushes into the passage than can be conveniently 

 accommodated ; and if the breathing be in any way hurried from 

 exercise, this air, forcing itself through the half-opened passage, 

 produces the roaring noise. 



502. The wasting of the muscles above referred to is considered to be 

 due to loss of nerve power. The nerve supplying them is the inferior 

 laryngeal, a branch of the pneumogastric. The nerves on the two 

 sides of the neck and chest are known as the right and left recurrent 

 laryngeals. The latter passes down into the chest, winds round the 

 aorta, just above the heart, then proceeds up the neck with the carotid 

 artery to supply the muscles of the left side of the larynx. It has a 

 much longer course than the right nerve, and it is generally considered 

 to be more liable to derangement. Thus it is thought that the left side 

 of the larynx is more especially affected in roaring ; be this as it may, 

 mares and ponies are rarely so much affected as the heavier stallions 

 and geldings. Several operations have been tried for its cure, but, 



