THE RESPIRATORY ORGANS 317 



acid, in 1 pint of cold water. Hypodermic injections of nuclein can 

 also be given with advantage, whilst the injections of prepared serums 

 is thought to have a preventive influence. 



504. 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. 



505. Roaring" is a peculiar noise made by the horse during the 

 act of inspiration 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, etc., 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 expanding 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. 



506. 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 lavyngeals. 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 



