DISEASES OF THE LARYNX 511 



is rendered specially liable to derangement, in consequence of its having 

 to wind round one of the larger vessels (aorta) emerging from the heart 

 before ascending the neck. This conclusion may or may not be the correct 

 one, but the fact remains that the right nerve, which does not take this 

 course, is seldom or never affected. Microscopic examination of the nerve 

 trunk has failed to elicit any information as to the intimate cause of the 

 paralysis, as no change in the structure of the fibres is observable, and 

 we are left to assume that whatever interruption there may have been 

 in the nerve current during life it was not of this nature. In its chronic 

 form roaring prevails in males to a much greater extent than in females, 

 and more frequently in stallions than geldings. It is seldom or never 

 seen in ponies under 14 hands, and the liability to the disease increases 

 with the height of the animal and the length of neck. 



Acute Roaring. We have hitherto spoken of the one principal cause 

 of roaring, but, as we have already pointed out, there are others of a less 

 serious character, and some of them amenable to treatment. It will be 

 understood that any obstruction to the free ingress arid egress of air in 

 the respiratory passage, and especially that portion of it which extends 

 from the nostrils to the lungs, may have the effect of producing a roaring 

 noise. A horse will roar when any tumour or obstructive thickening 

 exists in the nasal chambers, or from any undue pressure on the wind- 

 pipe. Eoaring may also be induced by pressure on the larynx, by an 

 accumulation of "matter" in the guttural pouches, by an enlargement of 

 the glands of the throat, or by a spasmodic contraction of the muscles. 

 Moreover, it may, and does, too frequently result from distortion of 

 the larynx following the abuse of the bearing rein, but whether this is 

 the explanation or not it is difficult to say. 



Symptoms. That grunting is a common accompaniment of roaring 

 is so well known among horse-dealers that they may be seen, in auction 

 sale-yards and other confined places, threatening the animals with a stick 

 to see if they grunt with fear, and pinching the throat to provoke a cough, 

 the quality of which is in a certain measure, and to an experienced man, 

 a guide to the existence of the disease. Though roarers very frequently 

 have this deep cough, which is a mixture of groan and cough, there are 

 many horses only moderately affected with the malady, who do not, 

 and will not, cough when the larynx is pressed, as there are also whistlers 

 who do not grunt on a feint being made to strike them. It has also to 

 be borne in mind that many horses of nervous temperament, and others 

 when out of condition, will grunt on being threatened with a 

 although perfectly sound in the wind. 



In this affection the patient, while at rest, shows no symptoms 



nor 



