438 DISEASES OF THE LARYNX AND TRACHEA. 



a pig. An abscess had formed in the submucous tissue of the right 

 arytenoid cartilage, and caused marked narrowing of the glottis, 

 with dyspnoea ; the animal was slaughtered. Leisering detected 

 swelling of the vocal cords and of the mucous membrane of the 

 laryngeal pouches in a dog which had suffered from severe cough ; 

 and Hutchinson makes a similar report of a pig, killed on account 

 of dyspnoea. Necrosis of the cricoid cartilage had occurred. 



Perilaryngitis chronica fibrosa is commonest in horses. Pro- 

 gressive increase of connective tissue occurs, which sometimes under- 

 goes ossification ; its retraction fixes the aryteniod cartilages, 

 narrowing the glottis, and producing more or less severe dyspnoea. 

 Guilt reports this condition in a horse which had suffered from 

 broken wind. The larynx was ossified. Werner writes of an ox 

 which, after suffering for over a year from gradually increasing 

 difficulty in breathing, was found to have a laryngeal growth which 

 extended into the trachea. Moller has often seen chronic perilaryngitis 

 in horses. In four cases no cause could be discovered ; another 

 happened after resection of the arytenoid cartilage, causing failure 

 of the operation. Chronic inflammatory diseases of the mucous 

 membrane of the larynx are not very rare. In cows tuberculous 

 processes occur. In horses and dogs chronic catarrh of the larynx 

 is occasionally seen, though it seldom requires surgical treatment. 

 Chronic irritation in the deep layers of the mucous membrane, causing 

 proliferation, occurs oftenest on the vocal cords, which become much 

 thickened. Lee found both vocal cords in a horse covered with 

 cartilaginous growths. 



Symptoms. Chronic laryngitis and perilaryngitis are recognised 

 primarily by dyspnoea, which ensues more rapidly in cases where 

 pus formation is proceeding than in those where connective tissue 

 is being formed. At first inspiratory dyspnoea is alone recognisable, 

 but later difficulty in expiration may also be noted. So long as the 

 difficulty is confined to inspiration, the disease cannot easily be 

 distinguished from paralysis of the recurrent nerve, and is clinically 

 included under the term whistling or roaring. External examination 

 seldom discovers any structural changes, but if the process has extended 

 to the outer surface of the cricoid and thyroid cartilages, the larynx 

 appears of unusual size, although its outlines seem less sharply defined. 

 Ossification is recognised by hardness and resistance to pressure, 

 usually first remarked on attempting to make the horse cough by 

 scpieezing the larynx. Laryngitis chronica, with thickening oi the 

 mucous membrane, gradually produces dyspnoea, whistling sets in, 

 sometimes in aggravated form, and may be noted both in inspiration 



