THE LARYNX 69 



attributing the affection to anatomical relationships of the additional 

 length of the left nerve which is found within the chest. Thus some 

 writers have endeavoured to connect the disease with certain pathological 

 conditions of the heart or great vessels on account of the close proximity 

 of the nerve to these structures. Enlargement and induration of the 

 bronchial lymphatic glands have also been cited as a cause. From an 

 anatomical point of view it will be easily understood that enlargement of 

 these glands would exert considerable pressure upon the nerve as the 

 latter passes forwards between the aorta and left bronchus. The 

 question, however, remains in obscurity, and the cause is not definitely 

 known. 



In a larynx the subject of this affection there is relaxation of the 

 left vocal cord, and during inspiration the left arytenoid cartilage 

 falls forwards and downwards towards the rima glottidis. The passage 

 of air through this part of the respiratory tube which has become 

 structurally so disarranged, leads to the production of the sound heard 

 in " roaring." 



No form of known treatment is effective in curing the paralysed 

 nerve and restoring the atrophied muscles to their pristine condition, 

 but there are methods of relieving the difficulty which the animal 

 experiences during respiration, and these methods are also effective 

 in causing a cessation of the abnormal sound which was heard. 



The two principal methods of treatment are the performance or the 

 operation of arytenectomy (excision of the affected arytenoid cartilage) 

 or of tracheotomy, which latter provides for the direct admittance of 

 air into the trachea. These operations will be described hereafter. 



Chronic Laryngitis. — This is usually due to injury by some sharp 

 substance taken in by the mouth. The anatomical position of the larynx 

 renders i-t to a great extent immune from external injury, since it is 

 protected by the vertical portions of the rami of the inferior maxillary 

 bone. The acute inflammation which follows the injury becomes 

 chronic and leads to extensive proliferation in the connective tissue 



