78 Roaring in Horses. 



of the tongue, brings it to its erect position again. Its base 

 is attached to the middle part of the inner surface of the 

 thyroid cartilage by elastic fibres, which form a ligament — 

 the thyro-epiglottic— and the lower part of its sides is 

 connected with the arytenoid cartilages behind, by a fold of 

 mucous membrane on each side — the ary-epiglottidean 

 fold (Figs. 1, /; 3, j) — which contains two little bodies, the 

 cuneiform cartilages, or cartilages of Wrisherg. It is also 

 connected with the tongue by three ligaments. 



On the outer side of each ary-epiglottidean fold, between 

 it and the thyroid cartilage, is a depression called the 

 *' pyriform sinus," or " hyoid fossa," containing a thin mucus 

 which is secreted by a row of glands lying on its floor. The 

 sinus on each side meets its fellow behind the arytsenoid 

 cartilages to form one channel, which passes into the 

 oesophagus. 



In young animals the cartilages of the larynx are very 

 flexible, but with age they become rigid, and all, except the 

 epiglottis, have a tendency to assume a bony density. 



Muscles. 



The intrinsic muscles of the larynx are divided into two 

 sets, according to their functions : diloiors and constrictors, 

 or abductors and adductors. 



DiLATOK OR Abductor Muscles (Figs. 1, j ; 2, h). — 

 These consist of only one pair, the posterior crico-arytsenoid 

 •ni\x^Q\.Q^{crico-arytoenoidei postici). As their name implies, 

 they dilate the opening in the larynx by abducting or 

 separating the vocal cords from each other. They are the 

 inspiratory, or rather respirator}^ muscles of this organ, and 

 are by far the most important with regard to Roaring. 

 They are the most powerful of all the laryngeal muscles, 

 and their full functional vigour is absolutely essential to 

 perfect respiration. 



Arising from the bezel surface of the cricoid carti- 

 lage, and separated from each other by the vertical ridge 



