452 



THE RESPIRATORY APPARATUS IN MAMMALIA. 



extremities of the cornua, by means of a short ligament interposed between 

 that extremity and the appendix of the superior border of the thyroid ; 2, 

 To the whole extent of the hyoid concavity, by an elastic membrane the 

 ihyro-liyoid membrane, attached to the body of the thyroid cartilage and the 

 superior border of the lateral plates of that cartilage (Fig. 228, 4). 



Fig. 227. 



Fig 228. 



SUPERIOR FACE. INFERIOR FACE. 



CARTILAGINOUS PIECES OF THE LARYNX, MAINTAINED IN THEIR NATURAL POSITION 

 BY THE ARTICULAR LIGAMENTS. 



a, Cricoid cartilage ; 6, 6, Arytenoid cartilages ; c, Body of the thyroid ; c', c', Lateral 

 plates of the thyroid; d, Epiglottis;' e, Body of "the hyoid; /, Trachea. 1, 

 Crico-arytenoid articulation ; 2, Capsule of the crico-thyroid articulation ; 3, 

 Crico-thyroid membrane ; 4, T hyro-hyoid membrane ; 5, Crico-trachealis ligament. 



B. The thyroid cartilage articulates with the cricoid by two small 

 arthrodise, which unite the posterior extremities of the branches of the first 

 cartilage with the facets on the external face of the second. A thin external 

 capsule incloses this articulation (Fig. 227, 2). These two cartilages are 

 also held together by means of a membranous elastic ligament the crico- 

 thyroid membrane, which passes from the angle comprised between the two 

 branches of the thyroid to the anterior notch of the cricoid (Fig. 228, 3). 



C. The two arytenoid cartilages are united, at their superior border, by 

 the arytenoid muscle and laryngeal mucous membrane. 



D. The latter cartilages are brought into contact with the anterior facets 

 of the cricoid bezel, by means of the concave articular surface of their posterior 

 border ; the result is a small, but very movable, arthrodial joint, inclosed 

 by a thin external capsule and by the surrounding muscles (Fig. 227, 1). 



E. These cartilages are also united to the thyroid through the medium of 

 the vocal cords. These are two elastic bands which project within the 

 larynx, and between them include the triangular space termed the glottis ; 

 their internal face is covered by the mucous membrane of the larynx ; the 

 thyro-hyoid muscles envelop their external face ; their inferior extremity is 

 fixed into the crico-thyroid membrane, and the angle of the thyroid cartilage ; 



