134 EQUINE ANATOMY. 



Thyroid. 



(Shield-like.) Composed of two portions united in front and 

 above to form its body; to its superior part the epiglottis is attached. 

 The lateral portions have an external surface, covered by muscles; 

 an internal, covered by mucous membrane; an anterior or supe- 

 rior border, to which the great cornua of the hyoid and the thyro- 

 hyoid membrane is attached; a posterior border, showing in front 

 the attachment of the crico-thyroid membrane, and behind an 

 articulating facet with the cricoid. 



Cricoid. 



(Like a ring.) Shaped like a seal ring with the seal upward, 

 and shows an external face, smooth, and on its flattened portion 

 spaces for the origin of the posterior crico-arytenoids, outside 

 these the articular facets for the thyroid; an internal face, covered 

 by mucous membrane; a superior border, with facets for the 

 arytenoids and attachment of crico-thyroid membrane; an infe- 

 rior border, responding to the trachea. 



Epiglottis. 



A soft, flexible lid that covers the entrance to the larynx. It 

 has an anterior face, which gives attachment to the hyo-epiglot- 

 tideus; a posterior, covered by mucous membrane; a circumference 

 and base attached to the thyroid. 



Arytenoids (two). 



(Like a pitcher.) Are situated above the cricoid and near the 

 top of the larynx. They are- irregularly quadrilateral and show 

 an internal face lined with mucous membrane; an external, giving 

 attachment to arytenoid, thyro-arytenoid and lateral crico-ary- 

 tenoid muscles; a superior border, united with the opposite; an 

 inferior, giving attachment to the vocal cord; an anterior, joining 

 with its fellow and giving the pitcher appearance; a posterior, 

 which articulates with cricoid. 

 Articulations of Cartilages. 



Thyroid, with cornua of hyoid, by thyro-hyoid ligament and 

 thyro-hyoid membrane. 



Thyroid with cricoid. 



Capsular ligaments for facets and crico-thyroid membrane. 



Arytenoids with cricoid. 



By capsular ligaments for facets. 



Arytenoids with thyroid. 



By vocal cords, a pair of fibrous bands which enclose a triangular 



