LARYNX. 71 



This cartilage is connected to the cricoid cartilage by a 

 membrane called the crico-thyroid. 



The CRICOID CARTILAGE forms a complete ring, and is 

 thicker than the thj-roid ; it is broader behind than in front, 

 and resembles somewhat in its shape a signet ring; the 

 inner surface is smooth, the outer is rough for the attach- 

 ment of muscles ; the lower border is straight, and united 

 by a fibrous membrane with the first ring of the trachea; 

 the upper border is irregular. 



The ARYTENOID CARTILAGES are two in number, one on 

 each side, and are placed on the upper border of the cricoid 

 cartilage at the back of the larynx ; they are pyramidal in 

 shape, having a base and three surfaces ; at the lower part 

 there is externally a short process called the muscular pro- 

 cess, and anteriorly a longer pointed process, the vocal 

 process. Attached to the apex of each cartilage is a small 

 fibrous body, called the cartilage of Santorini. 



The CUNEIFORM CARTILAGES, or CARTILAGES OF WRIS- 

 BERG, are attached to the middle of the external surface of 

 the arytenoid cartilages ; they are sometimes wanting. 



The EPIGLOTTIS is composed of yellow elastic fibre, and 

 resembles in shape a rounded leaf with the stalk down- 

 ward ; it is often indented in the middle of its free edge 

 and rolled in from the sides; it is connected with the 

 tongue by a central and two lateral folds of mucous mem- 

 brane, known as the glosso-epiglottidean ligament ; the cen- 

 tral fold is called the frenum epiglottidis. A fibrous band, 

 called the thyro-epiglottic ligament, unites the epiglottis to 

 the notch in the anterior border of the thyroid cartilage 

 below; it is also connected with the hyoid bone by strong 

 bands of fibrous tissue called the hyo-epiglottic ligament. 

 Between the epiglottis and the hyoid bone is a mass of 

 yellowish fat, which has been improperly named the epi- 

 gloftidean gland. 



The TRACHEA is composed of from sixteen to twenty in- 

 complete cartilaginous rings, each forming about three- 

 fourths of a circle ; some of them blend together, but for 

 the most part they are united by a fibrous tissue, extending 

 across between their ends and forming a flattened wall 

 which completes the tube. The posterior wall of the trachea, 

 in addition to this fibrous membrane, has a layer of muscu- 

 lar tissue closely connected with the mucous membrane, 

 and its surface is dotted with well-marked muciparous 



