VOICE AND SPEECH. 635 



of the unpaired cartilages, lias the shape of a signet-ring; its 

 broad part (,,, Fig. 181) is on the posterior side and lies at 

 the lower part of the opening between the halves of the 

 thyroid; in front and on the sides it is narrow, and a space, 

 occupied by the crico-tJiyroid membrane, intervenes between 

 its upper border and the lower edge of the thyroid cartilage. 

 The angles of the latter are produced above and below into 

 projecting horns (Cs and Ci, Fig. 181), and the lower horn 

 on each side forms a joint with the cricoid. The thyroid can 

 be rotated on an axis, passing through the joints on each 

 side, and rolled down so that its lower front edge shall come 

 nearer the cricoid cartilage, the membrane there intervening 

 being folded. The arytenoids (f,Fig. 181) are the largest of 

 the paired cartilages; they are seated on the upper edge of 

 the posterior wide portion of the cricoid, and form true 

 joints with it. Each is pyramidal with a triangular base, 

 and has on its tip a small nodule (co, Fig. 181), the cartilage 

 of Santorini. From the tip of each arytenoid cartilage the 

 aryteno-epiglottidean fold of mucous membrane (10, Fig. 182) 

 extends to the epiglottis; the cartilage of Santorini causes a 

 projection (8, Fig. 182) in this; and a little farther on (9) 

 is a similar eminence on each side, caused by the remaining 

 pair of cartilages, known as the cuneiform, or cartilages of 

 Wrisberg. 



The Vocal Cords are bands of elastic tissue which reach 

 from the inner angle (Pv, Fig. 181) of the base of each aryte- 

 noid cartilage to the angle on the inside of the thyroid where 

 the sides of the V unite; they thus meet in front but are 

 separated at their other ends. The cords are not, however, 

 bare strings, like those of a harp, but covered over with the 

 lining mucous membrane of the larynx, a slit, called the 

 glottis (c, Fig. 182), being left between them. It is the pro- 

 jecting cushions formed by them on each side of this slit 

 which, are set in vibration during phonation. Above each 

 vocal cord is a depression, the ventricle of the larynx (b f , 

 Fig. 182); this is bounded above by a somewhat prominent 

 edge, the false vocal cord. Over most of the interior of the 

 larynx its mucous membrane is thick and covered by ciliated 

 epithelium, and has many mucous glands imbedded in it. 

 Over the vocal cords, however, it is represented only by a 

 thin layer of flat non-ciliated cells, and contains no glands. 

 In quiet breathing, and after death, the free inner edges of the 



