VOICE AND SPEECH. 



867 



and widens the glottis. Paralysis of this muscle is a most serious condition, since 

 it is followed by approximation of, and inability to separate, the vocal cords. 

 The arytenoid, or transverse or posterior arytenoid muscle, the single unpaired 



-11 



17 



12- 



13 



FIG. 300. Larynx with its muscles, posterior 

 view (Stoerk) : 1, epiglottis ; 2, cushion ; 3, ary- 

 epiglottic ligament ; 4, cartilage of Wrisberg ; 

 5, cartilage of Santorini ; 6, oblique arytenoid 

 muscles ; 7, transverse arytenoid muscle ; 8, 

 posterior crico-arytenoid muscle ; 9, inferior 

 cornu of thyroid cartilage; 10, cricoid car- 

 tilage ; 11, posterior inferior cerato-cricoid lig- 

 ament; 12, cartilaginous portion; 13, mem- 

 branous portion of trachea. 



FIG. 299. Larynx and its lateral muscles after 

 removal of the left plate of the thyroid cartilage 

 (Stoerk) : 1, thyroid cartilage ; 2, thyro-epiglottic mus- 

 cle ; 3, cartilage of Wrisberg ; 4, ary-epiglottic mus- 

 <cle ; 5, cartilage of Santorini ; 6, oblique arytenoid 

 muscles; 7, thyro-arytenoid muscle; 8, transverse 

 arytenoid muscle ; 9, processus muscularis of aryte- 

 noid cartilage ; 10, lateral crico-arytenoid muscle ; 11, 

 posterior crico-arytenoid muscle ; 12, crico-thyroid 

 membrane ; 13, cricoid cartilage ; 14, attachment of 

 crico-thyroid muscle ; 15, articular surface for the 

 inferior cornu of the thyroid cartilage; 16, cricc- 

 tracheal ligament; 17, cartilages of trachea; 18, 

 membranous part of trachea. 



muscle of the larynx, is a considerable band passing across the middle line from 

 the posterior surface of one arytenoid cartilage to that of the other (Fig. 300). 

 Its action is to draw the arytenoid cartilages together in the middle line and 

 approximate the vocal processes ; its action is essential in closing the glottis. In 

 the resting larynx the arytenoid cartilages are kept apart by the elastic tension 

 of the parts. The aryteno-epiglottidean, sometimes called the oblique arytenoid, 

 muscles consist of two bundles of fibres seated upon the surface of the arytenoid 

 muscle (Fig. 300). Each muscle arises from the outer posterior angle of the 

 arytenoid cartilage, and, passing upward and inward, crosses in the middle line 

 partly to be inserted into the outer and upper part of the opposite cartilage, 

 partly to penetrate the ary-epiglottic fold as far as the epiglottis, and the 

 remainder to join some fibres of the thyro-arytenoid muscle. The action of 

 the aryteno-epiglottidean muscles is to close the glottis. The thyro-arytenoid 

 is a muscle of complex mechanism, usually described as formed of two parts, 

 an external and an internal. The external thyro-arytenoid arises from the lower 



