(500 



THE HUMAN BODY. 



muscular process. The posterior crico-arytenoids, working 

 alone, pull inwards and downwards the muscular processes, 

 turn upwards and outwards the vocal processes, and sepa- 

 rate the posterior ends of the vocal cords. The lateral 

 crico-thyroid, working alone, pulls downwards and forwards 

 the muscular process, and rotates inwards and upwards the 

 vocal 7 process, and narrows the glottis; it is the chief agent 

 in producing the approximation of the cords necessary for 



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FIG. 158. The larynx seen from behind and dissected so as to display some of 

 its muscles. The mucous membrane of the front of the pharynx (5, Fig. 157) 

 has been dissected away, so as to display the laryngeal muscles beneath it. 

 Part of the left half of the thyroid cartilage has been cut away, co, cartilage of 

 Santorini; CM, cartilage of Wrisberg. 



the production of voice. When both pairs of muscles act 

 together, however, each neutralizes the tendency of the other 

 to rotate the arytenoid cartilage; the downward part of the 

 pull of each is, thus, alone left, and this causes the arytenoid 

 to slip downwards and outwards, off the eminence on the 

 cricoid with which it articulates, as far as the loose capsu- 

 lar ligament of the joint will allow. The arytenoid car- 

 tilages are thus moved apart and the glottis greatly widened 



