INTRINSIC MUSCLES OF THE LARYNX. 



487 



part of the thyroid cartilage, the external thyro-arytenoid, and 

 the thyro-ary-epiglottic muscles (Henle). The other fibres, which 

 pass directly from the arytenoid to the thyroid cartilages inter- 

 nal and external thyro-arytenoid muscles in the same direction 

 as the vocal cords, complete the closure by helping to press to- 

 gether the vocal processes and by approximating the cords them- 

 selves. In spasmodic closure of the glottis, all these latter muscles 

 act violently together, and have been grouped by Henle as the 



FIG. 198. 



FIG. 199. 



FIG. 198. Diagram of the side view of the larynx showing the position 

 of the vocal cords (v). (Huxley.) Ar. Arytenoid cartilage. Hy. Hyoid 

 bone. Th. Thyroid cartilage. Or. Cricoid cartilage. Tr. Trachea. C.th. 

 Crico-thyroid muscle. Tli.A. Thyro-arytenoid muscle. Ep. Epiglottis. 



FIG. 199. Diagram of the opening of the larynx from above. (Huxley.) 

 Th. Thyroid cartilage. Cr. Cricoid cartilage. Ary. Superior extremities 

 of the arytenoid cartilages. V. Vocal cords. Th.A. Thyro-arytenoid 

 muscles. C.a.L Lateral crico-arytenoid muscle. C.a.p. Posterior crico- 

 arytenoid muscle. Ar.p. Posterior arytenoid muscle. 



constrictor of the glottis. Relaxation of the vocal cords accom- 

 panies voluntary closure of the glottis, as in holding the breath, 

 when the false vocal cords are said to have a valvular action. 

 But the muscular fibres, which run from the arytenoid cartilages 

 to the thyroid, nearly parallel to the true vocal cords, are those 

 concerned in the act of relaxation when the cords are active. 

 They pull forwards the arytenoid cartilages, and at the same time 



