ARRANGEMENT OF THE LARYNX. 



601 



processes of the arytenoid cartilages backward, downward, and toward 

 the median line (Fig. 208), these muscles cause the corresponding vocal 

 processes (/, /) to separate and move upward (77, 77). A large isosceles 

 triangle is thus formed between the vocal bands, and another between 

 the inner borders of the arytenoid cartilages, having their bases in con- 

 tact, so that the aperture assumes a rhomboidal form. 



Pathological. Paralysis of these muscles may cause intense inspiratory 

 dyspnea, on account of the failure of the glottis to dilate. The voice remains 

 unchanged. In a freshly excised larynx the dilators first lose their excitability. 



FIG. 204. Anterior View of the Larynx, with its Liga- 

 ments and Muscular Insertions: O. h, hyoid bone; 

 C. th., thyroid cartilage; Corp. trit., corpus triti- 

 ceum; C. c., cricoid cartilage; C. tr., tracheal 

 cartilages; Lig. thyr.-hyoid. med., median thyro- 

 hyoid ligament; Lig. th.-h. Int., lateral thyrp-hyoid 

 ligament; Lig. cric.-thyr. med., median crico-thy- 

 roid ligament; Lig. eric, track., crico-tracheal liga- 

 ment; M. sl.-h., sterno-hyoid muscle; M. th.- 

 hyoid, thyro-hyoid muscle; M. st.-th., sterno-thy- 

 roid muscle; M. cr.-lh., crico-thyroid muscle. 



FIG. 205. Posterior View of the Larynx, after Re- 

 moval of the Muscles: , epiglottis with the cush- 

 ion (IF); L. ar.-ep., ary-epiglottic ligament; M.m., 

 mucous membrane; C. W., cartilage of Wrisberg; 

 C. S., cartilages of Santorini; C. aryt., arytenoid 

 cartilages; O. c., cricoid cartilage; P. m., mus- 

 cular process of the arytenoid cartilage; L. cr. 

 ar., crico-arytenoid ligament; C. s, superior cornu, 

 C. i., inferior cornu of the thyroid cartilage; L. ce.- 

 cr. p. i., postero-inferior kerato-cricoid ligament; 

 C. tr., tracheal cartilages; P. m. tr., membranous 

 portion of the trachea. 



Also in the presence of organic disease in the distribution of the recurrent nerve, 

 the branch to the posterior crico-arytenoid muscle is the first to be paralyzed. 

 Likewise, in cooling the exposed recurrent nerve, this branch is always the first 

 to fail in its function. 



The constrictor of the entrance to the larynx is the transverse arytenoid 

 muscle, which connects the two outer borders of the arytenoid carti- 

 lages by transverse fibers throughout their length (Fig. 209). On the 

 posterior surface of this muscle are situated the crossed bundles of the 

 oblique arytenoid muscles (Fig. 206), which have a similar action. 



Pathological. Paralysis of these muscles renders the voice feeble and hoarse, 

 as much air escapes between the arytenoid cartilages during phonation. 



