482 GLOTTIS. 



septum fixed abruptly in the windpipe, with an aperture in it 

 of the figure of the rima glottidis. 



The anterior surface of the two arytenoid cartilages is con- 

 cave. This concavity is occupied in each by a glandular 

 substance, which lies between the cartilage and the lining 

 membrane ; and extends itself horizontally, covered by the 

 upper ligament of the glottis. The nature of these bodies is 

 not perfectly understood ; but they are supposed to secrete 

 mucus.* 



The membrane which lines the cavity of the glottis being 

 continued from the mouth and throat, resembles the membranes 

 which invest those parts. In some places, where it is in close 

 contact with the cartilages, it appears united with the perichon- 

 drium, and acquires more firmness and density. 



The general motions of the larynx are very intelligible to 

 those who are acquainted with the muscles which are con- 

 nected with the thyroid cartilage, and which move the os hy- 

 oides. They take place particularly in deglutition, and in 

 some modifications of the voice ; and also in vomiting.f 



The motions of the particular cartilages on each other can 

 also be well understood, by attending to the origin and inser- 

 tion of the various small muscles connected with them. The 

 most important of these muscles are the crico-arytenoidei pos- 

 tici and laterales, the thyreo-arytenoidei, the arytenoidei obli- 

 qui, and the arytenoideus transversus. The effects of their 

 actions appear to be the dilating or contracting the rima glotti- 

 dis, and relaxing or extending the ligaments which form it. 



The arteries of the larynx are derived from two sources, 

 namely, the superior thyroid, or laryngeal branch of the 

 external carotid, and the thyroid branch of the subclavian. 



The nerves of the larynx also come to it in two very differ- 

 ent directions on each side. It receives two branches from the 

 par vagum ; one which leaves that nerve high up in the neck, 

 and is called the Superior Laryngeal branch ; and another 



* They constitute the glandulce arytenoidea. p. 



j- For an excellent exposition of the uses of the larynx, see Dunglison's 

 Physiology, 5th edition. 



