324 HEAD AND NECK 



the posterior elevation is due to the anterior margin of the 

 arytaenoid cartilage and the corniculate cartilage. A shallow 

 groove descends between the two elevations; it terminates 

 below by running into the interval between the ventricular 

 and the vocal folds. The posterior wall of the vestibule .is 

 narrow. It is formed by the mucous membrane which 

 covers the anterior surface of the arytaenoideus muscle and 

 it occupies the interval between the two arytsenoid cartilages. 



The aditus laryngis has already been examined, in the 

 dissection of the pharynx (p. 291). The parts which bound 

 it should again be carefully studied. 



The epiglottis projects upwards, posterior to the median 

 thyreo-hyoid ligament, the hyoid bone and the base of the 

 tongue. Its lingual or anterior surface is free in the upper part 

 of its extent only, and is attached to the pharyngeal part of 

 the tongue by a prominent median fold of mucous mem- 

 brane, termed the glosso-epiglottic fold. Two lateral folds are 

 also present ; they connect its margins with the walls of 

 the pharynx at the side of the tongue, and are called the 

 pharyngo-epiglottic folds. Between the two layers of mucous 

 membrane which constitute each of the three folds, there is a 

 small amount of elastic tissue. The depression on each side, 

 between the tongue and the epiglottis, which is bounded 

 by the glosso-epiglottic and a pharyngo-epiglottic fold is 

 termed a vallecula (Fig. 119). The posterior free surface of 

 the epiglottis forms the greater part of the anterior boundary 

 of the vestibule of the larynx. The upper part of this surface 

 is convex, owing to the manner in which the upper margin 

 is curved towards the tongue ; below the convexity there is a 

 slight concavity, and still lower there is a marked bulging, 

 over the upper part of the thyreo-epiglottic ligament. The 

 last projection is called the tubercle of the epiglottis ; it is a con- 

 spicuous object in laryngoscopic examinations of the larynx. 



Each ary-epiglottic fold of mucous membrane encloses 

 between its two layers some connective tissue, the ary- 

 epiglottic muscle, and, posteriorly, the cuneiform cartilage, 

 and the corniculate cartilage, which surmounts the arytaenoid 

 cartilage. As already mentioned, the two small nodules of 

 cartilage produce elevations on the medial layer of the 

 posterior part of the ary-epiglottic fold, which are easily seen 

 when the larynx is examined with the laryngoscope. 



The Middle Subdivision of the Laryngeal Cavity (Fig. 1 1 8) 



