Till. 1. M:\.\\ 451 



tin- opposite plato,a receding angle occupied by the cricc-thyroid membrane . 



tlu' posterior gives attachment to the crico-thyroid muscle. '1 In- ./////,///* 



constitute the acute angles of the thyroid pluto. The anterior is confoiiu<l< >1 



with tliat of the opposite branch, to form the body of the cartilage. The 



//or, slightly curved downwards, is terminated by a small. convex 



diarthrodial facet, which articulates with the concave facets of the external 



>f the cricoid cartilage. 



The thyroid cartilage is frequently partially, or even entirely, ORB! tied. 



EPIGLOTTIS. This piece forms a soft and flexible appendix, shaped like 

 a sage-leaf; inferiorly, it circumscribes the entrance to the larynx, and 

 :it over it, so as to close it hermetically when the alimentary bolus is 

 traversing the pharyngeal vestibule. 



This cartilage has two faces, two lateral borders, & base, and a suiitn.it. 

 The anterior face is convex from side to side, concave from above to below, 

 and covered by the mucous membrane of the pharynx ; it gives attachment 

 to the hyo epiglottidean muscle. 



The posterior face shows an inverse configuration, and is covered by the 

 lining membrane of the larynx, which is perforated by glandular orifices. 

 The borders offer a free portion, which aids in circumscribing the entrance 

 to the larynx; as well as an adherent part fixed to the arytenoid cartilage by 

 means of a mucous fold, and made irregular by the little cartilaginous bodies 

 which are superadded to it. (These are the cuneiform cartilage*, or 

 << i rl ilages of Wrisbery, placed in the aryteno-epiglottidean fold of mucous 

 membrane which extends from the apex of the arytenoid cartilage to the side of 

 the epiglottis.) The base is thick, and articulated with the middle part of 

 the thyroid ; it gives origin, posteriorly, to two lateral prolongations, which 

 pass to the inferior border of the arytcnoids, but usually without joining 



these. 



The summit unites the free portion of both borders, and is thrown forwards 

 on the upper face of the soft palate (Fig. 174, 9). 



AIIYTENOID CABTILAGES. These two pieces have been so designated from 

 their resemblance, when approximated, to the mouth of a pitcher (apvrauva, 

 ct8o?, like a pitcher). They are situated in front of the cricoid, 

 above the entrance to the larynx ; each affects an irregular quadrilateral 

 form, and presents for study tvco faces and four borders. The internal face 

 is smooth, almost flat, and lined by the laryngcal mucous membrane. 

 The external face is divided by a ridge into two portions : a superior, covered 

 by the arytenoid muscle ; and an inferior, giving attachment to the thyro- 

 arytcnoid and lateral crico-arytenoid muscles. The superior border is concave, 

 and joined to that of the opposite cartilage. The inferior border gives 

 attachment, posteriorly, to the vocal cord. The anterior border, thick and 

 convex, and covered by the mucous membrane, circumscribes, superiorly 

 and laterally, the entrance to the larynx : it is in joining above, with tlm 

 homologous bonier of the other arytenoid cartilage, that the pitcher beak 

 ly mentioned is formed The posterior bordtr projects into the larynx 

 l>y its inferior jKirtion ; superiorly, this border is very thick, and is boll 

 by a small articular facet, which responds to the anterior facet of tin be /.el 

 Of tin ericoid. Above, and to the outside of this facet, is a very prominent 

 tiuVrch; \\hich terminates behind the crest of the external face, and gives 

 hment to the posterior crico-arytenoid muscle. 



AllTICl I.. \TIo\S OK THK L\I:\N<;KU, CAUTU,AGK8 (Ki?- r <. -'-!7, 22ft). TllOSO 



re of the simplest kind. Tin y are as follows: 



The thyroid HtftUMp i> joiin d to the os hyoidcs : 1, At the 



2 ; 2 



