204 Mr. Bishop's Experimental Researches into 



and convex articular surfaces on which the arytenoid cartilages 

 rest : ridges appear on the outside of the cricoid for the in- 

 sertion of muscles, and its inferior margin is joined by a fibro- 

 cartilaginous membrane to the first ring of the trachea. 



The Arytenoid Cai-tilages * are two exceedingly irregularly 

 shaped bodies, situated at the posterior, inner, and upper sur- 

 face of the cricoid ; their figure approaches somewhat to the 

 pyramidal and triangular ; their posterior surfaces, to which 

 are attached the oblique and transverse mugcles, are concave ; 

 they have likewise a concave surface anteriorly, especially to- 

 wards the lower part, where they are contiguous with a cor- 

 responding portion of the arytenoid gland. Their internal 

 surfaces are closely connected with the mucous membrane of 

 the larynx : the planes of these surfaces are perpendicular to 

 the axes of their motion, and adapted to approximate closely 

 with each other. They are terminated by three ridges, one 

 internally, the second externally, and the third anteriorly, 

 which last abounds with inequalities. The bases of the ary- 

 tenoid cartilages have curved, grooved, oval, articular sur- 

 faces, which are furnished with synovial membranes ; the 

 grooves are directed downwards, and outwards, corresponding 

 with the convex articulating surface of the cricoid. In front 

 of these cartilages are two conical or pyramidal prominences, 

 forming the posterior part of the chink of the glottis ; these 

 prominences project over the tube, about four twentieths of 

 an inch in the male and about three twentieths in the fe- 

 male. At the point of these projections there are often small 

 distinct cartilages, which give attachment to the thyro-aryte- 

 noid ligaments. The perpendicular projections of these bo- 

 dies have also on each of their summits a small, distinct, iso- 

 lated cartilage united by perichondrium. The arytenoids are 

 endowed with extensive freedom of motion, including a rota- 

 tory motion, a sliding one transverse to their axes of rotation, 

 and an oblique tilting motion. They are destined for the at- 

 tachment of several muscles, whose forces are directed to re- 

 gulate the movements of the glottis, and the modulations of 

 the voice. 



The Ej)iglottis\ is a fibro-cartilage occupying a position be- 

 tween the summit of the larynx and the base of the tongue. 

 It is articulated to the superior margin of the angle formed by 

 the union of the lateral portions of the thyroid cartilage, and 

 in its passive state stands almost perpendicular, but assumes 

 a horizontal direction when the larynx is raised in the act of 

 deglutition. In form it has been aptly compared to the leaf 

 of an artichoke ; and on both surfaces^ but more especially on 

 * Fig. 1 . t Fig. 4 



