i8i6 



HUMAN ANATOMY. 



rior horns of the thyroid and the tips of the greater horns of the hyoid. They 

 may be artificially dissected to resemble cords (Ugainenta thyreohyoidea lateralia), 

 although in fact they are continuous, not only with the rest of the membrane, but 

 with its expansion which mingles with the fasciae of the neck. As a rule, a little 

 nodule {cartJlago triticea) is found in the middle of this lateral thickening (Fig. 

 1 541). According to Gegenbaur, it is the remnant of a closer connection between 

 the third and fourth branchial bars. The more membranous part of the ligament 

 extends from the superior border and the inner side of the superior horns of the 

 thyroid to the upper border of the body of the hyoid and its greater horn. A bursa, 

 extending under the body of the hyoid, lies on the anterior surface of this membrane, 

 which is denser beneath it. 



The Arytenoid Cartilages. — These are a pair of very irregular four-sided 

 pyramids (one side being the base) perched on the superior articular facets of the 

 cricoid. The vocal cords extend between them and the entering angle of the thyroid. 

 Besides the base, there is a posterior, an internal, and an antero-external surface, sep- 

 arated by tolerably distinct borders. A section near the base is semilunar, the bound- 

 ary between the posterior and internal surfaces being effaced. The two remaining 

 angles are each prolonged (Fig. 1542). The anterior, extending forward as the vocal 



process for the attachment 



Fig. 1542. 



B 



Crista arcuata 



Fovea oblongata, for 

 thyro-arytenoideus 

 muscle 

 Muscular process 



Cartilage of Santorini 

 ■Apex 



Tubercle for false vocal 



cord 

 Fovea triangularis 



Anterior border, 



Vocal process 



Articular facet 



Articular facet 



Right arytenoid cartilage, capped by cartilage of Santorini. 

 lateral aspect ; £, poslero-medial aspect. X |. 



Postero- 

 medial 

 surface 



Muscular 

 process 



A, antero- 



of the true vocal cord, is 

 long and slender ; the ex- 

 ternal or muscular process, 

 short and thick, projects out- 

 ward and backward. The 

 base is chiefly occupied by 

 an oval articular cavity rest- 

 ing on that of the cricoid. 

 The long axis of this articu- 

 lar facet, which does not 

 much surpass its transverse 

 one, extends in the main for- 

 ward, crossing that of the opposed facet. The concavity is nearly at right angles to 

 the long axis. The posterior surface is well defined and deeply concave, being filled 

 by the arytenoid muscle. The internal surface is nearly plane, offering nothing for 

 description. The antero- external surface is triangular. A ridge, the crista arcuata, 

 starts from the vocal process and runs backward and upward, ultimately describing 

 nearly a circle around a hollow, the fovea triayigularis, which is quite as often oval. 

 This little hollow is filled by a mass of glands, and is overlooked unless the cartilage 

 be cleaned very carefully. The false vocal cord is attached to a little tubercle on this 

 ridge either above or behind the fovea. The borders meet above at a blunt apex. 



The Crico-Arytenoid Joint. — From the foregoing description of the two 

 opposed articular surfaces it is evident that in consequence of the crossing of their 

 long axes the whole of one is not in contact with the whole of the other. The joint 

 is surrounded by a lax capsule, strengthened behind by straight vertical fibres, which 

 have been called X\\e posterior crico-arytenoid ligament {Y\^. 1541). The motions 

 are very difficult to analyze. The arytenoid may tip on the elongated elevation of 

 the cricoid or slide along it ; moreover, it may rotate upon it at any point occupied. 

 This movement, from the nature of the surfaces, is a screw motion rather than a true 

 rotation, but the term is sufficiently accurate. 



The Epiglottis. — This is a leaf-shaped plate of elastic cartilage which, inserted 

 by its stalk into»the angle of the thyroid, rises above the hyoid bone and guards the 

 entrance into the larynx. The length is some 3. 5 cm. The epiglottis expands trans- 

 versely and curls forward over the root of the tongue. Its posterior surface is 

 entirely free, but less than the upper half of the anterior surface is exposed. Begin- 

 ning at the free border, which is bent forward towards the tongue, the posterior 

 surface is convex, slightly concave, and finally convex again, owing to a prominence, 

 called the tubercle, which its root forms in the larynx. The free edge is rounded 

 transversely and the posterior surface in the main concave across. The stalk, when 

 well developed, is triangular on section, fitting into the angle of the thyroid. The 



