PHONATION; ARTICULATE SPEECH. 575 



The epiglottis is a leaf-shaped piece of cartilage attached to the 

 thyroid at the median notch. It is firmly united by membranes and 

 ligaments to the thyroid and arytenoid cartilages and to the base of 

 the tongue. 



The arytenoid cartilages are two in number and symmetric in 

 shape. Each cartilage is a triangular pyramid, the apex of which is re- 

 curved, and directed backward and inward. The base presents three 

 angles an anterior, an external, and an internal. The anterior angle 

 is long and pointed and projects forward in a horizontal plane. It 

 serves for the attachment of the vocal membranes and is therefore 

 termed the vocal process. The external angle is short, rounded, and 

 prominent, and serves for the attachment of muscles. The internal 

 angle affords a point of insertion for a ligament. The inferior surface 

 of the arytenoid is concave for articulation with the convex surface 

 of the cricoid facet. Its long axis, however, is directed from before 

 backward and almost at right angles to the long axis of the cricoid 

 facet. 



The cornicula laryngis and the cuneiform cartilages are small 

 nodules of yellow elastic cartilage embedded in a fold of membrane 

 which unites the arytenoid and the epiglottis. They are fragments 

 of a ring of cartilage which in some animals e. g., anteater extends 

 between these two cartilages. 



The crico-thyroid articulation is formed by the apposition of the 

 tip of the inferior cornu of the thyroid cartilage and an articular 

 facet on the side of the cricoid. The joint is provided with a synovial 

 membrane and enclosed by a capsular ligament. The movements 

 permitted at this joint take place around a horizontal axis and consist 

 of an upward and downward movement of both the thyroid and 

 cricoid, combined with a sliding movement of the latter upward and 

 backward. 



. The crico-arytenoid articulation is formed by the apposition of 

 the articulating surfaces of the cricoid and arytenoid cartilages. 

 This joint is provided with a synovial membrane and enclosed by 

 a loose capsular ligament which would permit of an extensive sliding 

 of the arytenoid cartilage downward and outward were it not pre- 

 vented by the posterior crico-arytenoid ligament, which is attached, 

 on the one hand, to the cricoid,- and, on the other, to the inner angle 

 of the arytenoid. The movements permitted at this joint are: (i) 

 Rotation of the arytenoid around a vertical axis which lies close to 

 its inner surface. (2) A sliding motion inward and forward with 

 inward rotation of the vocal process, or a sliding motion outward and 

 backward with outward rotation of the vocal process. In either case 

 the process describes an arc of a circle. (3) A sliding movement 

 towards the median line in consequence of which the inner surfaces 

 of the arytenoids are brought almost in contact. 



