THE LARYNX. 127 



superior margin has on each side, behind, a little head, or con- * 

 vexity, which receives the base of the corresponding arytenoid 

 cartilage, and forms with it a ball and socket joint. 



The interior surface of the cricoid cartilage is smooth, and 

 covered by the lining membrane of the larynx. Its exterior 

 surface is flattened behind on ach side, by the posterior crico- 

 arytenoid muscles; it is marked also laterally by other mus- 

 cles, and by the inferior cornu of the thyroid cartilage. 



The cricoid cartilage is embraced by the inferior margin of 

 the thyroid, but in such a way that a triangular interval is left 

 in front between the two cartilages. 



This interval is filled by a ligament adhering to its margins 

 called the Middle Crico-Thyroid, to distinguish it from the li- 

 gamentous junction between the inferior cornua of the thyroid, 

 and the sides of the cricoid. The middle ligament has some 

 small apertures in it for the passage of blood vessels and of 

 nerves. It is the part commonly cut in the operation of laryn- 

 gotomy. 



The Arytenoid Cartilages (Cartilagines Arytccnoidece) re- 

 semble triangular pyramids curved backwards, and about six 

 lines long. They are placed on the upper margin of the cri- 

 coid cartilage behind. The anterior face of each is uneven, 

 and divided into two concavities; the posterior face forms a 

 single cylindrical concavity; and the internal face, by which it 

 approximates its fellow, is nearly flat. When joined together, 

 the two cartilages resemble the mouth or spout of a pitcher, 

 from whence their name. Their bases are hollowed into a 

 small glenoid cavity, for articulating with the cricoid cartilage. 



A synovial capsule is reflected over the articulation, between 

 the arytenoid and the cricoid cartilage: this capsule is strength- 

 ened by a few scattered ligamentous fibres. 



The Epiglottis Cartilage (Epiglottis) is situated on the pos- 

 terior face of the base of the os hyoides, being enclosed partially 

 by the two sides of the thyroid cartilage. Its general form is 

 that of an oval disk; the upper margin of it is thin and rounded, 

 partially curled 'forwards, and the lower part is elongated into 

 a pedicle which adheres to the entering angle of the thyroid 

 cartilage. 



