248 THE VISCERA. 
is a longitudinal ridge for attachment of the vocal cords and 
origin of the thyroarytenoid muscles (Fig. 105, @), and at the 
caudal end of this ridge the caudal border presents a consider- 
able rounded notch. 
The cricoid cartilage (cartilago cricoidea) (3) has the form 
of a seal ring with its broader part dorsad. The broad dorsal 
part of the ring is partly embraced by the wings of the thyroid 
cartilage (1). Its caudal border is undulating and nearly at 
right angles to its caudocranial axis. It is connected by 
membrane with the first tracheal ring. The cranial border is 
oblique to the long axis and lies in a plane which passes from 
the ventral side craniodorsad. Near the median line on each 
side it articulates by an oblique facet with one of the two 
arytenoid cartilages (4). Near the midventral line the crico- 
thyroid ligament (5) is attached and it stretches thence to the 
midcaudal notch of the thyroid cartilage (1). 
The outer surface presents at the middle of each side a 
facet for articulation with the thyroid, and is marked in the 
median dorsal line by a ridge for the posterior cricoarytenoid 
muscle (Fig. 105, 4). 
The arytenoid cartilages (cartilago arytenoidea) (Fig. 
104, 4) are triangular pyramids with base and sides nearly 
equilateral triangles. One side articulates with an oblique facet 
on the cranial border of the cricoid near the mid-dorsal line. 
Near the opposite apex is attached the vocal cord. At the 
lateral angle of the base is attached on its dorsal side the pos- 
terior cricoarytenoid muscle (Fig. 105, 4), and on its ventral 
side the thyroarytenoid (Fig. 105, @) and lateral cricoaryte- 
noid (Fig. 105, c) muscles. The movements produced by 
these muscles carry the arytenoid ends of the vocal cords toward 
or from the median plane and thus open or close the glottis. 
The epiglottic cartilage (Fig. 104, 2) is flexible (fibro- 
cartilage) and of a cordate form. It is so curved that its caudal 
surface is convex dorsoventrally and concave from side to side. 
It supports the epiglottis. Its cranial surface presents a slight 
median ridge for attachment of muscles. By its base it is 
attached to the midventral part of the cranial border of the 
thyroid cartilage (1). Its position varies so that it either stands 
