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JOINTS, LIGAMENTS, AND MEMBRANES OF THE LARYNX 517 
toward the root of the tongue. It is shaped somewhat like a pointed ovate leaf, 
and presents two surfaces, two borders, a base, and an apex. The oral (or anterior) 
surface is concave in its length, convex transversely; the pharyngeal (or posterior) 
surface has the reverse configuration. The borders are thin, irregular, and some- 
what everted. The base is thick, and is attached to the dorsal surface of the body 
of the thyroid cartilage by elastic tissue. From each side of it a cartilaginous bar 
projects upward and backward; these are the cuneiform processes (Processus 
cuneiformes) and correspond to the cuneiform cartilages of man. The apex is 
pointed and curved ventrally. Nearly all of the epiglottic cartilage is covered with 
mucous membrane. It usually projects into the isthmus faucium, but is often 
on the pharyngeal side of the soft palate. 
The arytenoid cartilages (Cartilagines arytenoidez) are situated on either side, 
in front of the cricoid, and partly medial to the lamine of the thyroid cartilage. 
They are somewhat pyramidal in form, and may be described as having three 
surfaces, three borders, a base, and an apex. The medial surface is concavo- 
convex, but very slightly curved, and is smooth and covered by mucous membrane. 
The lateral surface is concave and is separated from the lamina of the thyroid 
cartilage by the crico-arytenoideus lateralis and vocalis muscles, and the laryn- 
geal saccule. The dorsal surface is also concave, and is covered by the aryte- 
noideus muscle, which is attached to it. The dorsal and lateral surfaces are 
separated (except in front) by a ridge which increases in size toward the lateral 
angle of the base, where it forms a rounded prominence, the muscular process 
(Processus muscularis). The anterior and posterior borders are convex; they 
converge ventrally to a thin, wide angle, the vocal process (Processus vocalis). 
The process is so named because it furnishes attachment to the vocal ligament. 
The dorsal border forms a deep notch with the apex. The base is concave and 
faces chiefly backward; it presents laterally an oval concave facet (Facies artic- 
ularis) for articulation with the anterior border of the lamina of the cricoid ecarti- 
lage. The medial angle of the base is attached to its fellow by the transverse 
arytenoid ligament. The apex (Cartilago corniculata) curves upward and back- 
ward, forming with its fellow the pitcher-shaped lip from which the cartilages derive 
their name. 
The cricoid and thyroid cartilages and the greater part of the arytenoid 
cartilages are hyaline. The apices and vocal processes of the arytenoid and the 
epiglottis (including the cuneiform processes) consist of elastic cartilage; they 
show no tendency toward ossification at any age. The thyroid and cricoid carti- 
lages regularly undergo considerable ossification; the process begins in the body of 
the thyroid, and often involves the greater part of the cartilage.’ 
JOINTS, LIGAMENTS, AND MEMBRANES OF THE LARYNX 
The crico-thyroid joints (Articulationes crico-thyreoidee) are diarthroses 
formed by the apposition of the convex facets on the ends of the posterior cornua 
of the thyroid cartilage with corresponding facets on the sides of the cricoid car- 
tilage. The capsule is thin, but is strengthened by accessory bands dorsally, 
laterally, and medially. The movements are chiefly rotation around a trans- 
verse axis passing through the centers of the two joints. 
The crico-arytenoid joints (Articulationes crico-arytznoidea) are also diar- 
throdial. They are formed by the apposition of the convex facets on the anterior 
border of the cricoid cartilages with the concave facets on the bases of the arytenoid 
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cartilages. Each has a very thin, loose capsule, strengthened by accessory bundles 
: 'Caleareous deposits are present in the body of the thyroid cartilage even before adult age 
is reached. Scheier (by use of X-rays) found complete calcification of the thyroid in two mares 
eight and ten years of age; in the former the process also involved a large part of the lamina and 
the adjacent part of the arch of the cricoid. 
