246 THE VISCERA. 
The nasopharynx and pharynx are considered under the 
alimentary canal (page 231). 
2. The Larynx. 
The larynx is the enlarged upper end of the air-passage 
which leads from the pharynx to the lungs. It is a box com- 
posed of pieces of cartilage connected by ligaments and moved 
by muscles, and it is lined by mucous membrane. At the root 
of the tongue about one centimeter caudad of the body of the 
hyoid bone is the triangular leaf-like epiglottis (Fig. 95, ¢, 
page 227). When food is taken this closes the opening into 
the larynx, and the food passes over it into the cesophagus. 
It is so curved ‘that its apex is directed craniad. A fold of 
mucous membrane, the plica glossoepiglottica or frenulum of 
the epiglottis, extends from the middle of its cranial surface 
to the root of the tongue, and on each side of this fold is a 
depression. , 
From each side of the base of the epiglottis a fold, plica 
aryepiglottica (Fig. 95, 7), extends caudad to the base of the, 
arytenoid cartilage (g). Dorsad of this fold and separated 
from it by a depression is a ridge which marks the position of 
the caudal hyoid cornu. The plice aryepiglottice (/) and the 
epiglottis (¢) form the boundaries of the aditus laryngis, or 
opening into the larynx. 
The cavity of the larynx is divided into three portions. 
The upper one of these is the vestibule of the larynx. It 
is bounded caudad by two folds of mucosa (7) that stretch 
from the caudal surface of the epiglottis near its base to the 
tips of the arytenoid cartilages. These folds are the false 
vocal cords (7). Their vibration is said to produce purring. 
Caudad of the false vocal cords two folds of the mucosa 
stretch from the apices of the arytenoid cartilages to the thyroid 
cartilages, near the base of the epiglottis. These folds are 
nearer the median plane than the false vocal cords. They 
are the true vocal cords (7). The middle portion of the 
laryngeal cavity is that between the true and the false vocal 
cords. It is produced laterally into a very small pouch or 
pocket on each side, the ventriculus. The narrow slit between 
the true vocal cords is the glottis (2). It can be narrowed 
