178 ANTHROPOLOGY. 
by the epiglottis: the sides are composed of the aryteno-epiglottidean folds 
of mucous membrane; and the apex, which is posteriorly notched or bifid, 
is formed by the appendices of the arytenoid cartilages. The enferior open- 
ing of the larynx is always free, and nearly a perfect circle, formed by the 
lower border of the cricoid cartilage, which is connected to and continuous 
with the trachea. 
Intermediate between these two openings, and nearly midway within the 
larynx, 1s a very remarkable slit-like narrowing of its cavity, named the 
rima glottidis. This, the seat of the vocal function, is bounded laterally by 
the chordz vocales. Its form is variable; and depends on muscular action, 
being subject to change in shape and size during every act of respiration, 
voice, and speech. Immediately above the true chords vocales, the larynx 
presents on each side a lateral dilatation, called the ventricle or sinus of the 
larynx. ‘This space is bounded by the semilunar folds known as the false 
or superior chordze vocales. From each ventricle the mucous membrane is 
prolonged upwards in a thimble-like form, constituting a pouch, the sacculus 
laryngis. 
The arteries which supply the larynx are derived from the superior and 
inferior thyroid, the former a branch of the external carotid, the latter of 
the subclavian. The laryngeal nerves are four in number, a superior and 
an inferior on each side. | 
Pl. 129, fig. 82, thyroid cartilage ; jig. 33, cricoid do.; fig. 34, arytenoid 
do. ; fig. 85, epiglottis ; fig. 36, section of the larynx: ', upper, *, lower vocal 
cord; *, ventricle. %g. 37, larynx from before: ’, os hyoides; *, hgament 
connecting the os hyoides with the thyroid cartilage; *, thyroid cartilage ; 
‘, hgament between the thyroid and the cricoid cartilage ; °, cricoid carti- 
lage. ig. 38, larynx from behind: ', glottis and epiglottis; * °, ventricles. 
Pl. 127, fig. 5", transverse and oblique arytenoid muscles. /g. 8, larynx 
from the left side, one half of the thyroid cartilage removed: *, posterior 
crico-arytenoid muscle; *, lateral do.; *, thyro-arytenoid muscle ; ‘, muscles 
of the epiglottis. 
2. THE TRACHEA. 
The trachea, continuous inferiorly with the larynx, is a tube composed 
of from sixteen to twenty-six C-shaped cartilaginous rings, open posteriorly. 
It commences opposite to the fifth cervical vertebra, and descends to about 
the third dorsal, where it divides into two branches, called bronchi, one of 
which passes to each lung, and there again subdivides. The right bronchus, 
shorter and broader, extends for an inch before it divides into three branches. 
The left bronchus, about an inch longer, sinks into the lung on the left side, 
below the corresponding pulmonary artery, and opposite the fifth dorsal 
vertebra. The cartilaginous rings determine the shape and diameter of the 
trachea, but do not lie in immediate contact, being separated and connected 
by elastic fibrous ligaments, by which the elongation and contraction of the 
tube are rendered possible. The posterior portion of the trachea corresponding 
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