546 RESPIRATORY SYSTEM OF THE PIG 
into two branches: one of these extends upward and backward between the lateral 
mass of the ethmoid bone and the dorsal turbinate; the other widens and joins the 
ventral meatus. The opening between the maxillary sinus and the middle meatus 
lies in a transverse plane through the last cheek teeth. The middle meatus is 
continuous with the space enclosed by the dorsal part of the ventral turbinate and 
with the cavity of the dorsal turbinate. The dorsal division of the middle meatus 
presents several openings into the frontal sinus. The ventral meatus is relatively 
roomy; it communicates with the space enclosed by the lower coil of the ventral 
turbinate. The opening of the naso-lacrimal duct is in the posterior part of the 
ventral meatus. The incisive duct and the vomero-nasal organ resemble those of 
the ox. 
THE LARYNX 
The larynx is remarkable for its great length and mobility. The cartilages 
are more loosely attached to each other than in the other animals. The cricoid 
cartilage is thick and compressed laterally; its lamina is long and narrow; its 
arch is directed obliquely downward and backward. The thyroid cartilage is very 
long; its lamin are united ventrally and form a median ridge. The anterior 
cornua are absent, and no joints are formed with the hyoid bone. The posterior 
cornua are broad, bent inward, and articulate with the cricoid cartilage. The 
epiglottis is relatively very large, and is more closely attached to the hyoid bone 
than to the rest of the larynx. The middle part of its base is turned forward, and 
rests on the thyro-hyoid membrane; it is closely connected with the body of the 
hyoid bone by the hyo-epiglottic ligament and the strong hyo-epiglottic muscle.! 
The apex of the arytenoid cartilage is very large, and is divided into two parts at 
its extremity; the medial part is fused with that of the opposite cartilage. There 
is a small interarytenoid cartilage in the transverse ligament. The rima glottidis 
is very narrow. The vocal cords are directed obliquely downward and backward; 
and each is pierced by a long, slit-like opening, which leads into the large laryngeal 
saccule. The vocal ligament is similarly divided into a larger anterior and a smaller 
posterior part. There is a middle ventricle near the base of the epiglottis. The 
thyro-arytenoid muscle is very strong and is undivided; it is equivalent (as in the 
ox) to the vocalis and ventricularis muscles of the horse. The arytenoideus trans- 
versus is very small. The crico-thyroid consists of two strata: the superficial 
layer corresponds to the muscle of the other animals; the deep part consists of 
transverse fibers. 
TRACHEA AND BRONCHI 
The trachea is about six to eight inches (ca. 15-20 em.) long, and contains 
thirty-two to thirty-five rings, which overlap dorsally. It is slightly depressed 
dorsally, except the terminal part, which is circular in cross-section. A special 
bronchus is detached for the apical lobe of the right lung, as in the ox. In the 
right lung the stem-bronchus sends branches (one each) to the cardiac and inter- 
mediate lobes and continues backward in the diaphragmatic lobe, in which it | 
ramifies. In the left lung the stem-bronchus gives off a bronchus which divides | 
into two branches for the anterior part of the lung (fused apical and cardiac lobes), | 
and continues backward in the diaphragmatic lobe. 
The arrangement here is one of the most striking features of the pig’s larynx. The short 
and thick middle hyo-epiglottic ligament and the anterior part of the thyro-hyoid membrane are | 
inelastic, while the posterior part of the membrane is thin and elastic and allows the epiglottis | 
to be separated by a considerable interval from the thyroid cartilage. Moreover, the borders of | 
the epiglottis are connected with the thyroid cornua of the hyoid bone by lateral hyo-epiglottic | 
ligaments. | 
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