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 

 ^\ith 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 ■nath 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 laminae 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 cartUage 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 larjmgeal 

 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 cm.) 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. 



1 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 inter\-al 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. 



