Part 135

a, Parotid gland; a′, a″, cervical and submaxillary angles of a; b, c, ventral and dorsal buccal glands; d, labial glands; e, masseter muscle; f, f′, lymph glands; g, dotted line indicating outline of submaxillary gland, which is concealed. (Ellenberger-Baum, Anat. d. Haustiere.) ]

The average periods of =eruption= of the teeth are given in the subjoined table.

TOOTH│ ERUPTION │ CHANGE │ │ I{1}│2 to 4 weeks │12 months I{2}│upper 2 to 3 months│ │lower 1½ to 2 month│16 to 20 months I{3}│Before birth │8 to 10 months C │Before birth │9 to 10 months P{1}│5 months │ ─────┼───────────────────┼─────────────────── P{2}│5 to 7 weeks │12 to 15 months P{3}│upper 4 to 8 days │ „ │lower 2 to 4 weeks.│ P{4}│upper 4 to 8 days │ „ │lower 2 to 4 weeks │ ─────┼───────────────────┼─────────────────── M{1}│4 to 6 months │ M{2}│8 to 12 months │ M{3}│18 to 20 months │

The =cheek teeth= increase in size from before backward. They have (with certain exceptions noted below) complex tuberculate crowns; the term bunodont is applied to this condition, as distinguished from the selenodont structure in horses and cattle, in which there are prominent ridges of enamel. They are short-crowned teeth with a distinct neck and root. The first tooth in each jaw is small, simple, and appears only once; in the lower jaw it is near the canine, in the upper near the second cheek tooth. The next two teeth are larger, laterally compressed, and sectorial. The fourth tooth below is larger, but otherwise like the preceding ones, while the upper one is much wider and is tuberculate.

FIG. 310.—DISSECTION OF MOUTH AND PHARYNGEAL REGION OF PIG.

1, Hard palate; 2, tongue showing distinctly fungiform papillæ; 3, foliate papilla; 4, lymph nodules of soft palate; 5, stylo-glossus muscle, out of which a portion has been cut; 6, hyo-glossus; 7, genio-glossus; 8, genio-hyoideus; 9, mylo-hyoideus (reflected); 10, stylo-hyoideus; 11, great cornu of hyoid bone; 12, tensor palati; 13, levator palati; 14, pterygo- et palato-pharyngeus; 15, stylo-pharyngeus; 16, chondro-pharyngeus; 17, sterno- et omo-hyoideus; 18, retropharyngeal lymph glands; a, bulla ossea; b, paramastoid process. (Ellenberger-Baum, Anat. d. Haustiere.) ]

The =parotid gland= is large and triradiate. It extends very little on to the masseter muscle and its upper angle does not quite reach the base of the ear. It is pale in color, and is embedded in fat in animals in good condition. On its deep face are several large subparotid lymph glands, some of which are only partially covered by the parotid. The =duct= arises on the deep face, has a course similar to that of the ox, and perforates the cheek opposite the fourth or fifth upper cheek tooth. Small accessory glands (Glandulæ parotideæ accessoriæ) may be found along the course of the duct.

The =submaxillary gland= is small, reddish in color, and oval in outline; it is covered by the parotid. Its superficial face is convex, and is marked by rounded prominences. From its deep face a narrow process extends forward about two or three inches (ca. 5 to 7.5 cm.) beneath the mylo-hyoideus muscle along with the duct. The latter opens near the frenum linguæ, but there is no papilla.

FIG. 311.—SAGITTAL SECTION OF PHARYNGEAL REGION OF PIG, PARTLY SCHEMATIC.

1, Palate bone; 2, sphenoid bone; 2′, sphenoidal sinus; 2″ occipital bone; 3, epiglottis; 4, arytenoid cartilage; 5, thyroid cartilage; 6, root of tongue; 7, mouth cavity; 8, isthmus faucium; 9, hard palate; 10, septum nasi; 11, ventral muscles of head; a, soft palate; a′, free edge of a; b, dorsal wall of pharynx; c, fornix of pharynx; d, cavity of larynx; e, g, naso-pharynx; f, oro-pharynx; h, posterior pillar of soft palate; i, dotted line indicating lateral boundary between nasal cavity and pharynx; k, aditus laryngis; l, entrance to œsophagus; m, Eustachian orifice; n, pharyngeal recess; o, posterior naris. (After Ellenberger, in Leisering’s Atlas.) ]

FIG. 312.—STOMACH OF PIG, PARIETAL SURFACE.

The organ contained a rather small amount of ingesta and hence is somewhat contracted. ]

FIG. 313.—STOMACH OF PIG, VISCERAL SURFACE.

Organ was fixed in situ and is somewhat contracted. ]

The =sublingual gland= has an arrangement similar to that of the ox. The posterior part (Glandula sublingualis grandicanalaris) is reddish-yellow in color, and is about two inches (ca. 5 cm.) long, and half an inch wide; its posterior end is in relation to the submaxillary gland and its duct. The anterior part is much larger, being two or three inches (ca. 5 to 7 cm.) long and about twice the width and thickness of the posterior part. All or most of the ducts from the posterior part unite to form the =ductus sublingualis major=, which opens near the ductus submaxillaris. Eight or ten =ductus sublinguales minores= convey the secretion from the anterior part through the floor of the mouth.

FIG. 314.—DIAGRAM OF ZONES OF MUCOUS MEMBRANE OF STOMACH OF PIG. ]

FIG. 315.—VISCERAL SURFACE OF STOMACH OF PIG, FROM WHICH THE SEROUS COAT HAS BEEN REMOVED. ]

FIG. 316.—EVERTED STOMACH OF PIG, FROM WHICH THE MUCOUS MEMBRANE HAS BEEN REMOVED.

O, Œsophagus; D, duodenum; Di, diverticulum; a, a′, a″, a‴, longitudinal fibers; b, circular fibers; c, external oblique fibers; c′, internal oblique fibers; c″, cardiac loop; d, fibers which connect branches of cardiac loop; f, fold at entrance to diverticulum; p, pyloric sphincter; p′, pyloric prominence. (Ellenberger-Baum, Anat. d. Haustiere.) ]

THE PHARYNX

The =pharynx= presents in its posterior part a median cul-de-sac about an inch and a half (ca. 3 to 4 cm.) long, which is situated between the ventral straight muscles of the head and the origin of the œsophagus. Its lower margin is formed by the junction of the posterior pillars of the soft palate, which contain muscular tissue derived from the palatinus and palato-pharyngeus. The vault of the pharynx (Fornix pharyngis) is divided by a median fold of mucous membrane which is a direct continuation of the septum nasi. On either side of this is an infundibulum in which the Eustachian tube opens.

THE ŒSOPHAGUS

The =œsophagus= is short and nearly straight. It has (according to Rubeli) a potential caliber of nearly 3 inches (ca. 7 cm.) at either end, and about 1⁷⁄₁₀ inches (ca. 4.2 cm.) in its middle part. The muscular coat, except near the cardia, is striated. There are mucous glands in the submucosa to about the middle of the tube.

FIG. 317.—ABDOMINAL VISCERA OF YOUNG PIG, VENTRAL ASPECT.

The stomach was very large in this subject. ]

FIG. 318.—DIAGRAM OF CÆCUM AND COLON OF PIG.

Coils of colon have been pulled apart somewhat. ]

FIG. 319.—SOLITARY NODULES FROM LARGE INTESTINE OF PIG. (Ellenberger-Baum, Anat. d. Haustiere.) ]