The Mouth

Digestive System of the Ox

The cavity of the mouth is shorter and wider than that of the horse, and the vestibule is more capacious.

The lips are thick, wide, and comparatively immobile. The middle part of the upper lip and the surface between the nostrils is bare, and is termed the muzzle (Planum nasolabiale). It is smooth, and (in health) is kept cool and moist by a clear fluid secreted by a layer of subcutaneous glands (Glandulæ nasolabiales) about half an inch (ca. 1.5 cm.) thick. It shows irregular lines, mapping out small polygonal areas on which the orifices of the gland-ducts are visible. A narrow bare strip also exists along the edge of the lower lip. The remainder of the integument is provided with ordinary and tactile hairs. The free edge and the lining membrane present verrucose, horny papillæ. The labial glands form compact masses near the angles of the mouth.

The cheeks are more capacious than in the horse. The mucous membrane presents large conical pointed papillæ, which are directed toward the fauces and are covered with a horny epithelium. The largest of these have a length of about half an inch (ca. 1 to 1.5 cm.) and are situated around the angle of the mouth and parallel with the cheek teeth. The orifice of the parotid duct is opposite the fifth upper cheek tooth. (In the sheep and goat it is opposite the fourth tooth.) The buccal or molar glands are very well developed, and are arranged in three parts. The dorsal row extends from the maxillary tuberosity to the angle of the mouth. Its lobules are of a light yellow color. The ventral part consists of a compact brownish mass which reaches from the angle of the mouth a short distance under the masseter muscle. The middle part consists of loosely arranged yellow lobules.

A linear series of large papillæ exists on the floor of the mouth on each side of the frenum linguæ. Near these are found the openings of the small ducts of the sublingual gland. The papilla on which the submaxillary duct opens is wide, hard, and has a serrated edge.

The hard palate is wide, and is usually more or less pigmented. The body of the premaxilla is covered with a thick layer of dense connective tissue, which has a thick, horny epithelial covering—forming the so-called dental plate or pad. The palatine ridges extend from this backward about two-thirds of the length of the hard palate. They are nearly straight, and, for the most part, are serrated on the free edge. A median furrow extends between the ridges. The posterior third of the palate is smooth. Between the dental plate and the first ridge is the triangular papilla incisiva; on either side of this is a deep furrow, in which is the oral opening of the naso-palatine canal. This canal is two inches or more (ca. 5 to 6 cm.) in length and opens on the floor of the nasal cavity; it also communicates by a slit-like opening with the organ of Jacobson.

The soft palate is somewhat shorter than that of the horse, but is long enough to close the isthmus of the fauces. The posterior pillars do not extend to the entrance of the œsophagus. The azygos muscle is much better developed than in the horse. The fibrous aponeurosis is for the most part replaced by muscular tissue.

The isthmus faucium is wide and dilatable. On either side, behind the anterior pillar of the soft palate, is a deep depression, the sinus tonsillaris; external to this is the compact bean-shaped tonsil, which is about one to one and a half inches (ca. 3 to 4 cm.) in length. The tonsil does not project into the fauces, but outward instead: hence it does not occupy the tonsillar sinus, and is not visible internally, as is the case in most animals.