_60_, Tip of tongue. (After Ellenberger-Baum, Anat. für Künstler.)
]
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.
[Illustration:
FIG. 281.—SAGITTAL SECTION OF HEAD OF COW, CUT A LITTLE TO THE RIGHT
OF THE MEDIAN PLANE.
_1_, Cerebral hemisphere; _2_, corpus striatum; _3_, hippocampus; _4_,
olfactory bulb; _5_, corpora quadrigemina; _6_, optic nerve; _7_,
pons; _8_, medulla oblongata; _9_, spinal cord; _10_, pituitary
body; _11_, sphenoid sinus; _12_, lateral mass of ethmoid; _13_,
ventral straight muscles; _14_, pharyngeal (retropharyngeal) lymph
gland; _15_, longus colli; _16_, soft palate; _17_, vallate papillæ;
_18_, tonsillar sinus; _19_, conical papillæ of cheek; _20_,
hyo-epiglotticus muscle; _21_, epiglottis; _22_, hyo-glossus muscle;
_C1_, _C2_, atlas, axis. Subject was hardened with mouth open.
]
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.
[Illustration: