Part 99

The =orbicularis oris= does not form a complete ring, the defect being in the middle of the upper lip.

The =levator nasolabialis= is extensive, thin, and not very distinct from the frontalis; it divides into two layers, between which the levator labii superioris proprius and the lateral dilator of the nostril pass. The superficial layer ends in the nostril and upper lip, the deep layer on the accessory (lateral) nasal cartilages and on the nasal process of the premaxilla.

The =levator labii superioris proprius= arises on and before the facial tuberosity and terminates by several tendons in the muzzle. It passes between the two layers of the preceding muscle, blending in part with the deep layer.

The =zygomaticus= is much stronger than in the horse. It arises on the masseteric fascia, and ends chiefly in the upper lip.

The =depressor labii superioris= does not resemble the muscle of the same name in the horse. It arises just in front of the facial tuberosity, and divides usually into two branches, which terminate in a number of tendons that form a network in the muzzle and upper lip.

The =incisivus inferior= is a small, rounded muscle, which arises on the body of the mandible below the second and third incisors, and ends in the lower lip, blending with the orbicularis.

The =depressor labii inferioris= is thin, and does not extend as far backward as in the horse; only the anterior end is distinct from the buccinator.

The =buccinator= shows no marked variation, but its superficial layer is well developed.

The =dilatator naris lateralis= arises in front of the facial tuberosity, passes forward between the branches of the levator nasolabialis, and terminates in the outer wing of the nostril.

The dilatator naris transversus is replaced by the =dilatator naris apicalis=, which is situated in the muzzle and joins its fellow at a median raphé. It arises on the border and upper surface of the body of the premaxilla, the fibers passing obliquely upward and outward to the inner wing of the nostril.

The =dilatator naris superior= arises from the alar cartilage of the nostril and ends in the inner wing of the nostril.

FIG. 207.—MUSCLES OF HEAD OF OX, LATERAL VIEW.

a, Levator labii superioris proprius; b, levator nasolabialis; c, trapezius; c′, mastoido-humeralis; d, d′, sterno-cephalicus; e, omo-hyoideus; f, dilatator naris lateralis; g, zygomaticus; g′, malaris; h, buccinator; i, depressor labii inferioris; k, orbicularis oris; m, masseter; n, parotido-auricularis; o′, zygomatico-auricularis and scutulo-auricularis superficialis inferior; o″, scutulo-auricularis superficialis superior; o‴, scutulo-auricularis superficialis accessorius; p, p′, scutularis; u, frontalis; w, mylo-hyoideus; 1, concha; 2, 3, posterior and anterior borders of 1; 8, scutiform cartilage; 9, zygomatic arch; 28′, ramus of mandible; 37, external maxillary vein; 38, jugular vein; 39, facial vein; 44, parotid gland; 50, 50′, submaxillary gland; dotted line at 50 indicates position of large lymph gland, and another lies partly under parotid gland, just in front of 44; 58, internal palpebral ligament; 59, laryngeal prominence. (After Ellenberger-Baum, Anat. für Künstler.) ]

The =dilatator naris inferior= consists of two layers which arise on the nasal process of the premaxilla and the lateral nasal cartilage and end in the outer wing of the nostril.

The =orbicularis oculi= is well developed.

The corrugator supercilii is not present as a separate muscle, its place and function being taken by the frontalis.

The =malaris= is broad, and spreads out below on the fascia over the buccinator and masseter; it is divided into two parts.

MUSCLES OF MASTICATION

The =masseter= is not so large as in the horse; a considerable part of it arises on the facial tuberosity and is directed obliquely backward and downward, so that it would draw the lower jaw forward as well as upward.

The =temporalis= conforms to the temporal fossa, and is therefore longer and entirely lateral in position.

The =pterygoidei= are not quite clearly separated; their direction is more oblique, and the origin of the pterygoideus internus is nearer the median plane than in the horse.

FIG. 208.—MUSCLES OF HEAD OF OX, DORSAL VIEW.

a, a′, Levator labii superioris proprius; b, levator nasolabialis; f, dilatator naris lateralis; g′, malaris; o, zygo-inatico-auricularis and scutulo-auricularis superficialis inferior; o″, scutulo-auricularis superficialis superior; o‴, scutulo-auricularis superficialis accessorius; p, scutularis; u, frontalis; z, orbicularis oculi; 1, concave surface of concha; 3, 2, anterior and posterior borders of concha; 8, scutiform cartilage; 34, parietal cartilage; 39, facial vein; 49, muzzle; 58, internal palpebral ligament. (After Ellenberger-Baum, Anat. für Künstler.) ]

The =stylo-mandibularis= is absent.

The =digastricus= has a tendinous origin on the paramastoid or styloid process of the occipital bone; its bellies are short and thick. It does not perforate the stylo-hyoideus. The two digastrici are connected beneath the root of the tongue by a layer of transverse muscle-fibers (Transversus mandibulæ).

HYOID MUSCLES

The =mylo-hyoideus= is thicker and more extensive than in the horse.

The =stylo-hyoideus= has a long thin tendinous origin and is not perforated by the digastricus.