Part 100

The =genio-hyoideus= is more developed.

The =kerato-hyoideus= has an additional attachment on the middle cornu of the hyoid bone.

The =hyoideus transversus= is bifid.

The =sterno-thyro-hyoideus= has no intermediate tendon and is thicker.

The =omo-hyoideus= arises as a thin band from the fascia over the third and fourth cervical vertebræ. It blends here with the rectus capitis anterior major. The =occipito-hyoideus= is thick.

FIG. 209.—MUSCLES OF HEAD OF OX, VENTRAL VIEW.

d, d′, Sterno-cephalicus; e, omo-hyoideus; g, zygomaticus; h, buccinator; i, depressor labii inferioris; k, orbicularis oris; m, masseter; n, parotido-auricularis; o′, zygomatico-auricularis; w, mylo-hyoideus; 1, concha, convex surface; 2, anterior border of concha; 30′, angle of jaw; 39, facial vein; 44, parotid gland; 45, lower lip; 48, angle of mouth; 50, 50′, submaxillary gland; 59, larynx; x, wing of atlas. (After Ellenberger-Baum, Anat. für Künstler.) ]

MUSCLES OF THE NECK

A. VENTRAL GROUP

The =sterno-cephalicus= consists of two muscles. They arise from the manubrium sterni and first rib. The superficial muscle (Sterno-mandibularis) is inserted on the anterior border of the masseter, the ramus of the mandible, and the buccal fascia. The deep muscle (Sterno-mastoideus) crosses under the preceding and ends on the mastoid process, the mandible, and, in common with the rectus capitis anterior major, on the basilar process of the occipital bone.

FIG. 210.—SUPERFICIAL MUSCLES OF OX, AFTER REMOVAL OF PANNICULUS.

a, Trapezius; b, omo-transversarius; c, c′, mastoido-humeralis (c, cleido-mastoideus; c′, cleido-occipitalis); d, sterno-cephalicus; e, deltoid; f, long head, f′, external head of triceps; g, superficial pectoral; h, posterior deep pectoral; i, serratus magnus; k, latissimus dorsi; l, obliquus abdominis externus; l′, aponeurosis of l; m, serratus posterior; m′, lumbo-dorsal fascia; n, obliquus abdominis internus; o, tensor fasciæ latæ; o′, fascia lata; p, gluteus medius; q, q′, biceps femoris; r, semitendinosus; s, sacro-coccygeus superior; t, sacro-coccygeus lateralis; u, coccygeus. (After Ellenberger-Baum, Anat. f Künstler.) ]

There are two scaleni. The =scalenus ventralis= (s. primæ costæ) arises on the first rib and ends on the transverse processes of the third to the seventh cervical vertebræ. It is traversed by the roots of the brachial plexus, which partially divide it into a small dorsal and a large ventral part. The brachial vessels lie below the latter. The =scalenus dorsalis= (s. supracostalis) arises usually on the second, third, and fourth ribs, and ends on the transverse processes of the third to the sixth cervical vertebræ.

The =rectus capitis anterior major= arises on the third to the sixth cervical transverse processes, and blends at its insertion with the sterno-mastoideus and the mastoid portion of the mastoido-humeralis.

The =rectus capitis anterior minor= is larger than in the horse.

The =rectus capitis lateralis= and =longus colli= resemble those of the horse.

The =intertransversales= are large. From the sixth cervical vertebra forward they form a muscular mass (M. intertransversarius longus) which is inserted into the wing of the atlas.

B. LATERAL GROUP

The =splenius= is thin. It arises directly from the first three or four thoracic spines, and ends by a thin tendon on the occipital bone, the wing of the atlas, and the transverse process of the axis, blending with the mastoido-humeralis, trachelo-mastoideus, and omo-transversarius. The remaining muscles present no very marked differential features.

MUSCLES OF THE THORAX

The =levatores costarum= number ten or eleven pairs.

The =diaphragm= presents several important differential features. Its slope is much steeper and its width is greater than in the horse. The costal attachment extends almost in a straight line from the upper fourth of the last rib to the junction of the eighth rib with its cartilage, and along the latter to the sternum. The mid-line slopes from the twelfth thoracic vertebra obliquely as far as the vena cava, beyond which it is almost vertical. The right crus divides into two branches, which circumscribe the œsophageal opening, unite below, and then spread out in the tendinous center. The left crus is small. The œsophageal opening is situated about four to five inches (10 to 12 cm.) below the eighth thoracic vertebra, a little to the left of the median plane. The foramen venæ cavæ is a little more ventral and almost in the median plane. The other muscles resemble those of the horse.

MUSCLES OF THE BACK AND LOINS

The =serratus anticus= is very thin. It is inserted on the fifth to the eighth ribs. It may be reduced to two or three digitations or may be absent. The =serratus posticus= is usually inserted on the last three or four ribs.

The =transversalis costarum= (Iliocostalis) has a distinct lumbar portion which is attached to the lumbar transverse processes and the external angle of the ilium.

The =longissimus= resembles that of the horse, but it is more fleshy anteriorly, and the spinalis dorsi is clearly distinguishable from the common mass. In the lumbar region the tendons meet across the summits of the spines.

=Intertransversales= are present in the back, and =interspinales= in the back and loins.

MUSCLES OF THE TAIL