Part 106

The =obliquus capitis posterior= is relatively thin.

The =recti capitis= are thick and more or less fused.

MUSCLES OF THE THORAX

The =levatores costarum= and =rectus thoracis= present no special features.

The =external intercostal= muscles are absent under the serratus anticus and posticus and the digitations of the external oblique.

The =internal intercostals= are thick between the cartilages of the sternal ribs.

The =retractor costæ= and the =transversus thoracis= resemble those of the horse; the latter extends back to the eighth cartilage and fuses with the transversus abdominis.

The =diaphragm= has seven costal digitations on each side, the posterior ones being attached to the ribs at some distance (ca. one-third to one-fourth of rib-length) from the costo-chondral junction. The line of attachment reaches the latter at the tenth rib, and passes along the eighth cartilage to the xiphoid process. The tendinous center is more rounded than in the horse. The crura are well developed. The right crus is very large, and is perforated by the extensive slit-like opening for the œsophagus, which is median in position, and lies about two and one-half to three inches (ca. 6 to 8 cm.) below the twelfth thoracic vertebra. The hiatus aorticus is between the crura.

ABDOMINAL MUSCLES

The =abdominal tunic= is little developed.

The =obliquus abdominis externus= has an extensive fleshy portion and a correspondingly narrow aponeurosis; the latter does not detach a femoral lamina, but is reflected in toto to form the inguinal (Poupart’s) ligament.

The =obliquus abdominis internus= resembles that of the ox; a small fusiform muscle, which crosses the inguinal canal obliquely and is attached on the abdominal surface of the inguinal ligament, is apparently a detached slip of the internal oblique.

The =rectus abdominis= is extensive and thick. It has seven to ten intersections. Its tendon of insertion fuses largely with the common tendon of the gracilis, and does not give off an accessory band to the head of the femur.

The fleshy part of the =transversus abdominis= is well developed. It blends in front with the transversus thoracis.

The =cremaster externus= is present in the female as well as in the male.

MUSCLES OF THE BACK AND LOINS

The =serratus anticus= is inserted into the fifth to the eighth ribs inclusive, the serratus posticus into the last four or five ribs. There are usually no digitations attached to the ninth and tenth ribs.

The =transversalis costarum= (Iliocostalis) extends to the wing of the atlas.

The =spinalis et semispinalis= can be separated without much difficulty from the longissimus dorsi, the division from the common mass of the loins beginning about the first lumbar vertebra.

The =multifidus= resembles that of the horse.

=Interspinales= are present, as well as distinct =intertransversales= of the back and loins.

MUSCLES OF THE TAIL

The superior and lateral =sacro-coccygei= arise as far forward as the last lumbar vertebra. Gurlt explains the twist of the tail as being due to the spiral arrangement of the insertions of the tendons.

MUSCLES OF THE THORACIC LIMB

MUSCLES OF THE SHOULDER GIRDLE

The =trapezius= is very wide, its line of origin extending from the occipital bone to the tenth thoracic vertebra. There is no clear division between its two parts, which are both inserted into the scapular spine.

The =omo-transversarius= resembles that of the ox.

The =rhomboideus= consists of three portions. The =cervical portion= (Rhomboideus cervicalis) is greatly developed, its origin extending from the second cervical to the sixth thoracic vertebra. The =cephalic portion= (Rhomboideus capitis) arises with the splenius on the occipital bone, and is inserted with the cervical part. The =dorsal portion= (Rhomboideus thoracalis) extends as far back as the ninth or tenth thoracic vertebra.