← A text-book of veterinary anatomy
Chapter 161
Muscles of Mastication
The digastricus has only one belly. It ends on the inner and lower surface of the mandible, in front of the groove for the facial vessels.
The other muscles have no important differential features.
The same is true of the oral hyoid muscles.
Muscles of the Neck
The panniculus carnosus consists of two layers which cross each other obliquely. The fibers of the superficial layer are directed nearly vertically, those of the deep layer toward the face, on which they are continued to form the facial portion.
The mastoido-humeralis is described on p. .
The sterno-cephalicus (Sterno-mastoideus) arises on the sternum and is inserted by a long round tendon on the mastoid process.
The thyroid portion of the sterno-thyro-hyoideus has a peculiar arrangement. It arises (separately from the opposite muscle) on the manubrium sterni. About the middle of the neck it has an oblique tendinous intersection, beyond which it divides into two branches; one of these is inserted in the usual fashion, the other ends on the laryngeal prominence. The hyoid portion is well developed.
The omo-hyoideus is thin. It arises as in the horse, but has no connection with the mastoido-humeralis nor with the opposite muscle.
The omo-transversarius arises on the first or second cervical vertebra (under cover of the mastoido-humeralis), and is inserted into the lower part of the scapular spine.
There are two scaleni. The scalenus ventralis (s. primæ costæ) resembles that of the ox, is attached to the last four cervical vertebræ, and is perforated by the nerves of the brachial plexus. The scalenus dorsalis (s. supracostalis) arises on the transverse processes of the third to the sixth cervical vertebra, and ends on the third rib.
The straight muscles of the head present no special features.
The longus colli is separated from the opposite muscle, so that part of the bodies of the cervical vertebræ is exposed as in man.
The intertransversales resemble those of the ox.
The splenius is thick and extensive. It ends in three parts on the occipital, the temporal, and the wing of the atlas (inconstant).
The trachelo-mastoideus is small, and its atlantal portion is blended with the longissimus.
The complexus is large, and is clearly divided into two portions: the dorsal portion (Biventer cervicis) is marked by several tendinous intersections; the ventral part is the complexus proper.
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.