Part 113

There are twelve pairs of =levatores costarum=.

The =external intercostals= do not occupy the spaces between the costal cartilages.

The =diaphragm= has a small tendinous center. The =œsophageal opening= is between the pillars. The fleshy rim is attached at the costo-chondral junctions from the eighth backward, and along the thirteenth rib nearly its entire length.

MUSCLES OF THE BACK AND LOINS

The =serratus anticus= arises from the median raphé of the neck and the first six or seven thoracic spines, and is inserted into the second to the ninth ribs. It is well developed. The =serratus posticus=—much weaker—arises on the lumbo-dorsal fascia, and is inserted into the last three or four ribs. Thus one or two ribs intervene between the two.

The =transversalis costarum= (Iliocostalis) is well developed, and extends from the ilium to the sixth, fifth, or fourth cervical vertebra.

The =longissimus= resembles that of the other animals, but the spinalis et semispinalis separates clearly at the sixth or seventh thoracic vertebra. It is inserted into the articular and spinous processes of the last six cervical vertebræ. It has no depression in the lumbar region for the gluteus medius.

The =intertransversales= are fleshy, as in the ox.

The =interspinales= are distinct, especially in the lumbar region.

MUSCLES OF THE TAIL

These present the same general arrangement as in the horse. The =sacro-coccygei=, however, arise on the lumbar vertebræ also, and the =coccygeus= on the ischiatic spine. There is found a =sacro-coccygeus accessorius=, which arises on the internal border of the ilium, the edge of the sacrum, and the transverse processes of the first coccygeal vertebræ, and is inserted between the superior and lateral sacro-coccygei. It is homologous with the intertransversales.

MUSCLES OF THE ABDOMEN

The abdominal tunic is practically absent.

The =obliquus abdominis externus= has an extensive fleshy portion. It arises from the last eight or nine ribs and the lumbo-dorsal fascia.

The =obliquus abdominis internus= arises from the external angle of the ilium and the lumbo-dorsal fascia. The fibers have an almost vertical direction, and there is a fleshy attachment to the last rib.

The =rectus abdominis= is attached by a long tendon on the first five or six costal cartilages, and by fleshy fibers on the xiphoid cartilage. It has three to six indistinct tendinous inscriptions.

The =transversus abdominis= presents no special features except that the posterior part of its aponeurosis splits into two layers which include the rectus between them.

MUSCLES OF THE PELVIC LIMB

FIG. 235.—MUSCLES OF TAIL, ANUS, AND GENITAL ORGANS OF DOG.

1, Ilium; 2, femur; 3, tuber ischii; 4, sacro-sciatic lig.; 5, sacral region; 6, tail; 7, penis; 8, anus; 9, rectum; a, sacro-coccygeus superior; b, sacro-coccygeus accessorius; c, coccygeus; d, sacro-coccygeus inferior; e, retractor ani; f, f′, sphincter ani externus; g, retractor penis; h, bulbo-cavernosus; i, transversus perinei (?); k, m, ischio-urethrales; l, ischio-cavernosus; n, tendon of obturator internus; o, gemellus; p, urethral muscle. (After Ellenberger, in Leisering’s Atlas.) ]

The =psoas minor= arises on the last thoracic and first four or five lumbar vertebræ, and is inserted into the ilio-pectineal line.

The =psoas major= is short, arising from the last four lumbar vertebræ.

The outer head of the =iliacus= is small, while the inner head is large and fuses with the psoas major.

The =quadratus lumborum= is well developed, and extends laterally beyond the outer edge of the ilio-psoas. It arises from the last four ribs and the lumbar transverse processes, and ends on the pelvic surface of the wing of the ilium.

The =tensor fasciæ latæ= consists of two parts. The anterior part is long and rounded; the posterior is shorter and fan-like.

The =gluteus superficialis= is small. It arises on the sacrum, first coccygeal vertebræ, and sacro-sciatic ligament. It is inserted below and behind the trochanter major of the femur, on the outer branch of the linea aspera.

The =gluteus medius= has no lumbar portion. It is inserted into the trochanter major by a strong tendon.

The =gluteus profundus= is broad and fan-shaped. It arises on the superior ischiatic spine and on the ilium as far forward as the gluteal line, and is inserted into the trochanter major below the medius.