MUSCLES OF THE ABDOMEN 



377 



costal cartilage, to the tenth and eleventh cartilages a little (ca. 1 to 2 cm.) below 

 the junction with the rib, to the twelfth rib at its ventral end and to the last rib 

 below its middle. The cupola is very unsymmetrical ; on the left side it is opposite 

 the sixth rib, while on the right it is an intercostal space further back. 



Muscles OF the Back and Loins 



The serratus dorsalis anterior arises from the median raphe 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 dorsalis posterior — much weaker — arises from 

 the lumbo-dorsal fascia, and is inserted into the last three or four ribs. Thus one 

 or two ribs intervene between the two. 



The longissimus costarum is well developed, and extends from the ilium to the 

 sixth, fifth, or fourth cervical vertebra. 



The longissimus dorsi resembles that of the other animals, but the spinalis et 

 semispinalis separates clearly from the longissimus proper at the sixth or seventh 

 thoracic vertebra. It is inserted into the articular and spinous processes of the 

 last six cervical vertebrae. 

 It has no depression in the 

 lumbar region for the glu- 

 teus medius. 



The intertransversales 

 are fleshy, as in the ox. 



The interspinales are 

 distinct and are most devel- 

 oped 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 vertebrae also, 

 and the coccygeus on the 

 ischiatic spine. There is a 

 sacro-coccygeus accessor- 

 ius, which arises on the 



Fig. 325. — Muscles of Tail, Anus, and Genital Organs of Dog. 

 1, Ilium; a, femur; S, tuber ischii; .4, sacro-soiatic ligament; B, sacral 

 region; S, tail; 7, penis; g, anus; 9, rectum; o, sacro-coccygeus dorsalis; 

 ti, sacro-coccygeus accessorius; cicoccygeus; d, sacro-coccygeus ventralis; c, 

 retractor ani; /, /', sphincter ani externus; g, retractor penis; h, bulbo- 

 cavernosus; t, transversus perinei (?) ; i, m. ischio-urethrales; Z, ischio- 

 cavernosus; n, tendon of obturator internus; o, [gemellus, p, urethral 

 muscle. (After Ellenberger, in Leisering's Atlas.) 



medial border of the ihum, 



the edge of the sacriun, and 



the transverse processes of , , , , x i 



the first coccygeal vertebra, and is inserted between the dorsal and lateral sacro- 



coccygei. It is homologous with the intertransversales. 



It arises from 



Muscles of the Abdomen 



The abdominal tunic is practically absent. 



The obliquus abdominis externus has an extensive fleshy part, 

 the last eight or nine ribs and the lumbo-dorsal fascia. 



The obliquus abdominis internus arises from the tuber coxae and the lumbo- 

 dorsal fascia. The fibers have an almost vertical direction, and there is a fleshy at- 



