LATERAL CERVICAL MUSCLES 273 



wing of the atlas by a ribbon-like tendon in common with the splenius and 

 brachiocephalicus. 



Relations. — Superficially, the splenius muscle and dorsal branches of the 

 cervical nerves; deeply, the complexus, the spinalis colli, and the oblique muscles 

 of the head. The deep cervical vessels cross the deep face of the muscle obliquely 

 at the level of the sixth and seventh cervical vertebrae. 



Blood-supply. — Vertebral and deep cervical arteries. 



Nerve-supply. — Dorsal branches of the last six cervical nerves. 

 ^ 6. Complexus (M. semispinalis capitis) .^This is a large triangular muscle 

 which lies chiefly on the ligamentum nuchse, under cover of the splenius. 



Origin. — (1) The second, third, and fourth thoracic spines, in common with 

 the splenius and serratus dorsalis; (2) the transverse processes of the first six or 

 seven thoracic vertebrs; (3) the articular processes of the cervical vertebrae. 



Insertion. — A rough area on the occipital bone just ventral to the nuchal crest. 



Action. — It is the chief extensor of the head and neck. Acting singly, the 

 muscle inclines the head to the same side. 



Structure. — The origin of the muscle at the withers is aponeurotic. In the 

 neck the bundles arising from the articular processes run obliquely upward 

 and forward, giving the lower part of the muscle a distinct pennate character. 

 The dorsal part of the belly is crossed obliquely by four or five tendinous 

 intersections. The insertion is by a strong tendon. 



Relations. — Superficially, the rhomboideus, serratus ventralis, splenius, and 

 longissimus capitis et atlantis; deeply, the ligamentum nuchse, the multifidua^^ 

 cervicis, longissimus dorsi, and the oblique and dorsal straight muscles of the head, 

 the deep cervical vessels, and the dorsal cutaneous branches of the cervical nerves. 



Blood-supply. — Deep cervical, vertebral, and occipital arteries. 



Nerve-supply. — Dorsal branches of the last six cervical nerves. 



7. Multifidus cervicis. — This muscle lies on the arches of the last five cervical 

 vertebrae. It consists of five or six segments. 



Origin. — The articular processes of the last four or five cervical and the first 

 thoracic vertebrae. 



Insertion. — The spinous and articular processes of the cervical vertebrae. 



Action. — ^Acting together, to extend the neck; acting singly, to flex the neck on 

 the side of the muscle contracting and to rotate the neck to the opposite side. 



Structure. — The muscle is composed of two sets of bundles. The superficial 

 bundles are directed obliquely forward and inward, each passing from an articular 

 process to the spine of the preceding vertebra. The deep bundles are shorter and 

 run straight from an articular process to that of the preceding vertebra. 



Relations. — Superficially, the complexus, longissimi, and obliquus capitis poster- 

 ior; deeply, the spinalis, the ligamentum nuchse, and the arches of the vertebrae. 



Blood-supply. — Deep cervical and vertebral arteries. 



Nerve-supply. — Dorsal branches of the last six cervical nerves. 



8. Spinalis. — Described with the longissimus on p. 278. 



9. Obliquus capitis posterior (s. caudalis). — This is a strong, quadrilateral 

 muscle, which covers the dorso-lateral aspect of the atlas and axis. 



Origin. — The side of the spine and the posterior articular process of the axis. 



Insertion. — The dorsal surface of the wing of the atlas. 



Action. — Chiefly to rotate the atlas, and with it the head, to the same side; 

 also to assist in extending and fixing the atlanto-axial joint. 



Structure. — The muscle is composed almost entirely of parallel fleshy fibers 

 directed obliquely forward and outward. It is covered by a special fascia. 



Relations. — Superficially, the splenius, complexus, longissimus capitis, and 

 brachiocephalicus muscles; deeply, the arch and spine of the axis, the wing of 

 the atlas, the atlantoaxial joint, the rectus capitis dorsalis minor, the occipital and 

 18 



