The panniculus, except the cervical part, has been removed. _a_,
Trapezius cervicalis; _a′_, trapezius thoracalis; _c_, _c′_,
mastoido-humeralis; _d_, sterno-cephalicus; _e_, deltoid; _f_, long
head of triceps; _f′_, external head of triceps; _g_, anterior
superficial pectoral; _h_, posterior deep pectoral; _h′_, anterior
deep pectoral; _i_, serratus thoracis; _i′_, serratus cervicis; _k_,
latissimus dorsi; _l_, obliquus abdominis externus; _l′_,
aponeurosis of _l_; _m_, serratus posticus; _m′_, lumbo-dorsal
fascia; _o_, tensor fasciæ latæ; _o′_, fascia lata; _o″_, gluteus
superficialis; _q_, _q′_, _q″_, biceps femoris; _r_, semitendinosus;
_s_, sacro-coccygeus superior; _t_, sacro-coccygeus lateralis; _u_,
coccygeus; _v_, cervical panniculus; _w_, splenius; _x_,
rhomboideus; _y_, tendon of trachelo-mastoideus and
mastoido-humeralis; _z_, suprasinatus; _X_, wing of atlas; _2_,
spine of scapula; _4′_, external epicondyle of humerus; _6_, deltoid
tuberosity; _8_, olecranon; _16_, external angle of ilium; _20_,
patella; _21′_, external condyle of tibia. (After Ellenberger-Baum,
Anat. für Künstler.)
]
_Action._—Acting together, to extend the head and neck; acting singly,
to flex the head and neck laterally or to rotate the atlas.
_Structure._—The origin from the thoracic vertebræ is by aponeurotic
slips which blend with the complexus. The succeeding fleshy portion, in
passing along the neck, receives fasciculi from each of the cervical
vertebræ except the first two. The dorsal division of the muscle is
inserted into the mastoid process by a flat tendon which fuses with that
of the splenius; the ventral division is inserted into the wing of the
atlas by a ribbon-like tendon in common with the splenius and
mastoido-humeralis.
_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 superior cervical vessels cross the
deep face of the muscle obliquely at the level of the sixth and seventh
cervical vertebræ.
_Blood-supply._—Vertebral and superior 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 nuchæ, under cover of the
splenius and trachelo-mastoideus muscles.
_Origin._—(1) The second, third, and fourth thoracic spines, in common
with the splenius and serratus anticus; (2) the transverse processes of
the first six or seven thoracic vertebræ; (3) the articular processes of
the cervical vertebræ.
_Insertion._—The posterior surface of the occipital bone, external to
the funicular portion of the ligamentum nuchæ.
_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 upper 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 magnus, splenius,
and trachelo-mastoideus muscles; deeply, the ligamentum nuchæ, the
multifidus cervicis, longissimus, and the oblique and posterior straight
muscles of the head, the deep or superior 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= (M. semispinalis colli; transverse spinous
muscle of neck).—This muscle lies on the arches of the last five
cervical vertebræ. It consists of five or six segments.
_Origin._—The articular processes of the last five (or four) cervical
and the first thoracic vertebræ.
_Insertion._—The spinous processes of the cervical vertebræ.
[Illustration: