_Insertion_ by a strong tendon into the medial part of the lambdoidal crest.
_Relations._--Outer surface with the splenius (Fig. 73, _b_) and at the caudal end with the longissimus dorsi (Fig. 69, _f″_). Inner surface with the spinalis dorsi (Fig. 69, _g_), the semispinalis cervicis (Fig. 71, _c_), and the rectus capitis posterior major (Fig. 71, _a_). Medial edge with the muscle of the opposite side; lateral edge with the complexus (Fig. 69, _b_).
=M. complexus= (Fig. 69, _b_) (=lateral portion of M. semispinalis cervicis et capitis=).--The complexus is closely associated with the biventer cervicis (_a_) and lies on its lateral side beneath the splenius (Fig. 73, _b_).
_Origin_ by tendinous bands from the anterior articular processes of the last five or six cervical and the first one, two, or three thoracic vertebræ. The same bands give origin externally to the fibres of the longissimus capitis (Fig. 69, _e_), and internally to those of deeper muscles of the neck. The six or more muscular slips continued from these tendons unite to form a flat band, the
_Insertion_ of which is by a flat tendon into the medial third of the lambdoidal crest some distance ventrad of the free edge of the crest. Near the insertion the lateral border of the muscle is connected by an aponeurotic band to the lateral border of the transverse process of the atlas.
_Relations._--Outer surface at the dorsal border with the biventer cervicis (Fig. 69, _a_); at the middle with the splenius (Fig. 73, _b_); at the ventral border with the longissimus capitis (Fig. 69, _e_) and the longissimus dorsi (Fig. 69, _f″_). Inner surface with the cervical portion of the spinalis dorsi, with the semispinalis cervicis (Fig. 71, _c_), the obliquus capitis inferior (Fig. 71, _b_), the rectus capitis posterior major (Fig. 71, _a_), and the obliquus superior (Fig. 71, _e_).
=M. spinalis dorsi= extends into the cervical region; it has been described.
=M. semispinalis cervicis= (Fig. 71, _c_).--This represents that portion of the multifidus spinæ which extends into the cervical region. It is not composed of distinct bundles, like the multifidus of the thoracic region, but all the fibres are united into a fairly well-defined muscle.