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BONES. 53

the attachment of the odontoid ligament of the axis (the second cervical
vertebra). Immediately above the anterior facet on either side are tlie
anterior condyloid foramina, situated at the side and above the foramen
mau-num ; they transmit the hypoglossal nerves. Occasionally these
foramina are found doubled, which allows the superior and inferior bun-
dles of the hvpoglossal nerve to pass through separate foramina in their
exit. Behind the posterior facet is the condyloid fossa, which usually
contains the posterior condyloid foramen, for the transmission of the
occipital emissary vein to the lateral sinus. Two foramina are also
occasionally found in this situation. The outer surface of the tabular
portion of the occipital bone (supraoccipital) is divided transversely into
three sections by the superior and inferior curved lines. The superior
curved line runs inwardly from the lateral angles of the bone, at the
temporo-parietal suture, to the external occipital protuberance ; it forms
the major portion of that line, which extends in the articulated skull
from the apex of the mastoid portion of* the temporal bone on the one
side of the cranium to the same point on the opposite side. The inferior
curved line runs almost parallel with the superior. Its extremities are
situated at each jugular process, from which point it ascends to the
occipital crest. The lower two-thirds of the external surface is divided
longitudinally by the occipital crest. This crest is a slight ridge run-
ning from the external occipital protuberance to the foramen magnum.
The upper third, or that portion above the superior curved lines, is
comparatively smooth. The external occipital protuberance, A^hich
gives attachment to the liy-amentum nuchne, is situated in the centre of
the superior curved line, and is analogous to the spinous process of a
vertebra. Its size varies in diiferent individuals, being much larger in
some persons than in others. The upper margin of the superior curved
line gives attachment to the occi])ito-frontalis muscle, its inner extremity
to the trapezius, and just beneath the outer extremity are the points of
attachment of the splenius capitis nniscle. On either side of the crest,
between tlie curved lines, are marked depressions for the attachment of
the complexus muscles, and just below and to the outer side of these is
a smooth surface for the insertion of the superior oblique muscles. The
space below the inferior curved line gives attachment to the rectus capitis
posticus major and minor muscles.
The Internal Surface of the bone is divided into four fossae In' two
distinct ridges, transverse and longitudinal : the former runs from the
lateral angles to the internal occipital protuberance, the longitudinal
ridge extending from the superior angle of the bone to the foramen
magnum. The point where these ridges intersect is called the internal
occipital protuberance. The superior fossfe afford lodgment to tlie lobes
of the cerebrum, while the inferior accommodate those of the cei-ebel-
lum. The superior part of the longitudinal and the transverse ridges
are generally grooved, to accommodate the longitudinal and the lateral
venous sinuses. Frequently the longitudinal sinus is found to the right
side of the superior longitudinal ridge, particularly Avhere it approaches
the intersection of the ridges.
The inferior portion of the longitudinal ridge is rounded, and is gen-
erally called the internal occipital crest.