OSTEOLOGY AND SYNDESMOLOGY. 15 
magnum (pl. 121, fig. 17*), through which pass the medulla oblongata, the 
vertebral arteries and veins, and the spinal accessory nerves; on each side 
are seen the condyles (jig. 6*, 177) or surfaces of articulation between the 
head and the vertebral column, constituting a hinge-joint by which the for- 
mer may be moved backwards and forwards. In a depression behind each 
condyle is the posterior condyloid foramen, which conducts a cervical vein 
to the lateral sinus. There is likewise the anterior condyloid foramen for 
conducting the hypoglossal nerve to the tongue. On the interior surface, 
behind the foramen magnum, is seen a rectangular cross (fig. 18"*), form- 
ing at the centre the internal occipital protuberance. To this cross the 
dura mater is attached, and it also exhibits the impressions of cerebral 
bloodvessels. In the angles of the cross are seen broad concavities, the 
two superior of which receive the posterior lobes of the cerebrum, and the 
two inferior those of the cerebellum (jig. 18° °). 
Anterior to the lower part of the occipital bone, and placed transversely 
in the-middle of the base of the cranium, is the sphenoid bone, os sphe- 
noideum (pl. 122, fig. 6 above, jig. 7 below). In the middle of this highly 
complicated bone is seen the body or centrum, which is hollow and contains 
the sphenoidal sinuses (pl. 128, fig. 2°, fig. 3°), communicating with the nose. 
A deep depression on the upper surface, bounded anteriorly and posteriorly 
by projecting spines and ridges, is the sella turcica for the reception of 
the pituitary gland (pl. 122, fig. 6"). The inferior surface presents a 
longitudinal rising in the middle called the sphenoidal or azygos sprocess 
(jig. 7°), for articulation with the vomer. From the upper anterior part 
of the body arise, one on each side, the apophyses of Ingrassias, the ensiform 
processes or the little wings (fig. 6*), with the bases perforated by the foramen 
opticum for transmitting the optic nerve with the ophthalmic artery. The 
‘two great wings, ale magne (jig. 7°"), arise from the sides of the body by 
‘a small irregular base. ‘They present three faces: one anterior, called 
orbital from its forming part of the orbit; one external, called temporal ; 
and a third turned towards the brain, forming part of the fossa, for contain- 
ing its middle lobe. Between the great and the small wings is a consider- 
able fissure called foramen sphenordale, or foramen lacerum superius (fig. 6°), 
for transmitting the third, fourth, sixth, and first branch of the fifth pairs 
of nerves and the ophthalmic vein. Below the base of this hole is the jora- 
men rotundum ( fig. 6") for the passage of the second branch of the fifth pair, 
and behind the foramen rotundum again, is the foramen ovale (fig. 6°) for 
the exit of the third branch of the fifth pair. About two lines behind the 
foramen ovale is the foramen spinale (fig. 6°) for transmitting the middle 
artery of the dura mater. 
From the lower part of the two great wings project downwards on each 
side the two pterygoid processes constituting the posterior portion of the 
mouth (fig. 6"). They serve for the attachment of certain muscles, and 
are pierced at their base by the pterygoid foramen for transmitting the 
nerve of the same name. 
The sphenoid bone articulates above and in front with the vomer, the 
frontal, ethmoidal, malar, and parietal bones, laterally with the temporal, 
ICONOGRAPHIC ENCYCLOP£DIA.—VOL, II. 46 721 
