40 THE BONES. 



orbital tiatus ; h, the suhspJienoidal, or pterygoid process, a long eminence, 

 flattened on both sides, inclining downwards, articulating with the palate 

 and pterygoid bones, and traversed at its base by the vidian canal ; c, a 

 little behind and above this eminence, the superior orifice of the sub- 

 sphenoidal foramen, a large canal which bifurcates inferiorly ; d, more in 

 front, the orbital hiatus, a kind of vestibule into which open in common the 

 principal branch of the subsphenoidal canal, the three supersphenoidal 

 canals, the vidian and optic canals, and the orbital opening : this hiatus is 

 surmounted by a thin and sharp bony plate, above which opens the smallest 

 branch of the subsphenoidal foramen ; e, altogether wifhout ' the hiatus is 

 remarked a smooth surface belonging to the wing of the sphenoid, and 

 which concurs to form the orbital cavity. 



The internal face is concave from side to side. It shows : 1, On the 

 median line, and from before to behind, a small projection united to the 

 crista-gaUi ; the optic fossa, elongated transversely in the form of a shuttle, 

 and presenting at the bottom, and on each side, the superior orifice of the 

 optic foramen, a cylindrical canal directed obliquely downwards,' forwards, 

 and outwards, to reach the orbital hiatus ; the supersphenoidal or pituitary 

 fossa, also named the sella turcica, a slight depression, limited behind by a 

 scarcely noticeable transverse projection separating it from the superior 

 channel of the basilar process ; 2, On the sides, and in front, the internal 

 surface of the wings, depressed by very superficial digital impressions ; 

 more behind and outwards, a fossa, elongated from before to behind, which 

 lodges the mastoid lobule of the brain ; between this fossa and the sella 

 turcica, two vertical fissures : an internal, named the cavernotis sinus, and an 

 external, wider and deeper, for the passage of a large nervous branch. 

 These two fissures open below, near the junction of the three super- 

 sphenoidal canals. Two of these, which are very wide, are placed one before 

 the other, and sepai'ated only by a slight partition. The superior of these 

 constitutes the great sphenoidal fissure ; the other, the lower, is the foramen 

 rotundum, and opens into the orbital hiatus. The third, very small, is situated 

 outside the great anterior canal, opens above the optic foramen, within the 

 bony mass surmounting the hiatus, and sometimes on ihe free margin of 

 this lamina. 



Borders. — The superior is a little concave, and shows, in its middle, the 

 superior extremity of the body, mammillated and articulated with the 

 summit of the basilar process ; on each side, two notches which circumscribe 

 below the ocoipito-spheno-temporal hiatus (foramina lacera basis cranii). 

 The internal notch is the narrowest, and from its affording a passage for the 

 internal carotid artery, is called the carotid notch ; it is continued 6n the 

 external face of the bone by a smooth excavation to which Eigot has given 

 the name of carotid fossa. The external is also prolonged on the exterior 

 surface cf the sphenoid by a short and wide fissure ; it lodges the inferior 

 maxillary nerve. Outside this is another very narrow notch, intended for 

 the passage of the middle meningeal artery. The fibro-cartilaginous sub- 

 stance that partly fills the ocoipito-spheno-temporal hiatus, transforms these 

 notches into foramina, the first of which is named the carotid canal, the 

 second, the foramen ovale, and the third, the foramen spinosum. The inferior 

 border, also concave, is likewise divided into three portions, a middle and 

 two lateral. The first is thick, and formed by the inferior extremity of the 

 body ; it is excavated by two large cavities belonging to the sphenoidal sinus. 

 These cavities are separated from one another by a vertical osseous plate, 

 often perforated, which, at an early period, is fused with the perpendicular 



