SPHENOID. 53 



fossa or sella turcica, in which the pituitary gland is lodged : in 

 front of the sella turcica is a slight elevation formed by the pre- 

 sphenoid, the olivary process, which supports the commissure of 

 the optic nerves. Immediately in front of the olivary process is 

 the optic hiatus, a tranverse notch which leads to the two optic 

 foramina for the optic nerves ; and anteriorly is a sharp central 

 process which articulates with the crista galli process of the 

 ethmoid bone. A concavity on each side of the anterior part of 

 the body helps to form the ethmoid fossa, which contains the 

 olfactory bulb. 



On each side of the sella turcica are two shallow grooves, the 

 internal being the cavernous fossa, which contains the cavernous 

 sinus of the brain, and the ophthalmic, third, and sixth nerves ; 

 the external, which is the larger and deeper, is the sphenoidal 

 . which transmits the superior maxillary division of the fifth 

 nerve. In front of these lateral grooves, and continuous with 

 them, two foramina open into the orbital hiatus, the inner and 

 uppermost being the foramen lacerum orbitale, for the alveolar 

 vein, and the third and sixth nerves ; the inferior is the for-, 

 rotundum, for the passage of the superior maxillary division of 

 the fifth nerve ; it is joined by the pterygoid foramen. Above 

 these, and passing through the base of the pterygoid process, the 

 foramen patheticttm gives passage to the fourth nerve. 



The wings project outwards and upwards ; their internal sur- 

 faces are smooth, and help to form the lateral walls of the 

 cranium, the posterior part being hollowed for the mastoid lobes 

 of the cerebrum. The external surface of the wing is slightly 

 convex anteriorly, where it joins the frontal bone to form the 

 orbital fossa, and rough posteriorly, where it articulates with the 

 squamosal bone. The pterygoid processes project downwards and 

 forwards, are broad and flat, and articulate with the vomer and 

 palatine bones. 



The posterior border of the body articulates with the basi- 

 occipital bone. The portion of the wing next to the body bounds 

 anteriorly the foramen lacerum basis cranii ; in this portion there 

 are two notches, an internal one, the carotid notch, which gives 

 passage to the endocarotid artery, and is continued under the 

 body of the bone, and an external, the inferior maxillary notch, 

 which transmits the nerve of the same name, a branch of the 

 fifth. 



The anterior face of the body of the bone presents two deep 



