THE SPHENOID BONE. 119 
pituitary body. Behind, this is overhung by a sloping ridge, the dorsum sella, the 
posterior surface of which is inclined upwards, and is in continuation with the 
basilar groove of the occipital bone. Anteriorly and externally the angles of this 
ridge pr roject over the pituitary fossa in the form of prominent tubercles, called the 
Great 
wing 
, Posterior 
S l wing ic ¢ “4 rin 
mall wing Optic groove clinoid Anterior 
process clinoid 
| Dorsum 
Optic ‘ame 
Iptic for vumen Riles 
— Cerebral 
Groove for 
VI. nerve j Pes rote surface 
- : : WZ 
7) =: _y > a 1 = oe 
Foramen (33 3y Y Z j Sphenoidal 
' ‘ it5 z *P fissure 
rotundum 
Groove for 
Eustachian tube 
Vidian canal — 
— Spine 
Carotid 
groove 
“Lingula 
Scaphoid fossa 
External pterygoid plate — 
Pterygoid fossa 
/ 
Internal pterygoid plate i 
>, ~——. Pterygoid notch 
Pterygoid tubercle 
Vaginal process 
Ns 
Hamular process 
Fia. 92.—SPHENOID AS SEEN FROM BEHIND. 
posterior clinoid processes (processus clinoidei posteriores). In front of the pituitary 
fossa there is a transverse elevation, the olivary eminence (tuberculum selle) 
towards the outer extremities of which, and somewhat behind, there are often- 
times little spurs of bone, the middle clinoid processes (processus clinoidei medii). 
Sphenoidal 
fissure 
{ 
Sphenoidal sinus 
\ 
y _ Optic foramen 
Ethmoidal spine 
Temporal 
surface 
Orbital surface 
Infra-temporal crest 
Zygomatic 
surface Spine 
Foramen 
‘otunduln 
rotundu wan Rostrum! 
Vidian canal~ Nasal surf. 
No diekacnmmniines surface 
Vaginal 
process External pterygoid plate 
Pterygo- 
palatine Fy 
STOOVO NF Hamular process of 
> ———_internal pterygoid plate 
Pterygoid notch 
Fic, 93.—SPHENOID AS SEEN FROM THE FRONT. 
In front of the olivary eminence is the optic groove (sulcus chiasmatis), which 
passes outwards on either side to become continuous, between the roots of the 
lesser wings, with the optic foramina. 
This groove is liable to considerable var iations, and apparently does not always serve for the 
lodgment of the optic chiasma. (Lawrence, “Proc. Soc. Anat. ” Journ. Anat. and Physiol. 
vol. xxviii. p- 18.) 
In front of the optic groove, from which it is often separated by a thin sharp edge, 
the superior surface continues forwards on the same plane as the upper surfaces “of 
8¢ 
