THE SPHEXOID BONE. 



39 



The BODY. The superior surface presents in the middle a deep pit, the 

 pituitary fossa, sella turcica, or ephippium, which lodges the pituitary body. 

 In front of the fossa, separated from it by a shallow transverse groove, is 

 a narrow portion of bone on a level with the optic foramina, the olivary 

 process, on which rests the commissure of the optic nerves ; and in front of 

 this is a surface on a slightly higher level, continuous with the superior 

 surfaces of the small wings, and having a slight projection forwards of its 

 anterior border, which articulates with the cribriform plate of the ethmoid, 

 and is called the ethmoidal spine. Behind the pituitary fossa is a prominent 

 lamella, the dorsum sellce, the posterior surface of which is sloped upwards 

 and forwards in continuation of the basilar groove of the occipital bone. 

 The angles of this lamella project over the fossa, and are called the posterior 

 clinoid processes. On each side of the body the surface descends obliquely 

 to a considerably lower level than the fossa ; it presents close to the margin 

 of the fossa a superficial curved groove directed from behind forwards, marking 

 the course of the internal carotid artery. 



Fig. 35. 



JO 



Fig. 35. THE SPHENOID BONE FROM ABOVE AND BEHIND. 



1, the basilar surface, sawn separate from the occipital bone ; 2, dorsum sellae, or 

 inclined surface of the body terminating superiorly in the two posterior clinoid processes ; 

 3, is placed on the olivary eminence or process, and between it and 2 is the sella turcica, 

 or pituitary fossa ; in front of 3 is the transverse groove of the optic commissure ; 4, the 

 side of the body with the sigmoid groove of the internal carotid artery and cavernous 

 sinus ; 5, the lesser wings ; x , the anterior clinoid process ; 6, the ethmoid spine ; ?, 

 the cerebral surface of the greater wings ; 8, the upper angle of the great wings, which 

 articulates with the parietal bone ; 9, the spinous process ; 10, the external, and 11, the 

 internal pterygoid process; 11, is placed opposite the hamular process and groove for the 

 tendon of the tensor palati muscle ; 12, the optic foramen; 13, the sphenoidal fissure or 

 foramen lacerum orbitale ; 14, the foramen rotundum ; 15, the foramen ovale ; 16, the 

 foramen spinosum ; 17, is placed above the posterior opening of" the pterygoid or Vidian 

 foramen. 



The posterior surface is flat, and united to the basilar process of the 

 occipital bone, in early life by cartilage, but in adult age by continuous 

 bony substance. 



Anterior and inferior surfaces. Posteriorly, the body of the sphenoid 

 is solid, but anteriorly and inferiorly it contains two large cavities, the 

 sphenoidal sinuses, separated by a thin mesial lamina, the sphenoidal septum, 

 and covered in front and below by the sphenoidal spongy bones. A promi- 

 nent spine, called the rostrum, formed partly by the septum, partly by the 



