THE ENTIEE SKULL 



485 



by the prespheno-basisphenoidal and orbitospheno-alisphenoidal 

 sutures. The surface is convex from before backward and slightly 

 concave from side to side. Behind the middle, on each side, is the 

 optic foramen, and behind this, separated by the anterior clinoid 



FIG. 393. 



Sagittal Suture. 

 Frontal. 

 Postorbital Process of Frontal. 



MU*""tf . . i / , ,' 7 



^ 1 /I 



Anterior Fossa. 

 Frontal. 



Alisphenoid. 



Optic Foramen. 



Inner Wall of Sphenoidal 

 Fissure. 



External Pterygoid Process 

 of Alisphenoid. 



Hamular Process of 

 Pterygoid. 



Middle 

 Pterygoid Fossa. 



For Optic Chiasma. 

 Presphenoid. 



External Pterygoid Fossa. 



TRANSVERSE VERTICAL SECTION OF THE SKULL THROUGH THE 

 SPHENOIDAL FISSURE, SEEN FROM BEHIND. 



plate, is the sphenoidal fissure (Fig. 393). The anterior and lateral 

 walls and the roof are contributed by the frontals. 



The anterior wall (Fig. 393) occupies the entire width of the skull, 

 and on each side of the olfactory fossa faces backward, upward, and 

 slightly inward. The lateral walls are narrow below and wide above ; 

 they face inward and slightly backward. They are impressed above 

 by shallow fossas for the anterior cerebral convolutions, and at the 

 posterior lower part by an arborescent arterial groove. 



The roof is directed upward and forward ; it is narrow in front, 

 wide behind, and evenly arched. In the middle line, at the sagittal 

 suture, is a ridge for the attachment of a tough membrane of the brain, 

 known as the falx cerebri. The roof also is impressed by the cerebral 

 convolutions. 



The Middle Fossa is the largest of the four. It is longer above 

 than below, inasmuch as its anterior point on the roof lies nearly over 

 its anterior point on the floor, while the upper posterior point lies 



