28 PRACTICAL ANATOMY. 



sella turcica posteriorly is a plate of bone which termi- 

 nates at each side in well-marked processes, the posterior 

 clinoid. This plate is notched at the sides for the passage 

 of the sixth pair of nerves, and is also centrally notched 

 for the accommodation of the infundihulum. The su- 

 perior surface behind the posterior clinoid processes forms 

 a descending quadrilateral plate of bone, the os planum 

 of the sphenoid, which is continuous with the superior 

 surface of the basilar process of the occipital. It is 

 smooth and polished, and supports the pons Varolii. At 

 its posterior inferior angle it is grooved for the passage 

 of the sixth nerve. At each side of the body the su- 

 perior surface presents a well-marked groove, slightly 

 sinuous, which lodges the cavernous sinus and the in- 

 ternal carotid artery ; it is called the cavernous groove. 



The anterior surface presents in the median line a 

 vertical, plate-like process of bone, called the sphenoidal 

 crest. It articulates with the vertical plate of the 

 ethmoid, and assists in forming the septum nasi. The 

 sphenoidal crest is not simply a projection from the sur- 

 face, but extends into the interior of the body, forming 

 a vertical partition. After the age of puberty the body is 

 hollow, forming the sphenoidal air sinuses. These 

 sinuses are frequently subdivided by other bony par- 

 titions, and are lined by a continuation of the Schnei- 

 derian mucous membrane of the nose, with which they 

 communicate. On each side of the crest the large, 

 irregular openings of these sinuses are observed. They 

 are largely covered in by small scroll-like bones, the 

 sphenoidal turbinated. Laterally, the anterior surface 

 articulates with the os planum of the ethmoid ; its upper 

 border, with the frontal ; its lower, with the orbital proc- 

 ess of the palate bone. The inferior surface presents, 

 in the middle line, the rostrum, a ridge of bone con tin- 



