44 THE BONES OF THE HEAD. 



jection 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 sella, 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 

 winding groove directed from behind forwards, marking the course of the internal 

 carotid artery. Behind the commencement of the groove, and at the lower end of 

 the lateral margin of the dorsum sellse is a compressed projection, the petrosal 



BODY SMALL WING GREAT WINC 



FOR. ROTUNOUM 

 POST. CLIN. PROC. 

 FOR. OVALE 

 FOR. SPINOSUM 



Fig. 44. THE SPHENOID BONE, FROM ABOVE. (Drawn by D. Gunn.) 



process of the sphenoid, which fits against the apex of the petrous part of the 

 temporal bone ; and opposite to this, on the outer side of the groove, the more 

 slender tongue-like process termed lingula sphenoidalis projects backwards in the 

 angle between the body and great wing. 



The posterior surface is united to the basilar process of the occipital bone, in 

 early life by cartilage, but in adult age by continuous bony substance. 



The anterior surface is marked in the middle line by the sphenoidal crest, a thin 

 projecting edge which descends from the ethmoidal spine, and articulates with the 

 vertical plate of the ethmoid. The oblong surface on each side of the crest is 

 divided into a mesial and a lateral part : the lateral part is irregularly excavated, 

 and articulates with the lateral mass of the ethmoid and the orbital process of the 

 palate bone : the mesial part is smooth and free, entering into the formation of the 

 roof of the nasal fossa, and presenting near its upper end the rounded orifice of the 

 sphenoidal sinus. The sphenoidal crest terminates below in the rostrum, a sharp 

 vertical prominence which is continued back some distance on the inferior surface, 

 and fits in between the alae of the vomer. These last and the vaginal processes of 

 the internal pterygoid plates cover the great part of the inferior surface of the body. 



The sphenoidal turbinate or spongy bones (cornua splicnoidalia, l>onc$ of Bertiri) form a 

 considerable part of the anterior wall of the body of the sphenoid, bounding the foramen of 

 each sinus. These bones have a triangular form, with the apex directed downwards and back- 

 wards, and are in the adult usually incorporated with the sphenoid, but as explained in the 



