42 BONES OF TEE liEAD. 



sions called the r/rm/ ir/'/ir/!^, a pair of smaller horizontal processes in 

 front, called the sma/l ivings, and a pair which project downwards, the 

 pfeii/goid procesftri^. 



The s])henoid is articulated with all the seven other bones of the 

 cranium and with five of those of the face, viz., posteriorly with the 

 occipital and with the petrous portions of the temporals, anterior!}' with 

 the ethmoid, frontal, and malars, lat(!rally with the squamous itortion 

 of the temporals, the parietals and frontals, and inferiorly with the 

 vomer and palate bones. 



The body. — Posteriorly the body of the sphenoid is solid, but 

 anteriorly it is hollowed out into two large cavities, the spiienoidal 

 sinuses, separated by a thin mesial lamina and opening into the upper 

 part of the nasal fossa by two rounded apertures. The stiperiov surface 

 presents in the middle a deep pit, the 'piUiifnnj fossa, or sella turcica, 

 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 oUrar// process, (tnberculum 

 sella — Henle), on which rests the commissure of the optic nerves ; and in 

 front of this is a surfiice on a slightly higher level, continuous with the 

 superior surfaces of the small wings, and having a slight projection for- 

 wards of its anterior border, which articulates with the cribriform plate 

 of the ethmoid, and is called the cfhmoicM spine. Behind the pituitary 

 fossa is a prominent lamella, the dorsum scike, 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 cJinoid j)rocesses. 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 super- 

 ficial curved groove directed from behind forwards, marking the course 

 of the internal carotid artery. At the bottom of this groove, and in 

 the angle between the body and the great wing, there projects the small 

 ridge of bone termed ti/ir/uJa sphenoidalis. 



The posterior surface is flat, and 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 presents in the middle line the splienoidcd crest, 

 a thin projecting edge which extends downwards from the ethmoidal 

 spine and terminates in the ro.?/rw??, a sharp bony prommence projecting 

 vertically between the anterior and inferior surfaces. The sphenoidal 

 crest articulates with the central plate of the ethmoid ; the rostrum is 

 inserted between the al^ of the vomer. 



The sphenoidal spongy bones {cornua spheuoididia, liones of Bert in), 

 form a considerable part of the anterior wall of the body of the sphenoid, 

 including the foramen of each sinus. These bones haA^e a triangular 

 form, with the apex directed downwards, and are in the adult usually 

 incorporated with the sphenoid, but as explained in the account of 

 their development, they are originally distinct. They are frequently 

 united by earlier or stronger anchylosis with the ethmoid or palate 

 bones, so as to come away, at least in part, with either of these in dis- 

 articulation of the skull, and thus lay open the sphenoidal sinuses. A 

 small jjortion of these bones sometimes appears on the inner wall of 

 the orbit, between the ethmoid, frontal, sphenoid, and palate bones 

 (Cleland in Trans, of Rov. Soc. for 1SG2). 



