84 A MANUAL OF ANATOMY 



the rostrum, which is continuous with the sphenoidal crest on the 

 anterior surface, and is received into the cleft between the alae 

 of the vomer. At either side of the rostrum there is a thin scale 

 of bone projecting inwards for a short distance from the root of 

 the internal pterygoid plate, called the vaginal process, which 

 articulates with the ala on the upper border of the vomer, and 

 with it covers the greater part of the inferior surface of the body 

 at either side of the middle line. On the inferior surface of this 

 process there is a groove, which is converted by the sphenoidal 

 process of the palate bone into a canal, called the pterygo-palatine 

 canal, for the passage of the pharyngeal nerve and pterygo-palatine 

 artery. 



The anterior surface presents in the middle line a vertical ridge, 

 continuous above with the ethmoidal spine and below with the 

 rostrum, called the sphenoidal crest, which articulates with the 

 perpendicular plate of the ethmoid and forms part of the nasal 

 septum. On either side of this crest the surface is divided into 

 two parts, outer and inner. The outer part is rough, and articulates 

 with the back part of the lateral mass of the ethmoid and the orbital 

 process of the palate bone. The inner part presents the opening of 

 the sphenoidal air sinus of its own side, with the margins of which 

 the sphenoidal turbinate or spongy bone articulates. When this 

 bone is in position the opening of the sinus is small and circular, 

 and is placed superiorly, but when the bone has been removed 

 the opening is of large size and irregular outline. It communi- 

 cates anteriorly with the spheno-ethmoidal recess of the nasal 

 fossa above and behind the superior meatus. The part of the 

 anterior surface which presents the opening of the sphenoidal 

 air sinus enters into the formation of the roof of the corresponding 

 nasal fossa. 



The posterior surface is rough and truncated. It articulates 

 with the basilar process of the occipital by synchondrosis up to 

 the twentieth year, after which ankylosis takes place. 



The lateral surface gives attachment to the great wing and a 

 portion of the small wing. Anteriorly, beneath the small wing, it 

 forms the inner boundary of the sphenoidal fissure and the back 

 part of the inner wall of the orbit. Above the attachment of the 

 great wing it presents a winding groove, called the cavernous or 

 carotid groove, which contains the cavernous venous sinus and 

 the internal carotid artery. The direction of this groove is from 

 behind forwards, and its deepest part is placed posteriorly, where 

 it is bounded internally by the posterior petrosal process, and 

 externally by the lingula sphenoidalis or anterior petrosal process. 

 This latter process is a sharp scale of bone which projects back- 

 wards in the angle between the great wing and body. 



The small or orbital wings (orbito-sphenoids) extend almost 

 horizontally outwards on a level with the anterior part of 

 the upper surface of the body. Each arises by two roots — an 

 upper, which is expanded and compressed from above downward.s, 



