182 THE SKELETON. 



with the posterior ethmoidal cells or sinuses. The lateral margins of this surface 

 present a serrated edge, which articulates with the os planum of the ethmoid, 

 completing the posterior ethmoidal cells ; the lower margin, also rough and 

 serrated, articulates with the orbital process of the palate bone, and the upper 

 margin with the orbital plate of the frontal bone. The inferior surface presents, 

 in the middle line, a triangular spine, the rostrum, which is continuous with the 

 ethmoidal crest on the anterior surface, and is received into a deep fissure between 

 the alge of the vomer. On each side may be seen a projecting lamina of bone, 

 which runs horizontally inward from near the base of the pterygoid process : 

 these plates, termed the vaginal processes, articulate with the edges of the vomer. 

 Close to the root of the pterygoid process is a groove, formed into a complete canal 

 when articulated with the sphenoidal process of the palate bone ; it is called the 

 ptery go-palatine canal, and transmits the pterygo-palatine vessels and pharyngeal 

 nerve. 



The Greater Wings are two strong processes of bone which arise from the 

 sides of the body, and are curved in a direction upward, outward, and backward, 

 being prolonged behind into a sharp-pointed extremity, the spinous process of the 

 sphenoid. Each wing presents three surfaces and a circumference. The superior 

 or cerebral surface (Fig. 143) forms part of the middle fossa of the skull ; it is 

 deeply concave, and presents eminences and depressions for the convolutions of the 

 brain. At its anterior and internal part is seen a circular aperture, the foramen 

 rotundum, for the transmission of the second division of the fifth nerve. Behind 

 and external to this is a large oval foramen, the foramen ovale, for the trans- 

 mission of the third division of the fifth nerve, the small meningeal artery, and 

 sometimes the small petrosal nerve. 1 At the inner side of the foramen ovale a 

 small aperture may occasionally be seen opposite the root of the pterygoid process ; 

 it is the foramen Vesalii, transmitting a small vein. Lastly, in the posterior angle, 

 near to the spine of the sphenoid, is a short canal, sometimes double, fae foramen 

 spinosum ; it transmits the middle meningeal artery. The external surface 

 (Fig. 144) is convex, and divided by a transverse ridge, the pterygoid ridge, 2 into 

 two portions. The superior or larger, convex from above downward, concave 

 from before backward, enters into the formation of the temporal fossa, and gives 

 attachment to part of the Temporal muscle. The inferior portion, smaller in size 

 and concave, enters into the formation of the zygomatic fossa, and affords attach- 

 ment to the External pterygoid muscle. It presents, at its posterior part, a 

 sharp-pointed eminence of bone, the spinous process, to which are connected the 

 internal lateral ligament of the lower jaw and the Tensor palati muscle. The 

 pterygoid ridge, dividing the temporal and zygomatic portions, gives attachment to 

 part of the External pterygoid muscle. At its inner and anterior extremity is a 

 triangular spine of bone which serves to increase the extent of origin of this 

 muscle. The anterior or orbital surface, smooth and quadrilateral in form, assists 

 in forming the outer wall of the orbit. It is bounded above by a serrated edge, 

 for articulation with the frontal bone ; below, by a rounded border which enters 

 into the formation of the spheno-maxillary fissure. Internally, it presents a sharp 

 border, which forms the lower boundary of the sphenoidal fissure, and has pro- 

 jecting from about its centre a little tubercle of bone, which gives origin to one 

 head of the External rectus muscle of the eye; and at its upper part is a notch 

 for the transmission of a branch of the lachrymal artery ; externally it presents a 

 serrated margin for articulation with the malar bone. One or two small foramina 

 may occasionally be seen for the passage of branches of the deep temporal 

 arteries ; they are called the external orbital foramina. Circumference of the 

 great wing (Fig. 143) : commencing from behind, from the body of the sphenoid 

 to the spine, the outer half of this margin is serrated, for articulation with the 

 petrous portion of the temporal bone, whilst the inner half forms the anterior 



1 The small petrosal nerve sometimes passes through a special foramen between the foramen 

 ovale and foramen spinosum. 



a Sometimes called infratemporal crest. 



