74 OSTEOLOGY. 



they increase in size as age advances. They are partially closed, in front and 

 below, by two thin curved plates of bone, the sphenoidal turbinated bones, 

 leaving a round opening at their upper parts, by which they communicate with 

 the upper and back part of the nose, and occasionally with the posterior ethmoidal 

 cells. The lateral margins of this surface present a serrated edge, which articu- 

 lates 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 vertical plate on the anterior surface, and is received 

 into a deep fissure between the alas of the vomer. On each side may be seen a 

 projecting lamina of bone, which runs horizontally inwards 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 pterygo-palatine canal, and transmits the ptery go- 

 palatine vessels and pharyngeal nerve. 



The Greater Wings are two strong processes of bone, which arise at the sides 

 of the body, and are curved in a direction upwards, outwards, and backwards ; 

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

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

 or cerebral surface 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 transmission 

 of the third division of the fifth, the small meningeal artery, and the small petrosal 

 nerve. 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 Yesalii, 

 transmitting a small vein. Lastly, in the apex of the spine of the sphenoid is a 

 short canal, sometimes double, the foramen spinosum ; it transmits the middle 

 meningeal artery. The external surface is convex, and divided by a transverse 

 ridge, the pterygoid ridge, into two portions. The superior or larger, convex 

 from above downwards, concave from before backwards, enters into the formation 

 of the temporal fossa, and attaches part of the Temporal muscle. The inferior 

 portion, smaller in size and concave, enters into the formation of the zygomatic 

 fossa, and affords attachment 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 Laxator 

 tympani muscle. The pterygoid ridge, dividing the temporal and zygomatic 

 portions, gives attachment to part of the External pterygoid muscle. At its inner 

 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 

 enters into the formation of the sphenoidal fissure ; whilst externally it presents a 

 serrated margin, for articulation with the malar bone. At the upper part of the 

 inner border is a notch, for the transmission of a branch of the ophthalmic artery; 

 and at its lower part a small pointed spine of bone, which serves for the attachment 

 of part of the lower head of the External rectus muscle. One or two small foramina 

 may occasionally be seen, for the passage of arteries; they are called the external 

 orbitar foramina. Circumference : from the body of the sphenoid to the spine, 

 commencing from behind, the outer half of this margin is serrated, for articula- 

 tion with the petrous portion of the temporal bone ; whilst the inner half forms 

 the anterior boundary of the foramen lacerum medium, and presents the posterior 

 aperture of the Yidian canal. In front of the spine, the circumference of the 



