74 77/7;; SKELETON. 



ethmoidal crest, which articulates in front with the perpendicular plate of the 

 ethmoid, forming part of the septum of the nose. On either side of it are irregular 

 openings leading into the sphenoidal cells or sinuses. These are two large irregular 

 cavities hollowed out of the interior of the body of the sphenoid bone, and separated 

 from one another by a more or less complete perpendicular bony septum. Their 

 form and size vary considerably ; they are seldom symmetrical, and are often 

 partially subdivided by irregular osseous laminae. Occasionally, they extend into 

 the basilar process of the occipital nearly as far as the foramen magnum. The 

 septum is seldom quite vertical, being commonly bent to one or the other side. 

 These sinuses do not exist in children, but 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 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 

 sphenoidal 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. 37) 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, the foramen 

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

 (Fig. 38) is convex, and divided by a transverse ridge, the pterygoid ridge or 

 infratemporal crest, 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 attachment to the External pterygoid muscle. It 

 presents, at its posterior part, a sharp-pointed eminence of bone, the spinous proc- 

 ess, 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 



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

 ovale and foramen spinosum. 



