32 THE SKELETON 



till- foramen rotundum for the second division of the fifth nerve; behind and 

 external to thi^ i:? the foramen ovale, for the motor root and the third divi.sion of 

 the fifth nerve, tlie small ju'trosal nerve, the small meningeal artery, and an emis- 

 sary vein from the caverndus sinus. Behind and external to the foramen ovale is 

 the small eireular foramen spinosum, for the middle meningeal artery, its venae 

 comites, and the recurrent branch of the third division of the fifth nerve. To the 

 inner side of the foramen ovale a small opening, the foramen Vesalii, is occasion- 

 ally present; it transmits a vein. A foramen may exist near the foramen ovale for 

 tlie small superficial petrosal nerve, the canaliculus innominatus. The external 

 surface is divided by the prominent malar crest into an orbital and a temporo- 

 zygomatic portion. The orbital surface forms the chief part of the outer wall 

 of the orbit; its internal segment forms part of the spheno-maxillary fossa, and 

 })resents the anterior orifice of the foramen rotundum. Near the middle of the 

 upper border there is a small tubercle for the origin of the outer head of the external 

 rectus muscle; and at the highest part of this surface one or more foramina are often 

 present, for the transmission of twigs from the middle meningeal artery to the orbit 

 and the lachrymal gland. The malar crest is serrated for articulation with the 

 malar bone; its lower angle, in many bones, articulates with the maxilla. A 

 foramen exists in the suture between the sphenoid and malar, for the temporal twig 

 of tlie orbital nerve. The surface of bone outside this ridge is subdivided by a low 



Fig. 39. — Kight Half of Sphenoid. (Anterior view.) 



Ext. Pterygoid Muscle 



THE ALAR SPINE 



TEMPORAL SURFACE 



SPHENOIDAL CREST 



RIDGE WHICH FORMS THE UPPER '"HKs A'i'iMii'.^SfMt' — SPHENOIDAL SINUS 



BOUNDARY OF THE SPHENO-MAX- 

 ILLARY FISSURE 



crest, the pterygoid ridge. The surface above the ridge forms part of the temporal 

 fossa, and affords attachment to the temporal muscle; the part below the crest be- 

 Vmgs to the zygomatic fossa; it furnishes attachment to the external pterygoid muscle, 

 and is continuous with the outer surface of the external pterygoid plate; it contains 

 the inferior orifices of the foramina spinosum, ovale, and Vesalii, and forms part of 

 the roof of the zygomatic fossa. 



The circumference of the great wing, commencing at its anterior attachment to 

 the body, is at first smooth, and forms the lower boundary of the sphenoidal 

 fissure ; this serves for the passage of the third, fourth, first division (ophthalmic) 

 of the fifth, and the sixth nerves, with the ophthalmic vein. External to this, the 

 margin is broad and serrated for the frontal bone; quite at the tip it is bevelled on 

 its inner aspect for the anterior inferior angle of the parietal; behind this, the edge, 

 at first thin and bevelled, becomes gradually broader, and deeply serrated for the 

 squamosal, and runs into the prominent alar spine of the sphenoid, to which 

 the si)heno-mandil)ular ligament is attached and which is grooved internally by 

 the chorda tympani nerve. That portion of the circumference extending from the 

 spine to the body of the sphenoid articulates by the outer third with the petrosal, 

 but the inner two-thirds forms the anterior boundary of the foramen lacerum 

 medium, and contains the posterior orifice of the Vidian canal. 



Projecting at right angles from the greater wing, near its junction with the 

 lingulse, are the pterygoid processes. Of these, the external plate, broad and 



