1 88 



HUMAN ANATOMY. 



hole, the foramen of Vesalhis^ for a minute vein. Farther back and outward near 

 the angle is the fora7?ien ovale, transmitting the mandibular division of the fifth 

 cranial nerve to the base of the skull, and admitting the small meningeal branch 

 of the internal maxillary artery. Just beyond this, in the extreme angle, so as some- 

 times to be completed by the temporal, is the forame^i spinos2im, admitting the 

 middle meningeal artery to supply the bone and the dura. The external surface 

 is divided into a larger, superior, vertical part, looking towards the temporal fossa, 

 and one looking into the zygomatic fossa. These are separated by the infratem- 

 poral crest, which near the front points downward as a strong prominence, the infra- 

 temporal spine. The inferior surface contains the foramen ovale and the foramen 

 spinosum. Just behind the latter, at the posterior angle, is the spijie of the sphenoid, 

 pointing downward, grooved at the inner side by the chorda tympani nerve. The 

 external surface has an anterior border where it meets the orbital surface, which 

 joins the malar. The superior border slants upward, overlapping the frontal and 

 parietal bones. The posterior border is about vertical as far down as the infra- 

 temporal crest, and bevelled, especially above, to be overlapped by the squamous 

 part of the temporal. The lower part of this border runs backward and somewhat 

 overlaps the squamosal. The posterior border of this surface, from the spine to the 



Articulates with frontal 



Fig. 2IO. 



Ethmoidal crest 



Cerebral' 

 surface 



Articulates, 

 with pa- 

 rietal 



Sphenoidal 

 fissure 



Anterior clinoid process. 



process 



The sphenoid bone from above. 



t 



body, is slightly rough for the petrous, making with it a groove on the under side 

 for the cartilaginous Eustachian tube. The smooth orbital surface, facing inward 

 and forward, is quadrilateral, broader in front than behind. Almost the whole of it is 

 in the outer wall of the orbit, of which it forms the greater part ; but a small portion, 

 narrow behind and expanding in front, looks into the spheno-maxillary fissure, which 

 bounds this surface below. It joins the malar in front. On the top of the bone 

 there is a rough triangular region in the angle formed by the meeting of the external 

 and orbital surfaces, on which the frontal bone rests. This is above the front half 

 of the orbital plate. The remainder of the upper and the whole of the posterior 

 border of the latter bound the sphenoidal fissure.^ This cleft is an elongated aper- 

 ture, directed obliquely outward and upward between the great and lesser wings of 

 the sphenoid, completed externally by the frontal. It opens anteriorly into the 

 orbit and transmits the third, the fourth, the ophthalmic division of the fifth and 

 sixth cranial nerves, and the ophthalmic veins. There is a small projection near the 

 middle of the hind border for a ligament crossing the fissure and for the outer head 

 of the external rectus. 



The lesser wings,' forming the back part of the anterior fossa and of the roof 

 of the orbit, arise by two roots. The superior is a plate covering the presphenoid ; 

 Jhe inferior is a strong process from the side of the body. With the latter they 



' Fisstira orbitalis superior. ' Alae parvae. 



