THE SPHENOID BONE 



93 



Circumference (Fig. 56). Commencing from behind, that portion of the cir- 

 cumference of the body of the sphenoid to the spine is serrated and articulates 

 by its outer half with the petrous portion of the temporal bone, while the inner 

 half forms the anterior boundary of the middle lacerated foramen, and presents the 

 posterior aperture of the Vidian canal (canalis pteryyoideus) for the passage of the 

 Vidian nerve and artery. In front of the spine, the circumference of the greater 

 wing presents a serrated edge, bevelled at the expense of the inner table below 

 and of the external above, which articulates with the squamous portion of the tem- 

 poral bone. At the tip of the greater wing a triangular portion is seen, bevelled 

 at the expense of the internal surface, for articulation with the anterior inferior 

 angle of the parietal bone. Internal to this is a triangular, serrated surface, for 

 articulation with the frontal bone; this surface is continuous internally with the 

 sharp inner edge of the orbital plate, which assists in the formation of the sphe- 

 noidal fissure, and externally with the serrated margin for articulation with the 

 malar bone. 



GROOVE FOR 

 OPT.C TRACT 



GROOVE FOR ABDUCENS 

 NERVE 



HAMULAR PROCESS 



FIG. 58. Sphenoid bone. Posterior view. 



The Lesser or Orbital Wings (aloe parvae). The lesser wings are two thin 

 triangular plates of bone which arise from the upper and lateral parts of the 

 body of the sphenoid, and, projecting transversely outward, terminate in a sharp 

 point (Fig. 56). The superior surface of each is smooth, flat, broader internally 

 than externally, and supports part of the frontal lobe of the cerebrum. The 

 inferior surface forms the back part of the roof of the orbit and the upper 

 boundary of the sphenoidal fissure, or foramen lacerum anterius (fissura orbitalis 

 superior}. This fissure is of a triangular form, and leads from the cavity of 

 the cranium into the orbit. It transmits the third, the fourth, the three 

 branches of the ophthalmic division of the trigeminal, the abducent nerve, some 

 filaments from the cavernous plexus of the sympathetic, the orbital branch of 

 the middle meningeal artery, a recurrent branch from the lacrimal artery to the 

 dura and the ophthalmic vein. The anterior border of the lesser wing is serrated 

 for articulation with the frontal bone; the posterior border, smooth and rounded, 

 is received into the sylvian fissure of the cerebrum. The inner extremity of this 

 border forms the anterior clinoid process (process-us clinoideus anterior}. The lesser 



