136 OSTEOLOGY. 



angle terminates in a pointed process which reaches the region of the pterion and 

 there articulates with the frontal, and may come in contact with the great wing. 

 The superior aspect is smooth, and forms, in part, the floor of the anterior cranial 

 fossa. The inferior surface constitutes part of the posterior portion of the upper 

 wall of the orbit, and also serves to roof in the superior orbital fissure (O.T. sphenoidal 

 fissure), which separates the small wing from the great wing below. The anterior 

 edge is ragged and irregular, and articulates with the orbital parts of the 

 frontal. The posterior margin, sharp and sickle-shaped, , separates the anterior 

 from the middle cranial fossa, and corresponds to the position of the stem of the 

 lateral cerebral fissure on the inferior surface of the cerebrum. 



Alae Magnae.: The great wings, as seen from above, are of a somewhat 

 crescentic shape and form a considerable portion of the floor of the middle 

 cranial fossa. If the medial convex edge of the crescent be divided into fifths, the 

 posterior fifth extends backwards and laterally beyond the body of the bone, 

 presenting a free posterior edge, which forms the anterior boundary of the 

 foramen lacerum. This border ends behind in the horn of the crescent, from 

 which a pointed process projects downwards, called the spina angularis ; this is 

 wedged into the angle between the petrous and squamous parts of the temporal 

 bone. The medial surface of the posterior border and spine is furrowed for the 

 cartilaginous part of the auditory tube (sulcus tubae), whilst on the medial side of 

 the spine the course of the chorda tyrnpani nerve is indicated by a groove (Lucas). 

 The second fifth of the convex border of the crescent is fused to the side of the 

 body and united below with the root of the pterygoid process. The angle formed 

 by the union of the great wing with the side of the body posteriorly corresponds 

 to the posterior end of the carotid groove, the lateral lip of which is formed by a 

 projecting lamina called the lingula. The remaining three-fifths of the convex 

 border is divisible into two nearly equal parts ; the medial is a free, curved, sharp 

 margin, which forms the inferior margin of the superior orbital fissure, the cleft 

 which separates the great wing from the small wing, and which establishes a 

 wide channel of communication between the middle cranial fossa and the cavity 

 of the orbit, transmitting the oculomotor, trochlear, ophthalmic division of the 

 trigeminal, and the abducent nerves, together with the ophthalmic veins. Wide of 

 the superior orbital fissure this edge becomes broad and serrated, articulating 

 with the frontal bone medially, and at the part corresponding to the anterior 

 horn of the crescent, by a surface of variable width, it unites with the sphenoidal 

 angle of the parietal bone. The lateral border corresponds to the concave side 

 of the crescent, and is serrated for articulation with the squamous part of the 

 temporal, being thin and bevelled at the expense of its parietal surface above and 

 laterally, and broad and thick behind as it passes towards the angular spine. 



The internal or cerebral surface is concave from behind forwards, and, in its anterior 

 part, from side to side also; it forms a considerable part of the floor of the 

 middle cranial fossa, and bears the impress of the gyri of the extremity of the 

 temporal lobe of the cerebrum, which rests upon it ; towards its lateral side it is 

 grooved obliquely by an anterior branch of the middle meningeal artery. 



The following foramina pierce the great wing : Close to and in front of the alar 

 spine is the foramen spinosum, for the transmission of the middle meningeal 

 artery and its companion vein, together with the nervus spinosus from the man- 

 dibular division of the trigeminal nerve. In front of and medial to this, and close 

 to the posterior free border, is the foramen ovale, of large size and elongated 

 form. This gives passage to the motor root and mandibular division of the 

 trigeminal nerve, and admits the accessory meningeal branch of the middle 

 meningeal artery ; a small emissary vein from the cavernous sinus usually passes 

 through this foramen, and occasionally also the lesser superficial petrosal nerve. 

 Near the anterior part of the root of the great wing, and just below the sphenoidal 

 fissure, is the foramen rotundum, of smaller size and circular form. Through this 

 the maxillary division of the trigeminal nerve escapes from the cranium. Occasion- 

 ally there is a small canal the foramen of Vesalius which pierces the root of 

 the great wing to the medial side of the foramen ovale. This opens below into 

 the scaphoid fossa at the base of the medial pterygoid lamina, and transmits a 



