30 PRACTICAL ANATOMY. 



process. Its surfaces are smooth, the upper polished, 

 and form part of the floor of the anterior fossa of the 

 skull. The inferior surface, near its junction with the 

 hody, is slightly roughened for attachment of the recti 

 muscles. It forms the posterior part of the roof of the 

 orbit and the superior boundary of the anterior lacerated 

 foramen. The lesser wings arise by obliquely-placed and 

 flattened roots, which are perforated by the optic fora- 

 mina for the transmission of the optic nerves and the 

 ophthalmic arteries. They are frequently considered as 

 arising by two roots each. The greater wings arise 

 from the sides of the body of the sphenoid by broad, 

 flattened roots, and curve upward, outward, and forward. 

 Each wing presents three surfaces, a superior, an an- 

 terior, and an external. The superior surface passes 

 obliquely upward, outward, and forward. Its posterior 

 projecting extremity is called the spine. It is strongly 

 concave from front to back, is smooth, impressed by the 

 convolutions of the brain, and enters into the forma- 

 tion of the middle cranial fossa. At its junction with 

 the body anteriorly, it is pierced by the foramen rotun- 

 dum, a round foramen which is directed horizontally 

 forward. Near its junction with the body posteriorly, is 

 the foramen ovale, an oval foramen, the axis of which 

 is vertical. Near the extremity of the greater wing, pos- 

 teriorly is the foramen spinosum. These are the prin- 

 cipal foramina; in addition, there are some minute 

 foramina for the entrance of vessels into the bone; one 

 of these, between the foramen ovale and the body of the 

 sphenoid, is known as the foramen of Vesalius, and trans- 

 mits a small vein. The anterior surface of the greater 

 wing is quadrilateral, smooth, slightly concave from 

 above downward, and at its lower posterior part presents 

 one or two small tubercles for the origin of the lower 



