THE SPHENOID BONE.

The Lesser Wings (proces8es of Ingrassias) 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. 37). The superior surface of each is smooth, flat, broader internally than externally, and supports part of the frontal lobe of the brain. 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. This fissure is of a triangular form, and leads from the cavity of the cr&nium into the orbit; it is bounded internally by the body of the sphenoid-above, by the lesser wing; below, by the internal margin of the orbital surface of the great wing-and is converted into a foramen by the articu¬lation of this bone with the frontal. It transmits the third, the fourth, the three branches of the ophthalmic division of the fifth, the sixth nerve, some filaments from the cavernous plexus of the sympathetic, the orbital branch of the middle meningeal artery, a recurrent branch from the lachrymal artery to the dura mater, and the ophthalmic vein. The anterior border of the lesser wing is ser¬rated for articulation with the frontal bone; the posterior, smooth and rounded, is received into the fissure of Sylvius of the brain. The inner extremity of this border forms the anterior clinoid process.• The lesser wing is connected to the side of the body by two roots, the upper thin and flat, the lower thicker, obliquely directed, and presenting on its outer side, near its junction with the body, a smail tubercle, for the attachment of the common tendon of origin of three of the muscles of the eye. Between the two roots is the optic foramen, for the transmission of

The Pterygoid Processes (rrripu;, a wing; 0100" likeness), one on each side, descend perpendicularly from the point where the body and greater wing unite (Fig. 39). Each process consists of an external and an internal plate, which are joined together by their anterior borders above, but are separated below, leaving an angular cleft, the pterygoid notch, in which the pterygoid process or tuberosity of the palate bone is received. 'I'he two plates diverge from each other from their line of connection in front, so as to form a V-shaped fossa, the pterygoid f08sa. The external pterygoid plate is broad and thin, turned a little outward, and, by its outer surface, forms part of the inner wall of the zygomatic fossa, giving attachment to the External pterygoid; its inner surface forms part