SPHENOID BONE. 73 



surface presenting, in the median line, a slight longitudinal eminence, with a 

 depression on each side, for lodging the olfactory nerves. A narrow transverse 

 groove, the optic groove, bounds the above-mentioned surface behind ; it lodges 

 the optic commissure, and terminates on either side in the optic foramen, for the 

 passage of the optic nerve and ophthalmic artery. Behind the optic groove is a 

 small eminence, olive-like in shape, the olivary process ; and still more posteriorly, 

 a deep depression, the pituitary fossa, or sella Turcica, which lodges the pituitary 

 body. This fossa is perforated by numerous foramina, for the transmission of 

 nutrient vessels to the substance of the bone. It is bounded in front by two small 

 eminences, one on either side, called the middle clinoid processes (*;uV?, a led), 

 and behind by a square-shaped plate of bone, terminating at each superior angle 

 in a tubercle, the posterior clinoid processes, the size and form of which vary 

 considerably in different individuals. These processes deepen the pituitary fossa, 

 and serve for the attachment of prolongations from the tentorium. The sides of 

 the plate of bone supporting the posterior clinoid processes are notched, for the 

 passage of the sixth pair of nerves ; and behind, it presents a shallow depression, 

 which slopes obliquely backwards, and is continuous with the basilar groove of 

 the occipital bone ; it supports the medulla oblongata. On either side of the body 

 is a broad groove, curved somewhat like the italic letter/; it lodges the internal 

 carotid artery and the cavernous sinus, and is called the cavernous groove. The 



Fig. 35. Sphenoid Bone. Anterior Surface. 



J'te-ryyoui Ridye 



posterior surface, quadrilateral in form, articulates with the basilar process of the 

 occipital bone. During childhood, a separation between these bones exists by 

 means of a layer of cartilage ; but in after-life this becomes ossified, ossification 

 commencing above, and extending downward, and the two bones are then im- 

 movably connected together. The anterior surface (fig. 35) presents, in the 

 middle line, a vertical lamella of bone, which articulates in front with the per- 

 pendicular plate of the ethmoid, forming part of the septum of the nose. On 

 either side of it are the irregular openings leading into the sphenoidal sinuses. 

 These are two large irregular cavities, hollowed out of the interior of the body 

 of the sphenoid bone, and separated from one another by a more or less complete 

 perpendicular bony septum. Their form and size vary considerably; they are 

 seldom symmetrical, and are often partially subdivided by irregular osseous 

 larninte. Occasionally they extend into the basilar process of the occipital nearly 

 as far as the foramen magnum. The septum is seldom quite vertical, commonly 

 being bent to one or the other side. These sinuses do not exist in children ; but 



