160 SKELETON. 



anterior and middle lobes of the brain. Just anterior to this edge 

 is the fronto-sphenoidal suture. 



On the sides of the sella turcica are the middle fossae of the 

 base of the cranium. They are very wide externally, where 

 they are bounded by the squamous portions of the temporal bones, 

 but narrow internally, where they are bounded by the Sella 

 Turcica. The little wings of the sphenoidal bone terminate 

 them in front, and form there a crescentic edge hanging over 

 their cavity. Their posterior margin is the superior ridge of 

 the petrous bone. This bone is placed very obliquely, inwards 

 and forwards, and its point almost reaches the posterior clinoid 

 process. At the anterior part of the fossa is the sphenoidal 

 fissure or foramen, of the sphenoidal bone. Just above the 

 base of this fissure is the foramen opticum, partially concealed 

 by the anterior clinoid process. Just below the base of the fis- 

 sure is the foramen rotundum. At the point of the petrous 

 bone, by the side of the posterior clinoid process, is the in- 

 ternal orifice of the carotid canal. On a line with the latter, 

 exteriorly, is the foramen ovale. Two lines behind the latter 

 is the foramen spinale. The groove formed by the middle arte- 

 ry of the dura mater, may be traced from the foramen spinale 

 along the anterior margin of the squamous bone. Near the 

 upper part of this bone the groove bifurcates; the larger chan- 

 nel runs upwards into a groove on the tip of the great sphe- 

 noidal wing, into the principal groove of the parietal bone, 

 which commences at the temporal angle of the latter. The 

 smaller groove runs horizontally backwards, and just above 

 the base of the petrous bone is continued also into the parietal 

 bone. On the front of the petrous portion may be seen the 

 hiatus Fallopii. The sphenoidal suture runs through these fossae, 

 in the examination of which, the reception of the spinous pro- 

 cess of the sphenoid bone, between the squamous and petrous 

 portions of the temporal, will be readily understood. 



On each side of the foramen magnum occipitis are the two pos- 

 terior fossas of the base of the cranium, formed by the posterior 

 faces of the petrous bones, the angles of the mastoid portions of 

 the temporal bones and by that surface of the occipital bone be- 

 low its horizontal ridges. These two fossae are very partially se- 



