60 



BONES OF THE HEAD. 



THE INTERIOR OF THE SKULL. 



1. THE CRANIAL CAVITY. The walls of the cranium present two layers 

 of compact tissue, the outer and inner tables, and between these, in the 

 greater part of their extent, cancellated substance, called diploe. The inner 



Fig. 52. INTERNAL 

 BASIS OP THE SKULL, 

 OPENED BY A HORI- 

 ZONTAL INCISION ONE 



INCH ABOVE THE Su- 



PRA-ORBITAL ARCHES 

 AND EXTERNAL OC- 

 CIPITAL PROTUBER- 

 ANCE. ^ 



1, anterior fossa and 

 roof of the orbit, as 

 formed by the frontal 

 bone, marked by im- 

 pressions of cerebral 

 convolutions ; 2, is close 

 to the foramen ccecum 

 and in front of the 

 crista galli and cribri- 

 form plate of ethmoid ; 



3, is close behind the 

 ethmoidal spine of the 

 sphenoid and behind 

 the cribriform plate ; 



4, lesser wing of Ingras- 

 sias, terminating pos- 

 teriorly in the anterior 

 clinoid process, inside 

 which the inner open- 

 ing of the optic fo- 

 ramen is seen ; 5, the 

 pituitary fossa, in front 

 of it the olivary emin- 

 ence and transverse 

 groove of the optic 



commissure ; 6, the inclined plate of the body of the sphenoid, or dorsum Bellas, ter- 

 minating in the posterior clinoid processes, and to the side of these the sigmoid groove of 

 the internal carotid artery ; 7, foramen rotundum, to the inner side of which anteriorly, 

 but not seen, is Ihe foramen lacerum orbitale ; 8, foramen ovale ; 9, foramen spinosum ; 

 10, is placed on the ridge of the petrous bone, near its apex, and to the inside of the 

 hollow occupied by the Gasserian ganglion ; in front of this is the foramen lacerum ante- 

 rius ; 11, is placed in front of the eminence of the superior semicircular canal of the 

 labyrinth, and behind the hiatus Fallopii ; 12, is upon the prominent ridge of the petrous 

 bone, marked by the superior petrosal groove ; 13, is upon the posterior surface of the 

 petrous bone to the inside, the meatus auditorius internus, behind, the scale of bone 

 covering the aqueduct of the vestibule ; 14, basilar groove; 15, inner or upper opening 

 of the anterior condyloid foramen ; 16, jugular part of the foramen lacerum posterius; 

 17, outer part of the groove of the lateral sinus, where it crosses the lower angle of the 

 parietal bone ; 1 8, internal occipital protuberance, and between it and the foramen 

 magnum, the internal occipital spine; between 17 and 18, the upper part of the groove 

 of the lateral sinus, between 17 and 16 the lower part ; 19, cerebellar fossa. 



or vitreous table, has a smooth, close-grained, shining appearance, is hard and 

 brittle, and is thrown into irregular digitate impressions corresponding to the 

 convolutions of the brain. The thinnest portions of the cranial wall are the 

 cribriform plate of the ethmoid and the orbital plates of the frontal bone, 

 in both of which the diploe is entirely absent ; in the middle part of the 

 inferior occipital fossae, and in the squama and glenoid fossa of the temporal, 

 the bone is also very thin and compact. 



