220 GENERAL REMARKS ON THE SKULL. 



feature, the mastoid process, has been already noticed in 

 the description of the base. The superior region, or vertex, 

 is smooth and marked off by sutures (Fig. 53,) already 

 detailed. 



The inner or cerebral surface consists of the arch or vault, 

 and the base. 



The vault presents along the median line a sulcus for the 

 superior longitudinal sinus. There are also seen grooves for 

 the middle meningeal artery, and depressions for the convo- 

 lutions of the brain. 



The base has three divisions, an anterior, middle, and 

 posterior. The anterior division includes the crista galli and 

 cribriform plate of the etlimoid bone, the orbital processes of 

 the frontal, and the aloe, minores of the sphenoid. The 

 foramina of this division are the olfactory, foramen ccecum, 

 and the optic. 



The middle division, called also the middle fossa, is situ- 

 ated between the lesser wings of the sphenoid and the supe- 

 rior ridge of the petrous bone, and bounded laterally by the 

 squamous portion of the temporal. In the centre or on the 

 median line, where the two fossa3 approach, is seen the 

 sella turcica bounded by its four processes, two anterior, 

 and two posterior clinoid on either side is a groove for the 

 cavernous sinus and carotid artery, and external to this is 

 the middle fossa for lodging the middle lobes of the cere- 

 brum on the anterior surface of the petrous bone are seen 

 a depression for the Gasserian ganglion, the hiatus Fallopii, 

 and the eminences marking the vertical semi-circular canals. 



The foramina of this division are the superior lacerated, 

 the rotundum, the ovale, the spinale, the middle lacerated 

 foramen, and the hiatus Fallopii. 



The posterior division extends from the superior ridge of 

 the petrous bone and posterior clinoid processes, to the trans- 

 verse ridge of the occipital. It includes the posterior sur- 

 face of the petrous bones, on which are seen the internal au- 

 ditory foramina, and the aqueducts of the vestibule. In the 

 middle is the cuneiform process, on either side of and between 

 it and the petrous bone are the posterior lacerated foramina ; 



