BASE OF THE SKULL. 



87 



of the temporal bones. In the centre of this fossa is the sdla turcica, 

 which lodges the pituitary gland, bounded in frpnt by the anterior and 

 middle, and behind by the posterior clinoid processes. On each side of the 

 sella turcica is the carotid groove for the internal carotid artery, the 

 cavernous plexus of nerves, the cavernous sinus, and the orbital nerves ; 

 and a little farther outwards the following foramina, from before back- 

 wards : sphenoidal fissure (foramen lacerum anterius), for the transmission 

 of the third, fourth, three branches of the ophthalmic division of the fifth, 

 and the sixth nerve, and ophthalmic vein ; foramen rotundum, for the 

 superior maxillary nerve ; foramen ovale, for the inferior maxillary nerve, 

 arteria meningea parva, and nervus petrosus superficialis minor ; foramen 

 spinosum, for the arteria meningea media ; foramen lacerum basis cranii, 

 which gives passage to the internal carotid artery, carotid plexus, and 

 petrosal branch of the Vidian nerve. On the anterior surface of the 

 petrous portion of the temporal bone is a groove, leading to a fissured 

 opening, the hiatus Fallopii, for the petrosal branch of the Vidian nerve ; 

 and, immediately beneath this, a smaller foramen, for the nervus petrosus 

 superficialis minor. Towards the apex of the petrous portion is the notch 

 for the fifth nerve, and below it a slight depression for the Casserian gan- 

 glion. Farther outwards is the eminence which marks the position of the 

 perpendicular semicircular canal. Proceeding from the foramen spinosum, 

 are two grooves which indicate the course of the trunks of the arteria 

 meningea media. The whole fossa lodges the middle lobes of the 

 cerebrum. 



The posterior fossa, larger than the other two, is formed by the occipital 

 bone, by the petrous and mastoid portion of the temporals, and by a 

 part of the sphenoid and parietals. It is 

 bounded in front by the upper border 

 of the petrous portion and dorsum ephip- 

 pii, and along its posterior circumference 

 by the groove for the lateral sinuses ; it 

 gives support to the pons Varolii, medulla 

 oblongata, and cerebellum. In the centre 

 of this fossa is the foramen magnum, 

 bounded on each side rjy a rough tuber- 

 cle, which gives attachment to the odon- 

 toid ligament, and by the anterior condy- 

 loid foramen. In front of the foramen 

 magnum is the concave surface (clivus 

 Blumenba-chii) which supports the me- 

 dulla oblongata and pons Varolii, and on 

 each side the following foramina, from 

 oefore backwards : the internal auditory 

 foramen, for the auditory and facial nerve 

 and auditory artery ; behind, and exter- 

 nally to this, is a small foramen leading 



*The external or basilar surface of the base of the skull. 1, 1. The hard palata 

 The figures are placed upon the palate processes of the superior maxillary bones 

 2. The incisive, or anterior palatine foramen. 3. The palate process of the palate bon^ 

 The large opening near the figure is the posterior palatine foramen. 4. The palate 

 spine ; the curved line upon which the number rests is the transverse ridge. 5. Th< 

 vomer, dividing the openings of the posterior nares. 6. The internal pterygoid plate 



Fig. 41 * 



