FKONTAL SECTIONS OF THE CKANIUM. 



191 



The next figure (Fig. 179). displays the anterior surface of the section immediately 



jhind that above described. In the centre is seen the body of the sphenoid, and the 



osterior wall of the sinus is now exposed ; on either side the apex of the petrous part of the 



mporal abuts upon the side of the body of the sphenoid, and the large orifice of the carotid 



inal is seen opening on to the 



Dsterior wall of the foramen 



.cerum, which is here divided. 



i the recess between the lateral 



all of the carotid canal and the 



oine of the sphenoid is the 



roove leading into the osseous 



art of the auditory tube, in front 



f which the base is pierced by 



le foramen spinosum. Lateral 



h the angular spine, the man- 



ibular fossa is divided and its 



iin roof displayed. Crossing it 



;an aversely is seen the petro- 



nnpanic fissure which divides 



lie fossa into an articular and 



on- articular part. The floor of 



be middle cranial fossa is here 



pen to be formed by the upward 



rlope of the anterior surface of 



he petrous part of the temporal, 



rhich is pierced by the hiatus 



analis facialis, and the foramen 



pr the lesser superficial petrosal 



[ erve. On the upper surface of 



[he summit of the petrous part 



If the temporal the depression 



pr the lodgment of the semi- 



Lmar ganglion is well seen on 



fither side. 



The last section, the an- 

 lerior surface of which Fig. 

 [80 is a representation, passes 

 fertically through the base 

 Immediately in front of the root 

 [f the styloid process. In the 

 [aedian plane the basi-occipital is 

 j.ivided a little in front of the 

 Interior extremities of the oc- 

 I ipital condyles ; its upper sur- 

 face is concave from side to side 

 rnd forms a wide groove for the 

 [nedulla oblongata and pons. 

 |)n either side there is a narrow 

 interval between the lateral edge 

 [if the basi-occipital and the 

 X)sterior border of the petrous 

 Ibart of the temporal, which in 



H) 



1213 14 



4. 



5. 



7. 



12. 



15 16 17 18 19 20 21 22 23 



FIG. 179. ANTERIOR SURFACE OF THE SECTION OF THE SKULL 



IMMEDIATELY BEHIND THE PRECEDING SECTION. 

 . Impressio trigemini on apex of 13. Angular spine of the sphenoid. 



petrous bone. 14. Styloid process. 



Squamo-parietal suture. 15. Canalforauricularbranchofthe 



vagus with opening of carotid 

 canal in front and above it. 



16. Position of osseous opening of 



auditory tube. 



17. Jugular foramen. 



18. Medial wall of open carotid 



canal. 



19. Canalis hypoglossi. 



20. Condyle of occipital bone. 



21. Petro-occipital suture. 



22. Posterior wall of sphenoidal 



sinus. 



23. Position of pharyngeal tubercle. 



24. Anterior margin 



magnum. 



25. Occipital condyle. 



Groove for posterior branch of 

 middle meningeal artery. 



Eminence of superior semi- 

 circular canal (eminentia 

 arcuata). 



Hiatus facialis. 



Posterior root of zygomatic 

 process of temporal. 



Leads into external acoustic 

 meatus. 



Mandibular fossa. 



Tympanic plate. 



of foramen 



foramen. 

 Roof of carotid canal. 



: ife is occupied by dense fibrous 

 issue ; running along the upper 10. Mastoid process. 

 j ;urface of this suture is the in- H- Leading into stylo -mastoid 

 ! erior petrosal sinus. Laterally 

 i -he section passes through the 

 '.emporal bone, dividing the cavity of the tympanum and laying open the external acoustic 

 : neatus. To the medial side of the tympanic wall the cochlea is exposed, whilst above and 

 'ateral to it the canalis facialis is twice divided, the section passing posterior to the 

 Single formed by its genu. Below the cochlea, and separated from it and the medial part 

 !>f the floor of the tympanum, the carotid canal is in part exposed. Above the tympanum 

 ' ! s the epitympanic recess ("attic") leading into the tympanic antrum, the whole being 



