56 



BASE OF THE SKULL. 



sphenoid, parietal, squamous portion of the temporal, and malar 

 bone, and lodges the temporal muscle. 



Fig. 23 . 



Fig. 24.t 



The mastoid portion is rough, for the attachment of muscles. 

 Upon its posterior part is the mastoid foramen, and below, the mas- 

 toid process. In front of the mastoid process is the external audi- 

 tory foramen, surrounded by the external auditory process ; and 



* A front view of the skull. 1. The frontal portion of the frontal bone. The 2 im- 

 mediately over the root of the nose, refers to the nasal tuberosity ; the 3 over the orbit, 

 to the supra-orbital ridge. 4. The optic foramen. 5. The sphenoidal fissure. 6. The 

 spheno-maxillary fissure. 7. The lachrymal fossa in the lachrymal bone, the com- 

 mencement of the nasal duct. The figures 4, 5, 6, 7, are within the orbit. 8. The 

 opening of the anterior nares, divided into two parts by the vomer ; the number is 

 placed upon the latter. 9, The infra-orbital foramen. 10. The malar bone. 11. The 

 symphysis of the lower jaw. 12. The mental foramen. 13. The ramus of the lower 

 jaw. 14. The parietal bone. 15. The coronal suture. 16. The temporal bone. 17. 

 The squamous suture. 18. The upper part of the great ala of the sphenoid bone. 19. 

 The commencement of the temporal ridge. 20. The zygoma of the temporal bone, 

 assisting to form the zygomatic arch. 21. The mastoid process. 



t The cerebral surface of the base of the skull. 1. One side of the anterior fossa ; 

 the number is placed on the roof of the orbit, formed by the orbital plate of the frontal 

 bone. 2. The lesser wing of the sphenoid. 3. The crista galli. 4. The foramen 

 cfficum. 5. The cribriform lamella of the ethmoid. 6. The processus olivaris. 7. The 

 foramen opticum. 8. The anterior clinoid process. 9. The carotid groove upon the 

 side of the sella Turcica, for the internal carotid artery and cavernous sinus. 10, 11, 

 12. The middle fossa of the base of the skull. 10. Marks the great ala of the sphe- 

 noid. 11. The squamous portion of the temporal bone. 12. The petrous portion of 

 the temporal. 13. The sella Turcica. 14. The basilar portion of the sphenoid bone 

 surmounted by the posterior clinoid processes. 15. The foramen rotundum. 16. The 

 foramen ovale. 17. The foramen spinosum; the small irregular opening between 17, 

 and 12 is the hiatus Fallopii. 18. The posterior fossa of the base of the skull. 19, 

 19. The groove for the lateral sinus. 20. The ridge upon the occipital bone, which 

 gives attachment to the falx cerebelli. 21. The foramen magnum. 22. The meatus 

 auditorius internus. 23. The jugular foramen. 



