70 OSSA TEMPORUM. 



almost perpendicularly from the Fig. 15.* 



basis of the cranium, and 



gives origin to a muscle of the 



tongue, of the os hyoides, and 



of the pharynx, and also to 



several ligaments. The base 



of this process is surrounded 



by a flat projection of bone, 



occasionally called the vaginal 



process. 



On the inside of this pro- 

 cess, and rather before it, is 

 the jugular fossa, which, when applied to a corresponding part 

 of the occipital bone, makes the posterior foramen lacerum, 

 through which the internal jugular vein, and the eighth pair 

 of nerves pass out. A small spine called the jugular process 

 often projects into this foramen from the temporal bone, and 

 separates the nerve from the vein ; the nerve being anterior. 

 Upon a ridge which is found at the root of this spine, and 

 just behind the margin of the carotid foramen, there is a small 

 opening leading into the canal which transmits Jacobson's 

 tympanic branch of the glosso-pharyngeal nerve, which forms 



* The left temporal bone, seen from within. 1. The squamous portion. 

 2. The mastoid portion. The number is placed immediately above the inner 

 opening of the mastoid foramen. 3. The petrous portion. 4. The groove for 

 the posterior branch of the arteria meningea media. 5. The bevelled edge of 

 the squamous border of the bone. 6. The zygoma. 7. The digastric fossa 

 immediately internal to the mastoid process. 8. The occipital groove. 9. The 

 groove for the lateral sinus. 10. The elevation upon the anterior surface of the 

 petrous bone marking the situation of the perpendicular semicircular canal. 

 11. The opening or termination of the carotid canal. 12. The meatus auditorius 

 internus. 13. A dotted line leads upwards from this number to the narrow 

 fissure which lodges a process of the dura mater. Another line leads down- 

 wards to the sharp edge which conceals the opening of the aquseductus cochleae, 

 while the number itself is situated on the bony lamina which overlies the open- 

 ing of the aquaeductus vestibuli. 14. The styloid process. 15. The stylo-mas- 

 toid foramen. 16. The carotid foramen. 17. The jugular process. The deep 

 excavation to the left of this process forms part of the jugular fossa, and that to 

 the right is the groove for the vein of the cochlea. 18. The notch for the fifth 

 nerve upon the upper border of the petrous bone, near to its apex. 19. The 

 extremity of the petrous bone which gives origin to the levator palati and tensor 

 tympani muscles. 



