88 BASE OF THE SKULL. 



into the aquceductus vestibuli ; and below it, partly concealed by the edge 

 of the petrous bone, the aquaductus cochlea; next, a long fissure, the 

 foramen laceru?n posterius, or jugular foramen, giving passage externally 

 to the commencement of the internal jugular vein, and internally to the 

 eighth pair of nerves. Converging towards this foramen from behind is 

 the deep groove for the lateral sinus, and from the front the groove for the 

 inferior petrosal sinus. 



Behind the foramen magnum is a longitudinal ridge, which gives at- 

 tachment to the falx cerebelli, and divides the two inferior fossae of the 

 occipital bone ; and above the ridge is the internal occipital protuberance 

 and the transverse groove lodging the lateral sinus. 



The external surface of the base of the skull is extremely irregular. 

 From before backwards it is formed by the palate processes of the superior 

 maxillary and palate bones ; the vomer ; pterygoid, spinous processes, and 

 part of the body of the sphenoid ; under surface of the squamous, petrous, 

 and mastoid portion of the temporals ; and by the occipital bone. The 

 palate processes of the superior maxillary and palate bones constitute the 

 hard palate, which is raised above the level of the rest of the base, and is 

 surrounded by the alveolar processes containing the teeth of the upper 

 jaw. At the anterior extremity of the hard palate, and directly behind 

 the front incisor teeth, is the anterior palatine or incisive for 'amen , the ter- 

 mination of the anterior palatine canal, which contains the naso-palatine 

 ganglion, and transmits the anterior palatine nerves. At the posterior 

 angles of the palate are the posterior palatine foramina, for the posterior 

 palatine nerves and arteries. Passing inwards from these foramina are the 

 transverse ridges to which are attached the aponeurotic expansions of the 

 tensor palati muscles ; and at the middle line of the posterior border, the 

 palate spine, which gives origin to the azygos uvulae. The hard palate 

 is marked by a crucial suture, which distinguishes the four processes of 

 which it is composed. Behind, and above the hard palate, are the poste- 

 rior nares, separated by the vomer, and bounded on each side by the pte- 

 rygoid processes. At the base of the pterygoid processes are the pterygo- 

 palatine canals. The internal pterygoid plate is long and narrow, termi- 

 nated at its apex by the hamular process, and at its base by the scaphoid 

 fossa. The external plate is broad; the space* between the two is the 

 pterygoid fossa ; it contains part of the internal pterygoid muscle, and the 

 tensor palati. Externally to the external pterygoid plate is the zygomatic 

 fossa. Behind the nasal fossae, in the middle line, is the under surface of 

 the body of the sphenoid, and the basilar process of the occipital bone, 

 and, still further back, the foramen magnum. At the base of the external 

 pterygoid plate, on each side, is the foramen ovale, and behind this the 

 foramen spinosum with the prominent spine which gives attachment to the 

 internal lateral ligament of the lower jaw and the laxator tympani muscle. 

 Running outwards from the apex of the spinous process of the sphenoid 



7. The scaphoid fossa. 8. The external pterygoid plate. The interval between G and 

 8 (right side of the figure) is the pterygoid fossa. 9. The zygomatic fossa. 10. The 

 basilar process of the occipital bone. 11. The foramen magnum. 12. The foramen 

 ovale. 13. The foramen spinosum. 14. The glenoid fossa. 15. The meatus audito- 

 nus externus. 16. The foramen lacerum anterius basis cranii. 17. The carotid fora- 

 men of the left side. 18. The foramen lacerum posterius, or jugular foramen. 19. The 

 fjtyioid process. 20. The stylo-mastoid foramen. 21. The mastoid process. 22. Ono 

 of the condyles Df the occipital bone. 23. The posterior condyloid fossa. 



