128 



EXTERNAL BASIS OF THE SKULL. 



the anterior part of this foramen is most commonly a small bony 

 process, which separates the eighth pair of nerves from the 

 internal jugular vein, as they pass out here. 



The anterior condyloid foramen for the passage of the ninth 

 pair of nerves, appears in the surface of the great occipital hole, 

 immediately below the foramen lacerum. From the back part 

 of this hole the spine, which forms the lower limb of the cross, 

 passes up; and on each side of it are the great depressions 

 which accommodate the two lobes of the cerebellum. 



External Basis of the Skull. 



The external surface of the base of the skull is very irre- 

 gular. When the head is inverted, we see the external protu- 

 berances of the OS occipitis, formerly described. Tiie mastoid 

 processes of the ossa temporum are on the same transverse 

 line with the great foramen of the os occipitis ; but the foramen 

 being larger extends farther forward. On the inside of the 

 mastoid process, the fissure for the digastric muscle is very con- 

 spicuous, and also the suture between the mastoid process and 

 the occipital bone. 



Fii 



11. 



The oblique direction of 

 the occipital condyles and 

 the slanting position of 

 their articulating surfaces 

 are particularly striking. 

 The posterior condyloid 

 foramina for the cervical 

 veins, and the anterior for 

 the ninth pair of nerves, 

 are also in view. The 

 position of the cuneiform 

 process of the os occipitis 

 is by no means horizontal, 

 but extends forwards and 

 upwards. The petrous or 

 pyramidal portion of the 

 temporal bone commences 



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

 palate. The figures are placed upon the palate processes of the superior niaxil- 



