THE SKULL THE CRANIUM 169 



mits the hypoglossal nerve. A rough pit and tubercle within the pos- 

 terior border, just below the most prominent projection of the condyle, 

 mark the attachment of the check or odontoid ligament of the axis. 



The Basilar Process of the occipital bone is a simple horizontal 

 plate, projecting forward below and in front of the foramen magnum 

 and at right angles to the rest of the bone. It is slightly longer than 

 wide, and it has an upper and a lower surface and an anterior and 

 two lateral borders. 



The upper surface (Fig. Ill) appears in the interior of the 

 cranium as the floor of the posterior cranial fossa. It is narrower 

 in front than behind, concave from side to side, especially at the back, 

 and supports the part of the brain called the pons. It articulates in 

 front by a straight suture with the basisphenoid. Each lateral border 

 is directed from the anterior border backward and slightly outward as 

 far as the posterior quarter, where it is emarginate and forms the inner 

 boundary of the jugular foramen. The lateral border is sometimes 

 grooved for the inferior petrosal sinus, which lies between it and the 

 contiguous border of the petrous part of the temporal. 



The lower surface (Fig. 107) is about as long as wide ; it begins 

 behind at a line connecting the inferior margins of the paroccipital 

 processes and ends at the anterior border. In front of the jugular 

 notch, each lateral margin is bevelled at the expense of the lower 

 surface and is applied to the entotympanic portion of the auditory 

 bulla. The inner edge of this bevelled border is more or less raised, 

 and, near the jugular notch, is incised for the passage of nerves and 

 vessels. On each side of the middle line the surface is crossed, anterior 

 to the centre, by a transverse or slightly oblique rough line which 

 marks the anterior limit of a fossa, whereof the deepest point is 

 anterior and lateral. In this fossa is inserted the rectus capitis anticus 

 minor muscle. The median space between the fossre is elevated into 

 a more or less prominent crest. On each side of a faintly depressed 

 median longitudinal area, in front of the transverse rough lines, the 

 lower surface is slightly convex transversely for the insertion of the 

 rectus capitis anticus major muscle. 



The anterior border of the basilar process is wide and low. In 

 young skulls it is joined by cartilage to the posterior surface of the 

 sphenoid bone ; in full-grown and old skulls the cartilage is converted 

 into bone and all truces of the original suture disappear. 



