THE SKULL. 411 



end of the skull, and the apex being directed for- 

 wards. In the young skull the outlines of the com- 

 ponent bones can easily be followed, but in the 

 adult they are indistinguishable. The following are 

 the main points to be noticed : 



a. The hinder end of the cranium. 



i. The foramen magnum is a large nearly circular 

 aperture, in the middle of the posterior end of 

 the skull, through which the spinal cord enters 

 the cranial cavity. 



ii. The occipital condyle is a rounded knob, im- 

 mediately below the foramen magnum, into 

 which it projects slightly. It is notched in 

 the mid-dorsal line, and has below it a deep 

 pit-like depression. 



iii. The foramen of exit for the hypoglossal nerve, 



on each side, is a small aperture, immediately 

 to the outer side of the occipital condyle, and 

 slightly ventral to it 



iv. The foramen of exit for the pneumogastric and 

 glossopharyngeal nerves, on each side, is a 

 larger hole about an eighth of an inch to the 

 outer side of that for the hypoglossal nerve, 

 and midway between the condyle and the rim 

 of the tympanic cavity. 



v. To the outer side of the above foramen, and 

 between it and the tympanic rim, is a group 

 of three or four larger holes : some of these 

 lead into the tympanic cavity ; while the most 

 ventrally situated one is the entrance to the 

 carotid canal, which traverses the base of the 

 skull, and lodges the carotid artery. 



vi. The lambdoidal crest is a prominent ridge of 

 bone surrounding the dorsal half of the hinder 

 end of the skull, and separating the occipital 

 "from the parietal region. 



