THE SKULL 365 



can be readily 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 

 glosso-pharyngeal 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. 



b. The ventral surface of the cranium. 



i. The base of the skull is wide behind, where it is 

 covered by the broad transverse basi -temporal, 



