504 



MAMMALIAN ANATOMY 



It is sometimes necessary to compare the length of the true base of 

 the cranium with the length of the true base of the skull. 



The base of the skull extends from the basion, on the anterior 

 margin of the foramen magnum, to the alveolar point. 



The base of the cranial cavity extends from the basion to the ante- 

 rior edge of the anterior sphenoid. This diameter is termed the basi- 

 cranial axis. It is impossible to fix accurately on the exterior of the 



FIG. 408. 



THE SKULL, NINETY DAYS AFTER BIRTH. 



(Natural size.) 



skull the anterior end of the cranial base ; in adult skulls it is near 

 the root of the palatine postnasal spine ; in young skulls it is further 

 forward, on a line joining the maxillary tuberosities. 



The height of the cranial cavity is the intracranial vertical diam- 

 eter of the skull from the bregma to the suture between the anterior 

 and posterior sphenoids. In the young skulls the bones of the cranial 



