THE EXTERIOR OF THE CRANIUM. 



219 



lines are to be seen in whole or in part. The inferior ahvays ends in the supra- 

 mastoid ridge. The mastoid process varies much in development. 



Anterior Aspect. '—The cranial portion of the skull is seen only above the 

 orbits and the root of the nose. Much of its lower part is occupied by the frontal 

 sinuses. 



Inferior Aspect.- — (The lower jaw is supposed to be removed.) This aspect 

 may be divided into three regions by two cross-lines, one being at the roots of 

 the pterygoid plates and one at the front edge of the foramen magnum. Passing 

 from behind forward, near the posterior surface, are seen the external occipital pro- 



FiG. 253. 



Anterior palatine canal 



Posterior nasal spine 



Posterior palatine canal 



Hamular process 



Great wine of 

 sphenoid 



Carotid canal 

 Styloid process' 



Jugular fossa 



Stylo-mastoid 

 foramen 



Mastoid process. 



Digastric fossai 

 Occipital groov 



Parietal bone. 



Posterior condyloid foramen 



Posterior nares 



\'omer 



Foramen ovate 



Eminentia 



articularis 

 Middle lacerated 



foramen 

 Foramen spino- 



sum 

 Glenoid fossa 



Fissure of Glaser 



Condyle 



Inferior curved line 



External occipital protuberance Superior curved line 



Base of skull from below, the lower jaw removed. 



tuberance and the superior and inferior curved lines. In front of the latter the 

 occipital bone is convex to the outer side of the foramen magnum. A line con- 

 necting the backs of the condyles halves the foramen magnum. The -mastoid pro- 

 cesses appear laterally. Internal to them are the digastric grooves, and just internal 

 to these the occipital grooves, nearly or quite in the suture. Between the mastoid 

 and styloid processes is the stylo-mastoid foramen. The region between the two 

 above-mentioned lines includes the gutttiral fossa in the middle for the pharynx ; 

 on each side of this are openings for great vessels and nerves, and, externally, the 

 joint of the jaw. The basilar process in front of the foramen magnum forms the 



^ Norma frontalis. - Norma basalis. 



