THE ENTIRE SKULL 459 



indeed, the face appears to be little more than a bony framework for 

 these openings. At its lower part is the transverse oral aperture, the 

 opening of the mouth ; above the mouth, in the middle line, is the 

 smaller, nearly circular nasal aperture, or opening of the anterior 

 nares ; above this, on each side, are the large openings of the orbits. 



After the removal of the lower jaw the outline of the front of 

 the skull becomes distinctly greater than a semicircle. If the lower 

 border be held horizontally, the sides are seen to be directed upward 

 and outward to the level of the zygoma ; they then curve upward and 

 inward to meet in the middle line above. The area bounded by this 

 outline consists of (1) a wide, arched, superior portion, the region of 

 the forehead ; (2) a middle, laterally constricted, nasal portion, which 

 lies between the orbits, faces upward and forward in front, faces upward, 

 forward, and outward at the sides, and forms the anterior lateral wall 

 of the nasal cavity ; and (3) a lower, wider, oral portion, which runs 

 out under the orbits, bounds the mouth above, and carries the upper 

 teeth. 



The anterior aspect of the skull is divided into two equal and 

 symmetrical parts by a median vertical suture, which begins above 

 as the metopic suture, between the frontal bones, is continued to the 

 anterior nares as the internasal suture, between the nasals, and ends 

 below the anterior nares as the interpremaxillary suture, between the 

 premaxillaries. 



In each half of the face the orbit is the most conspicuous feature. 

 Its opening appears to be circular, but this is due to foreshortening, 

 as its plane slopes backward, upward, and outward from a transverse 

 plane vertical to the straight lower border. Above and between the 

 highest parts of the orbital openings is the region of the forehead, 

 which is flattened on top and slopes gently downward at the sides. 

 When the base of the skull is placed on a horizontal plane, owing 

 to the downward anterior pitch of the roof of the cranium, the fore- 

 head faces more upward than forward. A swelling on each frontal 

 bone above the orbital opening, made apparent by a groove running 

 close to the orbital rim and parallel to it, is known as the superciliary 

 ridge. 



Beginning above where the metopic suture ends, and passing- 

 downward and slightly outward to the side of the nasal aperture, is 

 seen the suture which joins the outer edge of the nasal bone to the 



