THE FACE 



369 



FIG. 288. 



Frontal Process. 



Together they form a wedge which separates the nasal processes of 

 the frontals, and the upper ends of the nasal processes of the maxil- 

 laries and premaxillaries. They contribute the greater part of the 

 front wall of the nasal chamber and all of the superior margin of the 

 nasal aperture. 



Each bone has four surfaces, an anterior, a posterior, an external, 

 and an internal, and a superior and an inferior border. Inasmuch as 

 the bone is compressed at its lower end from above downward and at 

 its upper end from side to side, the inferior border is directed from side 

 to side and the superior border is directed from in front backward. 

 All four surfaces are triangular, the anterior and posterior with their 

 apices superior, the external and internal with their apices inferior. 



The anterior surface (Fig. 288) is the only part of the bone which 

 is visible on the exterior of the skull. It is triangular ; its length is 

 about four times greater than the 

 width at the base. The inferior- 

 external angle is produced 

 downward in a long, blunt, and 

 slightly curved external nasal 

 process. The external posterior 

 border of this process is applied 

 to the front of the premaxillary, 

 and the inner border forms part 

 of the boundary of the nasal 

 aperture. The inferior border 

 of the external surface between 

 the base of this process and the 

 inner angle is sharp, and slightly 



emarginate. The inferior-internal angle is sometimes slightly promi- 

 nent, and sometimes forms with the angle of the opposite bone a 

 faint superior median nasal spine, to which the median cartilaginous 

 septum of the external nose is attached. The internal or median 

 border is straight and joins the opposite bone ; the superior extremity 

 of the iuternasal suture marks the point on the skull known as the 

 nasion. The external border is sinuate and directed downward and 

 outward. In its upper and lower thirds it is arcuate, and in the 

 middle third emarginate ; it joins the borders of the nasal processes of 



the frontal, maxillary, and premaxillary bones (Fig. 287). 



24 



Median Border, with Oppo- 

 site Nasal. 



Internal Angle. 



External Angle of Inferior 

 Border. 



With Frontal. 



External Border. 



With Maxillary. 



With Premaxillary. 



LEFT NASAL BONE, ANTERIOR SURFACE. 



