280 



MAMMALIAN ANATOMY 



The temporal portion of the vertical plate is triangular, the apex 

 pointing downward and backward. It passes without a break into the 

 orbital plate in front and into the horizontal plate above. It is convex 

 in both directions, and behind is largely encroached upon by the over- 

 lapping anterior border of the parietal. 



The internal surface of the vertical plate of the frontal (Fig. 203) 

 is divided, like the external surface, into two parts, but with the dif- 

 ference that in this case the anterior part is small and the posterior is 

 large. The two parts are separated from each other by a crooked, 



FIG. 203. 



Median Plate. 



With Opposite Frontal. 



With Parietal. 



Part of Anterior Cerebral Fossa. 

 With Alisphenoid 



s * 



S -S, 



I 



(V. P 



Nasal Process. 



With Maxillary. 



With Lachrymal. 



LEFT FRONTAL BONE, INNER SURFACE. 



jagged line, running downward and backward, at the junction of the 

 anterior and middle thirds. To this line is attached the edge of the 

 cribriform plate of the ethmoid. 



The anterior part is rudely triangular, and produced in front on the 

 internal angular process. It passes, above, into the outer surface of that 

 upper part of the nasal cavity which is sometimes called the external 

 frontal sinus. It is nearly flat, and faces slightly downward and for- 

 ward as well as inward. It is marked by five ridges beginning at the 

 cribriform line and running obliquely downward and forward. The 



