12 PRACTICAL ANATOMY. 



position of the frontal sinuses ; below these are the 

 supra-orbital ridges, where the vertical and horizontal 

 portions join. These ridges present at their inner third a 

 notch or foramen, known as the supra-orbital, and which 

 transmit the supra-orbital nerVe and artery. The ridges 

 terminate externally in well-marked processes of bone, 

 known as the external angular processes, which are ser- 

 rated for articulation with the frontal process of the 

 malar ; internally, they approach one another and ter- 

 minate in the internal angular processes, also serrated for 

 articulation, with the superior maxillary and nasal ; they 

 are separated by a mass of bone, slightly elevated, from 

 one-half to three-quarters of an inch in breadth, and 

 known as the glabella. The supra-orbital ridges are 

 strongly arched, and assist in forming the rim of the 

 orbits. Passing down midway, dividing the bone into 

 halves, is the remains of the frontal suture, well marked 

 in young bones. It indicates the line of union of the 

 two halves of the bone. The superior border of the 

 frontal bone is strongly indented and toothed for articu- 

 lation with the parietal bones ; laterally it is beveled for 

 articulation with the great wing of the sphenoid. Pass- 

 ing upward and backward, in a curved direction from 

 the external angular process, is the commencement of the 

 temporal ridge. The process of bone posterior to the 

 ridge forms an angle with the vertical portion, and assists 

 in the formation of the temporal fossa. Projecting down- 

 ward midway from between the internal angular processes 

 is the nasal spine, which articulates in front with the 

 posterior borders of the nasal bones, and behind with the 

 anterior border of the ethmoid. The inner surface of 

 the vertical portion is concave in every direction, and 

 presents a number of shallow depressions for the accom- 

 modation of the convolutions of the brain. Besides tbese, 



