64 



OSTEOLOGY. 



cases of well-marked cerebral development. The whole surface of the bone above 

 this part is smooth, and covered by the aponeurosis of the Occipito-frontalis 

 muscle. Below the frontal eminence, and separated from it by a slight groove, is 

 the superciliary ridge, broad internally where it is continuous with the nasal 

 eminence, but less distinct as it arches outwards. These ridges are caused by the 

 projection outwards of the frontal sinuses. Beneath the superciliary ridge is the 

 supra-orbital arch, a curved and prominent margin, which forms the upper 

 boundary of the orbit, and separates the vertical from the horizontal portion of 

 the bone. The outer part of the arch is sharp and prominent, affording to the 

 eye, in that situation, considerable protection from injury ; the inner part is less 

 prominent. At the inner third of this arch is a notch, sometimes converted into 



Fig. 27. Frontal Bone : Outer Surface. 



a foramen by a bony process or ligament, and called the supra-orbital notch or 

 foramen. It transmits the supra-orbital artery, veins, and nerve. A small 

 aperture is seen in the upper part of the notch, which transmits a vein from the 

 diploe to join the ophthalmic vein. The supra-orbital arch terminates externally 

 in the external angular process, and internally in the interal angular process. 

 The external angular process is strong, prominent, and articulates with the malar 

 bone : running upwards and backwards from it is a sharp curved crest, the tem- 

 poral ridge, for the attachment of the temporal fascia; and beneath it a _ slight 

 concavity, that forms the anterior part of the temporal fossa, and gives origin to 

 the Temporal muscle. The internal angular processes are less marked than the 

 external, and articulate with the lachrymal bones. Between the two is a rough, 

 uneven interval, the nasal notch, which articulates in the middle line with the 

 nasal, and on either side with the nasal process of the superior maxillary bone. 

 The notch is continuous below, with a long pointed process, the nasal spine. 



