60 



THE SKELETON 



median line, but are separated by a smooth surface called the glabella (nasal 

 eminence). Below the arch the bone presents a sharp curved margin, the supra- 

 orbital border, forming the upper boundary of the circumference of the orbit and 

 separating the frontal from the orbital portion of the bone. At the junction of 

 its medial and intermediate third is a notch, sometimes converted into a foramen, 

 and known as the supra-orbital notch or foramen ; it transmits the supra-orbital 

 nerve, artery, and vein, and at the bottom of the notch is a small opening for 

 a vein of the diploe which terminates in the supra-orbital. Sometimes, a second 

 less marked notch is present, medial to the supra-orbital, and known as the 

 frontal notch; it transmits one of the divisions of the supra-orbital nerve. The 

 extremities of the supra-orbital border are directed downward and form the 

 medial and zygomatic (lateral angular) processes. The prominent zygomatic proc- 

 ess articulates with the zj^gomatic bone and receives superiorly two well-marked 

 lines which converge somewhat as they curve downward and forward across the 

 bone. These are the superior and inferior temporal lines, continuous with the 



Fig. 75. — The Frontal. (Anterior view.) 



Temporal line 



Supra-orbital notch 

 Zygomatic process 



Medial process 

 Frontal spine 



temporal lines on the parietal bone, the upper giving attachment to the temporal 

 fascia and the lower to the temporal muscle. Behind the lines is a slight con- 

 cavity which forms part of the floor of the temporal fossa and gives origin to the 

 temporal muscle. The medial angular processes articulate with the lacrimals 

 and form the lateral limits of the nasal notch, bounded in front by a rough, 

 semilunar surface which articulates with the upper ends of the nasal bones and 

 the frontal (nasal) processes of the maxillse. 



In the concavity of the notch lies the nasal portion of the frontal, which projects somewhat 

 beneath the naHul l)one8 and the nasal i^roccKKcs of the maxilhi). It is divisible into three parts: 

 — a median frontal (nasal) spine, which dfssccnds in the nasal septum between the crest of the 

 nasal bones in front and the vertical plate of the ethmoid behind, and, on the posterior 

 aspect of the process, two alae, one on either side of the median ridge from which the frontal 

 (nasal) spine is continued. Each ala forms a small j^rooved surface which enters into the 

 formation of the roof of the nasal fo.ssa. 



The cerebral surface presents in the middle line a vertical groove — the sagittal 

 sulcus — which descends from the middle of the upper margin and lodges the 

 su{)erior sagittal (longitudinal) sinus. Below, the groove is succeeded by the 

 frontal crest, which terminates near the lower margin at a small notch, converted 

 into a foramen by articulation with the ethmoid. 



