BONES OP THE CRANIUM. 179 



course of the superior longitudinal sinus by a groove. The 

 inferior portion of this groove presents a ridge to which 

 ihefalx major is attached. And at this point where it joins 

 the ethmoid is seen a small hole, the foramen ccecum, for 

 transmitting a vein which communicates with the nasal 

 veins, and for lodging a process of the dura-mater. On 

 either side of the median line, many eminences and de- 

 pressions are observed, which correspond to the convolu- 

 tions of the brain, called mammillary eminences, and digital 



The circumference is rough and serrated to unite with 

 the parietal bones. At its superior border the internal 

 table is deficient, and rests upon the junction of the two 

 parietal bones above; while, at the sides and below, the 

 external is wanting and is overlapped by the parietal. 



The inferior or orbi- FIG. 35. 



tal division of the fron- 

 tal bone presents in its 

 centre the azthmoidal 

 notch, in front of which 

 is the nasal spine; and 

 on either side, the ori- 

 fices of the frontal sin- 

 uses. It communicates 

 with the cells of the ethmoid by means of its edges, whi ch 

 are cellular. Along the margins of this notch, where it 

 unites with the ethmoid, are two foramina, the anterior and 

 posterior orbital, the first transmitting the nasal twig of 

 the ophthalmic nerve and anterior ethmoidal artery the 

 second the posterior ethmoidal artery. 



The orbital processes, on either side of this notch, are 

 triangular, having the apex behind, smooth and concave 

 below, rough and convex above. Near the external angu- 

 lar process, each of them has a depression for the lachrymal 



FIG. 35 presents a view of the lower part of Frontal Bone, a Line where 

 the two halves of the bone join. 6 Frontal protuberances, c Supra orbitar 

 notch, d Nasal spine and space occupied by the sethmoid bone, e Frontal 

 sinuses. / Orbitar plates, g External angular process, h Surface for tem- 

 poral muscle. 



