THE FRONTAL BONE. 



33 



canal, and throughout the inner surface the dimpling of the convolutions of the cerebrum ; 

 8, the parietal foramen ; 9, the irregular pits for the gland ulse Pacchionii. 



On the inner surface, the hollow corresponding to the eminence is called 

 the parietal fossa. This surface is marked by grooves branching upwards and 

 backwards, corresponding with the course of the middle meningeal vessels, 

 and by depressions corresponding with the convolutions of the brain. A 

 slight depression along the superior border completes with the one of the 

 opposite side a groove marking the course of the longitudinal sinus ; and a 

 depression at the posterior inferior angle forms a small part of the groove 

 of the lateral sinus. Near the upper border there are in most skulls, but 

 particularly in those of old persons, small irregular pits, fovece glandular es, 

 the result of absorption produced by the so-named glandulae Pacchionii. 



Borders. The anterior, superior, and posterior borders are serrated. The 

 inferior border presents in the greater part of its extent a sharp or squa- 

 mous edge, with a slightly fluted surface directed outwards and overlapped at 

 its anterior extremity by the great wing of the sphenoid, and behind that 

 by the squamous part of the temporal bone ; but at its posterior part it is 

 serrated, and articulates with the mastoid portion of the temporal. The 

 posterior border is the most deeply serrated. The anterior border is slightly 

 overlapped by the frontal bone above, but overlaps the edge of that bone 

 inferiorly. 



THE FRONTAL BONE. 



The frontal bone, arching upwards and backwards from above the orbits, 

 forms the fore part of the vault of the skull. It likewise presents inferiorly 

 two thin horizontal laminse, the orbital plates, which form the roofs of the 

 orbits and are separated by a mesial excavation, the incisura ethmoidalis. 



Fig. 30. FRONTAL BONE FROM 



BEFORE, SHOWING ITS EXTER- 



NAL SURFACE. 



1, frontal protuberance ; 2, 

 nasal spine, and above this the 

 serrated surface for articulation 

 of the nasal and superior maxil- 

 lary bones ; 3 to 4, supra-orbital 

 edge 3, internal, and 4, exter- 

 nal angular process ; 5, supra- 

 orbital notch or foramen; 6, 

 glabella; 7, superciliary emin- 

 ence and ridge ; 8, temporal 

 ridge, and behind this a part of 

 the temporal fossa. 



The frontal is articulated 



with twelve bones, viz., 



posteriorly with the parie- 



tals and sphenoid ; outside 



the orbits with the malars ; 



and between the orbits, 

 from before backwards, with 

 the nasal, superior maxillary, lachrymal and ethmoid bones. 



Anterior Surface. The part forming the greatest convexity of the fore- 

 head on each side is called the frontal eminence. It is separated by a 

 slight depression below from the superciliary ridge, a curved elevation of 



