THE PARIETAL BONES. 



169 



fifths of an inch above the temporal ridge ; it marks the attachment of the temporal 

 fascia. Above these ridges the surface of the bone is rough and porous, and 

 covered by the aponeurosis of the Occipito-frontalis ; between them the bone is 

 smoother *and more polished than the rest ; below them the bone forms part of 

 the temporal fossa, and affords attachment to the temporal muscle. At the back 

 part of the superior border, close to the sagittal suture, is a small foramen, the 

 parietal foramen, which transmits a vein to the superior longitudinal sinus, and 

 sometimes a small branch of the occipital artery. Its existence is not constant, 

 and its size varies considerably. 



The internal surface (Fig/ 134), concave, presents eminences and depressions 

 for lodging the convolutions of the cerebrum and numerous furrows for the rami- 

 fications of the meningeal arteries; the latter run upward and backward from the 



Posterior 



superior 



angle. 



Posterior 



inferior 



angle. 



nterior 

 superior 

 angle. 



Anterior 

 J inferior 

 angle. 



FIG. 134. Left parietal bone. Internal surface. 



anterior inferior angle and from the central and posterior part of the lower border 

 of the bone. Along the upper margin is part of a shallow groove, which, when 

 joined to the opposite parietal, forms a channel for the superior longitudinal 

 sinus, the elevated edges of which afford attachment to the falx cerebri. Near 

 the groove are seen several depressions, especially in the skulls of old persons ; 

 they lodge the Pacchionian bodies. The internal opening of the parietal foramen 

 is also seen when that aperture exists. 



Borders. The superior, the longest and thickest, is dentated to articulate with 

 its fellow of the opposite side, forming the sagittal suture. The inferior is divided 

 into three parts : of these, the anterior is thin and pointed, bevelled at the expense 

 of the outer surface, and overlapped by the tip of the great wing of the sphenoid ; 

 the middle portion is arched, bevelled at the expense of the outer surface, and 

 overlapped by the squamous portion of the temporal ; the posterior portion is thick 

 and serrated for articulation with the mastoid portion of the temporal. The 

 anterior border, deeply serrated, is bevelled at the expense of the outer surface 

 above and of the inner below ; it articulates witb^ the frontal bone, forming the 



