PARIETAL BONES. 



139 



and covered by the aponeurosis of the Occipito-frontalis; below it the bone is 

 smooth, 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. Its existence is not constant, and its size varies consider- 

 ably. 



The internal surface (Fig. 93), concave, presents eminences and depressions 

 for lodging the convolutions of the cerebrum, and numerous furrows for the 



Fig. 93. Left Parietal Bone. Internal Surface. 



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ramifications of the meningeal arteries ; the latter run upwards and backwards 

 from the 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; they lodge the Pac- 

 chionian 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 with the frontal 

 bone, forming the coronal suture. The posterior border, deeply denticulated, 

 articulates with the occipital, forming the lambdoid suture. 



