PARIETAL BONE. 



26 



superior border is straight,- to articulate with its fellow of the opposite 

 side. The inferior border is arched and thin, to articulate with the 

 temporal bone. The anterior border is concave, and the posterior 

 somewhat convex. 



External Surface. Crossing the bone in a longitudinal direction 

 from the anterior to the posterior border, is an arched line, the tem- 

 poral 'ridge, to which the temporal fascia is attached. In the middle 

 of this line, and nearly in the centre of the bone, is the projection 

 called the parietal eminence, which marks the centre of ossification. 

 Above the temporal ridge the surface is rough, and covered by the 

 aponeurosis of the occipito-frontalis ; below the ridge the bone is 

 smooth (planum semicirculare) for the attachment of the fleshy fibres 

 of the temporal muscle. Near the superior border of the bone, and at 

 about one-third from its posterior extremity, is the parietal foramen^ 

 which transmits a vein to the superior longitudinal sinus. This fora- 

 men is often absent. 



Fig. 14.* 



Internal Surface. The internal table is smooth ; it is marked by 

 numerous furrows which lodge the ramifications of the arteria menin- 

 gea media, and by digital fossae which correspond with the convolutions 

 of the brain. Along the upper border is part of a shallow groove, 



* The internal surface of the left parietal bone. 1 . The superior, or sagittal 

 border. 2. The inferior, or squamous border. 3. The anterior, or coronal 

 border. 4. The posterior, or lambdoidal border. 5. Part of the groove for the 

 superior longitudinal sinus. 6. The internal termination of the parietal fora- 

 men. 7. The anterior inferior angle of the bone, on which is seen the groove 

 for the trunk of the arteria meningea media. 8. The posterior inferior angle, 

 upon which is seen a portion of the groove for the lateral sinus. 



