HONES OF THE HEAD. 



THE PARIETAL BONE. 



The parietal bones form a principal part of the roof of the skull. They 

 have the shape of quadrilateral plates, ccnvex externally, concave internally. 

 They are a little broader above than below, and the anterior inferior angle 

 is the most acute. They articulate with one another in the middle line, 

 with the frontal bone anteriorly, the occipital posteriorly, and the temporal 

 and sphenoid below. 



Fig. 28. 



Fig. 23. EXTERNAL SURFACE OP 



THE RIGHT PARIETAL BoNE. | 



1, posterior superior angle ; 

 2, anterior superior angle ; 3, 

 posterior inferior angle ; 4, ante- 

 rior inferior angle ; from 1 to 2, 

 superior border in the sagittal 

 suture ; from 2 to 4, anterior 

 border in the coronal suture ; 

 from 1 to 3, posterior border in 

 the lambdoidal suture ; from 

 4 to 6, the part of the inferior 

 border in the squamous suture ; 

 from 3 to 6, the part in the ad- 

 ditamentum suturas squamof-ae ; 

 5, the temporal or semicircular 

 line above which is the parietal 

 eminence. 



On the outer surface, the 

 point of greatest convexity 

 is called the parietal emi- 

 nence. Below this a curved 

 line is directed from the 



anterior to the lower part of the posterior margin ; it is the parietal part 

 of the temporal ridge, and bounds a surface somewhat flatter than the rest, 



planum temporale t which 



* forms part of the tempo- 



ral fossa. Near the pos- 

 terior and upper angle, 

 close to the middle line, 

 there is often a small 

 perforation of variable 

 dimensions, the parietal 

 foramen, which trans- 

 mits a communicating 

 vein. 



Fig. 29. THE PARIETAL 

 BONE FROM THE INSIDE. 



1, 2, 3, 4, & 6 indicate 

 the same parts as in the last 

 figure : between 1 & 2 the 

 half groove of the superior 

 longitudinal sinus ; 7, the 

 ramified grooves of the 

 meningeal vessels ; at x this 

 groove is converted into a 



