THE SKULL THE CRANIUM 181 



of this portion, and separated by a sharp overhanging oblique line, is 

 a roughened triangular fossa, which is applied to the superior surface 

 of the petrous part of the temporal bone. 



Nomenclature. The word parietal is derived from the Latin 

 paries, a wall. Os parietale, das Scheitelbein, and le parietal are the 

 names in Latin, German, and French respectively. 



Determination. When the concave surface is held toward the 

 student and the straight median border upward, the tentorial plate will 

 be on the side to which the bone belongs. 



Articulation. The parietal articulates with the frontal, the inter- 

 parietal, the sphenoid, the temporal, and the occipital, and with its 

 fellow of the opposite side. 



Muscular Attachment. The temporal muscle is attached to the 

 outer surface of the parietal. 



Ossification. The parietal appears to develop from two centres 

 of ossification near the parietal eminence. 



VARIATIONS IN THE PARIETAL BONE. 

 VARIATIONS IN SIZE. 



The following list exhibits the variations in the size of fifty 

 parietals. The first number represents the length ; the second, the 

 height ; R or L shows the side of the skull to which the bone belongs. 



The length is the maximum length from the anterior superior 

 angle to the point where the superior border intersects an imaginary 

 straight line drawn at right angles to it through the most convex point 

 of the posterior border. 



The height is the greatest vertical diameter measured from the 

 inferior border at right angles to the long diameter : 



42, 30, R; 42, 27, L; 41, 27, R; 40.5, 26, L; 40, 30, R; 40, 27, 

 R, L ; 40, 24, R ; 39.5, 27, R ; 39, 27.5, R ; 39, 27, R, L ; 39, 26, R ; 

 39, 25, L ; 38.5, 28, R ; 38:5, 27, R ; 38.5, 24, L ; 38.5, 22, R ; 38, 

 30, R ; 38, 28, L ; 38, 27, L ; 38, 26, R, L ; 38, 25, L ; 37, 28, R ; 

 37, 27.5, R ; 37, 27, L ; 37, 26, R, L ; 37, 25.5, R ; 37, 25, R ; 36.5, 

 27, L; 36.5, 25.5, L; 36.5, 24.5, L; 36, 27, R, L; 36, 26, L; 36, 

 25.5, R, L ; 35.5, 25, L ; 35, 28, L ; 35, 27, L ; 35, 26, L ; 35, 25.5, 

 L ; 35, 25, R ; 35, 24, R ; 35, 23, L ; 34.5, 26, L ; 34, 28, R, L ; 34, 

 26, L ; 34, 25, L ; 33.5, 25, L ; 33.5, 24, L ; 33, 27, L ; 33, 23, R ; 

 30, 23, L. 



