PARIETAL BONK. 



33 



above the superior semicircular ridge, the occipito-frontalis ; to the 

 superior semicircular ridge, the trapezius and sterno-mastoid ; to the 

 rough space between the ridges, complexus and splenius capitis ; to 

 the space between the inferior semicircular ridge and the foramen 

 magnum, the rectus posticus major and minor, and obliquus supe- 

 rior; to the transverse process, the rectus lateralis; and to the 

 basilar process, the rectus anticus major and minor, and superior 

 and middle constrictor muscles. 



PARIETAL BONE. The pa- Fi g- 10 -* 



rietal bone is situated at the 

 side and vertex of the skull ; it 

 is quadrilateral in form, and di- 

 visible into an external and in- 

 ternal surface, four borders and" 

 four angles. The superior border 

 is straight, to articulate with its 

 fellow of the opposite side. The 

 inferior border is arched and 

 thin, to articulate with the tem- 

 poral 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 

 temporal ridge, to which the temporal fascia is attached. In the 

 middle of this line, and nearly in the centre of the bone, is the pro- 

 jection called the parietal boss 

 or 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 for the attach- 

 ment of the fleshy fibres of the 



Fig. ll.t 



temporal muscle. Near the 

 superior border of the bone, 

 and at about one-third from its 

 posterior extremity, is the pa- 

 rietal foramen, which transmits s 

 a vein to the superior longitu- 

 dinal sinus. 



Internal Surface. The internal table is smooth, and marked 



* The external 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 pos- 

 terior or lambdoidal border. 5. The temporal ridge; the figure is situated immediately 

 m front of the parietal eminence. 6. The parietal foramen, unusually large in the 

 bone from which this figure was drawn. 7. The anterior inferior or elongated angle. 

 o. The posterior inferior or truncated angle. 



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



5 



