1 98 



HUMAN ANATOMY. 



into which the temporal crest of the frontal divides. The superior crosses the bone, 

 ending at its posterior border. The inferior turns down towards the posterior 

 part so as to reach the lower border to become continuous with the supramastoid 

 crest of the temporal. In the middle of their course the lines are about two centi- 

 metres apart. The space between them is a little smoother than the surface above 

 and below. It is uncommon to be able to trace both lines throughout. The inferior 

 is usually the better marked. Sometimes a part of each is suppressed. The identity 

 of a single line is shown by its termination. Near the upper posterior angle is a 

 minute pin-hole, the parietal foramen,^ which transmits a vein. This foramen is very 

 often wanting, and, when visible, may be closed. In very rare cases it is a large 

 hole, which may even admit a finger. It is occasionally double. The internal 

 surface is smooth and glistening, as is the case throughout the inside of the cranium. 

 It is marked by tree-like grooves for the branches of the middle meningeal artery. 



Fig. 223. 



Groove for longitudi- 

 nal sinus 



Ant. sup. angle 



Pacchionian 

 depressions 



Grooves for middle 

 meningeal artery 



Anterior inf. angle 



Post. sup. angle 



Groove for 

 lateral sinus 



Posterior inferior angle 



Right parietal bone, mner surface. 



One of these starts close to the anterior lower angle, being at first very deep and 

 sometimes a canal for a short distance. Its situation is exceedingly constant. One 

 or two other branches appear in the posterior half of the lower border. The superior 

 longitudinal sinus rests in a groove '■' completed by both bones along the upper border. 

 This groove is rarely symmetrical, being generally largest on the right. At the 

 posterior inferior angle there is a small surface completing the groove'* of the lateral 

 sinus at the point at which it turns from the occipital into the temporal bone. Pacchi- 

 07iian depressions are small pits of varying size and number, found in the upper part 

 of the inner surface, and most commonly near the groove for the longitudinal sinus, 

 which contain the Pacchionian bodies of the arachnoid. The largest might receive 

 the tip of the little finger. 



The anterior, superior, and posterior borders are all jagged. The anterior 

 harder meets the frontal, overlapping it below, overlapped above. The superior 

 border meets that of its fellow. The serrations are most developed in the middle, 



^ Foramen parietale. - Sulcus sagittal-s. ''Sulcus transversus. 



