THE BONES OF THE HEAD 125 



superior surface of the skull in an arched manner, extending on 

 either side as low as the superior border of the great wing of the 

 sphenoid. As it crosses the median hne it is joined by the anterior 

 end of the interparietal suture. The place of junction is, as stated, 

 called the bregma, which indicates the position of the anterior 

 fontanelle of early Ufe. From the bregma three sutures radiate — 

 namel3^ the interparietal suture and the two hmbs, right and left, 

 of the fronto-parietal suture. Each hmb of the fronto-parietal 

 suture is serrated, but more so over the central part than the upper 

 and lower parts, and more so over the upper part near the median 

 line than over the lower part, in which two latter situations over- 

 lapping takes place. Superiorly the frontal bone shghtly overlaps 

 the parietal bone, and inferiorly the parietal bone distinctly over- 

 laps the frontal bone, the opposed bevelled surfaces in the latter 

 region being ridged. This latter portion of the coronal suture is 

 spoken of as a limbous suture. 



The metopic or frontal suture, which connects the two halves of 

 the frontal bone during the first year of hfe, may persist throughout 

 life. Under these circumstances, it extends in the median hne 

 from the bregma to the centre of the nasal notch of the frontal 

 bone. Superiorly it is continuous with the interparietal suture, 

 and inferiorly Nvith the internasal suture. Even though the suture 

 may not persist entirely, traces of it may be present inferiorly and 

 superiorly, especially inferiorly. As a rule, however, the suture is 

 entirely obhterated by the end of the sixth year of hfe. 



The parieto-mastoid suture connects the posterior part of the 

 inferior border of the parietal bone with the superior border of the 

 mastoid part of the temporal bone. Its direction is from behind 

 forwards, and, as stated, it is one of the bifurcations of the lower 

 end of the corresponding hmb of the occipito-parietal suture. It 

 is serrated, and anteriorly is continuous with the posterior end of 

 the squamo-parietal suture. It is on a level with the upper border 

 of the zygoma. The point, situated at its posterior extremity, 

 coincides with the asterlon, which indicates the situation of the 

 postero-lateral or mastoid fontanelle of early hfe. From this point 

 three sutures radiate — namely, the corresponding limb of the 

 occipito-parietal suture, the parieto-mastoid suture, and the occipito- 

 mastoid suture. Near the anterior part of the parieto-mastoid 

 suture there is the parietal notch on the superior border of the pars 

 mast&idea, which coincides with the entomion. 



The parieto-squamosal suture connects the greater part of the 

 inferior border of the parietal bone with the superior border of the 

 squamous part of the temporal bone. It is arched, the convexity 

 being directed upwards, and after haWng descended posteriorly, it 

 becomes continuous with the parieto-mastoid suture. Anteriorly it 

 is continuous with the spheno-parietal suture. The parieto-squamosal 

 suture presents a marked contrast to the foregoing serrated sutures, 

 inasmuch as it is a squamous suture, the squamous part of the 

 temporal overlapping the lower border of the parietal bone. 



