84 SUPERIOR REGION OF THE SKULL. 



triquetra, or ossa Wormiana. In the lambdoid suture there is generally 

 one or more of these bones ; and in a beautiful adult hydrocephalic skele- 

 ton, in the possession of Mr. Liston, there are upwards of one hundred. 



The coronal suture (fig. 39) extends transversely across the vertex of the 

 skull, from the upper part of the greater wing of the sphenoid of one side 

 to the same point on the opposite side ; it connects the frontal with the 

 parietal bones. In the formation of this suture the edges of the articu 

 lating bones are bevelled, so that the parietal rest upon the frontal at each 

 side, and in the middle the frontal rests upon the parietal bones ; they thus 

 afford each other mutual support in the consolidation of the skull. 



The sagittal suture (fig. 39) extends longitudinally backwards along 

 the vertex of the skull, from the middle of the coronal to the apex of the 

 lambdoid suture. It is very much serrated, and serves to unite the two 

 parietal bones. In the young subject, and sometimes in the adult, this 

 suture is continued through the middle of the frontal bone to the root of 

 the nose, under the name of the frontal suture. Ossa triquetra are some- 

 times found in the sagittal suture. 



The lambdoid suture is named from some resemblance to the Greek 

 letter A, consisting of two branches, which diverge at an acute angle from 

 the extremity of the sagittal suture. This suture connects the occipital 

 with the parietal bones. At the posterior and inferior angle of the parietal 

 bones, the lambdoid suture is continued onwards in a curved direction into 

 the base of the skull, and serves to unite the occipital bone with the mas- 

 toid portion of the temporal, under the name of additamentum sutura 

 lambdoidalis. It is in the lambdoid suture that ossa triquetra occur most 

 frequently. 



The squamous suture (fig. 39) unites the squamous portion of the tem- 

 poral bone with the greater ala of the sphenoid, and with the parietal, 

 overlapping the lower border of the latter. The portion of the suture 

 which is continued backwards from the squamous portion of the bone to 

 the lambdoid suture, and connects the mastoid portion with the posterior 

 inferior angle of the parietal, is the additamentum, sutura squamosa. 



The additamentum suturse lambdoidalis, and additamentum suturce 

 squamosse, constitute together the mastoid suture. 



Across the upper part of the face is an irregular suture, the transverse, 

 which connects the frontal bone with the nasal, superior maxillary, lachry- 

 mal, ethmoid, sphenoid, and malar bones. The remaining sutures are 

 too unimportant to deserve particular names or description. 



REGIONS OF THE SKULL. 



The skull, considered as a whole, is divisible into four regions: a supe- 

 rior region, or vertex; a lateral region; an inferior region, or base ; and 

 an anterior region, the face. 



The SUPERIOR REGION, or vertex of the skull, is bounded anteriorly by 

 the frontal eminences ; on each side by the temporal ridges and parietal 

 eminences ; and behind by the superior curved line of the occipital bone 

 and occipital protuberance. It is crossed transversely by the coronal 

 suture, and marked from before backwards by the sagittal, which termi- 

 nates posteriorly in the lambdoid suture. Near the posterior extremity 

 o f the region, and on each side of the sagittal suture, is the parietal 

 foramen. 



