SUPERIOR REGIONS OF THE SKULL. 55 



through the middle of the frontal bone to the root of the nose, under 

 the name of the frontal 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 con- 

 tinued onwards in a curved direction into the base of the skull, and 

 serves to unite the occipital bone with the mastoid portion of the 

 temporal, under the name of the additamentum suturce, lambdoid alls. 

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

 frequently. 



The squamous suture (fig. 23) unites the squamous portion of the 

 temporal 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 mas- 

 toid portion with the posterior inferior angle of the parietal is the 

 additamentum sutures squamoscs. 



Across the upper part of the face is an irregular suture, the trans- 

 verse, which connects the frontal bone with the nasal, superior max- 

 illary, lachrymal, ethmoid, sphenoid, and malar bones. The other 

 sutures are too unimportant to deserve particular names or descrip- 

 tion. 



REGIONS OF THE SKULL. 



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

 a superior 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 ridge and 

 parietal eminences ; and behind by the superior curved line of 

 the occipital bone and occipital protuberance. It is crossed trans- 

 versely by the coronal suture, and marked from before backwards 

 by the sagittal, which terminates posteriorly in the lambdoid suture. 

 Near the posterior extremity of the region, and on each side of the 

 sagittal suture, is the parietal foramen. Upon the inner, or cerebral 

 surface of this region, is a shallow groove, extending along the 

 middle line from before backwards, for the superior longitudinal 

 sinus ; on either side of this groove are several small fossae for the 

 Pacchionian bodies, and still further outwards numerous ramified 

 markings for lodging the branches of the arteria meningea media. 



TKe lateral region of the skull is divisible into three portions ; 

 temporal, mastoid, and zygomatic. 



The temporal portion, or temporal fossa, is bounded above and 

 behind by the temporal ridge, in front by the external angular pro- 

 cess of the frontal bone and by the malar bone, and below by the 

 zygoma. It is formed by part of the frontal, great wing of the 



