180 BONES OF THE CRANIUM. 



gland, and near the internal, one for the pulley of the 

 superior oblique muscle of the eye. Instead of a depres- 

 sion, there is sometimes a small eminence here. ' 



The frontal bone has seven foramina: 2 supra orbital, 

 which are special ; 2 anterior and 2 posterior orbital, with 



1 foramen ccecum, which are common to both the ethmoid 

 and frontal bones. 



The processes are nine : 1 nasal, 2 orbital, 4 angular, and 



2 superciliary. 



The structure consists of two compact laminae of bone, 

 called the external and internal tables, with an intervening 

 cellular substance, the diploe. 



The development of the frontal bone takes place by two 

 points of ossification, one for each frontal eminence, or 

 rather in the orbital arches, a little before that of the ver- 

 tebrae, whence the rays radiate to the circumference. At 

 birth the frontal bone still consists of two pieces, which 

 during the first year unite along the median line by the 

 frontal suture, which suture however sometimes remains 

 permanent through life. 



FIG 36 The articulations of this 



bone, are with four of the 

 cranium, viz : the 2 pari- 

 etal, the sphenoid and eth- 

 moid; and eight of the 

 face, viz: 2 nasal, 2 supe- 

 rior maxillary, 2 malar 

 and 2 lachrymal. 



Parietal Bones (oss-a 

 parietalia.) The parietal 

 bones are situated upon 

 the lateral and superior parts of the cranium. They are 

 symmetrical. Their form is quadrilateral ; their external 



FIG. 36 represents external surface of left Parietal Bone, a Superior or 

 sagittal surface. 6 Squamous or inferior surface, c Coronal or anterior sur- 

 face, d Lambdoidal or posterior surface, e Ridge where temporal muscle 

 is attached. / Parietal foramen, g Inferior anterior angle, h Inferior pos- 

 terior angle. 



