THE BONES. 53 



2. Internal, concave, with elevations (juga cerebralia). impressioms 

 and suld arteriosi (for the arteria meningea media), passing from the inferior 

 angle. In the centre fossa parietalis. 



Borders : 



1. The superior mar go sagittalis, the longest, very thick, dentated; presents 

 upon the concave surface a half groove which forms with the other half 

 groove upon its fellow bone the Sulcus longitudinalis. Forame.n parwtak (/. 

 emissarium Santorini). 



2. The inferior, mar go squamosus, the shortest, concave, sharpened off, 

 unites with the squamous portion of the temporal bone (Sut. Squamosa). 



3. The anterior, m. corona/is, toothed, forms with the frontal bone the 

 coronal suture. 



4. The posterior, m. lambdvideus, long indentations, unites with the occipital 

 bone. 



Angles: The two superior are right (ang. frontalis and ocripitalis}. 



The anterior inferior, ang. sphenoidalis, pointed, long, with the sulc. arte- 

 riosus. 



The posterior inferior, ang. mastoideus, obtuse, with sukus lateralis s. trans- 

 versus (for the transverse sinus). 



The two parietal bones unite anteriorly in an extended, poste- 

 riorly in a right angle. 



Conjunctions, with: os parietale,frontis, occipitis, temporum, 

 sphenoideum. 



Texture. On the external and internal surfaces, compact, bony tissue, 

 between the two, diploe. The thickness of the parietal bones diminishes 

 from above to below. In the diploe there are many veins. (Hence danger 

 from fractures.) 



Development. Ossification commences in the tuber parietale, at first in the 

 twelfth week; the angles are developed the last (hence the fontanelles). 



52. 6. Ossa temporum, temple-bones. 



Situation: one on either side of the skull, below the parietal, 

 before the occipital, behind the sphenoid, at the base and at the 

 sides of the cranium. 



Shape: irregular. Parts from behind forwards. Mastoid, squa- 

 mous and petrous portions. 



Conjunctions with 5: 3 cranial, 2 facial bones, parietal, occipi- 

 tal, sphenoid, superior and inferior maxillary bones. 



1. Pars squamosa, scale like, the anterior, superior, shell-formed portions of 

 the bone, the thinnest of the whole cranium, on its outer e-ide. 



a. External surface, convex, with grooves (for Art. temporal, pro/und.), and 

 the temporal fossa (for muse. temp.'). Processus zygomaticus s. ansa capitis (for 

 muse, masseter), forms the zygomati? arch with the process of the (os mala) ; 

 between its two roots, the cavitas gleiioidalis (the articular cavity for the head 

 of the lower jaw) ; the superior, two-armed, associated with the inferior in 

 the tuberculum articulare (for the ligam. lateral, extern.'). The proper anterior 

 articular cavity is separated from the posterior by the fissura Glascri (Chorda 

 tympani, Muse, malleus externus, Art. et Fen. tympanica}. 



