196 



Anatomy of Skeleton 



bony processes on the sphenoid : thus the cerebellum is altogether confined to the 

 posterior fossa. The bony sphenoidal points to which this sheet of dura mater is 

 attached are termed clinoid processes : the anterior process is a well-marked projection 

 from the root of the small wing on each side, the posterior, also prominent, project 

 at the upper angles of the dorsum sellae, while the middle, often absent, is a small 

 tubercle internal to each carotid groove. These processes are connected by interclinoid 

 ligaments. 



The position and connections of the great venous sinuses of the dura mater should 

 now be followed in the skull (Fig. 163). They are all in relation with the bones with the 



. exception of those that are en- 

 closed in the free parts of the 

 falx and tentorium, i.e., the in- 

 ferior longitudinal and straight 

 sinuses. 



The cranial bones are for the 

 most part plainly of the " tabu- 

 lar " variety, and are built in 

 two compact layers the inner 

 and outer tables of the skull 

 with an intervening stratum 

 composed of bony pillars con- 

 necting the tables and forming a 

 coarse cancellous layer contain- 

 ing red marrow : this is termed 

 the diploe, and large anasto- 

 mosing channels run through it 

 for the diploic veins that drain 

 the tissue. 



The diploe appears first 

 about the age of ten ; it becomes 

 most developed in bones and 

 regions that are thick. 



The cranial bones, with the 

 exception of the occipital and 

 parietals, are connected with the 

 bones of the face, so that it is 

 advisable to gain some general 



FIG. 163. Position of cranial sinuses. Cavernous sinus is on 

 the side of body of sphenoid ; sphenoparietal sinus 

 reaches it along the edge of lesser wing, and superior and 

 inferior petrosal connect it with sinuses in posterior fossa. 

 Transverse and circular sinuses are plexiform connec- 

 tions across the middle line. Observe that the right 

 lateral receives the blood from the superior longitudinal 

 sinus and is therefore larger than the left, which as a rule 

 only drains the straight sinus. The " torcular Herophili ' ' 

 is the small connection between the right and left systems 

 near the internal occipital protuberance. The right 

 lateral sinus usually comes further forward in the petro- 

 mastoid region than the left. 



notion of the arrangement of 

 the facial skeleton from a scrutiny 



of the complete or halved skull before entering upon a detailed examination of the 



individual bones of the cranium. 



FACIAL SKELETON. 



This is situated altogether in front of the level of the pterygoid processes, with the . 

 exception of the mandible. 



Looking at the skull from the front (Fig. 164), the two upper jaws or maxillce are 

 seen to constitute the side margins of the nasal opening and to meet each other below 

 it. Each maxilla forms, by its upper surface, the greater part of the floor of the orbit 

 and is prolonged up the inner margin of the orbital opening as a nasal process which 

 meets the frontal. The two nasal bones also articulate with the frontal and separate 



