THE CRANIUM AND FACE. 51 



where the arms of the cross meet. The occipital lobes 

 of the cerebrum lie in the two upper fossae and the hemi- 

 spheres of the cerebellum in the two lower ones. In the 

 grooves upon the ridge are the sinuses which collect the 

 blood from the brain. 



The occipital and frontal muscles, united by a thin 

 aponeurosis, cover the whole upper cranium and are 

 known as the occipito-frontalis muscle. At the back this 

 is attached to the occipital bone, while in front it inter- 

 laces with various face muscles. It is a powerful muscle 

 and raises the brows, wrinkles the forehead, and draws 

 the scalp forward. Long hair grows on the skin over it 

 as a further protection against blows upon the skull and 

 sudden variations in temperature. 



The temporal bones said to be so named because the 

 hair over them is the first to turn with age are situated 

 at the sides and base of the skull and are in three portions : 

 the squamous or scale-like, the mastoid or nipple-like, 

 and the petrous or stony portion. The squamous is 

 the upper portion and has projecting from its lower part 

 the long arched zygomatic process, which articulates 

 with the malar bone of the face and from which arises the 

 masseter muscle, one of the chief muscles of mastication, 

 ' which has its insertion in the ramus and angle of the lower 

 jaw. Just above the zygomatic process the temporal 

 muscle has its origin in part, while below is the glenoid 

 fossa for articulation with the condyle of the lower jaw, 

 the posterior portion of the fossa being occupied by part 

 of the parotid gland. 



The rough mastoid portion of the temporal bone is 

 toward the back and affords attachment to various mus- 

 cles, of which the most important are the occipito- 

 frontalis and the sterno-cleido-mastoid. Within it are 

 the mastoid cells, which communicate with the inner ear 

 and are lined with mucous membrane continuous with 

 that of the tympanum. They probably have something 

 to do with the hearing. In children they often become 

 the seat of inflammation (mastoid abscess) in infectious 



