THE SKULL THE CEANIUM 



159 



FIG. 105. 



CHAPTER IV 



THE SKULL THE CRANIUM 



THE bones of the head are often divided into two groups : (1)' those 

 which are closely united to form the skull, and (2) those which form 

 the hyoid apparatus, a loosely jointed ventral arch, attached above 

 to the back part of the skull, and supporting, below, the base of the 

 tongue and the larynx. This division, however, is for convenience 

 only ; the hyoid bones are parts of the skull, although in man and 

 in some other animals their relation to it is not obvious in the adult 

 condition. 



The skull proper is further divided artificially into the cranium 

 and the face. 



The cranium (Fig. 105) comprises the posterior part, which sur- 

 rounds the brain and articulates 

 behind with the atlas vertebra. 

 It is united to the face in front 

 and below by immovable sutures, 

 but enters into an articulation 

 on each side below with the only 

 movable face-bone, the mandible. 

 To the lower posterior part of 

 the sides of the cranium are at- 

 tached the superior hyoid bones. 



The face (Fig. 105) com- 

 prises the anterior part of the 

 skull, which surrounds the 



mouth, or oral cavity. With the anterior part of the cranium it 

 forms the orbital and nasal cavities. 



The cranium is composed of ten bones : the occipital, the two 

 temporals, the two parietals, the interparietal, the sphenoid, the two 

 frontals, and the ethmoid. 



If we remove the ethmoid, which is at the anterior end, almost 



THE SKULL, LATERAL ASPECT. 

 The cranium white, the face black. 



