CHAP. IV.] 



THE SKELETON. 



41 



also mitigate the effects of concussion arising from falls or 

 blows, and allow of a certain amount of motion between 

 the vertebrae. The amount of motion permitted is greatest 

 in the cervical region. Between each pair of vertebrae are 

 apertures through which the spinal nerves pass from the spinal 

 cord. 



The skull as a whole. The skull, formed by the union of the 

 cranial and facial bones already described, is divisible into cra- 

 nium or brain case, and the anterior region or face. 



FIG. 43. THE SKULL, a, nasal bone ; 6, superior maxillary ; c, inferior maxillary ; 

 d, occipital ; e, temporal ; /, parietal ; g, frontal bone. 



The bones of the cranium begin to develop at a very early 

 period of foetal life, owing to the importance of the organ they 

 have to protect. Before birth the bones at the top and sides of 

 the skull are separated from each other by membranous tissue 

 in which bone is not yet formed. The spaces occupied by this 

 membranous tissue are termed the fontanelles, so named from 

 the pulsations of the brain, which can be seen in some of them, 



