TISSUE-DIFFERENTIATION 



111 



lying the central nervous system and hence con- 

 stituting the longitudinal axis of the animal (axial 

 skeleton), and the other giving support and rigidity 

 to the limbs (appendicular skeleton). In addition, 



FIG. 40. Endoskeleton of man. (From Coleman.) 



the brain and connected sense organs are surrounded 

 and protected by an enveloping skull, to which is 

 attached the bony framework of the jaws. The axial 

 skeleton is divided into segments called vertebrae 

 which provide the proper balance between flexibility 



