236 



THE SKELETON 



the base of the skull which communicates with the neural 

 cavity of the spinal column permits the connection of 

 the brain and spinal cord without exposing these delicate 

 structures to blows or pressure; while the form of the 

 joint permits free play of the head in all directions. 



BoJSTE Stkuctuee. 



Shapes of bones. — These two hundred odd bones of the 

 skeleton may be classified into three groups according to 



Fig. 94 — Kinds of tones ; A, long bone (femur) ; B, flat bone (scapula) ; C, Irreg 

 ular bones (tarsals). 



shape. These are the long bones, the flat bones, and the 

 irregular bones. To the first group belong the humerus, 

 femm-, radius, tibia, ulna, fibula, metacarpals, etc. To 

 the second group belong the ribs, sternum, patellas, scap- 

 ulae, ilia, and the skull plates. In the third group are 

 included the carpals, tarsals, facial bones, vertebras, sacrum 

 and coccyx. 



