SKELETAL SYSTEM 



375 



~ Ij" _ Periosteum 



Spongy Bone 



: - Marrow Cavity 



-Hard .Bone 



Fig. 173. A long bone cut 

 lengthwise. 



firmly fastened to- 

 gether that little or 

 no movement is pos- 

 sible. In other cases, 

 they move easily, one 

 on the other. 



out, the periosteum adds new 

 cells which become bone tissue 

 and repair the injury. 



Joints. Where two bones come 

 together they form a joint. 

 Sometimes the bones are so 



Pefvis 



Fig. 174. The hip joint 



In joints, like the hip, the bones are held together 

 by bands of tough material called ligaments. They are 

 further held together by a covering of connective tissue 

 and by the muscles. 



Hygiene of the skeleton. Since the bones of children 

 are soft and flexible, it is very easy for them to 

 become distorted. Bowlegs, for example, are often the 

 result of allowing children to walk too soon. The bones 



