THE BONY FRAMEWORK 



21 



bones, except at the joints, where it is protected with cartilage. 

 Shreds of the periosteum may be stripped off with forceps, if the 

 bone is soaked for some time in water. This membrane plays a 

 very important part in the formation, growth, and repair of bones, 

 as the blood vessels of bones form a network in them before entering 

 the Haversian canals. It is therefore of great surgical importance. 

 Bones have been removed, leaving the periosteum, within which 

 remarkable tissue the entire bone has grown again. 



THE BONES OF THE HEAD 



30. The Skeleton and its Three Main Divisions. The 

 skeleton, or bony framework of the "house we live in," 

 consists of the bones of the head, 



the trunk, and the limbs. 



31. The Bones of the Head. 

 The bones of the head are usu- 

 ally described in two parts, 

 those of the cranium and those 

 of the face. Together they form 

 the skull. 



The general shape of the 

 head is that of an arch. The 

 arch is the strongest shape in 

 which the skull could be made, 

 just as the arched bridge is the 

 strongest shaped bridge which 

 can be made to bear the heavy 

 loads that pass over it. 



32. The Bones of the Cra- 

 nium. The greater part of 



the skull consists of a rounded, bony box, the cranium, 

 which holds and protects the brain under its domelike roof. 



FIG. 14. The Skull. (Front view.) 



A, frontal bone; B, parietal bone; 

 C, temporal bone ; D, sphenoid 

 bone ; , malar bone ; F, upper 

 jawbone ; G, lower jawbone. 



