BONE 



289 



lage. As new bone is developed peripherally, it is resorbed centrally to 

 form large marrow spaces. Eventually, all of the cartilage matrix, and 

 probably the cartilage cells as well, are destroyed. 



Perichondral Ossification. Compact bone is developed by the 

 osteogenic layer of the periosteum, and thus are produced the periosteal 

 lamellae. In the ribs this is said to be the only method of ossification. 

 Those bone lamellae deposited about a blood vessel are concentrically 

 arranged and form the concentric lamella of an Haversian system. The 

 Haversian canal of adult bone is merely the space occupied by bloodvessels. 

 Between the Haversian systems are interstitial lamella. 



-Cartilage 



Bony diaphysis 



-Bone marrow 



Epiphysis 



Diaphysis 



Epiphysis 



FIG. 296. Diagrams to show the method of growth of : A, vertebra; B, sacrum; C-F, a long 



bone (tibia). 



Growth of Cartilage Bones. In cartilage bones there is no inter- 

 stitial growth as in cartilage. Most of the cartilage bones have more than 

 one' center of ossification and growth is due to the expansion of the inter- 

 vening cartilage. Flat bones grow at the periphery; ring like bones, such 

 as the vertebrae, have three primary centers of ossification, between which 

 the cartilage continues to grow (Fig. 296 A). In the case of the numerous 

 long bones of the skeleton, the primitive ossification center forms the shaft, 

 or diaphysis (Fig. 296 C-F). The cartilage at either end of the diaphysis^ 

 grows rapidly and thus the bone increases in length. Eventually, osteo- 

 genic tissue invades these cartilages and new ossification centers, the 

 epiphyses, are formed, one at either end. When the growth of the bone 



