THE SKELETAL SYSTEM 



189 



outside and around ihe original cartilage this mode of bone formation is 

 known as perichondral bone formation. The diaphysis of the infant is 



GROWTH DISC 



DIAPHYSIS—^ 



PERICHONDRIAL 

 BONE 



EPIPHYSIS-J 

 GROWTH DISC 



EPIPHYSIS 



DIAPHYSIS - 



MARROW 



a_ PERICHONDRIAL 

 BONE 



i ENDOCHONDRAL 

 BONE 



GROWTH DISC 



Fig. 179. — Diagrams illustrating four stages in the development of a long bone. 

 Perichondral bone cross-hatched; endochondral bone stippled; maiTow black; cartilage 

 unshaded. (Redrawn from Coming's "Human Embryology," after Duval.) 



--'BLOOD VESSEL 



>COMPACT BONE 



»MARROW CAVITY 



ARTICULAR LIGAMENT 

 Pig. 180. — Diagram of the structure of a long bone. (Redrawn after Fritz Kahn, 

 "Der Mensch," Albert Muller, Zurich.) 



converted into that of the adult by the continuous addition of new bone on 

 the outside of the shaft. At the same time the marrow cavity of the shaft 

 is enlarged through the destruction of bone on the inside of the shaft. In 



