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CHAPTER IV. 

 THE GROWTH OF BONE. 



Recent change in our conception of the growth of bone— Osteo- 

 blasts — Increase in the length of bone — Increase in the girth of 

 bone — Function of the periosteum — The regenerative powers of 

 bone — Transplantation of bone — Application of modern researches 

 to surgical practice — Relation of the ductless glands to the growth 

 of bone. 



TWO closely allied problems, how bones increase in 

 length and girth in the child, and how regenera- 

 tion of new bone takes place after loss or injury, are 

 of great interest and practical importance in surgery. 

 Every case of separation of an epiphysis by accident, 

 and every operation on the growing end of a bone 

 in children, involves a consideration of the first 

 problem ; every case of fracture, necrosis, periostitis, 

 or osteomyelitis depends for its proper understand- 

 ing and rational treatment upon the second. A very 

 important research has recently been pubhshed which 

 necessitates a radical change in some of our con- 

 ceptions of this subject. 



We may summarize the traditional teaching thus. 

 Bone is laid down by certain cells called osteoblasts. 

 In young animals, these are the direct descendants 

 of cartilage cells. When the cartilage becomes 

 vascular, the cells undergo proliferation for a time ; 

 when they assume their individual maturity they 

 cease to divide, and lay down calcareous salts all 



