DEVELOPMENT OF BONE. 1*73 



same bone; thus, the body of a long bone is completed a 

 very considerable period before its extremity. 



The growth of bones occurs and steadily progresses, as 

 that of every other tissue, till the individual reaches the 

 full stature; and this is accomplished by successively add- 

 ing new matter to the old. 



Mr. Jno. Hunter showed that the long bones grew by the 

 addition of osseous matter at their extremities. This he 

 proved by boring a hole at each extremity in the tibia of a 

 pig, and inserting a shot in each, The distance between 

 the two holes was accurately measured. After some months 

 the same bone was again examined, and it was found that 

 the distance between the shots was precisely the same, but 

 that the extremities had extended very considerably. 



The flat bones grow in breadth by a deposition at their 

 margins, while the thickness of bone is believed to depend 

 upon a secretion from the internal surface of the perios- 

 teum. 



When the full size of the bones has been attained, the 

 subsequent changes which occur are those of interstitial 

 deposit and absorption. 



Formation of Callus. Callus is the mode of union between 

 fractured bones, and resembles very much the original pro- 

 cess in the formation of bone. 



When the swelling subsides and the effusion of blood is 

 absorbed, coagulable lymph is poured out in the cavity of 

 the fracture. This corresponds to the first or mucous stage 

 in the foetal bone. An osseous ring is seen to encircle the 

 place of fracture, while in the interior there is found an 

 osseous pin. These are simply temporary arrangements, 

 which are removed by absorption, when the bones begin to 

 coalesce and become fused the one into another.* 



* The recent observations of Messrs. Paget, Stanly and Dr. Hamilton throw 

 great doubt on this statement of Dupuytren, in regard to provisional calliis. In 

 the lower animals, whose fractured limbs are subjected to so much greater 

 motion than ours, and which, under such circumstances, secrete so much more 

 bony matter, this account of the process of repair is undoubtedly correct ; but 

 in man, according to these more recent observers, no provisional callus has 

 been formed, unless undue motion and excitement has induced irritation. The 



