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THE BOXES AND JOINTS. 



trabeculse in the stroma of granulation tissue. This constitutes the 

 so-called callus of a uniting fracture (Fig. 479). 



Gradually the osteoid tissue becomes osseous, and the masses of car- 

 tilage and bands of periosteal and other fibrous tissue, under transform- 

 ations practically identical with those seen 

 in normal development, are converted into 

 bone. Thus by gradual absorption and 

 re-formation of bone in the usually redun- 

 dant provisional bony mass, and by the re- 

 adjustment of its vascular channels, the 

 healing, with more or less permanent de- 

 formity, is accomplished (Fig. 480). 



If the conditions be not favorable, the 

 healing of fractures may occur only by 

 fibrous-tissue formation, so that so-called 

 "false joints" may result. The healing of 

 other injuries and losses of substance oc- 

 curs by a process similar to that described 

 in fractures. 



INFLAMMATION. 



The periosteum, bone tissue, and mar- 

 row are so intimately connected that in 

 most cases they all share to a greater or 

 less degree in the pathological alterations 

 of the bones. But as sometimes one, some- 

 times another is most markedly involved, 

 it is convenient to consider separately here 

 the inflammatory changes by which they 

 are respectively affected. 



PERIOSTITIS. 



We may distinguish several forms of 

 periosteal inflammation. 



Simple Exudative Periostitis. This is 

 apt to occur in children and ill-nourished 

 persons after comparatively slight injuries 

 or from unknown causes. The periosteum 

 is thickened, succulent, congested, and 

 more or less abundantly infiltrated with 

 leucocytes. The periosteum becomes less 

 firmly adherent to the bone, and the cells 

 of the inner layers are increased in num- 

 ber. This form of inflammation may ter- 

 minate in resolution, or it may lead to other phases of inflammation. 



Suppurative Periostitis may begin as a simple or as a purulent inflam- 

 mation. The pus is formed in the inner layers of the periosteum, and 



FIG. 480. HEALED BONE AFTER 



FRACTURE. 



Shows redundant hard bone about 

 seat of fracture. 



