Studies from the laboratories of the Deptof Surgery . estrum, with thick involucrumand zone of separation: SQ, sequestrum; lu, involucrum; S, zone of separation. there are zones of calcification and ossification, the calcification occurringin dead tissue and ossification occurring where living bone cells areobserved. The simplest ty[>e of bone repair is seen following fractures. In aseries of fractures on animals, I have been able to follow the repairat various stages. Immediately following the fractures, there is hemor-rhage between the broken ends. Fibrin is then deposited and con- 17 tra
Studies from the laboratories of the Deptof Surgery . estrum, with thick involucrumand zone of separation: SQ, sequestrum; lu, involucrum; S, zone of separation. there are zones of calcification and ossification, the calcification occurringin dead tissue and ossification occurring where living bone cells areobserved. The simplest ty[>e of bone repair is seen following fractures. In aseries of fractures on animals, I have been able to follow the repairat various stages. Immediately following the fractures, there is hemor-rhage between the broken ends. Fibrin is then deposited and con- 17 traction of the clot occurs. In from about tive to ten days theorganization of the clot by the ingrowth of connective tissue tissue appears to take a definite lobulated arrangement, sothat if we look at a cut section, we find blood vessels and then areasof thin areolar connective tissue (Figs. 1 to 4). Calcium salts are then deposited in the avascular zones between theblood vessels. Early callus looks very much like the lobules of the. Fig. 16.—Lower power magnitication of terminal portion of sequestrum withsurrounding involucrum: A, sequestrum; B. granulation tissue; C, involucrum;D, terminal spicule of sequestrum shown under liigh power in Figure 17. liver. At first the blood vessels appear ak)ut this area of areolar tissueand then an area of new bone ai)pears. At a later period, the areolarzone is almost completely replaced by osteogenetic tissue. This processcontinues until there is a definite haversian canal system of adult the zones of exuberant callous formation, absorption of the calciumsalts takes place and scar tissue results. Bone atrophy occurs almostuniversally near tlie fractured ends. A great number of nuclei of thebone cells in the lacunae disappear. 18
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