RESTORATION OF FRACTURED BONES. 49 



tion of callus, is due to Dupuytren* and Sanson. According 

 to these, the union of fragments of bone, is efiected by the for- 

 mation of two successive stages of callus. One which is pro- 

 visional or temporary, is completed usually in the space of 

 thirty or forty days, by the union and ossification of the perios- 

 teum, cellular tissue, and even in some cases of the muscles, 

 so as to constitute an external ring — and of the medullary mem- 

 brane, so as to constitute an internal plug. The other, which 

 he calls final or permanent, is formed by the re-union of 

 the surfaces of the fracture, with a solidity so much superior 

 to that of the bone in other parts, that it will break any where 

 again, rather than at that point, and which is never fully com- 

 pleted, notwithstanding the limb appears earlier than this restored 

 to its proper uses, under eight, ten, or twelve months, by which 

 time all the provisional callus has been removed, and the medul- 

 lary canal is completely re-established. 



— Dupuytren divides the successive organic changes, which 

 attend the formation of callus, \x\io five periods. 

 — The first period, extends from the time of the fracture to 

 the eighth or tenth day, and is characterized by the following 

 phenomena : the medullary membrane, the medulla, the perios- 

 teum, cellular tissue, and sometimes the muscles themselves, are 

 torn at the time the fracture takes place ; blood escapes from 

 the ruptured vessels, surrounds the fragments, spreads in the 

 medullary canal and infiltrates in the surrounding tissue : the 

 hemorrhage stops ; a slight inflammation is developed in all 

 these parts, which is the first step towards the production of 

 the callus. The cellular tissue surrounding the bone, becomes 

 very vascular, is thickened, loses its elasticity, and acquires a 

 great degree of consistence ; it sends irregular processes into 

 the neighboring muscles, transforms them to a greater or less 

 extent into an analogous tissue, and unites them in a common 

 structure with the periosteum, v^^hich is also much thickened 

 and very vascular. A nearly similar change takes place in the 

 cavity of the bone in respect to the medulla and its membrane. 

 The calibre of the medullary canal is contracted by the thickening 



♦Journal Univ. de Med. lorn. 20. 



5 



