MODES OF UNION. 



81 



laccomplialiea the union of a fracture without two successive de- 

 posits of callus, and Dupuytren arranged the phenomena, from 

 the time of fracture to the exact and complete revmion, into five 

 different periods. 



In the first stage, comprehending a period of eight or ten days, 

 hlood is extjavasated into the medullary canal between the 

 fragments, and under the periosteum, raising up the latter from 

 the bone for some distance above and below the fracture ; the 

 medullary membrane becomes swollen and separated from the 

 bone, and the periosteum is not only raised from the bone, but 

 also becomes red, soft, swollen, and pretematuraUy vascular. 

 The fragments of bone may thus be 

 said to be surrounded with blood, 

 which not only fills the medullary 

 canal and space between ihe frag- 

 ments, but also separates the latter 

 from the detached periosteum. This 

 blood may b^ organized or become 

 absorbed, and liquor sanguinis effused 

 into the parts at first occupied by it. 



In the second stage, comprising the 

 interval between the tenth or twelfth 

 to the twentieth or twenty-fifth day, 

 the " tumour of callus," as it is called 

 by Dupuytren, is formed. The sub- 

 stance between the periosteum and 

 bone is converted into a structure 

 like fibro-cartilage, and within the 

 medullary canal there is also deve- 

 loped a fibro-cartilage, but the sub- 

 stance between the fragments retains 

 the appearance of coagulable lymph. 



In the third stage, extending from 

 the twentieth or twenty -fifth day to 

 the thirtieth, fortieth, or sixtieth day, 



„„„^,^-„ . 1 . ■, , tarsal, showing the plug within 



accordmg to age and strength, the the medullary canaL The plug 

 fibro-cartilage between the periosteum ^ "^^^^^ 

 and bone, and that within the medullary canal, are both con- 

 verted into bone, the external forming a ring, ferrule, or clasp ; 

 and the internal a plug, or peg, filling up the medullary can^l, 



u 



Fio. 10. — Fractnre of meta- 



