80 



FRACTURES AND DISEASES OF BONES. 



joint having extensive motion, and that the frachired ends can be 



kept at rest. 



An early consequence of fracture appears to be an exudation 



of lymph, which is at first dimly granular, but becomes, at a 



later period, ruddy, elastic, or moderately firm and succulent. 



It soon attains firmness, when it is called a callus. 



There are two methods according to which the callus may 



be placed. In one method the broken 

 ends or smaller fragments of bone 

 are completely enclosed in a new 

 material ; they are ensheathed or held 

 together by it, as two portions of a rod 

 might be by a ring fastened round them 

 both. 



The new material, in such a case, 

 surroundim? the fracture is termed 

 " provisional," " external," or " en- 

 sheathing" callus. 



In the other method the new mate- 

 rial is only placed between those 

 parts of the broken bone whose sur- 

 faces are opposed ; between these, it 

 is inlaid, filling the space that would 

 else exist between them, and uniting 

 them by being fixed to both (like 

 the process of gluing two pieces of 

 wood). Eeparative material thus 

 placed has been called intermediate 

 callus. In either method, tliere is 

 usually some reparative material de- 

 posited in and near the medullary 

 tissue, and this is called interior 

 callus. 



In fractures that occur in the lower 

 animals, with the exception of those 

 Fig. 9.— Oblique fracture of found in the fixed bones, the en- 



tae tibia, with external (ensheath- ... ^ . 



irig) callus, marked a and b. The sheathmg calhlS IS USUal. 



Hne extending from a indicates j^j,^^^^ ^|^q researches of Hallcr, 



the seat of the fracture, the new , 



deposit (callus) being purposely Duhamcl, Huntcr, Dupuytrcn, raget, 

 ^^°^°^^^- and Stanley, we find that nature never 



