6o Journal of Agriculture . [8 Jan., 1908. 



is called a " soft callus." In the case of long bones with a medullary 

 canal this soft callus ensheaths the fracture on the outside and also exisits 

 as a plug on the inside. A quantity of the jelly-like lymiph is also exuded 

 between the broken surfaces and serves to prevent their rubbing together. 

 From the twelfth until the thirtieth day the soft callus is undergoing con- 

 version into bone, so forming what is called a " provisional callus." In 

 long bones the provisional callus exists as a ring or ferrule of 

 bone embracing the broken ends externally and as a bony plug filling 

 the medullarv canal ; and by means of it the broken surfaces are kept 

 fixed in position. During this stage the soft callus between the broken 

 surfaces is converted into dense fibro-cartilage which during the next month 

 becomes transformed into bone. When this is accomplished it is called a 

 " permanent callus." The union of the fractured surfaces being now 

 completed there is no need for the continuance of the provisional bony 

 callus ensheathing the bone and plugging the medullary canal. It is con- 

 sequently gradually absorbed, but the process is a slow one, taking four 

 or five months to accomplish, and during this time the permanent callus 

 becomes hardened and strengthened to a normal degree. The ensheathing 

 tonv callus is seldom completely removed, a roughened surface usually 

 remaining bv which on careful manipulation the previous existence of a 

 fracture can be determined. (See Figs. 4 and 5.) 



Fig. 5. Repair of fractures. Section of fractured bone (femur) showing 

 "provisional callus'" surrounding fractured ends and also filling the medullary or 

 marrow canal. (After Williams.) 



When movement is allowed to occur the " knitting " process occupies 

 a much longer period and oftentimes the (permanent callus or bony union 

 is never formed. Instead, the material between the broken surfaces 

 develops into fibrous tissue by which the broken bones are held together, 

 so forming what is called a false joint. 



Diagnosis of Fractures, 



In situations where the fractured bone is thickly covered with flesh 

 the symptoms of fracture are obscure and the diagnosis difficult. In most 

 cases, however, there is sudden and extreme lameness the seat of which is 

 ea.sily ascertained by an evident deformity of the part and by its abnormal 

 mobility. When limb bones are broken the parts below hang loose and 

 pendulous, no weight can be borne on the limb, there is usually great pain 

 evinced on movement or manipulation of the part and a grating or crepita- 

 tion rnay be felt or perhaps heard when the broken surfaces rub together 

 during movement. An exception to the foregoing occurs in some fractures 

 of the tibia (bone of the gaskin) when the strong periosteum holds the 

 fractured bones in position and prevents displacement. A considerable 

 swelling quickly appears if the tissues round about are loose, and general 

 fever or distress mav be exhibited. 



