302 DISEASES OP THE HORSE. 



When a simple fracture has been properly treated and the broken 

 ends of the bone have been securely held in coaptation, one of two 

 things will occur. Either and this is the more common event there 

 will be a union of the two ends by a solid cicatrix, the callus, or the 

 ends will continue separated or become only partially united by an 

 intermediate fibrous structure. In the first instance the fracture is 

 consolidated, or united; in the second there is a false articulation, or 

 pseudarthrosis. 



The time required for a firm union or true consolidation of a frac- 

 ture will vary with the character of the bone affected, the age and 

 constitution of the patient, and the general conditions of the case. 

 The union will be perfected earlier in a young than in an adult ani- 

 mal, and sooner in the latter than in the aged, and a general healthy 

 condition is, of course, in every respect, an advantage. 



The mode of cicatrization, or method of repair in lesions of the 

 bones, has been a subject of much study among investigators in 

 pathology, and has elicited various expressions of opinion from those 

 high in authority. But the weight of evidence and preponderance of 

 opinion are about settled in favor of the theory that the law of repa- 

 ration is the same for both the hard and the soft tissues. In one case 

 a simple exudation of material, with the proper organization of newly 

 formed tissue, will bring about a union by the first intention, and in 

 another the work will be accompanied by suppuration, or union by the 

 second intention, a process so familiar in the repair of the soft struc- 

 tures by granulation. 



Considering the process in its simplest form, in a case in which it 

 advances without interruption or complication to a favorable result, 

 it may probably be correctly described in this wise: 



On the occurrence of the injury an effusion of blood takes place be- 

 tween the ends of the bone. The coagulation of the fluid soon fol- 

 lows, and this, after a few days, undergoes absorption. There is then 

 an excess of inflammation in the surrounding structure, which soon 

 spreads to the bony tissue, when a true ostitis is established, and the 

 compact tissue of the bone becomes the seat of a new vascular organi- 

 zation, and of a certain exudation of plastic lymph, appearing be- 

 tween the periosteum and the external surface of the bone, as well as 

 on the inner side of the medullary cavity. After a few days the ends 

 of the bone thus surrounded by this exudate become involved in it, 

 and the lymph, becoming vascular, is soon transformed into cartilag- 

 inous, and in due time into bony, tissue. 



Thus the time required for the consolidation of the fractured seg- 

 ments is divisible into two distinct periods. In the first they are sur- 

 rounded by an external bony ring, and the medullary cavity is closed 

 by a bony plug or stopper, constituting the period of the provisional 

 callus. This is followed by the period of pernmnent cattv*, during 



