222 



HEALTH AND DISEASE 



throughout the healing process, a condition favourable of course to re- 

 paration, and very much to be desired. 



In others, however, the fracture is accompanied or followed by more 

 or less displacement of the divided parts, and all the bad consequences 

 which attach to it. 



This separation of the broken pieces may result from the same cause, 

 and at the same time, as the fracture, or it may occur some time afterwards 

 by the weight of the body forcing the parts asunder; or by movement, or 

 as a result of the contraction of muscles which are attached to them. 



The liability to displace- 

 ment is much greater in 

 some bones than in others. 

 In the canon it is almost 

 invariable, while in the pas- 

 tern it is comparatively rare. 

 This difference will be best 

 understood by reference to 

 fig. 327, where it will be seen 

 that nearly the whole of the 

 front and back of the pastern 

 bones, and to a less extent 

 the sides, have attached to 

 them strong ligaments and 

 tendons, so that when either 

 of them is broken the parts 

 are held firmly in their po- 

 sition, and unless the force 

 acting upon them is very considerable, displacement is prevented. 



Displacement of the broken fragments may be immediate, i.e. may occur 

 at the time of the accident, or it may be deferred for a period varying 

 between a few hours and a few days, and during the interval between 

 the fracture and the separation of the broken pieces many animals have 

 been known to continue to perform ordinary work without showing in- 

 convenience. 



Causes. Two classes of causes are recognized as conducing to the 

 fracture of bones, viz., predisposing and exciting. 



Predisposing Causes. For various reasons some bones are more 

 liable to fracture than others, and this represents their predisposition. 



In looking over the body it is not difficult to see that certain bones 

 are much more exposed to collision and to external violence by virtue 

 of their position than others Of these the points of the haunch projoot- 



Fig. 326. Fractures 

 1, Transverse. 2, Oblique. 3, Longitudinal. 



