DISEASES or BONES 151 



DISEASES OP BONES. 



Fractures. 



Whai is a fracture f 



A sudden forcible separation of the continuity of a bone. 



What are the causes offractv/re ? 



1. Exciting or immediate causes. 



2. Predisposing causes. 



Describe the exciting causes. 



Fractures of this last class are subdivided into (a) frac- 

 tures by external violence, (6) fractures by muscular action. 

 In those due to external violence, as a blow, kick, etc., the 

 fracture occurs at the point struck, or through transmission 

 of the force by a bone or chain of bones at a distant point 

 with more or less damage to the overlying soft parts. In 

 those due to muscular action the bone is broken by sudden 

 and violent contraction of muscles directly or indirectly 

 attached to the bone. Again, those the result of external 

 violence may be by direct violence or indirect violence ; the 

 former occur at the point struck, the latter at a distance from 

 the point of application of the force, the blow being trans- 

 mitted through a bone or chain of bones. 



Exemplify the direct causes of fractures. 



Direct external violence : Fracture of the metatarsus 

 from a kick. 



Indirect external violence : The animal falls and sits 

 down like a dog, followed by fracture of some portion of the 

 vertebral -column. The animal's hoof is caught in a street 



