DISEASES OF THE HOESE. 209 



bility to fractures is too constant and well-established a pathological 

 fact to need more than a passing reference. The history of rachitis, 

 of melanosis, and of osteoporosis, as related to an abnormal frangi- 

 bility of the bones, is a part of our common medical knowledge. 

 There are few persons who have not known of cases among their 

 friends of frequent and almost spontaneous fractures, or at least of 

 such as seem to be produced by the slightest and most inadequate vio- 

 lence, and there is no tangible reason for doubting an analogous con- 

 dition in individuals of the equine race. Among local predisposing 

 causes mention must not be omitted of such bon}^ diseases as caries, 

 tuberculosis, and others of the same class. 



Exciting, occasional, or "efficient" causes of fracture are in most 

 instances external traumatisms, as violent contacts, collisions, falls, 

 etc., or sudden muscular contractions. These external accidents are 

 various in their character, and are usually associated with quick mus- 

 cular exertion. A violent, ineffectual effort to move 'too heav}^ a load; 

 a semispasmodic bracing of the frame to avoid a fall or resist a pres- 

 sure; a quick jump to escape a blow; stopping too suddenly after 

 speeding; struggling to liberate a foot from a rail, perhaps to be 

 thrown in the effort — all these are familiar and easy examples of acci- 

 dents happening hourl}^ l)y which our equine servants become suffer- 

 ers. We may add to these the fracture of the bones of the vertebrro, 

 occurring w^hen casting a patient for the purpose of undergoing a 

 surgical operation, quite as much the result of muscular contraction 

 as of a preexisting diseased condition of the bones. A fracture 

 occurring under these circumstances may be called with propriety 

 indirect, while one which has resulted from a blow or a fall differently 

 caused is of the direct kind. 



Symptoms. — We now return to the first items in our classification 

 of the varieties of fractures for the purpose of bringing them in turn 

 under an orderly review, and our first examination will include those 

 which belong to the first category, or the complete kind. Irregularity 

 in the performance of the functions of the apparatus to which the 

 fractured bone belongs is a necessary consequence of the existing 

 lesion, and this is lameness. If the broken bone belongs to one of the 

 extremities, the impossibilit}^ of the performance of its natural func- 

 tion, in sustaining the weight of the body and contributing to the act 

 of locomotion, is usually complete, though the deg-ree of disability will 

 vary according to the kind of fracture and the bone which is injured. 

 For example, a fracture of the cannon bone without displacement, or 

 of one of the phalanges which are surrounded and sustained by a com- 

 plex fibrous .structure, is, in a certain degree, not incompatible with 

 some amount of resting on the foot. But, on the contrary, if the 

 shank bone, or that of the forearm be the implicated member, it would 

 be very difficult for the leg to exercise any agency whatever in the 



