293 



the eqaine constitution. Among local predisposing affections mention 

 must not be omitted of such bony diseases as caries, tuberculosis, and 

 others of the same class. 



Occasional or '^ efficient " causes of fracture are in most instances ex- 

 ternal traumatisms, as violent contacts, collisions, falls, etc., or sud- 

 den muscular contractions. These external accidents are various in 

 their character, and are usually associated with quick muscular exer- 

 tion. A violent, ineffectual effort to move too heavy a load ; a semi- 

 spasmodic bracing of the frame to avoid a fall or resist a pressure 5 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 accidents happen- 

 ing hourly, by which our equine servants become sufferers. We may 

 add to these the fracture of the bones of the vertebra, occurring when 

 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 nnder these cir- 

 cumstances may be called with propriety indirect, while one which 

 has resulted from a blow or a fall differently caused is of the direct kind. 



We now return to the first items in our classification of the varieties 

 of lameness, 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 impossibility of 

 the performance of its natural function, in sustaining the weight of the 

 body and contributing to the act of locomotion, is usually complete, 

 though the degree of powerlessness 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 complex fibrous structure, is, in a 

 certain degree, not incompatible with some amount of resting of 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 exer- 

 cise any agency whatever in the support of the body. And in a frac- 

 ture of the lower jaw it would be obviously futile to expect it to con- 

 tribute materially to the mastication of food. 



A fracture seldom occurs which is not accompanied with a degree of 

 deformity, greater or less, of the region or the leg affected. This is 

 due to the exudation of the blood into the meshes of the surrounding 

 tissues and to the displacement which occurs between the fragments of 

 the bones, with subsequently the swelling which follows the inflamma- 

 tion of the surrounding tissues. The character of the deformity will 

 mainly depend upon the manner in which the displacement occurs. 



In Q, normal state of things the legs perform their movements with 



