lameness: its causes and tbeatment. 323 



Causes. — Two varieties of originating cause may be recognized in 

 cases of fracture. They are the predisposing and the occasional. 

 As to the first, different species of animals diifer in the degree of their 

 liability. That of the dog is greater than that of the horse, and in 

 horses the various questions of age, the mode of labor, the season of 

 the year, the portion of the body most exposed, and the existence of 

 ailments, local and general, are all to be taken into account. 



Among horses, those employed in heavy draft work or that are 

 driven over bad roads are more exposed than light-draft or saddle 

 horses, and animals of different ages are not equally liable. Dogs 

 and young horses, with those which have become sufficiently aged for 

 their bones to have acquired an enhanced degree of frangibility, are 

 more liable than those which have not exceeded the time of their 

 prime. The season of the year is undoubtedly, though in an inci- 

 dental way, an important factor in the problem of the etiology of 

 these accidents, for though they may be observed at all times, it is 

 during the months when the slippery condition of the icy roads ren- 

 ders it difficult for both men and beasts to keep their feet that they 

 occur most frequently. The long bones, those especially which belong 

 to the extremities, are most frequently the seat of fractures, from the 

 circumstance of their superficial position, their exposure to contact 

 and collision, and the violent muscular efforts involved both in their 

 constant, rapid movement and their labor in the shafts or at the pole 

 of heavy and heavily laden carriages. 



The relation between sundry idiosyncrasies and diathesis and a lia- 

 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 dividuals of the equine race. Among local predisposing 

 causes mention must not be omitted of such bony 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 heavy 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- 



