lameness: its causes and treatment. 323 



Caunett. — Tavo varieties of ori^inatinjj: cause may be reeognized ill 

 cases of fracture. Thev are the i)redisi)osin<^ and the occasional. 

 As to the first, ditierent species of animals ditl'er in the dejj:ree of their 

 liahility. That of the dojr is frreater 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 «reneral. are all to be taken into account. 



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

 ilriven over bad loatls are more exposed than light-draft or saddle 

 horses, and animals <:f dirt'erent ages are not ecjually liable. Dogs 

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

 their bones to have accjuircil 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 comlition of the icy roads ren- 

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

 occur most fre<|uently. The long bones, those especially which belong 

 to the extremities, are most fre<iuently the seat of fractures, from the 

 circumstance of their superficial position, their exposure to contact 

 and collision, and the violent muscidar etl'orts involved both in their 

 constant, rapid movement and their laI)or 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-estal)lished a pathological 

 fact to neeil 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 fiactures. or at least of 

 siich 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 ])redisposing 

 causes mention must not be omitted of such I>ony diseases as caries, 

 tubci-culosis, and others of the same class. 



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

 instances external traumatisms, as violent ctmtacts, 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 efl'ort to move too heavy a load : 

 a semisjiasmodic 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. perha])s to l)e 

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



