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the outer parts of the wall, or it may be deep, involving the whole 

 thickness of the wall aud the soft tissues beneath. 



The toecrack is most likely to be complete — that is extending from 

 the coronary band to the sole — while the quarter- crack is nearly al- 

 ways incomplete, at least when of comparatively recent origin. Sand- 

 cracks are most serious when they involve the coronary band in the 

 injury. They may be complicated at any time by hemorrhage, inflam- 

 mation of the laminse, suppuration, gangrene of the lateral cartilage 

 and of the extensor tendon, caries of the coffin bone, or the growth of 

 a horny tumor known as a keraphyllocele. 



Causes. — Relative dryness of the horn is the principal predisposing 

 cause of sand-cracks. Excessive dr^mess is perhaps not a more prolific 

 cause of cracks in the horn than alternate changes from damp to dry. 

 It is even claimed that these injuries are more common in animals 

 working on wet roads than in those working on roads that are rough 

 and dry; at least these injuries are not common in mountainous coun- 

 tries. Animals used to running at pasture when trausferj^-ed to stables 

 with, hard, dry floors are more liable, especially to quarter-cracks, than 

 those accustomed to stables. Small feet, with thick, hard hoofs, and 

 feet which are excessively large, are more susceptible to sand-cracks 

 than those of better proportion. A predisposition to quarter crack ex- 

 ists in contracted feet, and in those where the toe turns out or the inside 

 quarter turns under. 



Heavy shoes, large nails, and nails set too far back toward the heels, 

 together with such diseases as canker, quittor, grease, and suppurative 

 corns must be included as occasional ijredisposing causes of sand-cracks. 



Fast work on hard roads, jumping, and blows on the coronet, together 

 with calk wounds of the feet, are accidental causes of quarter-cracks in 

 particular. Toe-cracks are more likely to be caused by heavy pulling 

 on slippery roads and pavements or on steep hills. 



Symptoms. — The fissure in the horn is ofttimes the only evidence of 

 the disease ; and even this may be accidentally or purposely hidden 

 from casual view by mud, ointments, tar, wax, putty, gutta purcha, or 

 by the long hairs of the coronet. 



Sand-cracks sometimes commence on the internal face of the wall, 

 involving its whole thickness, excepting a thin layer on the outer sur- 

 face. In these cases the existence of the injury may be suspected from 

 a slight depression, which begins near the coronary band and follows 

 the direction of the horny fibers, but the trouble can only be positively 

 diagnosed by paring away the outside layers of horn until the fissure 

 is exposed. In toe-cracks the walls of the fissure are in close apposi- 

 tion when the foot receives the weight of the body, but when the foot 

 is raised from the ground the fissure opens. In quarter crack the op- 

 Ijosite is true, and the fissure closes when the weight is removed from 

 the foot. As a rule sand-cracks begin at the coronary band, and aa 

 they become older they not only extend downward, but they also grow 



