406 



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

 cracks, than those accustomed to stables. Small feet, with tliick, 

 hard hoofs, and feet which are excessively large, are more susceptible 

 to sand-cracks than those of better in-oportion. A ijredisposition to 

 quarter-crack exists in contracted feet, and in those where the toe 

 turns out or the inside quarter turns under. 



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

 together with such diseases as canker, quittor, grease, and suppura- 

 tive corns, must be included as occasional predisposing causes of sand- 

 cracks. 



Fast work on hard roads, jumping, and blov.s on the coronet, 

 together with calk wounds of the feet, are accidental causes of quar- 

 ter-cracks in particular. Toe-cracks are more likely to be caused bj' 

 heavy jJuUing on slippery roads and pavements or on steep hills. 



Si/nqdoms. — The fissure in the horn is ofttimes the onl3' evidence 

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

 from casual view by mud, ointments, tar, wax, jiutty, gutta-percha, 

 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 

 surface. In these cases the existence of the injury maj' be suspected 

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

 follows the direction of the horny fillers, but the trouble can only be 

 positively diagnosed by paring away the outside laj'Crs of horn until 

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

 close apposition when the foot receives the weight of the body, but 

 when the foot is raised from the ground the fissure opens. In quar- 

 ter-crack the opposite is true, and the fissure closes when the weight 

 is removed from the foot. As a rule sand-ci-acks begin at the coro- 

 nary band, and as they become older they not only extend downward, 

 but they also grow deeper. In old cases, particularly in toe-crack, 

 the horn on the borders of the fissure loses its vitalitj-^ and scales off, 

 sometimes through the greater part of its thickness, leaving behind a 

 rough and irregular channel exteaiding from the coronet to tlie end of 

 the toe. 



In many cases of quarter-crack, and in some cases of toe-crack as 

 Avell, if the edges remain close together, with but little motion, the 

 fissure is dry, but in other cases a thin, offensive discharge issues 

 from the crack and the ulcerated soft tissues, or a fungus-like growth 

 protrudes from the narrow oi^ening. 



Wlion the cracks are deep and the ])iotion of their edges consider- 

 able, so that the soft tissues are bruised and pinched with every move- 

 ment, a constant inflammation of the parts is maintained and the 

 lameness is s(^vere. 



Ordinarilj^, the lameness of sand crack is slight Avhen the patient 

 walks; but it is greatly aggravated Avhen he is made to trot, and the 



