A left fore os pedis viewed in profile, showing ossification of the external lateral cartilage: _a_, dotted line shows normal line of union of cartilage with wing of os pedis; _b_, ossified portion (“side bone”). The unossified cartilage has been removed by maceration.] The disease can only be diagnosed with certainty after the upper part of the cartilage has ossified. The coronet is then rather prominent (bulging), and feels hard. The gait is short, and cautious, and well-marked lameness often follows severe work. As _causes_, may be mentioned predisposition in heavy lymphatic horses, and violent concussion or shock due to fast work upon hard roads. The disease is _incurable_. A special method of shoeing is only necessary when the outer cartilage is ossified and the quarter upon that side is contracted. After removing the old shoe, whose outer branch is, as a rule, more worn away than the inner, the outer wall will always be found too high, due to the fact that there has been little or no expansion and contraction in this quarter and, therefore, little or no wear of the horn against the shoe. The hoof is therefore wry,—on the outside too high, and on the inside too low. This shows us how the foot should be dressed so as to obtain a proper base of support and a uniform wear of the shoe. The most suitable shoe is a _flat shoe_, whose outer branch must be wider than the inner. It is so applied that the inner branch follows the edge of the wall closely, while the outer branch must be full and at the quarter must extend beyond the wall far enough to touch a perpendicular line dropped from the coronet (Fig. 215). The shoe must, therefore, be punched deep (coarse) on the outer branch and fine on the inner. A side-clip must be placed on the outer branch, because in time the outer half of the hoof will again be too high. _Bar-shoes and rubber pads are injurious when both cartilages are ossified_, but may be used when there is partial ossification of _but one cartilage_, especially if corns are present. [Illustration: FIG. 214. Right fore-hoof whose form has changed as a result of ossification of the external lateral cartilage.] [Illustration: FIG. 215. Shoe with broad outer branch, for the hoof shown in the preceding cut.] B. Disturbances of Continuity of the Hoof. 1. CRACKS. Interruptions of continuity of the wall extending in the direction of the horn-tubes are known as cracks or seams. They have, according to their location, degree, and extent, not only various names, but also a varying significance. _Occurrence._—On the inner side of front hoofs, especially of horses that stand base-wide; on hind hoofs, usually at the toe. [Illustration: _Fig. 216._ Hoof exhibiting a coronary crack, a plantar or low crack, and a complete deep crack, the latter with a nail ready to be clinched.]