_Classification._—According to location we distinguish toe-cracks, side-cracks, quarter-cracks, and bar-cracks. Those cracks which affect only the upper border of the hoof are called _coronary cracks_; those which are limited to the lower border of the hoof are sometimes designated _low cracks_ (plantar cracks); while those which are continuous from one border to the other are called _complete cracks_. If the crack passes through the entire thickness of the wall to the sensitive tissues underneath, it is called a _deep_ or _penetrating crack_, in contradistinction to the _superficial crack_ (Fig. 216). _Causes._—There are many. Besides wounds of the coronet, everything that impairs the elasticity of the horn, weakens the hoof, and causes an overloading of one-half of the hoof. Furthermore, great dryness and excessive work on hard streets. _Prognosis._—This will depend upon the age, kind, and location of the crack. A _low crack is without significance_ unless it is the remnant of an old coronary crack which has grown down. _Coronary cracks_, on the contrary, _are more serious_ because of the lameness which often accompanies them, and especially on account of the long duration of the healing process. The borders of the crack =never= grow together, and healing can only take place through healthy, unbroken horn growing down from the coronary band. (_a_) _Treatment of Coronary and Bar-Cracks._—If practicable, allow the affected horse to go barefoot; otherwise, the use of the =bar-shoe= for _all cracks_ is advised, because it will continuously protect the diseased section of wall from pressure by the shoe. If there are present still other diseases of the hoof (corns, contraction, flat or full hoof), the addition of a leather sole with packing will be most beneficial, not only in favoring the healing of the crack, but also in improving the form of the hoof and in favoring the cure of the other lesions. In all coronary cracks it is of advantage to assist healing by fastening or immobilizing the borders of the crack by one of the following methods: 1. By rivets (nails), which pass across the crack through holes previously drilled in the horn (Fig. 217). 2. By clamps or hooks, which by means of special pincers are forced into pockets previously burnt into the horn on opposite sides of the crack (Fig. 219, B). 3. By a thin iron plate placed across the crack and secured by small screws, such as are used in wood (Figs. 220, 221). 4. By means of a bandage to last one shoeing.