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.
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.
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.