A hollow wall is one in which a separation has occurred between the middle layer of the wall and the keraphyllous layer. This crack or separation always extends in the direction of the layers of the wall ([Fig. 223, b]).
Fig. 223.
An imaginary transverse vertical section of a hoof
showing (a) loose wall and (b) hollow wall.
Occurrence.—Quite rare.
We should suspect a hollow wall when a part of the wall rounds out prominently beyond the rest, and gives forth a hollow (resonant) sound when struck. The white line presents a crack, yet we should hesitate to form a conclusion as to the extent of the separation from the extent of the crack along the white line, since the latter may be considerably smaller. The separation extends higher up the wall than in the case of loose wall, frequently to the coronet. The cavity is usually filled with crumbling, disintegrated horn.
Hollow wall is not often accompanied by pain. Lameness may arise, however, if the hollow section of wall assists in bearing the body-weight, and if the animal does fast work upon paved streets.
Causes.—Mechanical influences resulting in chronic inflammation of fleshy leaves.
Treatment.—A cure is possible, but requires considerable time. In shoeing, which should always aim to relieve pressure from the hollow section of wall, we cleanse the cavity and fill it with oakum and tar, crude turpentine, or wax. Where the separation is very extensive we use a bar-shoe.
The time required for complete cure of hollow and loose walls will depend upon the height of the separation (see growth of the hoof, [page 82]).