Hind hoofs are more often affected than fore-hoofs. A favorite point of entrance is the lateral lacuna of the frog. Street-nail is favored by excessive thinning of the sole and frog. _Symptoms._—The symptoms are, as a rule, sudden pain followed by lameness. The first assistance is usually sought in the shoeing shop. If the cause of lameness be found to be a penetrating nail, piece of glass, or other pointed foreign body, it must be _carefully drawn out_, in doing which we should remove the _entire object_, not allowing pieces to break off and remain in the wound. Since it is always important to know in what direction and how deep the foreign body has penetrated, in order to be able to estimate the gravity of the wound, it is advisable in all cases to preserve the penetrating body, that it may be shown to the veterinarian, in case his services are required. [Illustration: FIG. 188. Shod hind foot, with splint dressing.] In slight injuries to the velvety tissue of the sole or frog, accompanied with moderate pain, it is of no benefit to enlarge the opening, though the horn of the sole or frog should be thinned for the space of an inch or more around the wound, followed by cooling applications. Deep, penetrating wounds accompanied with intense pain require the attention of a veterinarian. Often some form of dressing is necessary, and this is usually held in place by a special shoe. For slight injuries, such _splint-dressings_ as are shown in Figs. 188 and 189 are sufficient. Whether such a dressing be applied to the front or hind feet, the shoe should be _well concaved_ upon the hoof-surface. The dressing is held in place by thin splints of tough wood, which are firmly wedged between the shoe and hoof. [Illustration: FIG. 189. A practical “splint shoe” for hospital use.] In those rare cases in which it is necessary to maintain continuous pressure upon the seat of the wound, and to protect the entire plantar surface of the hoof, a _covered shoe_ (Figs. 190 and 191) is recommended. This shoe is provided with a sheet-iron cover, having at the toe a spur which fits into a corresponding hole in the toe of the shoe, and fastened at the heels by means of screw heel-calks. 3. Calk-Wounds of the Coronet. All tread-wounds of the coronet, caused by the calks of the opposite shoe, by the shoes of other horses, or by forging, are known as calk wounds, or simply as “calking.” The injury itself is either a bruise or a bruised wound, followed by inflammation of the coronary cushion and an interruption in the formation of horn at that point. It occurs most often in winter from sharp calks, especially on the hind feet. The common seat of the injury is the coronet of the toe and inner side of the foot. [Illustration: FIG. 190.] [Illustration: FIG. 191.