_(c) Necrosis of the Extensor Pedis_.--This may arise either as a result of spreading purulent infection of the coronary cushion, or as a result of direct injury immediately over it. The close relation of the terminal portion of this tendon with the pedal articulation, and the incomplete protection from outside injuries here afforded to the joint by the horny box, sufficiently points out the gravity of the condition. _(d) Penetration of the Articulation_.--This also may be a result either of the inroads made by pus, or of an actual wound. When occurring from the latter, it is seen more often than not in the hind-foot, being there caused by the calkin of the opposite foot. Where a wound in this position is characterized by an excessive flow of synovia, the condition should be suspected, and, if the wound be large enough, the little finger should be introduced in order to ascertain. Needless to say, the injury is a grave one. _(e) Sand-crack_.--Sand-crack is likely to result from tread when an injury is inflicted in the region of the quarter by a severe overreach. Treads, too, especially with the calkin of the hind-shoe, are especially apt to end in this way. In this latter instance the sand-crack usually has its origin in a nasty jagged tear at the top of the wall of the toe. _(f) Quittor_.--In one respect any suppurating wound at the coronet may be deemed a quittor. By indicating quittor as a complication of coronitis, however, we denote the more serious form of this disease, in which the wound has taken on a sinuous character, and conducted pus to invasion of the lateral cartilage. It is one of the worst complications we are likely to meet with in this condition, and will be found fully described in Chapter X. _(g) False Quarter_.--This complication of coronitis occurs when the injury or after-effect of the formation of pus has been severe enough to destroy outright a comparatively large portion of the papillary layer of the coronary cushion. To this condition we devote Section D of this chapter. _Prognosis_.--In giving a prognosis in a case of coronitis, attention should be paid to the manner in which the condition originated, and the extent, when present, of the wound. When the inflammatory swelling has arisen from bruising alone, without actual division of the skin, when the weather is that of winter, and the swelling showing a marked tendency to spread, then the prognosis must be guarded. As we have seen, this state of affairs is probably ushering in a condition of spreading suppuration of the coronary cushion, and considerable gangrene and sloughing of the skin. We have here no intimation as yet of how far the suppurative process may run, nor what important structures it may involve. Consequently, the guarded prognosis we have mentioned is imperative.