Always, however, the presence of septic infection must be suspected and looked for. When this has occurred, the inflammatory swelling becomes larger and more diffuse, and the animal fevered. This is then followed by a slough of the injured part. A portion of the skin first becomes gray, or even black, in appearance, and around it oozes an inflammatory exudate, or even pus. The skin immediately adjoining the spot of necrosis is swollen and hyperaæmic, and extremely painful and sensitive. Later, the necrosed portion becomes cast off, and an open wound remains. This as a rule marks the turning-point in the case. The pain and other symptoms rapidly abate, and the wound, with proper attention, is not more than ordinarily difficult to treat. In the case of an actual wound the symptoms are probably less severe. The injury is, in this instance, the sooner detected, and remedial measures put into operation. In this manner the formation of septic material is often checked, and nothing but the treatment of a simple wound demands attention. There are, however, complications. _Complications--(a) Diffuse Purulent Inflammation of the Sub-coronary Tissue_.--This condition is brought about by the spread into the loose tissue of the coronary cushion of the septic material introduced by the tread. The whole coronet in this instance becomes excessively swollen, hot, and painful, and the dangerous nature of the complication is evident enough when the structure and situation of the parts involved is considered. The amount of tendinous and ligamentous material in the neighbourhood offers a strong predisposition to necrosis, and the necrosis, with its attendant formation of pus, offers a further danger when the close proximity of the pedal articulation and the unyielding character of the horny box is considered with it. The pus formed in this condition may remain confined to the coronet and break through the skin as an ordinary abscess, or it may, before so doing, burrow beneath the wall, and invade the sensitive laminæ. In this case, whenever portions of the secreting layer of the keratogenous membrane are destroyed, or perhaps only temporarily prevented from fulfilling their horn-producing functions, then corresponding cavities in the horn are the result (see Fig. 109). _(b) Purulent Arthritis_.--Only too readily the pus so formed tends to penetration of the articulation and the causation of an incurable arthritis (see Chapter XII.). [Illustration: FIG. 109.--MESIAL SECTION OF A HOOF ILLUSTRATING THE CONDITIONS FOLLOWING UPON CORONITIS. _a_, Cavity in the horn of the wall; _b_, enlargement of the coronet and the horn of the wall following subcoronary suppuration; _c_, cavity in the wall following purulent inflammation of the sensitive laminæ; _d_, hollow in the horn of the sole consequent upon suppuration of the sensitive sole.]