In the Suppurating Corn, as in moist corn, we have pathological changes due to the tissue reaction to the injury, plus the addition of pus organisms.  Confined within the horny box we have a discharge that, by reason of the living and constantly multiplying elements it contains—­the pus organisms—­is always increasing in bulk.  This must be at the expense of the softer structures of the foot.  Accordingly, as the formation of pus increases, we get pressure upon and final gangrene of the sensitive sole and of the sensitive laminae of the bars and the wall.  With no outlet below, the pus formation increases until finally it finds its way out of the hoof by emerging at the coronet.

This in some instances it may do by confining its necrotic influences solely to the sensitive laminae of the wall, in which case, if a dependent orifice is quickly made at the sole, the injury to the laminae is soon repaired by the healthy tissue remaining.

In other cases, however, the necrosis has spread deeper.  Caries of the os pedis, of the lateral ligaments of the pedal-joint, or of the lateral cartilages, is a result.  When this occurs the exuding discharge from the coronet becomes thinner and more putrescent, and its feel, when rubbed between the fingers, sometimes gritty with minute fragments of broken-up bone.  Here, unless operative measures prevent it, necrosis soon spreads deeper still.  The deeper portions of the os pedis become affected.  The capsular ligament of the joint is penetrated by the suppurative process, and a condition of septic arthritis results.  The cavity of the joint becomes more or less tensely distended, according to the amount of drainage present, which in this case is almost nil, with matter in a state of putrescence.  As a consequence, the surrounding ligaments become softened and yield, and the articular surfaces displaced.  The articular cartilages also suffer, become necrotic in patches, and frequently wholly destroyed.  The end result is one of anchylosis of the joint and permanent lameness.

Prognosis.—­With the ordinary dry corn a return to the normal may nearly always be looked for.  Similarly, with moist corn, and even with careful treatment of the suppurating variety, the same favourable termination may be looked for and promised.

What cannot so safely be assured is that a relapse will not occur.  In other words, the extent of the injury, no matter how serious, does not often offer anything that cannot be overcome by Nature and careful surgery; but the conformation of the animal does.  A vicious predisposing conformation once there is there always, and although the injury resulting from it may easily give way to correct treatment, the same injury is bound to re-occur when the animal is again put to work.