Causes.—­This form of quittor has its origin more often than not in contusions, punctures, or wounds of the region severe enough to cause death of a small portion of the tissues.  In this case the low vitality of the parts does not allow of the dead portion being removed piecemeal by a process of phagacytosis, as is usually the case with similar injuries elsewhere.  Instead, the tissues around, aided by a process of suppuration, cast the offending portion off as a slough.  It is the wound remaining after the slough which we may really regard as a quittor.  In this connection may be considered as causes blows from falling shafts, self-inflicted treads, or treads from other horses, overreach, etc.  On the other hand, simple or cutaneous quittor may occur without ascertainable cause.  In this case we can only explain its appearance, as we did that of simple coronitis (see p. 231), by attributing it to septic infection through a wound or a blow that is able to inoculate the skin, yet which is insufficient to cause pain, or in any other way attract the attendant’s notice.  Meanwhile, the spot of infection thus started spreads, and the end result is an abscess in the coronary region, again accompanied with necrosis and sloughing of more or less skin and other tissue, which terminates by discharging its contents and leaving behind a wound which again constitutes a cutaneous quittor.  Thus, as with simple coronitis, anything lowering the vitality of the parts, and so favouring infection of the skin, may bring about a quittor.  Walking through much water in the winter months, through the dirt and mud of our streets, through melting ice and snow, or through anything in the nature of a chemical irritant, may be looked upon as a cause.

Symptoms.—­Whether commencing from an ascertainable injury, or beginning at first unnoticed, cutaneous quittor is characterized sooner or later by the appearance of an inflammatory swelling, usually confined to the seat of injury.  Heat and tenderness are present, and the animal is lame.

Later the inflammatory swelling becomes more profuse, the animal is fevered, and the symptoms of lameness increased.  Poulticing is at this stage perhaps resorted to.  By its means the process of suppuration is aided, and the swelling (at first tense and hard) either becomes gradually softened, its contents discharged, and a simple abscess cavity left behind, or the suppuration runs immediately round the necrosed structures, and casts them off bodily as a slough.  This latter condition is always manifested, where the hair does not hide it, by the colour of the skin.  At first this is only red in colour—­the angry red of an inflamed spot.  As its intention to slough away becomes evident, the red gradually gives way to a gray, or even blue-black appearance, while from around it oozes a slight discharge of pus, yellow in colour and non-offensive, or blood-stained and dark in appearance, and foetid to the smell.