Quittor is an infection of the collateral cartilage in the foot. This Cushing's mare has suffered from chronic infection of her hind left foot for years, resulting in disorganisation of the tubules and abscesses. The exit points of the infection are just above the medial hairline, along the medial bar laminae, and the medial quarter white line. This resection exposed the hollow tract of infection on the outside of the coffin bone's palmar process in the wall's laminae. I suspect there is another tract between the medial collateral cartilage and the palmar process that drains out into the bar's laminae. The area removed was insensitive, and the resection did not negatively impact her soundness in the slightest. The area was cleaned and treated with a topical antibiotic, and systemic antibiotics from the vet were also recommended to the owner. With this area resected, the infection will have a better chance at draining and will be exposed to air and sunlight for at least part of the day, which helps makes the area inhospitable to various microbes.