The ulcers of the legs, especially of the ankles, which are so frequently encountered in working-people, are of great interest on account of the difficulty of healing them. One of the characteristics of an ulcer is an open surface showing infiltration and necrotic process with no tendency to heal. The superficial molecular necrosis, or the disintegration of the connective tissues of the skin injured by long-standing infiltration, is the cause of the stubbornness of the ulcer. This molecular necrotic process is gradually produced, but sometimes is really a gangrene and the tissues are affected en masse.
In most of the cases the molecular necrosis is revealed by a yellowish coat on the ulcerated surface. As Kaposi1 wrote, an ulcer is not a primary affection, but a secondary one, because it requires always a precedent inflammatory or neoplastic process, which has caused the molecular necrosis of the tissues and in