​NECROSIS (Gr. νεκρός, corpse), a term restricted in surgery to death of bone. A severe inflammation, caused by a violent blow, by cold, or by the absorption of various poisons, as mercury and phosphorus, is the general precursor of necrosis. The dead part, analogous to the slough in the soft tissues, is called a sequestrum or exfoliation. At first it is nrmly attached to the living bone around; gradually, however, the dead portion is separated from the living tissue. The process of separation is a slow one. New bone is formed around the sequestrum, which often renders its removal difficult. As a rule the surgeon waits until the dead part is loose, and then cuts down through the new case and removes the sequestrum. The cavity in which it lay gradually closes, and a useful limb is the result.