Under gangrene, necrosis, is understood the death of an organ or part, as manifested by the more or less rapid breaking down and chemical decomposition of its texture. Gangrene may affect both soft and solid structures, the bones, for instance, or even fluids, as in necrosis or sepsis of the blood. The breaking down of solid structures, is generally a slow process, whilst in soft, juicy textures, and in fluids, it is rapidly consummated. Like normal textures, new formations of every kind, - tumors, exudates, pus, - are liable to become necrosed. Fluids degenerate through necrosis to gangrenous ichor, the most infectious and destructive of its tribe.

A general characteristic of gangrene is not easily given, so manifold are its forms, and so various its causes. Soft parenchymata commonly break down to a diffluent pulp, marked by a high degree of discoloration and of fetor. Exceptions are, however, numerously afforded in gangrene of the bones, mummifying, white gangrene.

Gangrene has the import sometimes of a local, sometimes of a symptom of general disease. The conditions necessary to the former case are nearly reducible to arrested afflux of blood, that is, stasis. It may begin by attacking fluid parts, and especially the blood, and extend from these to solid structures, or it may affect them all at once.