Gangrene, death of tissue following loss of blood supply, often after obstruction of arteries by injury, thrombosis (clot formation on a damaged artery wall), or embolism (blockage by an air bubble, clot, or other debris). Dry gangrene is seen when arterial blockage is followed by slow drying, blackening, and finally separation of dead tissue from healthy. Its treatment includes improvement of the blood flow to the healthy tissue and prevention of infection and further obstruction. Wet gangrene occurs when the dead tissue is infected with bacteria. Gas gangrene involves infection with gas-forming organisms (e.g., Clostridium welchii), and its spread is particularly rapid. Antibiotics, hyperbaric chambers (in which oxygen is kept at high pressure), and early amputation are often required.