Embalming is a process by which a corpse is prevented, at least temporarily, from decomposing. Under some circumstances bodies may be naturally embalmed, but artificial embalming first appeared in ancient Egypt (see mummy). Modern embalming began after William Harvey's discovery of the circulation of blood (1628). Embalming fluid is injected into an artery (arterial fluid) while blood is drained from a vein, then a stronger fluid (cavity fluid) is into body orifices and hollow organs.