DEFINITION OF A VAMPIRE: A vampire, by definition, is an entity that feeds on the life essence of other creatures. Vampires are typically described as "undead" — reanimated corpses possessed by evil spirits. The traditional vampire feeds on the blood of the living to prevent its body from decomposing. The image of the refined, gaunt, pale-skinned vampire is an early 19th century literary invention, beginning roughly with the publication of The Vampyre — a short story by John Polidori — in 1819. The original, folkloric vampire of Eastern Europe — where the legend began — was described as bloated with a dark or ruddy complexion from feeding on blood.
ORIGINS OF BELIEF: Many attribute belief in vampires to a combination of Slavic spiritualism and early ignorance of the body's decomposition cycle after death. In pre-industrial Slavic societies, it was believed that a person's spirit lingered for 40 days after death. Suicide victims, suspected witches, evil beings and even un-baptized children were thought to have "unclean" spirits. A vampire, according to this belief, was the manifestation of an unclean spirit possessing a decomposing body.
SIGNS OF VAMPIRISM? When the body of a suspected vampire was disinterred, it would sometimes look like it hadn't decomposed at all; like its hair, teeth and fingernails had been growing; and as if it had been gorging on blood due to its ruddy complexion, bloated body and blood seeping from the nose and mouth. We know now that a body's decomposition rate depends on factors like temperature and soil composition; that dead flesh loses fluids, causing it to pull back and expose the roots of hair, teeth and nails; and that gases from decomposition accumulate in the torso, making the body look bloated and forcing blood to ooze from the nose and mouth.
VAMPIRE SUPERSTITION: Common beliefs about vampires include that they are most active at night, but not necessarily vulnerable to sunlight (which was mainly a literary invention). Garlic, crucifixes and holy water were common devices for warding off vampires. It was also commonly believed that driving a wooden stake into the body would release the evil spirit, with decapitation also being a way to hasten the evil soul's departure.