
"As the human stomach decays, it releases a dark "purge fluid." This bloodlike liquid can flow freely from a corpse's nose and mouth, so it was apparently sometimes confused with traces of vampire victims' blood.
The fluid sometimes moistened the burial shroud near the corpse's mouth enough that it sagged into the jaw, creating tears in the cloth.
Since tombs were often reopened during plagues so other victims could be added, Italian gravediggers saw these decomposing bodies with partially "eaten" shrouds, Borrini said.
Vampires were thought by some to be causes of plagues, so the superstition took root that shroud-chewing was the "magical way" that vampires spread pestilence, he said. Inserting objects—such as bricks and stones—into the mouths of alleged vampires was thought to halt the disease."
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