In the 13th century AD, a priest, Peter of Prague, in the town of Bolsena in Italy, was troubled, like many Catholics, by the doctrine of transubstantiation (the conversion of bread and wine into the body and blood of Christ during Mass). As Peter was celebrating Mass the host began to bleed and blood fell onto his hands and the corporeal (a white linen cloth on which the consecrated host is placed during Mass). He asked to see the Pope, Urban 1V ,who was in Orvieto (about 15 km away), who confirmed the miracle and thus the feast of Corpus Christi was initiated.
The story, and the miracle, is slightly muddied by the discovery of the bacterium Serratia Marscences which produces a red pigment, prodigiosin. This pigment can colonize damp statues, polenta and communion wafers and may explain ‘bleeding’ statues and Peter’s experience.