In the Ghent Altarpiece: The Adoration of the Lamb by Jan van Eyck, the Lamb of God stands upon an altar dressed as for the Mass of the Precious Blood, with a blood-red frontal: the Lamb's blood is caught in a chalice, and its Eucharistic intention is signaled by the dove of the Holy Spirit above. In the foreground, offering the other means of grace, is the Fountain of the Living Water surrounded by the faithful. In the Prado, Madrid, is the Fountain of Living Water emanating from the Lamb of God, in which the open fountain is set into the outer wall of Heaven. That the water is not merely the purifying water of baptism is shown by the innumerable wafers that float upon its surface: the two sacraments are represented as one. , the Lutheran doctrine of Real presence of Christ in the Eucharist, after a woodcut by Lucas Cranach the Elder. In the front Communion under both kinds is pictured with Martin Luther giving the chalice to John, Elector of Saxony and on the right Jan Hus giving the eucharistic bread to Frederick III, Elector of Saxony. In the back a Fountain of Living Water: The blood of Christ's Five Holy Wounds spills in a fountain on the altar. In a miniature in a Book of Hours, probably painted at Ghent at the end of the 15th century, the Fountain of Living Water has given way to a fountain of blood, the Fountain of Life, in which the figure of Christ stands upon a Gothic pedestal at the center and fills the fountain from his wounds, though the aureole that surrounds him identifies him as the transfigured Christ and the location as Paradise.
In Flanders at the close of the Middle Ages an intense devotion to the Precious Blood of Christ gave rise to an iconographic tradition of the 15th and 16th centuries, which rendered the theological concept of Grace, expressing Roman Catholic dogmaallegorically as a fountain of blood. This transformation was first addressed in Evelyn Underhill in 1910, taking her point of departure an Assembly of Saints and the Fountain of Life of 1596 in Ghent, in which blood from the five Holy Wounds of Christ flows into the upper basin of a "Fountain of Life" and streams out through openings in the lower "Fountain of Mercy". Saints and martyrs, patriarchs and prophets hold golden chalices of blood, which some empty into the fountain. Below the faithful hold out their hearts to receive droplets of blood.