 The Virgin birth is indicated by the red bed and red womb @-@ shaped curtain @-@ sack . During the early @-@ 15th century hanging beds or curtain @-@ sacks became symbols of the Incarnation , and " served to affirm [ Christ 's ] humanity " . Blum notes that at a time " when artists did not hesitate to depict the breast of the Virgin , Memling did not shun her womb " . Christ 's humanity was a source of fascination , and it was only in Netherlandish art that a solution was found for visualizing his embryonic state with curtain @-@ sacks draped to suggest the shape of a womb . 
