The Feast of the Immaculate Conception has been celebrated on December 8th since 1476, when it was added to the Roman calendar, but the devotion to the Virgin Mary, who was conceived without the stain of original sin, dates back to ancient times. In 1854 Pope Pius IX proclaimed the dogma of the Immaculate Conception whose image, from then on, soon became widespread in most Catholic churches. There is such an image even in the third chapel of the right transept in this basilica. The painting on board, made by Pietro Pezzati in 1891, portrays Our Lady Immaculate between Saint Francis of Assisi and St. Maximilian Kolbe (the latter was added in 1973 by Aldo Marzi). Mary, with her hands joined in prayer, is draped in a white robe and light-blue cloak, her head crowned by a golden halo with twelve stars; she is standing on a crescent moon, which crushes the snake that is biting an apple, the symbol of original sin. This image is inspired by the twelfth chapter of the Book of Revelation where Saint John the Evangelist describes the apparition of the new Eve at the end of time: “And there appeared a great wonder in heaven;  a woman clothed with the sun, and the moon under her feet, and upon her head a crown of twelve stars". Under the figure of the Blessed Virgin lies an inscription in Latin: “Tota pulchra es Maria”, the first verse of the antiphon of the psalms for the Vespers . . .