In the Catholic church the festival of the Body and Blood of Our Lord (in folk tradition: Corpus Christi) constitutes a liturgical celebration in honour of the Holy Sacrament. Believers commemorate the Last Supper and Transubstantiation of bread and wine into the Body and Blood of Jesus Christ. Corpus Christi is a joyful thanksgiving celebration. In Poland the festival involves a procession with the Holy Sacrament along the streets of the parish. The procession stops at four altars, where a celebrant reads a Eucharist-related passage from each Gospel.