In the decrees of the Second Council of Tours, A.D. 557, “lay persons were not to enter the chancel, which is divided off by screens, except to partake of the sacrament of the altar.” A complete screen extended all round the choir later on. Eusebius describes the choir of the Church of the Apostles, erected by Constantine at Constantinople, as enclosed by screens or trellis work, marvellously wrought: “Interiorem ædis partem undique in ambitum circumductam, reticulato opere ex aere et auro affabre facto convestivit.”[97] Professor Willis describes the screen of old St. Peter’s at Rome as follows (and an engraving of it is also given by Pugin): “In front of the steps (to the altar) were placed twelve columns of Parian marble, arranged in two rows; these were of spiral form and decorated with sculpture of vine leaves: the bases were connected by lattice-work of metal or by walls of marble breast-high. The entrance was between the central pillars, where the _cancelli_ or lattices were formed into doors. Above these columns were laid beams or entablatures upon which were placed images, candelabra, and other decorations; and indeed the successive Popes seem to have lavished every species of decoration in gold, silver, and marble work upon this enclosure and the crypt below. The entire height, measured to the top of the entablature, was about 30 feet; the columns, with the connecting lattices and entablatures, formed, in fact, the screen of the chancel.”[98] At San Clemente, at Rome, the chancel is divided off by a screen wall all round, being 4 feet 6 inches high; each ambo, or reading-desk for Epistle or Gospel, is in the middle of the north and south walls and faces east. Between this choir and the sanctuary is a cross wall of marble, 6 feet high, with an opening in the centre. These existing screens are probably due to Adrian I., and date from the year 790, but they are almost certainly on the original lines.[99] At Giotto’s Chapel of the Arena, Padua, the chancel is formed by marble screens on each side of the nave, leaving a broad entrance-way between them, and enclosing about one-third of its length. Against the west sides of these screens are altars, each with a small carved marble reredos; whilst on the east are steps leading to the two ambones: that on the north being a book-rest, carved in marble, and fixed with its face to the east; that on the south of iron, and turning upon a pivot.