The lintel of the bronze door-frame bears a relief. This represents an arch, supported by columns above a throne with the book of the Gospel and the descent of the Holy Ghost in the form of a dove. On it are the words of S. John, ‘The Lord said, I am the door of the sheep; through me if any man enter, he shall enter and shall go out, and shall find pasture.’ The simple bronze door-plating now remaining does not seem to be original. [See p. 265.] Salzenberg,[273] as an example of the marble frames, gives the east door of north aisle. Like all Byzantine door-frames, the head does not cut across the jamb, but mitres. This perhaps made it easier for fixing within the openings left in the walls. Salzenberg[274] also represents the arched opening, which stands between the Baptistery and the small court on the south side of the church.[275] There are two tiers of columns, with a thin architrave band between them. The door stands between the lower columns; to avoid concealing them the frame is made as small as possible, as the plan shows. A similar arrangement is found in the earlier church of S. John Studius.[276] The bronze door-plating on the exterior of the south porch entrance is extremely interesting.[277] A wooden foundation four or five inches thick is covered with ornamental bronze casings. The borders to the panels are beautifully modelled, and must be ancient. The other outer margins, with knobs and rosettes, and the four panels, which are decorated with monograms, belong to the Byzantine school. In the more ancient parts the metal is one-eighth to one-fourth inch in thickness, in the latter it is three-eighths to half an inch. Antique doors must have been enlarged and fitted with new panel plates. _Marble Plating._--Broad horizontal bands run round the nave at different heights, and the spaces between them are filled with single panels and vertical sheathing. All the bands and panels have notched fillets, 1½″ wide, of white marble as borders. The more important panels have sculptured white marble frames, eleven inches wide with a “pater noster” and notched-fillet borders on either side. The spandrils of the upper arches and the bands beneath the topmost cornices are incrusted with designs of leaves, flowers, fruits, and birds formed of different kinds of marble. The marble casing to the walls of the nave is arranged as follows.[278] Above the skirting is a [3′.10″] band of verde antique, then the notched fillet, then a [1′.5½″] yellow band [oriental alabaster]; above this is a vertical sheeting [7′.10″] formed of Pavonazzetto marble, alternating with a yellowish brown marble; then another horizontal band of yellow.