This gorgeous jewelled work, flashing out beneath the splendour of the canopy, seems to gather into a point all the glory of this rich interior. From the choir, which is raised several steps above the sanctuary, one can get a complete view of the mosaic decoration of the apse, a grand and imposing composition, with a colossal figure of Christ enthroned in the centre, lifting His hand in benediction, and on either side of Him SS. Gervasio and Protasio, and the Archangels Michael and Gabriel above. The names of the two martyrs are written beside them, letter beneath letter. Under the central figure there are three medallions; S. Satiro, brother of St. Ambrose, in the centre, and S. Marcellina, their sister, and S. Candida to right and left. The sides of the composition depict the story related by S. Gregory of Tours about St. Ambrose and represented on the altar; how he fell into a trance as he celebrated Mass and was rapt in spirit to Tours, where he performed the burial rite over the body of S. Martin. This mosaic is of the twelfth century, and though it follows the Byzantine style in arrangement and general treatment, it shows a tendency to abandon the old rigid conventions for the sake of more life and expression in the attitudes and draperies of the figures, and so sacrifices something of the decorative effect. The colour is very sombre, lacking the richness and glow of the best mosaic. There is a marble episcopal seat of the ninth century in the choir. The stalls are very beautiful. Some are of the fourteenth century, as is also the triple seat on the right hand of the altar; the other stalls date from 1507. The designs carved upon them—trees and foliage, with small figures of men and animals, a peasant gathering grapes, a neglectful swineherd munching acorns, while the pig climbs the tree to reach some for itself, a man and a bear facing each other with comical hesitation beneath a tree, and other rustic scenes—are very graceful and delicate, and show a Renaissance spirit of gaiety.