In the third chapter I shall have occasion to describe the transformation of nearly all the great public buildings of imperial Rome into places of Christian worship, but it falls within the scope of this chapter to remark that, in many instances, the pagan decorations of those buildings were not affected by the change. When Felix IV. took possession of the _templum sacræ urbis_, and dedicated it to SS. Cosma and Damianus, the walls of the building were covered with incrustations of the time of Septimius Severus representing the wolf and other profane emblems. Pope Felix not only accepted them as an ornament to his church, but tried to copy them in the apse which he rebuilt. The same process was followed by Pope Simplicius (A. D. 468-483), in transforming the basilica of Junius Bassus on the Esquiline into the church of S. Andrea.[19] The faithful, raising their eyes towards the tribune, could see the figures of Christ and his apostles in mosaic; turning to the side walls, they could see Nero, Galba, and six other Roman emperors, Diana hunting the stag, Hylas stolen by the nymphs, Cybele on the chariot drawn by lions, a lion attacking a centaur, the chariot of Apollo, figures performing mysterious Egyptian rites, and other such profanities, represented in _opus sectile marmoreum_, a sort of Florentine mosaic. This unique set of intarsios was destroyed in the sixteenth century by the French Antonian monks for a reason worth relating. They believed that the glutinous substance by which the layer of marble or mother-of-pearl was kept fast was an excellent remedy against the ague; hence every time one of them was attacked by fever, a portion of those marvellous works was sacrificed. Fever must have raged quite fiercely among the French monks, because when this wanton practice was stopped, only four pictures were left. Two are now preserved in the church of S. Antonio, in the chapel of the saint; two in the Palazzo Albani del Drago alle Quattro Fontane, on the landing of the stairs.[20] [Illustration: Mosaic from the church of S. Andrea.] Intarsios of the same kind have been seen and described in the basilica of S. Croce in Gerusalemme, in the church of S. Stefano Rotondo, in that of S. Adriano, etc. When the offices adjoining the Senate Hall were transformed into the church of S. Martina, the side walls were adorned with the bas-reliefs of the triumphal arch of M. Aurelius, now in the Palazzo dei Conservatori (first landing, nos. 42, 43, 44). One of them, representing the emperor sacrificing before the Temple of Jupiter, is given opposite page 90.