appears as an infant on the lap of His holy mother, Who ever pure and modest is always veiled; and this lovely group is found not only on these paintings, but also on bas-reliefs and glass-vessels generally anterior to the 4th century, and consequently to the general council of Ephesus held in 431; although it is pretended that such figures were first designed after that period. (Instances are enumerated by Raoul-Rochette c.  VI).  Constantina, daughter of Constantine, whose tomb is still preserved at Rome, begged of Eusebius bishop of Cesarea a likeness of our Divine Saviour (Concil.  Labbe. t.  VII, 493 seq):  we must have recourse to the catacombs for His most ancient portraits.  See one resembling the ordinary type of His sacred head and taken from the cemetery of Calixtus, at the end of Raoul-Rochette’s work.  This type, repeated again and again on Christian monuments during the last sixteen hundred years or more, may suggest the hope that some traces of our Divine Saviour’s features are still preserved among us, notwithstanding the diversity of His portraits, of which S. Augustine complained, De Triniti l. 8, c, 4 5.  Raoul-Rochette’s opinion, that this likeness and the portraits of the apostles were of Gnostic origin, is altogether unsupported, as the Belgian editors of his work justly observe.  Christ is frequently represented also as seated amid His apostles, of whom SS.  Peter and Paul were favourite subjects of the old artists:  see Raoul-Rochette c.  VI, where he mentions, after the older antiquaries, the ancient representations of S. Ciriaca, S Priscilla, SS.  Stephen, Cyprian, Laurence, Agnes, and other martyrs.  During Diocletian’s persecution, the provincial council of Eliberis in Spain decreed, that there should be no paintings on the walls of churches:  its 36th canon was evidently intended to save sacred pictures from the profanations perpetrated by the pagans.  The faithful however, fertile in expedients to gratify their devotion, now began to use those portable representations of pious subjects called diptychs, because they generally consisted of two tablets which could at pleasure be folded together.  They were formed of ivory or wood, and resembled the presents of that name formerly sent by the consuls on the day of their entrance into office:  on these were usually inscribed the names and the portraits of the new magistrates. (Symmachus lib. 2, ep. 80, all 71).  The sacred diptychs, of which many are preserved in the Vatican Library, were easily saved from the fury of the Iconoclasts.  Their folding form without their portability is preserved in many of the ancient altar-pieces of Italian and other churches and from them the modern altar-pieces are derived:  they did not however supersede the use of frescoes, or mosaics, as is evident from innumerable ancient and modern ecclesiastical monuments of this city.  In the preceding chapter we laid before our readers the doctrine of the catholic church concerning respect paid to images, p. 80.]