+INTRODUCTORY.+ The official recognition of Christianity in the year 328 by Constantine simply legalized an institution which had been for three centuries gathering momentum for its final conquest of the antique world. The new religion rapidly enlisted in its service for a common purpose and under a common impulse races as wide apart in blood and culture as those which had built up the art of imperial Rome. It was Christianity which reduced to civilization in the West the Germanic hordes that had overthrown Rome, bringing their fresh and hitherto untamed vigor to the task of recreating architecture out of the decaying fragments of classic art. So in the East its life-giving influence awoke the slumbering Greek art-instinct to new triumphs in the arts of building, less refined and perfect indeed, but not less sublime than those of the Periclean age. Long before the Constantinian edict, the Christians in the Eastern provinces had enjoyed substantial freedom of worship. Meeting often in the private basilicas of wealthy converts, and finding these, and still more the great public basilicas, suited to the requirements of their worship, they early began to build in imitation of these edifices. There are many remains of these early churches in northern Africa and central Syria. +EARLY CHRISTIAN ART IN ROME.+ This was at first wholly sepulchral, developing in the catacombs the symbols of the new faith. Once liberated, however, Christianity appropriated bodily for its public rites the basilica-type and the general substance of Roman architecture. Shafts and capitals, architraves and rich linings of veined marble, even the pagan Bacchic symbolism of the vine, it adapted to new uses in its own service. Constantine led the way in architecture, endowing Bethlehem and Jerusalem with splendid churches, and his new capital on the Bosphorus with the first of the three historic basilicas dedicated to the Holy Wisdom (Hagia Sophia). One of the greatest of innovators, he seems to have had a special predilection for circular buildings, and the tombs and baptisteries which he erected in this form, especially that for his sister Constantia in Rome (known as Santa Costanza, Fig. 66), furnished the prototype for numberless Italian baptisteries in later ages. [Illustration: FIG. 66.--STA. COSTANZA, ROME.]