The sarcophagi are almost exclusively occupied with scenes from the biblical cycle, generally arranged in two rows in a continuous series, like the figures on the frieze of a Grecian temple. Frequently ten or twelve groups, embracing nearly forty figures, are found on the side of a sarcophagus. Sometimes the separate groups occupy a rhythmical arrangement of panel-like compartments, divided by columns of more or less ornamental character. (See Figs. 102, 103, and 104.) The busts of the deceased persons, man and wife, are often exhibited in bold relief in a concave recess in the centre, like the half of a bivalve shell. The table in the footnote on the following page exhibits the relative frequency of occurrence of the different subjects already described, as observed in fifty-five sarcophagi in the Lateran Museum by Mr. Burgon, and as shown in forty-eight examples copied by Bosio.[566] 341 The massiveness of the sarcophagi would during the ages of persecution prevent their use even for the wealthy, as their preparation and conveyance from the city would involve an amount of publicity that would imperil the safety of the living. After the time of Constantine the increased riches and perfect immunity of the Christians permitted the adoption of this costly entombment. The sarcophagi were no longer hidden in the subterranean crypts, but were exposed to view in the vestibules of the stately basilicas erected above ground.[567] Hence, Chrysostom speaks of Constantine being buried in the fisherman’s porch,[568] and of emperors occupying the place of porters at the graves of the apostles. Numerous sarcophagi, however, have been found in the Catacombs, some even reputed to be of the first century. 342 These were generally of simpler design, and adorned only with the series of doubly curving lines known as wave ornaments. They were frequently buried in the floor of the _cubicula_.[569] The reader, in examining the foregoing representations of the person of Our Lord,[570] must have been struck with their remarkably youthful and joyous character in this primitive cycle, as contrasted with the older aspect and more severe expression of the prevalent types of later art. This difference is indicative of a corresponding change of religious feeling, from the genial cheerfulness of the early centuries to the gloomy asceticism of the Middle Ages. In the art of the Catacombs Our Lord is represented, for the most part, in an ideal manner, and not in an historical sense; or, to use the language of Lord Lindsay, “as an abstraction, as the genius, so to speak, of Christianity.”[571] He is almost invariably exhibited as a youthful, beardless figure, to signify--say the ancient writers--“the everlasting prime of eternity;” with, where any definite expression is attempted, a countenance of sweet and tender grace, full of mildness and benignity.