AD CORPUS, BASILICA. - This is the technical term used by archaeologists to indicate a basilica that was built near or over the body of a saint in his honor or to provide more easily for his liturgical cult.
Since in antiquity this cult was paid only to martyrs, and these ordinarily lay buried in a cemetery, or had subsequently given rise to a cemetery, the basilica ad c. is in reality equivalent to a cemetery and suburban basilica, erected in honor of a martyr. As such it represents an exception to the rule according to which the ordinary basilica or church was built in urban centers and did not contain the body of any martyr, even if it was sometimes dedicated to one. These latter, moreover, were the only churches normally officiated and provided with their own stable clergy; whereas those ad c. had only a custodian or mansionarius, who could be any ecclesiastic whatsoever, and were officiated only on the feast of the martyr and a few other times during the year.
The basilica ad c., being built in a cemetery, among tombs and mausoleums, was generally erected on very difficult ground. Hence its forms were almost never regular, and only in the exceptional case of large proportions; moreover, although the basilical form absolutely predominates, it is nevertheless often not pure, but serves only as a schema.
In particular, one should note the tendency to widen the space around the altar to make room for the multitude of the devout; a thing that made the use of a broad transept almost normal. The devotion, moreover, of the faithful who sought to be buried near the martyr (v. AD SANCTOS) gave rise to many appendages of a cemetery character; indeed the church itself ordinarily became a vast cemetery (earthen tombs beneath the floor, lateral arcosolia, sarcophagi in every space, adjoining mausoleums). Furthermore, in order to draw closer to the venerated tomb, when this was situated deep underground, crypts were built, generally semicircular with horseshoe-shaped corridors. This practice then spread also to the urban churches, especially when they housed the bodies or relics of martyrs.
The essential requirement for satisfying the desire to draw near to the venerated body was that the altar be placed either above it or very close to it. For this purpose the ground was often cut deeply to bring the church to the level of the venerated tomb, or a small church was arranged almost entirely underground (St. Hermes, St. Agnes, Sts. Nereus and Achilleus in Rome); sometimes particular communications were established between the tomb and the altar; sometimes, since it was not possible to make the center of the church coincide with the tomb, the altar was placed in an eccentric location, provided only that it remain over the tomb of the martyr. In this way the martyr remained as if buried beneath the altar; he guarded the altar, as it was said. From this began the conception of the altar-tomb, which gradually came to be superimposed upon and then even to replace the primitive conception of the altar-table.
For the bibliography v. BASILICA.
Antonio Ferrua