r end wall above the entrances. Those of the
end wall disappeared long since, on the occasion of some repairs to
this part of the basilica. Those of the left side perished in the fire
of 1823; but those of the right side, beginning with S. Peter and
ending with Innocent (401-417), were saved. They have since been
detached from the wall, transferred first to canvas, then to stone,
and are now exhibited in one of the corridors of the monastery.[104]
As regards those which perished in the fire, they had already been
copied, first in the seventeenth century by order of Cardinal
Francesco Barberini, and again in 1751 by Marangoni. The new series in
mosaic is therefore not all fanciful and imaginary, but follows the
tradition of the likenesses as they were first produced in the fifth
century. At that time the study of the pontifical succession was
receiving considerable attention in Rome. There were written
catalogues inserted in liturgical books, which were read to the
congregation on certain days of the year, so that everybody could
argue on the subject, and remember the order of succession of the
bishops. To impress this more forcibly on the minds of the people, it
was written on the walls of the newly erected basilica of S. Paul, and
illustrated with portraits. The series must have struck the
imagination of visitors and pilgrims. The idea of apostolic
inheritance, of uninterrupted hierarchy, of the supremacy of the See
of Rome, took a definite shape in the array of these busts of bishops,
led by S. Peter, and congregated, as it were, around the grave of S.
Paul.

[Illustration: _A_ Portrait head of S. Peter; from a medallion in
repousse discovered by Boldetti in the Catacombs of Domitilla.--_B_
Portrait head of S. Paul; from a medallion preserved in the Museo
Sacro Vaticano.--Both are works of the second century.]

The custom found imitators in other churches and in other cities.
Speaking of the gallery of Popes in the duomo at Siena, Symonds
remarks how the accumulated majesty of their busts, larger than life,
with solemn faces, each leaning from his separate niche, brings the
whole past history of the Church into the presence of its living
members. A bishop walking up the nave of Siena must feel as a Roman
felt among the waxen images of ancestors renowned in council or war.
"Of course," Symonds concludes, "the portraits are imaginary for the
most part, but the artists have contrived to vary their features and
express