Upon the inner sides of the Avenue are represented on each balustrade
a boar, a ram, and a bull--the animals offered at the triple
sacrifice, or _suovetaurilia_ (from _sus_, _ovis_, _taurus_), which
was performed once every five years, or _lustrum_, for the
purification of the city.
It was an institution of Servius Tullius, the ceremony consisting in
leading the boar, ram, and bull thrice round the assembly of the
people, and then offering them to Mars. There is a similar
representation upon a relief of Trajan on the Arch of Constantine, and
upon a pedestal found near the Arch of Septimius Severus.
_To our left of the Arch of Severus is_