_pomoerium_. When the plough came to the place where there
was to be a gate, it was lifted over it, and the ploughing resumed
beyond it. This probably meant, as Plutarch expressed it, that the walls
(or rather the _pomoerium_), were sacred while the gates were profane;
had the gates been holy, scruple would necessarily have been felt about
the passage in and out of them of things profane. Thus the _pomoerium_
was a boundary line between the sacred and the profane, like that of the
farm; but in historical times it acquired a more definite religious
meaning, for within it there could only dwell those deities who belonged
to the city and its inhabitants, _i.e._ the _di indigetes_, and who were
recognised as its divine inhabitants.[451] And only within its limits
could the _auspicia_ of the city be taken.

We should naturally expect that this sacred boundary would have its
holiness secured or revived by an annual _lustratio_ like that of the
farm and _pagus_; and so no doubt it was. But the memory of this
survives only in the word _amburbium_, which, on the analogy of
_ambarvalia_, must mean a rite of this processional kind. Luckily we
have definite knowledge of the real _lustratio_ of a city in those
ritualistic inscriptions of Iguvium which I have more than once referred
to.[452] It is the _lustratio_ of the _arx_, the citadel of Iguvium,
which we may guess to have been the original _oppidum_ or germ of the
historical city. The details are complex, and show clear traces of
priestly organisation; but the main features stand out unmistakably. A
procession goes round the _arx_ (_ocris Fisia_), with the
_suovetaurilia_--ox, sheep, and pig--as in the Latin _lustratio_; at
each gate it stops, while sacrifice and prayer are offered on behalf of
the citadel, the city, and the whole people of Iguvium. There were three
gates, and each of them is the scene of sacrifice and prayer, because
they are the weak points in the wall, and they need to be strengthened
by annual religious operations; such at least is the most obvious
explanation. Whether the Fratres Attiedii would have been able to
explain it thus we may doubt; neither in the sacrificial ritual nor in
the prayers, as recorded in the inscription, do we find any clear trace
of a distinction between the sacred and the profane, or of the idea of a
hostile spiritual world outside the sacred boundary. So far as we can
judge from the prayers, the object is really a religious one, to i