CHAPTER II.
THE LOWER POPULATION (PLEBS URBANA) The walk we have been taking has led us only through the heart of the city, in which were the public buildings, temples, basilicas, porticos, etc., of which we hear so much in Latin literature.

It was on the hills which are spurs of the plain beyond, and which look down over the Forum and the Campus Martius, the Caelian, Esquiline, and Quirinal, with the hollows lying between them, and also on the Aventine by the river, that the mass of the population lived.

The most ancient fortification of completed Rome, the so-called Servian wall and _agger_, enclosed a singularly large space, larger, we are told, than the walls of any old city in Italy;[35] it is likely that a good part of this space was long unoccupied by houses, and served to shelter the cattle of the farmers living outside, when an enemy was threatening attack.

But in Cicero's time, as to-day, all this space was covered with dwellings; and as the centre of the city came to be occupied with public buildings, erected on sites often bought from private owners, the houses were gradually pushed out along the roads beyond the walls.

Exactly the same process has been going on for centuries in the University city of Oxford where the erection of colleges gradually absorbed the best sites within the old walls, so that many of the dwelling-houses are now quite two miles from the centre of the city.