King Servius Tullius inaugurated a political reform, intended to alleviate the condition of the plebeians oppressed by the patricians; and in preparation for it he took a census. At that time Rome had eighty-four thousand able-bodied citizens between the ages of eighteen and sixty years, or a total population of about four hundred thousand free persons of all ages and sexes. To this number must be added the plebeians, who were not yet citizens. The artisans, operatives, clients and strangers perhaps doubled this estimate of the population of Rome, the limits of which then stretched from the Tiber to the Anio, including, probably, the lands of Alba, and making in all, an area of about one hundred and twenty or one hundred and forty square miles. There would thus be more than five thousand five hundred inhabitants to a square mile; so that there could have remained but very little room for slaves. In the first stages of the republic, the patricians continually increased their landed estates, and by renting these to tenants, they acquired power over the poor free laborers, and by lending them money, got a claim on their bodies and also on the free yeomen and rustics. The patricians were hard creditors, and rigorously availed themselves of their legal rights, and their _ergastula_--caves or vaulted prisons--were almost continually filled with poor debtors. This impoverishment of the free yeomanry increased after the terrible devastations perpetrated by the Gauls under Brennus. Finally, these financial oppressions generated those revolts of the plebeians which terminated in their obtaining political rights and full citizenship, together with the jurisprudential reform known as the Twelve Tables. During the first three or four centuries of the republic, the number of slaves who were non-debtors was very limited. At the census made in the year of Rome 280, the free population amounted to over four hundred and ten thousand persons, and there were then only seventeen thousand slaves. Few, if any, women were originally enslaved. If the nursling of a Roman family often drew its milk from the paps of a slave woman, the Roman matron, in turn, often gave her breast to the babe of a slave. In those early times the slaves were kindly treated; they were regarded rather as members of the family than as chattels; they took their meals with their masters, and participated in the sacrifices and worship of the gods. They were not considered dangerous elements in the household or the state. From that early epoch also date certain privileges conceded to the slaves--such as their earnings or _peculium_, which, at first established only by common usage, became afterward defined and specified by the civil law, in which originally the slave was almost entirely ignored.