The constitution introduced two elements into the Roman system of government: a census of every male citizen, in order to establish his wealth, tax liabilities, military obligation, and the weight of his vote; and the comitia centuriata, an assembly with electoral, legislative and judicial powers.
[6] Until the Servian reforms, the passing of laws and judgment was the prerogative of the comitia curiata (curiate assembly), made up from thirty curiae; Roman sources describe ten curiae for each of the three aristocratic tribes, the Ramnes, the Tities, and the Luceres, each claiming patrician status and privilege to election as magistrates by virtue of their descent from Rome's founding families.
The senate advised the king, devised laws in his name, and was held to represent the entire populus Romanus (Roman people); but it could only debate and discuss.
Rome's far more populous citizen-commoners (plebeians) could participate in this assembly in limited fashion, and perhaps offer their opinions on decisions but only the comitia curiata could vote.
[8] The census was organised on military lines; citizens assembled by tribe in the Campus Martius, to register their social rank, household, property and income.
Adult male citizens were obliged, when called upon, to fulfill military service according to their means, which was supposedly assessed by as, a monetary unit that in the archaic period represented a particular weight of bronze or copper.
[12][13] This evaluated wealth of a citizen was based primarily on land ownership (jugera) and head of livestock (pecunia) until the introduction of a monetary system in the 2nd century BC.
Even after the institution of the comitia centuriata, the most immediate and effective plebeian defense against aristocratic power was the actual or threatened withdrawal of labour, including military service.
[23] The situation beyond the walls is unclear: similar tribal areas, perhaps known as pagi, may have extended into the surrounding Roman territories (the ancient ager Romanus), and some of their inhabitants would have qualified for citizenship under the Servian class reforms.