continued to function through the Regal and Republican eras, but the Servian reform had reduced its powers to those of a largely symbolic "upper house"; its noble members were expected to do no more than ratify decisions of the comitia centuriata. Classes The census grouped Rome's male citizen population in classes, according to status, wealth and age. Each class was subdivided into groups called centuriae (centuries), nominally of 100 men (Latin centum = 100) but in practice of variable number, further divided as seniores (men aged 46 – 60, of a suitable age to serve as "home guards" or city police) and iuniores (men aged 17 – 45, to serve as front–line troops when required). Adult male citizens were obliged, when called upon, to fulfill military service according to their means, which was supposedly assessed in archaic asses. A citizen's wealth and class would, therefore, have defined their position in the civil hierarchies, and up to a point, within the military; but despite its apparent military character, and its possible origins as the mustering of the citizenry–at–arms, the system would have primarily served to determine the voting qualifications and wealth of individual citizens for taxation purposes, and the weight of their vote – wars were occasional but taxation was a constant necessity – and the comitia centuriata met whenever required to do so, in peace or war. Though each century had voting rights, the wealthiest had the most centuries, and voted first. Those beneath them were convened only in the event of deadlock or indecision; the lowest class was unlikely to vote at all. The Roman army's centuria system and its order of battle are thought to be based on the civilian classifications established by the census. The military selection process picked men from civilian centuriae and slipped them into military ones. Their function depended on their age, experience, and the equipment they could afford. The wealthiest class of iuniores (aged 17–45) were armed as hoplites, heavy infantry with helmet, greaves, breastplate, shields (clipeus), and spears (hastae). Each battle line in the phalanx formation was composed of a single class. Military specialists, such as trumpeters, were chosen from the 5th class. The highest officers were of aristocratic origin until the early Republic, when the first plebeian tribunes were elected by the plebeians from their own number. Cornell suggests that this centuriate system made the equites, who "consisted mainly, if not