Circumstances had brought other changes; the tribuneship, without being abolished, had become an auxiliary of the aristocracy. The tribunes no longer exclusively represented the plebeian order; they were admitted into the Senate; they formed part of the government, and employed their authority in the interest of justice and the fatherland.[559] The three kinds of comitia still remained,[560] but some modifications had been introduced into them. The assembly of the curiæ[561] consisted now only of useless formalities. Their attributes, more limited every day, were reduced to the conferring of the _imperium_, and the deciding of certain questions about auspices and religion. The comitia by centuries, which in their origin were the assembly of the people in arms, voting in the Campus Martius, and nominating their military chiefs, retained the same privileges; only, the century had become a subdivision of the tribe. All the citizens inscribed in each of the thirty-five tribes were separated into five classes, according to their fortune; each class was divided into two centuries, the one of the young men (_juniores_) the other of the older men (_seniores_). As to the comitia by tribes, in which each voted without distinction of rank or fortune, their legislative power continued to increase as that of the comitia by centuries diminished. Thus the Roman institutions, while appearing to remain the same, were incessantly changing. The political assemblies, the laws of the Twelve Tables, the classes established by Servius Tullius, the yearly election to offices, the military services, the tribuneship, the edileship, all seemed to remain as in the past, and in reality all had changed through the force of circumstances. Nevertheless, this appearance of immobility in the midst of progressing society was one advantage of Roman manners. Religious observers of tradition and ancient customs, the Romans did not appear to destroy what they displaced; they applied ancient forms to new principles, and thus introduced innovations without disturbance, and without weakening the prestige of institutions consecrated by time. [Sidenote: The Macedonian War (554).]