Some of the concessions made at this time related to temporary provisions for relief of debtors; but the great innovation was that which established the office of tribune. The character of the office of tribune is absolutely unique in the political history of the world. The tribunes, elected by the people in the comitia tributa, were plebeian officers who were at first without any constructive part in the carrying on of the Roman government and whose sole duty at the outset was to protect the members of the plebeian order from the oppression of the patrician officials. This protection was exercised mainly through the use of the veto power given to the tribunes. Under this power the tribunes had the right at any time to put a stop to any act either by any of the public assemblies, by the Senate, or by any of the magistrates. It was a power which, if exercised to its fullest extent, could put a stop to the very carrying on of the government. It speaks much for the moderation of the Roman tribunes that through all the centuries of the Roman republic little serious inconvenience was experienced from the use of this power. With few and unimportant exceptions, it was exercised only in cases where the welfare of the plebeians as a class, or of some particular plebeian, demanded it. The creation of the office of tribune was merely one more example of that system of checks and balances which played so prominent a part in the framing of the government after the expulsion of the king--a system of checks and balances so strikingly resembling that in our Federal Constitution. The tribunes were introduced as a protection for the plebeians and an additional restraint upon the magistrates. While at first the power and duties of the tribunes were entirely of a negative nature, they gradually acquired an authority of a positive character. The tribunes generally presided over the comitia tributa and took the lead in securing the passage of laws by that body. In addition they acquired judicial powers, and in cases where a plebeian had been wronged they could summon any citizen, even the consuls, before them, and might impose even the death penalty. The persons of the tribunes were declared inviolable, and any one who attacked them was thought to be accursed. The number of the tribunes was at first two, but was later increased to five and still later to ten.