The Constitution of Florence offered many points of weakness to the attacks of such intriguers.  In the first place it was in its origin not a political but an industrial organisation—­a simple group of guilds invested with the sovereign authority.  Its two most powerful engines, the Gonfalonier of Justice and the Guelf College, had been formed, not with a view to the preservation of the government, but with the purpose of quelling the nobles and excluding a detested faction.  It had no permanent head, like the Doge of Venice; no fixed senate like the Venetian Grand Council; its chief magistrates, the Signory, were elected for short periods of two months, and their mode of election was open to the gravest criticism.  Supposed to be chosen by lot, they were really selected from lists drawn up by the factions in power from time to time.  These factions contrived to exclude the names of all but their adherents from the bags, or borse, in which the burghers eligible for election had to be inscribed.  Furthermore, it was not possible for this shifting Signory to conduct affairs requiring sustained effort and secret deliberation; therefore recourse was being continually had to dictatorial Commissions.  The people, summoned in parliament upon the Great Square, were asked to confer plenipotentiary authority upon a committee called Balia, who proceeded to do what they chose in the State, and who retained power after the emergency for which they were created passed away.  The same instability in the supreme magistracy led to the appointment of special commissioners for war, and special councils, or Pratiche, for the management of each department.  Such supplementary commissions not only proved the weakness of the central authority, but they were always liable to be made the instruments of party warfare.  The Guelf College was another and a different source of danger to the State.  Not acting under the control of the Signory, but using its own initiative, this powerful body could proscribe and punish burghers on the mere suspicion of Ghibellinism.  Though the Ghibelline faction had become an empty name, the Guelf College excluded from the franchise all and every whom they chose on any pretext to admonish.  Under this mild phrase, to admonish, was concealed a cruel exercise of tyranny—­it meant to warn a man that he was suspected of treason, and that he had better relinquish the exercise of his burghership.  By free use of this engine of Admonition, the Guelf College rendered their enemies voiceless in the State, and were able to pack the Signory and the councils with their own creatures.  Another important defect in the Florentine Constitution was the method of imposing taxes.  This was done by no regular system.  The party in power made what estimate it chose of a man’s capacity to bear taxation, and called upon him for extraordinary loans.  In this way citizens were frequently driven into bankruptcy and exile; and since to be a debtor to the State deprived a burgher of his civic rights, severe taxation was one of the best ways of silencing and neutralising a dissentient.