The praetor delegated his power to three classes of judges, called respectively _judex_, _arbiter_, and _recuperator_. When parties were at issue about facts, it was the custom for the praetor to fix the question of law upon which the action turned, and then to remit to a delegate, or judge, to inquire into the facts and pronounce judgment according to them. In the time of Augustus there were four thousand judices, who were merely private citizens, generally senators or men of consideration. The judex was invested by the magistrate with a judicial commission for a single case only. After being sworn to duty, he received from the praetor a formula containing a summary of all the points under litigation, from which he was not allowed to depart. He was required not merely to investigate facts, but to give sentence; and as law questions were more or less mixed up with the case, he was allowed to consult one or more jurisconsults. If the case was beyond his power to decide, he could decline to give judgment. The arbiter, like the judex, received a formula from the praetor, and seemed to have more extensive power. The recuperators heard and determined cases, but the number appointed for each case was usually three or five. The _centumvirs_ constituted a permanent tribunal composed of members annually elected, in equal numbers, from each tribe; and this tribunal was presided over by the praetor, and divided into four chambers, which under the republic was placed under the ancient quaestors. The centumvirs decided questions of property, embracing a wide range of subjects. The Romans had no class of men like the judges of modern times; the superior magistrates were changed annually, and political duties were mixed with judicial. The evil was partially remedied by the institution of legal assessors, selected from the most learned jurisconsults. Under the empire the praetors were greatly increased; under Tiberius there were sixteen who administered justice, besides the consuls, six ediles, and ten tribunes of the people. The Emperor himself became the supreme judge, and he was assisted in the discharge of his judicial duties by a council composed of the consuls, a magistrate of each grade, and fifteen senators. At first, the duties of the praetorian prefects were purely military, but finally they discharged important judicial functions. The prefect of the city, in the time of the emperors, was a great judicial personage, who heard appeals from the praetors themselves.