In considering the functions of the consuls we must distinguish between two periods of the history of the Republic. The first extends from their institution to the year 81 B.C.; the second from this year, when the reforms of Sulla introduced a change in their position which was felt as long as consuls continued to exist. This change caused no alteration in their powers, but only in the scope of their activity. During the first period they are the heads of the whole state, and are found ruling wherever Roman energy extends; during the second they are practically the chief magistrates only of the city of Rome and of Italy. The theory of colleagueship—that each individual member of a college was vested with the fullest power of action subject to the veto of his assessor—did not necessitate a united activity of the consuls in every department of state. They divided their functions, sometimes before their entry on office,[892] and in early times there are traces of the fundamental division of competence expressed by the terms _domi_ and _militiae_, one consul occasionally taking the field at the head of an army, while the other remained at home to transact the business of civil administration.[893] This arrangement, which divested colleagueship of its meaning as a safeguard against the rule of a single man, was, however, very unusual, and, as a rule, the consuls were present together in Rome or undertook a joint command abroad. But joint activity in the city—even after the duties of registration had been given to the censor and those of civil justice to the praetor—was in some departments almost impossible. It was obviated by a principle of rotation, which gave the administration and the fasces for a single month to each consul in turn,[894] the elder of the two being given the symbol of power first, and the one who possessed it at the moment being described as _consul major_.[895] This distinction never wholly vanished; for Caesar, we are told, revived in his consulship (59 B.C.) an old custom by which the lictors walked behind the consul who had not the fasces.[896] But long before Caesar’s time positive co-operation between the consuls in the city was common. They summoned the Senate together, and many consular laws bear the names of two rogators. There remained, however, several important acts which, while they, morally if not legally, demanded the assent of both consuls, could yet be performed only by one. Such were the election of magistrates and the nomination of a dictator. In these cases the question as to which consul should act was often decided by agreement (_comparatio_) or by lot (_sortitio_).