The _exaction_ of the _annones_ and _tributes_, expressions which virtually included all the imposts, was the incessant business of the official class. At the beginning of each financial year the measure of the precept to be paid by each district was determined in the office of the Praetorian Praefect, subscribed by the Emperor, and disseminated through the provinces by means of notices affixed in the most public places.[649] A grace of four months was conceded and then the gathering in of the _annones_ or canon of provisions, which included corn, wine, oil, flesh, and every other necessary for the support of the army and the free distributions to the urban populace, began. Delivery was enjoined in three instalments at intervals of four months,[650] but payments in gold were not enforced until the end of the year.[651] The _Exactors_, who waited on the tributaries to urge them to performance, were usually decurions or apparitors of the Rector.[652] The Imperial constitutions directed with studied benignity that no ungracious demeanour should be adopted towards the tax-payers,[653] that no application should be made on Sundays,[654] that they should not be approached by _opinators_, that is, by soldiers in charge of the military commissariat,[655] that they should, when possible, be allowed the privilege of _autopragias_ or voluntary delivery,[656] and that, if recalcitrant, they should not be sent to prison or tortured, but allowed their liberty under formal arrest.[657] Only in the last resource was anything of their substance seized as a pledge, to be sold “under the spear” if unredeemed,[658] but in general any valid excuse was accepted and the tributaries were allowed to run into arrears.[659] Consonantly, however, to the prevailing principle every effort was made by the Exactors to amass the full precept from the locality, and those who could pay were convened to make up for the defaulters.[660] The actual receivers of the canon were named _Susceptors_, and their usual place of custom was at the mansions or mutations of the public posts.[661] Scales and measures were regularly kept at these stations,[662] and on stated occasions a Susceptor was in attendance accompanied by a _tabularius_, a clerk who was in charge of the censual register which showed the liability of each person in the municipality.[663] The _tabularius_ gave a receipt couched in precise terms to each tributary for the amount of his payment or consignment, particulars of which he also entered in a book kept permanently for the purpose.[664] The system of _adaeratio_, or commutation of species for money, was extensively adopted to obviate difficulties of delivery in kind; and this was especially the case with respect to clothing or horses for the army, or when transit was arduous by reason of distance or rough country.[665] The transport of the annones and tributes to their destination was a work of some magnitude, and was under the special supervision of the Vicar of the diocese.[666] Inland the _bastagarii_, the appointed branch of the public service, effected the transmission by means of the beasts of burden kept at the mansions of the Posts;[667] by sea the _navicularii_ performed the same task. The latter formed a corporation of considerable importance to which they were addicted as the decurions were to the Curia. Selected from the seafaring population who possessed ships of sufficient tonnage, their vessels were chartered for the conveyance of the canon of provisions as a permanent and compulsory duty.[668] Money payments, in coin or ingots, went to the capital;[669] provisions to the public granaries of Constantinople or Alexandria, the two cities endowed with a free victualling market,[670] or were widely dispersed to various centres to supply rations for the troops.[671] Besides the ordinary officials engaged in exaction there were several of higher rank to supervise their proceedings: _Discussors_, the Greek _logothetes_, who made expeditions into the provinces from time to time to scrutinize and audit the accounts;[672] surveyors of taxes, Senators preferably, whose duties were defined by the term _protostasia_,[673] to whom the _Susceptors_ were immediately responsible; and lastly _Compulsors_, officers of the central bureaucracy, _Agentes-in-rebus_, palatines attached to the treasury, even Protectors, who were sent on special missions to stimulate the Rectors when the taxes of a province were coming in badly.[674]