The ordinary taxes sufficed for the usual light expenses; but in case of especial need an extraordinary tax was imposed upon the citizens. It was called tributum from tribuere, “to apportion,” because it was distributed among the citizens in proportion to their ratable property.[364] We hear of such a tax levied for ransoming the city from the Gauls[365] and another for the building of a wall;[366] but the most common use was for the payment of soldiers, hence the tributum was thought of primarily as a war tax.[367] For this reason tributum came to be correlative with stipendium.[368] It was not often imposed before the introduction of pay in 406.[369] Even then it was not levied every year; it was sometimes refunded when the condition of the treasury permitted; and it fell into disuse after 167.[370] As it was imposed on those only who were liable to military duty,[371] the tribe lists were followed in its collection, and in this sense we may say that it was collected tributim.[372] The work was done by state functionaries, as the tribe, so far as we know, had neither fiscal officers[373] nor a treasury; and possessing no property, it could not be held financially responsible. An epoch in the history of the tribes was made in 312 by Appius Claudius Caecus the censor, who enrolled the landless citizens, proletarians as well as aerarii, in the existing thirty-three tribes without discrimination.[374] Cives sine suffragio were alone excepted.[375] By giving the landless the upper hand in the assemblies this measure roused the animosity of the proprietors, and thus endangered the peace of the state. In order to soothe the excited feelings of the better class, Q. Fabius Rullianus, censor in 304, supported by his colleague Decius, removed the landless from the rural tribes; but not to deprive them wholly of tribal privileges, he registered them in the four urban tribes. Hence his measure is spoken of as a compromise. Thereafter the landholding and hence more respectable citizens were preferably enrolled in the rural tribes,[376] whereas the landless were confined to those of the city.[377] It was a permanent gain that henceforth tribal membership was a test of perfect citizenship. The censors still had the power to transfer a man from one tribe to another, for instance, from a rural to an urban tribe; but they could not exclude him wholly from the tribes, for that would be tantamount to depriving him of the citizenship.[378] There were still aerarii; individuals and sometimes large groups of citizens were still assigned as a punishment to this class, which, however, was henceforth included in the tribes of the city.[379] Although the ordinary urban tribesmen were usually exempt from military duty, the aerarii were required to serve, at times under especially hard conditions,[380] and were not disqualified for office.[381] In registering them in the tribes Claudius made them, like the landowners,