The enjoyment of full political rights in ancient Rome was conditioned only by membership of a patrician _gens_; full citizenship here, as in most ancient states, being dependent on birth, and the membership of a purely private association satisfying all the demands that the state made as a condition of the attainment of its rights. But there were other forms of association of a definitely political character, amongst which the citizens were distributed, and as members of which they exercised active political rights or were subject to personal burdens. These were the three patrician tribes of Ramnes, Tities, and Luceres, and the thirty _curiae_. With reference to the question whether these were primary and natural associations of an ethnic character or artificial creations made by a supreme authority after the founding of Rome, we have already seen[140] that the _tribus_ are probably an ethnic survival artificially employed; in the case of the _curiae_, it must remain far less certain whether they were of spontaneous growth or purely artificial creations, or (what is perhaps more probable) in the main natural associations, artificially regulated in number and grouping to suit a political purpose. The tribe, which was a division not merely of the citizen body but of the land, was the basis for taxation and the military levy.[141] We know nothing of the first burden, but it is probable that no detailed scheme of direct taxation existed in the early Roman state. The revenues from the king’s domains probably rendered him self-sufficing, while the patrician burgesses served in the army at their own cost, and were doubtless expected to defray the expenses of their retainers. It is probable that in cases of emergency a tax in kind was levied from the landholders of the tribes. Of the military burdens tradition has preserved some plausible details. The army was known as the _legio_ or “gathering,”[142] and was composed of three “thousands” (_milites_),[143] one from each of the three tribes. These foot-soldiers were commanded by three or nine tribal officers, the _tribuni militum_.[144] The cavalry consisted of three hundred _celeres_, one from each of the three tribes, each commanded by three _tribuni celerum_. When the Patriciate was enlarged by the addition of the _gentes minores_,[145] these three hundreds (_centuriae_) were increased to six.[146]