But it was no longer suited for the altered circumstances.  The better classes of society kept aloof more and more from service in the army, and the Roman and Italic middle class in general was disappearing; while on the other hand the considerable military resources of the extra-Italian allies and subjects had become available, and the Italian proletariate also, properly applied, afforded at least a very useful material for military objects.  The burgess-cavalry,(4) which was meant to be formed from the class of the wealthy, had practically ceased from service in the field even before the time of Marius.  It is last mentioned as an actual corps d’armee in the Spanish campaign of 614, when it drove the general to despair by its insolent arrogance and its insubordination, and a war broke out between the troopers and the general, waged on both sides with equal unscrupulousness.  In the Jugurthine war it continues to appear merely as a sort of guard of honour for the general and foreign princes; thenceforth it wholly disappears.  In like manner the filling up of the complement of the legions with properly qualified persons bound to serve proved in the ordinary course of things difficult; so that exertions, such as were necessary after the battle of Arausio, would have been in all probability really impracticable with the retention of the existing rules as to the obligation of service.  On the other hand even before the time of Marius, especially in the cavalry and the light infantry, extra-Italian subjects—­the heavy mounted troopers of Thrace, the light African cavalry, the excellent light infantry of the nimble Ligurians, the slingers from the Baleares—­were employed in ever-increasing numbers even beyond their own provinces for the Roman armies; and at the same time, while there was a want of qualified burgess-recruits, the non-qualified poorer burgesses pressed forward unbidden to enter the army; in fact, from the mass of the civic rabble without work or averse to it, and from the considerable advantages which the Roman war-service yielded, the enlistment of volunteers could not be difficult.  It was therefore simply a necessary consequence of the political and social changes in the state, that its military arrangements should exhibit a transition from the system of the burgess-levy to the system of contingents and enlisting; that the cavalry and light troops should be essentially formed out of the contingents of the subjects—­in the Cimbrian campaign, for instance, contingents were summoned from as far as Bithynia; and that in the case of the infantry of the line, while the former arrangement of obligation to service was not abolished, every free-born burgess should at the same time be permitted voluntarily to enter the army as was first done by Marius in 647.