Slavery, however, lasted in Europe for about 800 years after Constantine, and during the period with which alone this volume is concerned, although its character was changed and mitigated, the number of men who were subject to it was probably greater than in the Pagan Empire. In the West the barbarian conquests modified the conditions of labour in two directions. The cessation of the stream of barbarian captives, the impoverishment of great families, who had been surrounded by vast retinues of slaves, the general diminution of town life, and the barbarian habits of personal independence, checked the old form of slavery, while the misery and the precarious condition of the free peasants induced them in great numbers to barter their liberty for protection by the neighbouring lord.(137) In the East, the destruction of great fortunes through excessive taxation diminished the number of superfluous slaves; and the fiscal system of the Byzantine Empire, by which agricultural slaves were taxed according to their employments,(138) as well as the desire of emperors to encourage agriculture, led the legislators to attach the slaves permanently to the soil. In the course of time, almost the entire free peasantry, and the greater number of the old slaves, had sunk or risen into the qualified slavery called serfdom, which formed the basis of the great edifice of feudalism. Towards the end of the eighth century, the sale of slaves beyond their native provinces was in most countries prohibited.(139) The creation of the free cities of Italy, the custom of emancipating slaves who were enrolled in the army, and economical changes which made free labour more profitable than slave labour, conspired with religious motives in effecting the ultimate freedom of labour. The practice of manumitting, as an act of devotion, continued to the end; but the ecclesiastics, probably through the feeling that they had no right to alienate corporate property, in which they had only a life interest, were among the last to follow the counsels they so liberally bestowed upon the laity.(140) In the twelfth century, however, slaves in Europe were very rare. In the fourteenth century, slavery was almost unknown.(141)