[Sidenote: Islam stationary in area, and in civilization retrograde.] Having thus traced the rapid early spread of Islam to its proper source, I proceed to the remaining topics, namely, the causes which have checked its further extension, and those likewise which have depressed the followers of this religion in the scale of civilization. I shall take the former first--just remarking here, in respect of the latter, that the depression of Islam is itself one of the causes which retard the expansion of the faith. [Sidenote: The Arabs ceased, in second century, to be a crusading force.] As the first spread of Islam was due to the sword, so when the sword was sheathed Islam ceased to spread. The apostles and missionaries of Islam were, as we have seen, the martial tribes of Arabia--that is to say, the grand military force organized by Omar, and by him launched upon the surrounding nations. Gorged with the plunder of the world, these began, after a time, to settle on their lees and to mingle with the ordinary population. So soon as this came to pass they lost the fiery zeal which at the first had made them irresistible. By the second and third centuries the Arabs had disappeared as the standing army of the caliphate, or, in other words, as a body set apart for the dissemination of the faith. The crusading spirit, indeed, ever and anon burst forth--and it still bursts forth, as opportunity offers--simply for the reason that this spirit pervades the Koran, and is ingrained in the creed. But with the special agency created and maintained during the first ages for the spread of Islam the incentive of crusade ceased as a distinctive missionary spring of action, and degenerated into the common lust of conquest which we meet with in the world at large.