[Sidenote: Depopulation.] When a country is prosperous the population tends to increase. In the Roman Empire, even as early as Augustus, a falling off in numbers was apparent, which was bound to sap the vitality of the state. War, plague, the evil results of slavery, and the outrageous taxation all combined to hasten the depopulation; for when it is hard to make a living, men are deterred from marrying and find it difficult to bring up large families. [Sidenote: Infiltration of Germans into the Empire.] In order to replenish the population great numbers of the Germans were encouraged to settle within the Empire, where they became coloni. Constantine is said to have called in three hundred thousand of a single people. Barbarians were enlisted in the Roman legions to keep out their fellow-Germans. Julius Cæsar was the first to give them a place among his soldiers. The expedient became more and more common, until, finally, whole armies were German, entire tribes being enlisted under their own chiefs. Some of the Germans rose to be distinguished generals; others attained important positions among the officials of the government. In this way it came about that a great many of the inhabitants of the Roman Empire were Germans before the great invasions. The line dividing the Roman and the barbarian was growing indistinct. It is not unreasonable to suppose that the influx of barbarians smoothed the way for the break-up of the western part of the Empire. Although they had a great respect for the Roman state, they must have kept some of their German love of individual liberty and could have had little sympathy for the despotism under which they lived. [Sidenote: Decline of literature and art.] 6. As the Empire declined in strength and prosperity and was gradually permeated by the barbarians, its art and literature fell far below the standard of the great writers and artists of the golden age of Augustus. The sculpture of Constantine's time was far inferior to that of Trajan's. Cicero's exquisitely finished style lost its charm for the readers of the fourth and fifth centuries, and a florid, inferior species of oratory took its place. Tacitus, who died about A.D. 120, is perhaps the latest of the Latin authors whose works may be ranked among the classics. No more great men of letters arose. Few of those who understand and enjoy Latin literature to-day would think of reading any of the poetry or prose written after the beginning of the second century. [Sidenote: Reliance upon mere compendiums.]