Slaves were treated better under the empire than under the later republic (see p. 273), a change to be attributed doubtless to the softening influence of the Stoical philosophy and of Christianity. The feeling entertained towards this unfortunate class in the later republican period is illustrated by Varro's classification of slaves as "vocal agricultural implements," and again by Cato the Elder's recommendation that old and worn-out slaves be sold, as a matter of economy. Sick and hopelessly infirm slaves were taken to an island in the Tiber and left there to die of starvation and exposure. In many cases, as a measure of precaution, the slaves were forced to work in chains, and to sleep in subterranean prisons. Their bitter hatred towards their masters, engendered by harsh treatment, is witnessed by the well-known proverb, "As many enemies as slaves," and by the servile revolts and wars of the republican period. But from the first century of the empire there is observable a growing sentiment of humanity towards the bondsman. Imperial edicts take away from the master the right to kill his slave, or to sell him to the trader in gladiators, or even to treat him with any undue severity. This marks the beginning of a slow reform which in the course of ten or twelve centuries resulted in the complete abolition of slavery in Christian Europe. [Illustration: SARCOPHAGUS OF CORNELIUS SCIPIO BARBATUS (Consul 298 B.C.).] PART II. MEDIÆVAL AND MODERN HISTORY. INTRODUCTION. DIVISIONS OF THE SUBJECT.--As we have already noted, the fourteen centuries since the fall of the Roman empire in the West (A.D. 476) are usually divided into two periods,--the _Middle Ages_, or the period lying between the fall of Rome and the discovery of America by Columbus in 1492, and the _Modern Age_, which extends from the latter event to the present time. The Middle Ages, again, naturally subdivide into two periods,--the _Dark Ages_, and the _Age of Revival_; while the Modern Age also falls into two divisions,--the _Era of the Protestant Reformation_, and the _Era of the Political Revolution_. CHIEF CHARACTERISTICS OF THE FOUR PERIODS.--The so-called _Dark Ages_ embrace the years intervening between the fall of Rome and the opening of the eleventh century. The period was one of _origins_,--of the beginnings of peoples and languages and institutions. During this time arose the Papacy and Feudalism, the two great institutions of the Mediæval Ages.