As medical knowledge advanced, it seems certain, the practice of abortion must have been generally added to that of infanticide in Greece, as later in Rome. See Aristotle, _Politics_, vii, 16; Plutarch, _Lycurgus_, c. 3; and Plato, _Theætetus_, p. 149 (Jowett's trans. iv, 202), as to the normal resort to abortion. The Greeks must have communicated to the Romans the knowledge of the arts of abortion, as they did those of medicine generally. But it does not appear that with all these checks population really fell off in Greece until after the time of Alexander. Before that time it may very well have fallen off in Athens when she lost her position as sovereign and tribute-drawing State. The tribute would tend to maintain a population in excess of the natural amount. Dr. Mahaffy (_Rambles and Studies in Greece_, 4th ed. p. 11--a passage not squared with the data in _Greek Life and Thought_, pp. 328, 558) accepts the old view of a general and inexplicable depopulation. One of the _loci classici_ on that head, in the treatise _On the Cessation of Oracles_ (viii) attributed to Plutarch but probably not by him, is searchingly examined by Hume at the close of his essay _Of the Populousness of Ancient Nations_, and the critic comes to the conclusion that the extreme decay there asserted cannot have taken place. He was in all probability right in arguing that the number of slaves in Attica had been enormously exaggerated in the figures of Athenæus (cp. Cunningham, _Western Civilisation_, i, 109, note). There is reason to conclude, however, that Hume was unduly incredulous on some points. Strabo (refs. in Thirlwall, viii, 460) had found an immense decay of population in Greece more than a century before Plutarch; and his details prove a process of shrinkage which must have lasted long. In any case, a relative depopulation took place after the conquests of Alexander, from the operation of socio-economic causes, which are indicated by Finlay (_History of Greece_, Tozer's ed. i, 15; cp. Mahaffy, _Greek Life and Thought_, p. 328, and _The Greek World under Roman Sway_, 1890, p. 218). Broadly speaking, the Greeks went to lands where wealth was more easily acquired than in their own. Further depopulation took place under the Romans, partly from direct violence and deportation, partly from fiscal pressure, partly from the economic causes already noted.