capital, and contributed their elements to the final composition of the Roman people.  When we read of ninety-seven thousand Hebrews whom Titus sold into bondage after the fall of Jerusalem, of forty thousand Greeks sold by Lucullus after one victory, and the auction sub corona of whole tribes in Gaul by Caesar, the scale of this forcible transfer becomes apparent, and its power as an agent of race amalgamation.  Senator Sam Houston of Texas, speaking of the Comanche Indians, in the United States Senate, December 31, 1854, said:  “There are not less than two thousand prisoners (whites) in the hands of the Comanches, four hundred in one band in my own state....  They take no prisoners but women and boys."[157] It was customary among the Indians to use captured women as concubines and to adopt into the tribe such boys as survived the cruel treatment to which they were subjected.  Since the Comanches in 1847 were variously estimated to number from nine to twelve thousand,[158] so large a proportion of captives would modify the native stock.

In Africa slavery has been intimately associated with agriculture as a source of wealth, and therefore has lent motive to intertribal wars.  Captives were enslaved and then gradually absorbed into the tribe of their masters.  Thus war and slavery contributed greatly to that widespread blending of races which characterizes negro Africa.  Slaves became a medium of exchange and an article of commerce with other continents.  The negro slave trade had its chief importance in the eyes of ethnologists and historians because, in distributing the black races in white continents, it has given a “negro question” to the United States, superseded the native Indian stock of the Antilles by negroes, and left a broad negro strain in the blood of Colombia, Venezuela, and Brazil.  This particular historical movement, which during the two centuries of its greatest activity involved larger numbers than the Tartar invasion of Russia or the Turkish invasion of Europe, for a long period gave to black Africa the only historical importance which it possessed for the rest of the world.[159]

[Sidenote:  Fusion by deported and military colonies.]

In higher stages of political development, war aiming at the subjugation of large territories finds another means to fuse the subject peoples and assimilate them to a common standard of civilization.  The purpose is unification and the obliteration of local differences.  These are also the unconscious ends of evolution by historical movement.  With this object, conquerors the world over have used a system of tribal and racial exchanges.  It was the policy of the Incas of ancient Peru to remove conquered tribes to distant parts of the realm, and supply their places with colonists from other districts who had long been subjected and were more or less assimilated.[160] In 722 B.C. the Assyrian king, Sargon, overran Samaria, carried away the Ten Tribes of Israel beyond the Tigris and scattered