THE GREAT family of Slav peoples, which occupies most of eastern and south-eastern Europe and the northern portion of the continent of Asia, is composed of East Slavs (Great Russians, Ukrainians, Byelorussians); West Slavs (Poles, Czechs, Lusations); and South Slavs (Slovenes, Groats, Serbs, Bosnians and Montenegrins, Macedonians and Bulgars).  Divided today into five states , the mass of approximately 250,000,000 Slavs is particularly dense and homogeneous from the Oder to the Ural River, and from the Adriatic to the Black Sea.