and these, again, into _gr[=a]mas_. The names, however, are not
employed with strictness, and _jana_, etymologically gens but
politically tribus, sometimes is used as a synonym of _gr[=a]ma_.[4]
Of the ten books of the Rig-Veda seven are ascribed to various
priestly families. In the main, these books are rituals of song as
inculcated for the same rites by different family priests and their
descendants. Besides these there are books which are ascribed to no
family, and consist, in part, of more general material. The
distinction of priestly family-books was one, possibly, coextensive
with political demarcation. Each of the family-books represents a
priestly family, but it may represent, also, a political family. In at
least one case it represents a political body.[5]

These great political groups, which, perhaps, are represented by
family rituals, were essentially alike in language, custom and
religion (although minor ritualistic differences probably obtained, as
well as tribal preference for particular cults); while in all these
respects, as well as in color and other racial peculiarities, the
Aryans were distinguished from the dark-skinned aborigines, with whom,
until the end of the Rig Vedic period, they were perpetually at war.
At the close of this period the immigrant Aryans had reduced to
slavery many of their unbelieving and barbarian enemies, and formally
incorporated them into the state organization, where, as captives,
slaves, or sons of slaves, the latter formed the "fourth caste." But
while admitting these slaves into the body politic, the priestly
Aryans debarred them from the religious congregation. Between the
Aryans themselves there is in this period a loosely defined
distinction of classes, but no system of caste is known before the
close of the first Vedic Collection. Nevertheless, the emphasis in
this statement lies strongly upon system, and it may not be quite idle