Emphasis has sometimes been laid upon an affection for old sites, or an aversion to migration, as characteristic of Nagas, distinguishing them from the migratory Kuki, who, like the Hill Kachari, moves his village by preference, whereas the Naga only moves his under compulsion. This, however, as has already been pointed out, cannot by any means be applied to all tribes at present designated Naga. A perhaps trivial point is the belief that neglect of washing causes illness, and the concomitant habit of personal cleanliness which is so much more marked in the Angami tribe than among its neighbours to the north, though the Lhota seems to have it in a greater degree than the Rengma, Sema, or Ao; the Angami dwelling, on the other hand, is frequently filthy as compared to those of the other tribes mentioned, principally owing to his habit of keeping his cattle in the front room. Such are the more outstanding facts of the case, and it is almost superfluous to state the more obvious conclusions to be drawn from them, that no Naga tribe is of pure blood, but the area which they inhabit has been the scene of a series of immigrations from north-east, north-west and south, and that the different stocks introduced in this way have entered into their composition. [40] Indeed, in view of the struggles that have taken place for the fertile plains of Burma to the east and India to the west, it is inevitable that some elements of the races worsted in these struggles should have been pushed up into the hills. In particular the line of the Dikhu and the Ti-Ho rivers would seem to mark more or less the point of contact between movements southward from the north and northward from the south, roughly marking as it does, except indeed for the Ao tribe, the line south of which dead are always buried, [41] and also the marked cleavage between the languages of the Western Nagas and of the North-eastern Nagas, the latter bearing more resemblance perhaps to those of the Kukis in the south than to those of their immediate neighbours. The immigration of Singpho elements from the north and Tai elements from the east are absolutely clear.