The criticism of the text of the Rigveda itself is concerned with two periods. The first is that in which it existed alone before the other Vedas came into being; the second is that in which it appears in the phonetically modified form called the Samhita text, due to the labours of grammatical editors. Being handed down in the older period exclusively by oral tradition, it was not preserved in quite authentic form down to the time of its final redaction. It did not entirely escape the fate suffered by all works which, coming down from remote antiquity, survive into an age of changed linguistic conditions. Though there are undeniable corruptions in detail belonging to the older period, the text maintained a remarkably high level of authenticity till such modifications as it had undergone reached their conclusion in the Samhita text. This text differs in hundreds of places from that of the composers of the hymns; but its actual words are nearly always the same as those used by the ancient seers. Thus there would be no uncertainty as to whether the right word, for instance, was sumnam or dyumnam. The difference lies almost entirely in the phonetic changes which the words have undergone according to the rules of Sandhi prevailing in the classical language. Thus what was formerly pronounced as tuam hi agne now appears as tvam hy agne. The modernisation of the text thereby produced is, however, only partial, and is often inconsistently applied. The euphonic combinations introduced in the Samhita text have interfered with the metre. Hence by reading according to the latter the older text can be restored. At the same time the Samhita text has preserved the smallest minutiæ of detail most liable to corruption, and the slightest difference in the matter of accent and alternative forms, which might have been removed with the greatest ease. Such points furnish an additional proof that the extreme care with which the verbal integrity of the text was guarded goes back to the earlier period itself. Excepting single mistakes of tradition in the first, and those due to grammatical theories in the second period, the old text of the Rigveda thus shows itself to have been preserved from a very remote antiquity with marvellous accuracy even in the smallest details.