of linguistic investigations, for they mention various grammatical terms, such as "letter" (varṇa), "masculine" (vṛishan), "number" (vachana), "case-form" (vibhakti). Still more such references are to be found in the Āraṇyakas, the Upanishads, and the Sūtras. But the most important information we have of pre-Pāṇinean grammar is that found in Yāska's work.
Grammatical studies must have been cultivated to a considerable extent before Yāska's time, for he distinguishes a Northern and an Eastern school, besides mentioning nearly twenty predecessors, among whom Çākaṭāyana, Gārgya, and Çākalya are the most important. By the time of Yāska grammarians had learned to distinguish clearly between the stem and the formative elements of words; recognising the personal terminations and the tense affixes of the verb on the one hand, and primary (kṛit) or secondary (taddhita) nominal suffixes on the other. Yāska has an interesting discussion on the theory of Çākaṭāyana, which he himself follows, that nouns are derived from verbs. Gārgya and some other grammarians, he shows, admit this theory in a general way, but deny that it is applicable to all nouns. He criticises their objections, and finally dismisses them as untenable. On Çākaṭāyanas theory of the verbal origin of nouns the whole system of Pāṇini is founded. The sūtra of that grammarian contains hundreds of rules dealing with Vedic forms; but these are of the nature of exceptions to the main body of his rules, which are meant to describe the Sanskrit language. His work aimost entirely dominates the subsequent literature. Though belonging to the middle of the Sūtra period, it must be regarded as the definite starting-point of the post-Vedic age. Coming to be regarded as an infallible