PHONOLOGY. The regular interchange of cer tain sounds in the different languages of the Indo-European group was generally postulated at an early period without the later insistenee on the necessity of regularity. At first it seemed as if there were exceptions which could not be ex plained by any law. The sounds first compared were eonsonantal, as these seemed most regular. Their eorrespondence in certain of the Indo-Euro pean languages was formulated by what is known as Grimm's law (q.v.).
The vowel-system longer to explain and the consonantal system required modification. In the ease of the vowels, apart from the determina tion of the long disputed point whether the a, c, o of the Greek, or their equivalents in one a-sound, as in Sanskrit, represented the older state, the vowel-system was seen to be more regtilar as soon as the primitive existence of sonant nasals and liquids was recognized. The chief modifications of Grimm's law and further contrilmtary laws were established during the last quarter of the nineteenth century. At the same time was raised the question in regard to the original vowel-form of roots and that of its changes in Ablaut or modified vowels and diphthongs.
The priority of the Western c, 0. as com pared with the Asiatic monotone a, was proved by .Amelung and Brugmann at about the same time. Next was shown the existence of an Indo-Euro pean e, that is of a real palatal vowel. iu San skrit itself. This was proved by Collitz, and dependently by Verner. through demonstrating that when a Sanskrit a (= c) follows a guttural it palatalizes it and hence must itself be palatal.
Thus Sanskrit ca = quc. Osthoff and Brug mann, again, pointed out the existence in Greek of the Sanskrit 1 and r vowels, as shown e.g in rarpticrt ( = Sk. pitr;su), ropaKov, etc. Then, as opposed to the view of the Hindu grammarians and early European scholars, it was shown that in the series i, c, ai, the simple vowel is no more radical than is the yaw: form, r, ai, or, in other words, we cannot speak of the stein in cbetryw, to take an analogous ease, as being less original than that in gybtyov.
The chief modification of Grimm's law was made in l55 by the complementary law of ac cent, which goes by the name of Verner's law In discussing consonantism, the designations of other than the guttural series are self-explana tory, but in the guttural series there is great con fusion of nomenclature. Thus the Indo-European languages had palatal sounds, c, j; dentals, t, d; labials, p, b, both aspirated and non-aspirated. So they had aspirated and non-aspirated, surd and sonant, gutturals, 1,-, g (1:h, 0). But these latter, being, as explained above, of twofold form, have different designations. There are two series, the palatal and non-palatal guttural series. These are sometimes distinguished as palatal and velar, but the former is also called the h-series, and even the 1:-series; while the latter is called the q-series and also the k series. The velar k-series was from the beginning distinguished from the palatal guttural by being a sort of back guttural. with a tendency to de velop a sound or 10), which was lost in special languages. The two sounds either united or the guttural became more labialized, Sanskrit ka, Latin quo, Gothic bra, a tendency that reached an extreme iu Greek, where this guttural is often represented by a labial. ac in iro (also before nasals and liquids). though some times dentalized. as in re (before u, e), while sometimes coinciding with 1: (stZr). Besides guttural: and palatals. the Indo-European group possessed the eonsonantism just described. but it was defective in fricatives and spirants (e.g. f, English th, z). Peculiar to the older language are the aspirated sonants retained in the Indo frank group beside aspirated surds, as well as the modified nasals and sibilants. a, s, including the final half-nasal, and final half-sibilant. As already explained. Indo-European had as half voweis y, v, 1, r. Linguai sounds (found in San skrit) appear to be borrowed from the Dravid inns.