Notwithstanding their wide diffusion, interminglings with other races, varied grades of culture, and lack of political cohesion, the Tai-Shan groups acquire a certain ethnical and even national unity from their generally uniform type, social usages, Buddhist religion, and common Indo-Chinese speech. Amidst a chaos of radically distinct idioms current amongst the surrounding indigenous populations, they have everywhere preserved a remarkable degree of linguistic uniformity, all speaking various more or less divergent dialects of the same mother-tongue. Excluding a large percentage of Sanskrit terms introduced into the literary language by their Hindu educators, this radical mother-tongue comprises about 1860 distinct words or rather sounds, which have been reduced by phonetic decay to so many monosyllables, each uttered with five tones, the natural tone, two higher tones, and two lower[448]. Each term thus acquires five distinct meanings, and in fact represents five different words, which were phonetically distinct dissyllables, or even polysyllables in the primitive language. The same process of disintegration has been at work throughout the whole of the Indo-Chinese linguistic area, where all the leading tongues--Chinese, Annamese, Tai-Shan, Burmese--belong to the same isolating form of speech, which, as explained in _Ethnology_, Chap. IX., is not a primitive condition, but a later development, the outcome of profound phonetic corruption. The remarkable uniformity of the Tai-Shan member of this order of speech may be in part due to the conservative effects of the literary standard. Probably over 2000 years ago most of the Shan groups were brought under Hindu influences by the Brahman, and later by the Buddhist missionaries, who reduced their rude speech to written form, while introducing a large number of Sanskrit terms inseparable from the new religious ideas. The writing systems, all based on the square Pali form of the Devanagari syllabic characters, were adapted to the phonetic requirements of the various dialects, with the result that the Tai-Shan linguistic family is encumbered with four different scripts. "The Western Shans use one very like the Burmese; the Siamese have a character of their own, which is very like Pali; the Shans called Lue have another character of their own; and to the north of Siam the Lao Shans have another[449]."