1. It is well known that the earliest and probably best descriptive grammar in existence is the Sanskrit grammar of Panini (?350 B.C.). The subject of the following essay is Panini's phonological analysis of the Sanskrit consonants. This illustrates some of the more important techniques used by Panini and his colleagues. It also enables us to reconstruct some of the methods by means of which Panini constructed his grammar.' Though the analysis is of general interest, the object language is a particular one, Sanskrit. Some knowledge of the sound system of Sanskrit is therefore necessary to appreciate Panini's treatment. For this purpose I adapt here a part of the chart The Sanskrit Alphabet given by W. S. Alien in his book Phonetics in ancient India 20 (London, 1953). This chart explains at the same time the customary Roman transliteration used in the following paper. Similar enumerations or partial enumerations are given in some of the early phonetic treatises which are the special subject of Alien's monograph. In Panini's grammar itself the matter is stated differently. His grammar consists of rules or sutras grouped together in eight chapters and therefore often referred to as AstadhyiyZ 'the eight chapters'. Each chapter consists of four sections called pada and within each pada the sutras are numbered from one onward. Each sutra of the grammar is therefore determined by three numerals and is in general quoted accordingly. For example, 7.3.102 refers to the 102nd sutra of the 3rd pada of the 7th adhyaya. The Astadhyayt is preceded by the Sivasiltra, a list of the sounds which are used in the grammar. The order of sounds in this list is different from the order of the above chart. Reasons for this difference will be given in detail below, but the principle upon which they are based is accounted for, in Allen's words (ibid.), 'by the phonological, as opposed to phonetic, approach there adopted'.