It is now more than 90 years since Fortunatov first enunciated that rule of phonetic development in Sanskrit which has since borne his name. The article in which this theory was proposed appeared in A. Bezzenberger's Beiträge zur Kunde der indogermanischen Sprachen, VI, 1881, 215–20, and the rule formulated by him was that in the group l + dental in Sanskrit the l disappears and the dental is changed to lingual (cerebral, retroflex). This process of phonetic change is illustrated by the comparison of the Sanskrit word paṭa- ‘cloth’ with OSlav. platǐno, Russ. polotnó ‘linen cloth’, etc., where Sanskrit paṭa- has replaced a pre-Sanskrit *palta-. Fortunatov cited a large number of examples in support of this rule, and although many of these are unacceptable, there still remain enough good etymologies in his list to provide significant support for his theory. It is a noteworthy feature of this change that the cerebral replacing the combination of l with dental is a single consonant, in marked contrast to the later assimilation of r followed by dental in Middle Indo-Aryan where the result is always a double consonant (e.g. -ṭṭ- in vaṭṭai 〈 vartate, etc.). Another significant difference is that whereas in MIA the combination of r with dental results in dental as well as cerebral (vattai beside vaṭṭai, etc.), the product of l + dental in Sanskrit is invariably cerebral.