Certain forms of the Greek word for ‘mix’ which have γ instead of κ as the final of their root-syllable, e.g., the present μíγνυι and the 2nd aorist ἐμíγην , appear to be anomalous when compared not only with the other forms of the same Greek verb but also with its cognates in other Indo-European languages, where all forms point to as the primitive IE root-final. Boisacq derives μíγνυμι from pIE *mei - and states, without further comment, that ‘le grec a la gutturale douce’. Walde, s. v. misceo , gives the Greek cognate as ‘mit Media’, but makes no remark on the phenomenon except to reject Wackernagel's theory of an independent origin for μíγνυμι. Apparently, then, Boisacq and Walde explain the disagreement in root-finals by the theory of the socalled variation of the root-determinative.
Maria Wilkins Smith (Sat,) studied this question.