In Frajzyngier (1981) I attempted to reconstruct vowel-raising and vowellowering rules in Chadic. Vowel-raising rules were found in three branches of Chadic, and they operated under similar conditions, viz., vowels of the stem were raised when there was a high vowel added in the suffix. Vowel-lowering rules were found in two branches of Chadic, but I could not reconstruct them as being part of Proto-Chadic because they were essentially different rules: in the East branch the vowels of the stem were lowered when a low vowel suffix was added. In the West branch the last vowel of the word was lowered when a heavy syllable preceded it. In that paper I stated that unless vowel-lowering rules were found in some other branches of Chadic, these rules could not be reconstructed as existing in Proto-Chadic. It now appears that such rules do
exist in other branches. In Mulwi, or Munjuk, a Biu-Mandara language, there exists a vowel-lowering rule that operates under similar conditions as vowel-lowering rules in the East Branch l
anguages, Mubi and Migama.