The combintion IV+I was seldom, that is, e could stand after guttural vowels, but not before them. When we speak about the vowel harmony in old Japanese, we must keep in mind the exclusiveness of ö(o²) on the one hand and the incomplete neutrality of e(e²) on the other. The latter explains why the vowel e of the first syllable of the second component of a compositum had the tendency to be transformed into a. By this transformation(e>a) two components could, through the medium of vowel harmony, become a real compositum. The labial-attraction could also be observed to some extent. This may be recognized by the fact that, both a and ö could stand after ö, but after o stood d in many cases.