[1] The concept was defined and amply illustrated by Hagège & Haudricourt;[2] it has been mentioned by several followers of panchronic phonology,[3] and beyond.
Typically, the /i/ or /j/ was then lost, leading to a situation where a trace of the original /i/ or /j/ remains in the fronted quality of the preceding vowel.
Subsequent loss of final /i/, however, made /yː/ a phoneme and the primary indicator of plurality, leading to a distinction between /muːs/ "mouse" and /myːs/ "mice".
This distinction survives in the modern forms "mouse" /maʊs/ and "mice" /maɪs/, although the specifics have been modified by the Great Vowel Shift.
Before disappearing, a sound may trigger or prevent some phonetic change in its vicinity that would not otherwise have occurred, and which may remain long afterward.