The appearance of the huanhuan桓歡 rhyme in the history of Middle Chinese is not an accidental phenomenon. It can be proved by the fact that codas /n/ and /j/ differ in the intensity of co-articulation toward the vowels in front of them. Because of this difference, the vowels in front of these codas underwent different processes in the pathway from Middle Chinese to Modern Mandarin. The huanhuan桓歡 rhyme is the evidence of one of these processes.
