I was going to say you were wong, Murray, but you're not. The "Pange Lingua" I'm familiar with was written by St. Thomas Aquinas in the 13th century, one of five long eucharistic hymns he wrote for the Feast of Corpus Christi. Click here for information about the two hymns, both with the same title. As you can see, the earlier hymn by Venantius Fortunatus has a much more complex style. Aquinas wrote beautiful Latin, but it was of a style much different from that of the time of Caesar.
-Joe Offer-