Ave Verum Corpus ("Hail, true Body!") is a short Latin poem that was set to music by Mozart. For most of it, the language is quite plain and straightforward.
However, there's a bit in the middle where I can't understand the cases used.
cujus latus perforatum / fluxit aqua et sanguine
The general idea is that Christ's side (cujus latus) was pierced (perforatum), and water and blood (aqua et sanguine) flowed out (fluxit).
But I can't make heads nor tails of the noun cases used. Fluxit seems to be a singular verb with a plural subject in the ablative case, while the absolute clause before it is either nominative or accusative—which makes no sense to me.
What's going on here?