Demelza has done enough reading on the biology of procreation that she knows what Galen means when he says finishes and she nods thoughtfully, even though she still doesn't quite understand.

"So he wears it on his..." Trailing off, she flushes faintly, because whether she knows the biology or not, it's still awfully intimate and while she trusts Galen more than many folks, while she had intended on asking him all along, it's difficult for her to stumble along.

Instead of trying to figure out what to say, she decides to just continue. "And it blocks his... his semen?" she all but whispers. "It sounds terribly uncomfortable."