Tom didn't know that. Medical science still consists of leeches in large portions of his land, and ratskins heal so well they don't pay much attention to medicine anyway, except when it comes to diseases.

His response - the first genuine one he's given - is an interested, "Does it? Huh."

And then a final swing of his flask, which he slides into his back pocket. Wen might be interested in that bit of info - he's always trying to improve his mind.