Are people permitted to castrate themselves (with a potion)? What about indirect castration? What about drinking such a potion if you're already sterile? What if the person drinking the potion is an old woman? The mishnah seems to be a far broader statement than the cases that whittle down its meaning. Also: Vinegar for medicinal purposes vs. as a condiment at a meal. Or rose water. To what extent do economic advantages dictate what substances are limited to medicinal use? Rabbi Shimon's implicit answer: not at all.