What is the definition of "Chartzanim" and "Zag"?
Rashi (like R. Yosi, Nazir 34b): "Chartzanim" are (grape) pits and "Zag", the skin. 1
R. Yehudah (Nazir 34b): Chartzanim" are (grape) skins, and "Zag" is the pit.
Rashi: Like a striker inside the casing of a bell.
Why does the Torah forbid even grapes and grape leaves? They do not intoxicate!
Mesilas Yesharim (perek 11): Even though the primary Isur is drinking wine, the Torah forbade everything with a connection to wine. This taught Chachamim how to make a fence for Torah. Regarding Arayos, they forbade action, seeing, speaking, hearing and even thought.