He is liable for wine by itself, for grapes by themselves, for grape-seeds by themselves, and for grape-skins by themselves. R’ Elazar ben Azariah says: He is not liable until he eats two grape-seeds and their grape-skin.  Which are chartzanim and which are zagim? The chartzanim are the outer part, the zagim are the inner part; [these are] the words of R’ Yehudah. R’ Yose says: [In order] that you not err, it is like the zug-bell of an animal —- the outer part [is called] zug, and the inner part inbal.