[If] one flays either an animal or a beast, either kosher or nonkosher, either small or large, for a spread — enough to grasp it; for a flask — until he flays the breast. [If] he flays it from the feet, it is all [considered] attached as regards tumah, both to contract tumah and to convey tumah. The skin on the neck — R’ Yochanan ben Nuri says: It is not [considered] attached, but the Sages say: It is [considered] attached until he flays it completely.