1. אלו שעורותיהן כבשרן

The Mishnah on Daf 117b taught that the עור – skin of a נבלה is not tamei as נבלה (i.e., it is not considered meat). The next Mishnah states: אלו שעורותיהן כבשרן – the skins of the following are considered like their meat (and transmit the same tumah the meat transmits), because their skins are soft: human skin, the skin of a domestic pig (Rebbe Yehudah adds the skin of the wild pig), the skin of a tender camel’s hump (defined by the Gemara as before it has carried a burden), the skin of a tender calf’s head, and the skin of several parts of an animal. Regarding the skins of שרצים, the Mishnah records three opinions: the Tanna Kamma says the skins of an אנקה – porcupine, כח and לטאה (two species of lizard), and חומט – snail are all tamei like their meat. Rebbe Yehudah says the skin of a לטאה has the status of עור (not meat), like the skin of a חולדה – weasel. Rebbe Yochanan ben Nuri says that the skins of all eight שרצים are not considered like meat.

1. Human skin is tamei מדרבנן, to prevent making one’s parents’ skins into spreads

The Mishnah taught that human skin is tamei like flesh. Ulla says: דבר תורה עור אדם טהור – Biblically, human skin is tahor. The Rabbonon declared it tamei because of גזירה שמא יעשה אדם עורות אביו ואמו שטיחין – a decree lest a person will make the skins of his father and mother into spreads. In another version, Ulla’s statement refers to the סיפא of the Mishnah, which taught that all the listed skins are tahor when tanned, except for human skin, which is tamei even when tanned. Ulla explained that tanned human skin is only tamei מדרבנן. According to the first version of Ulla’s statement, human skin is always tahor מדאורייתא, and only tamei מדרבנן. According to the latter version, ordinary human skin is tamei מדאורייתא, and only tanned human skin requires the Rabbinical decree.

1. עורות used as patches or stepped upon

The Mishnah stated: וכולן שעבדן או שהילך בהן כדי עבודה – all of [the Mishnah’s listed skins] which were tanned into leather, or were spread out and stepped upon for the time necessary for tanning leather, are tahor (except for human skin). This implies that merely spreading them out to be stepped upon does not make them tahor. This is challenged from a Baraisa: אוזן חמור שטלאה לקופתו – a donkey’s ear which one patched to his basket becomes tahor, because it loses its status as (נבילה) meat, and is considered skin. This proves thar mere designation as leather suffices to remove tumah!? The Gemara answers that patching flesh to a basket renders it tahor without it being trodden upon (because the patching is a nullifying act). Merely spreading it out to be stepped upon, however, is insufficient unless it is actually stepped upon. Rebbe Yannai defines “the amount of time required for tanning leather” as four מילין. Reish Lakish listed three other halachos whose guideline is likewise four mil: לגבל – the distance a person hired for kneading dough must travel to immerse the customer’s tamei utensil, לתפלה – the distance one must travel to daven in a shul (with a minyan), and the distance one must travel to obtain water for נטילת ידים before eating bread.