(Mishnah): One who touches a femur of a Mes or Kodshim, whether or not there is a hole in it, becomes Tamei;

One who touches a femur of a Nevelah or Sheretz becomes Tamei only if there is a hole of in it, even arbitrarily small.

Question: What is the source that it is even Metamei b'Masa?

Answer: "One who touches... and one who carries" teaches that whatever has Tum'as Maga has Tum'as Masa.

(Gemara) Inference: A femur of a Mes has only Tum'as Maga, but not Tum'as Ohel.

Question: What is the case?

If there is a k'Zayis of flesh on the bone, it should also be Metamei b'Ohel!

Answer: There is not a k'Zayis of flesh on the bone.

Question: If there is a k'Zayis of marrow inside, the Tum'ah should exude and be Metamei b'Ohel!

Answer: There is not a k'Zayis of marrow inside.

Question: If we say that marrow inside nourishes meat outside, even if there is less than a k'Zayis of marrow inside (Tosfos; Rashi - there is no marrow inside, since marrow could grow again, and then it could help meat grow outside), we should consider the bone like a proper limb (which is Metamei b'Ohel)!

Answer (Rav Yehudah brei d'R. Chiya): Our Mishnah teaches that marrow inside does not nourish meat outside.

Question: If there is not a k'Zayis of meat (or marrow), why is it Tamei regarding Kodshim?

Furthermore, why is one Tamei if he touches a femur of a Nevelah or Sheretz that has a hole?

Answer #1: The Reisha (Tum'as Mes) discusses when there is not a k'Zayis of marrow. The Seifa (Kodshim) discusses when there is a k'Zayis. Each teaches a Chidush;

The Reisha teaches that marrow inside does not nourish meat outside;

The Seifa teaches that bones that held Nosar are Tamei (mid'Rabanan).

(Rav Mari): Bones of Kodshim that once held Nosar are Tamei, because they once held something forbidden.

Regarding Nevelah, even if there is a k'Zayis of marrow, a bone is Tamei only if it has a hole.

Answer #1A (Abaye): (The cases in the Mishnah are like above, but) marrow inside does nourish meat outside;

The intention is that the bone was scraped or planed, not cut.

(R. Elazar): If a femur was cut lengthwise, it is Tamei (for the marrow still nourishes meat outside). If it was cut widthwise, it is Tahor.

A way to remember this is a date tree. (If one cuts it lengthwise (from the ground up), it will live. If it is cut widthwise, it will die.)

Answer #2 (R. Yochanan): The entire Mishnah discusses when there is a k'Zayis of marrow inside. Marrow inside does nourish meat outside;

Regarding Tum'as Mes, the Mishnah says that it has Tum'as Maga, i.e. Tum'as Ohel. (Below (2:a), we show that a Tana equates these.)

Question: If marrow nourishes meat outside, regarding Nevelah and Sheratzim, the bone should be Tamei like a limb, even if there is no hole!

Answer (R. Binyamin bar Gidal): The case is, the marrow is dry (it cannot nourish meat outside).

Regarding Tum'as Mes, the Tum'ah pierces (goes straight through) the bone;

Regarding Nevelah, since dry marrow cannot nourish meat outside, it is not Tamei like a limb;

It is only Tamei if there is a hole.

Support (R. Avin - Mishnah): If one touches a half-k'Zayis (of Tum'as Mes) and towers over (or is towered over by) another half-k'Zayis, he is Tamei.

We understand this if Tum'as Ohel is just like Tum'as Maga.

Question: If Tum'as Ohel is not like Tum'as Maga, why do the half-k'Zeisim join?

(Mishnah): Tum'os of the same name (type) join up. Tum'os of different names do not join.

Counter-question: If Tum'as Ohel is like Tum'as Maga, the half-k'Zeisim should join also in the Seifa (but they do not)!

(Seifa): If one touches a half-k'Zayis (of Tum'as Mes) and is under a common roof with a half-k'Zayis, he is Tahor.

Question: The Reisha (that the half-k'Zeisim join) is difficult!

Resolution (R. Zeira): The Mishnah discusses Tum'ah between two chests. (There is not a Tefach in between. Only) in such a case, Tum'as Ohel is like touching. (This refutes the support for R. Yochanan, who said that normal towering is like touching.)

Question: Which Tana considers towering like touching?

Answer: It is R. Yosi;

(Beraisa - R. Yosi): A spoon full of Rekev (dust of a decayed Mes) has Tum'as Maga, Masa and Ohel.

Question: Granted, it has Tum'as Masa and Ohel. One moves or towers over the entire amount.

However, how can it be Metamei through Maga? One cannot touch the full amount! (It is not connected.)

Answer: We must say that Maga refers to Ohel. The Tana calls it Maga.

Question: It lists Tum'as Maga and Ohel!

Answer #1 (Abaye): Towering less than a Tefach above the Tum'ah is like Maga. Towering more than a Tefach above the Tum'ah is not like Maga.

Answer #2 (Rava): Also towering more than a Tefach above the Tum'ah is like Maga.

Question: What type of Ohel is not like Maga?

Answer: Being under a common roof with Tum'ah is unlike Maga.

Rava: I learn from a Mishnah;

(Mishnah - R. Yosi): If (interwoven) bed ropes or poles separate between a house and the second story, they block Tum'as Mes from passing from one to the other.

If the ropes (or poles) were stretched in the air over a Mes, one who touches (puts his hand) over a rope is Tahor. One who touches (over the Mes) in the airspace between the ropes is Tamei.

Question: What is the case?

If the ropes are less than a Tefach over the Mes, even over the ropes should be Tamei, just like Tum'ah pierces through the clothing on a Mes!

Answer: Rather, the ropes are more than a Tefach over the Mes, and the Tana calls this Maga.

Rejection (Abaye): Really, the ropes are less than a Tefach over the Mes;

This is unlike clothing on a Mes. One is Mevatel clothing on a Mes to the Mes (he decides to leave it on permanently), but one is not Mevatel the ropes!

Question: Still, it should be like covered Tum'ah (of Mes, with less than a Tefach between the Tum'ah and the covering), which pierces through the covering!

Answer: R. Yosi holds that covered Tum'ah does not pierce the covering.

Question: What is the source to say this? (The answer finishes on 126a.)

Answer (Mishnah): If a cupboard is a Tefach deep, but the opening is less than a Tefach:

If Tum'ah is in the cupboard, (everything in) the house is Tamei. If Tum'ah is in the house, (everything in) the cupboard is Tahor;

This is because it is the nature of Tum'ah to leave, but it is not the nature of Tum'ah to enter.

R. Yosi says, the house is Tahor, because the Tum'ah might leave less than a k'Zayis at a time, or it might be burned before it leaves.

(Seifa): If the cupboard is in the doorway, facing out:

If Tum'ah is in the cupboard, the house is Tahor. If Tum'ah is in the house, the cupboard is Tahor.