Question: A midwife who touches a fetus (in our Mishnah) is like two swallowed rings (the Tum'ah and Taharah are both Belu'ah), yet she becomes Teme'ah!

Answer #1 (Rabah): A fetus is not considered Tum'ah Belu'ah, because it is destined to leave the womb.

Objection (Rava): A swallowed ring is also destined to leave the digestive tract!

Answer #2 (Rava citing Rav Yosef): The midwife is not Teme'ah mid'Oraisa, rather mid'Rabanan.

Question: It suffices to say that she is Teme'ah only mid'Rabanan!

Answer: The extra words show that the Mishnah is not only like R. Akiva, who is Metamei a dead fetus inside the womb (mid'Oraisa). Rather, it is even like R. Yishmael, who is Metaher;

(Even though the fetus is not Tamei mid'Oraisa,) Chachamim decreed that a midwife who touches it becomes Teme'ah.

Question: Why did they decree?

Answer: Perhaps the fetus' head came out (and she did not see it), and she does not realize that she is Teme'ah.

Question: If so, also the mother should also be Teme'ah!

Answer: The mother can feel if the head came out.

Question: If so, she will tell the midwife!

Answer: In the throes of labor, she might neglect to tell her.

Question: Where do R. Akiva and R. Yishmael argue about this?

Answer (Beraisa - R. Yishmael): "Anything that will touch (a Mes) on the face of the field (will become Tamei)" excludes (touching) a fetus in the womb;

R. Akiva says, this includes (touching) a Golel and Dofek (Rashi - a coffin cover and a support for the cover; Tosfos - a monument and stones marking the location of the coffin).

R. Yishmael learns Golel and Dofek from a tradition from Moshe from Sinai.

Question: What is R. Akiva's source to say that a (dead) fetus in the womb is Tamei?

Answer (R. Oshaya): "If one touches a Mes in a Nefesh" refers to a fetus in the womb.

R. Yishmael learns from this verse that a Revi'is of blood from a corpse is Tamei (like a full corpse), for the blood is the Nefesh.

R. Akiva is Metamei a Revi'is of blood even if it came from two corpses;

(Beraisa - R. Akiva): "On all dead Nefashos he will not come" teaches that a Revi'is of blood from two corpses is Metamei in an Ohel.

(Mishnah): If a fetus stuck a limb out of the womb, and it was cut off, and then the mother was slaughtered, the meat (the rest of the fetus) is Tahor.

R. Meir says, if the mother was slaughtered and then the limb was cut off, the meat (of the fetus) is Tamei, because it touched a Nevelah;

Chachamim say, it is like meat that touched a slaughtered Terefah (this will be explained).

Chachamim: We find that slaughtering a Terefah is Metaher (inhibits Tum'as Nevelah). Similarly, slaughtering the mother is Metaher a limb of a fetus (that left the womb)!

R. Meir: Shechitah is Metaher the animal itself. You have no source that Shechitah is Metaher something else (i.e. the limb, which is not part of the mother)!

Question: What is the source that a slaughtered Terefah is Tahor?

We should compare it to a Tamei (species of) animal. Just like Shechitah does not permit eating a Tamei animal, and it becomes a Nevelah, the same should apply to a Terefah!

Answer #1: We do not learn from a Tamei animal, for it never had potential to be permitted.

Rejection: A Tahor animal that was born Terefah never had potential to be permitted, yet Shechitah prevents it from becoming Nevelah!

Answer #2: We do not learn from a Tamei animal, for Shechitah does not apply to the species (to permit eating it).

Shechitah is not Metaher a Nefel (stillborn calf), since Shechitah does not apply to Nefalim (they are like a species unto themselves.)

(Gemara) Question: According to R. Meir, how does the fetus become Tamei? It touches the forbidden limb internally, not externally!

Answer #1: This is consistent with R. Meir's opinion that Tum'ah is transferred through internal contact;

(Mishnah - R. Meir): If a Mishkav (something that people sit on) three by three Tefachim was Tamei Medras (e.g. a Zav or Nidah sat on it) and it was torn in two, each piece is not Tamei Medras (it is too small to sit on), but it is Tamei because it touched a Tamei Mishkav;

R. Yosi: The pieces did not touch the whole Mishkav! They are Tamei only if the Mishkav had (also) received (standard) Tum'ah (an Av ha'Tum'ah touched it).

Objection: Even R. Yosi agrees in our case!

(Ula): They argue only if each piece is less than three by three Tefachim, but if a piece three fingers by three fingers was cut off, and at least three by three Tefachim remained, all agree that the former piece became Tamei when it was cut off (for it touched the latter, which remained an Av ha'Tum'ah).

Here also, when the limb is cut off, it makes the fetus Tamei!