The Rabbis explain the rationale behind their opinion: Just as we found in the case of a tereifa that its slaughter renders it ritually pure according to Torah law, i.e., ritual slaughter prevents it from having the ritual impurity of a carcass despite not rendering the animal permitted for consumption, so too, the slaughter of the mother animal should render the limb of its fetus that left the womb ritually pure, despite the fact that its consumption is prohibited.

Rabbi Meir said to them: No, if the slaughter of a tereifa renders the body of the animal ritually pure, it is because the slaughter is performed on something that is part of its body, i.e., its throat. Does it necessarily follow that you should also render the limb that left the womb pure, given that it is something that is not part of the mother’s body? Certainly not.

The mishna asks: From where is it derived with regard to a tereifa that its slaughter renders it ritually pure, i.e., prevents it from having the ritual impurity of a carcass? The mishna notes there is a reason to say the slaughter should not render it pure, as one can compare a tereifa with a non-kosher animal: A non-kosher animal is prohibited for consumption; so too, a tereifa is prohibited for consumption. Therefore, conclude: Just as with regard to a non-kosher animal, its slaughter does not render it ritually pure, so too with regard to a tereifa, its slaughter should not render it ritually pure.

The mishna questions the comparison: No, if you said that slaughtering cannot prevent an animal from having the ritual impurity of a carcass in the case of a non-kosher animal, which is distinct in that it did not have a period of potential fitness when slaughtering it could have rendered its consumption permitted, does it necessarily follow that you should also say this in the case of a tereifa, which did have a period of potential fitness? Perhaps, since the animal had a period of potential fitness its slaughter remains effective in preventing it from having the ritual impurity of a carcass.

The mishna rejects this distinction: Take back to yourself this claim that you brought, as it is insufficient. What about a case where an animal was born as a tereifa from the womb, and so it never had a period of potential fitness? For such a case, from where is it derived that its slaughter renders it ritually pure?

The mishna reformulates the distinction: No, if you say that slaughtering cannot prevent a prohibited animal from having the ritual impurity of a carcass with regard to a non-kosher animal, which is distinct in that there are no animals of its kind that are permitted through slaughtering, as the Torah states the concept of slaughtering only with regard to kosher animals, does it necessarily follow that you should also say this with regard to a tereifa kosher animal, given that there are other animals of its kind that are permitted through slaughtering, i.e., kosher animals that are not tereifa? Perhaps, since the concept of slaughtering is relevant to that kind of animal it can serve to prevent the animal from having the ritual impurity of a carcass even if the slaughter cannot render it permitted for consumption.

The mishna notes: Based on this reasoning, one must conclude that with regard to an eight-month-old fetus that was born alive, slaughter does not render it ritually pure, as there are no animals of its kind that are permitted through slaughtering. The Torah applies the concept of slaughter only with regard to animals that were born full term.

GEMARA: The mishna states that according to Rabbi Meir, if a foreleg of a fetus emerges from the womb and is severed after the slaughter of the mother, it is regarded as a carcass with the associated ritual impurity. Furthermore, the rest of the fetus from which it was cut is thereby rendered ritually impure through its contact with the foreleg. The Gemara asks: Why should the rest of the fetus be impure? This is a case of impurity imparted within a concealed area, as the point of contact between the foreleg and the fetus existed when they were still naturally connected to each other. And the halakha is that an impure item within a concealed area does not impart impurity. If the two items were in contact in a concealed area and not on an external surface, impurity cannot be imparted from one item to the other. Shall we say that Rabbi Meir conforms to his standard line of reasoning in this regard, as he holds that an impure item within a concealed area does impart impurity?

This is as we learned in a mishna (Kelim 27:10) concerning ritual impurity imparted by treading: If a person who is ritually impure due to having experienced a bodily emission, such as a man who experiences a gonorrhea-like discharge [zav], sits or leans upon an item that was designated for that purpose, the item is rendered ritually impure due to ritual impurity imparted by treading. The item will then impart impurity to people or utensils that come in contact with it. In the case of a garment that is impure with ritual impurity imparted by treading that was three by three handbreadths in size, i.e., the minimum size to impart such impurity, that was split into smaller pieces, each part is ritually pure with regard to ritual impurity imparted by treading and will no longer impart impurity to people and utensils that come in contact with it.

The mishna continues: But each piece will still have the ritual impurity of having been in contact with an item that imparts ritual impurity imparted by treading. Before the garment was split, when it still imparted ritual impurity imparted by treading, each piece of the garment was in contact with another part of it. Through that connection, each piece was rendered ritually impure with the impurity of having been in contact with ritual impurity imparted by treading. When the garment was subsequently split, although the pieces were no longer able to impart ritual impurity imparted by treading, they retained the ritual impurity they acquired through their contact with the other pieces before the garment was split. This is the statement of Rabbi Meir. In this case, the contact between the pieces occurred within a concealed area, as the connection between parts of the same item has the status of a connection within a concealed area. Evidently, Rabbi Meir holds that impurity can be imparted within a concealed area.

And it is taught in that mishna that Rabbi Yosei says, disagreeing with Rabbi Meir: But what source of impurity imparted by treading did these pieces touch? Rabbi Yosei disregards the contact between the pieces that occurred before the garment was split, as that contact has the status of a connection within a concealed area. Rather, the only way the pieces could still be ritually impure is if a zav had touched the garment directly, e.g., when he sat on the garment he also touched it with his skin. In that case the garment would have also been rendered ritually impure due to contact with a zav, and that impurity would remain even after the garment was split. It would appear, then, that the opinion of Rabbi Meir in the mishna here can be reconciled only with the opinion of Rabbi Meir in the mishna in Kelim, but not with the opinion of Rabbi Yosei.

The Gemara responds: Wasn’t it stated with regard to that mishna in Kelim that Ulla said: They taught that Rabbi Yosei disagrees with Rabbi Meir only in the case of a garment of three by three handbreadths that was split into smaller pieces, as once it is split, there is no piece large enough to impart to the other pieces impurity imparted through treading.

But with regard to pieces of three by three fingerbreadths that come, i.e., are cut, from a large garment, everyone agrees that at the time of their separation from their original garment, before they are fully detached from it, they are rendered impure through their contact with the original garment, despite the fact that the contact occurs within a concealed area. In this case of the mishna here also, one can say that at the time of separation of the flesh of the fetus from the limb, i.e., the foreleg, it is rendered impure through its contact with the limb. According to Ulla, then, the mishna can be reconciled also with the opinion of Rabbi Yosei.

Ravina said there is a different explanation of how the mishna can be reconciled with the opinion of Rabbi Yosei: A garment does not stand, i.e., is not intended, to be cut. On the contrary, it is better for it to remain whole. Therefore, the connections between its pieces are regarded as being within a concealed area that cannot impart impurity. By contrast, with regard to a fetus that extends its foreleg, the foreleg does stand to be cut, as it is prohibited for consumption while the rest of the fetus is permitted, and the halakhic principle is that any item that stands to be cut