(Beraisa - R. Yehudah) Suggestion: Perhaps Nivlas Of Tamei (a Tamei species of bird that died without slaughter) has Tum'as Beis ha'Beli'ah (it is Metamei one who swallows a k'Zayis of it, and his garments)!

Rejection "Neveilah u'Treifah Lo Yochal" refers to birds forbidden due to Neveilah, but not to Tamei birds that are forbidden only due to eating a Tamei species.

Question: Above, we used "Treifah" to exclude Tamei animals (regarding Chelev). We should say that "Chelev Neveilah" discusses Chelev forbidden due to Chelev, but not due to eating a Tamei species!

Answer #1 (Abaye): Rather, "Treifah" is Metaher Chelev of a Treifah. One might have thought that since it is forbidden while alive, like a Tamei animal, its Chelev is Tamei. "Treifah" teaches that this is not so.

Objection #1: Likewise, we should need "Treifah" regarding Nivlas Of to teach that a Treifah has Tum'as Beis ha'Beli'ah. One might have thought that since one may not eat it, like a Tamei bird, it does not have Tum'as Beis ha'Beli'ah.

Objection #2: We cannot learn Treifah, which once was (potentially) permitted (it could have been slaughtered before it became Treifah), from Tamei, which was forbidden from birth!

Answer #2 (Rava): "Neveilah" teaches that when an animal becomes a Neveilah, the Isur of Neveilah is Chal (takes effect) on the Chelev (even though the Chelev was already forbidden). "Treifah" teaches that the Isur Tereifah is Chal on the Chelev.

The Torah must teach both. Had it said only "Neveilah", one might have thought that it is Chal on the Chelev, because Neveilah is Tamei, but Treifah is not Chal on it. Had it said only "Treifah", one might have thought that it is Chal on the Chelev, because Treifah is Chal on live animals, but Neveilah does not take effect on it.

78a (Reish Lakish): If one ate Pigul and Nosar (and Tamei) that were mixed together, he is exempt. Surely, there is more of one than the other, and it is Mevatel it.

This teaches that different Isurim (forbidden things) can be Mevatel each other;

Chulin 56a (R. Nechemyah): If a weasel bit an animal on the head, checking the membranes of the brain by hand is not reliable. This can permit a Neveilah!

Objection: It is not a Neveilah. It was slaughtered!

Correction: Really, it is only a Tereifah.

Rambam (Hilchos Ma'achalos Asuros 4:17): Neveilah joins with Tereifah. A half-k'Zayis of Neveilah joins with a half-k'Zayis of Tereifah or meat from a living Tahor animal. The general rule is, two Lavim do not join, except for Neveilah and Tereifah, since Tereifah is the beginning of Neveilah.

Or Some'ach: The Rambam holds that Tereifah and Neveilah are the same Shem (Isur), even though they are two Lavim. Similarly, meat from a live animal joins with Neveilah, since we learn its Isur from "u'Vasar ba'Sadeh Treifah." The Sifri (Re'eh) says that "Lo Sochal Kol Neveilah" includes Tereifah. They join because they are learned from the same Lav. R. Yochanan says so in the Yerushalmi. This is the Rambam's source. The Sugya in Zevachim supports him. It is difficult. We exclude Tamei birds because they are not forbidden due to "do not eat Neveilah." We should similarly exclude Tereifah and Chelev! This is good for the Rambam. Since Neveilah and Tereifah join, we cannot say that the Isur Neveilah will not take effect on Tereifah, for they are one Isur and Tereifah is the beginning of Neveilah. Therefore, if a Tereifah died, one is lashed for Neveilah. In Kidushin 77b, the Gemara suggested that one gets three sets of lashes for a woman widowed three times, according to the opinion that Ein Isur Chal Al Isur (a second Isur does not takes effect on something already forbidden). This must be because Ein Isur Chal Al Isur does not apply to one Isur and one Lav. The same applies to Tereifah and Neveilah.

Tosfos (78a DH ha'Pigul): A Mishnah (Me'ilah 17a) teaches that Pigul and Nosar do not join with each other, because they are different Isurim. The Gemara says that this refers to Tum'ah, but all Pasul Kodshim join regarding an Isur to eat them - "Lo Yochal Ki Kodesh Hem." That is when they were not mixed. Here, they were mixed, so they are Mevatel each other. Alternatively, here we discuss lashes for Pigul or Nosar. Indeed, they join with each other regarding "Lo Yochal Ki Kodesh Hem." Further, there are no lashes for that Lav, since it is Lav shebi'Chlalos (different Isurim forbidden by one Lav).

Tosfos (56a DH Neveilos): Why does the Gemara say that it is not a Neveilah? R. Yehudah holds that Shechitah of a Tereifah bird is not Metaher from Tum'ah! R. Nechemyah holds that it is Metaher, therefore he should not call it Neveilah.

Achiezer (2 YD 6:5): Pnei Moshe (Yerushalmi Nazir 6) says that R. Yochanan and Reish Lakish argue about a Tereifah that became a Neveilah. Reish Lakish obligates only one set of lashes because he does not expound "Kol Neveilah" to include a Tereifah. They are two Isurim, so Neveilah is not Chal on Tereifah. What was Tosfos' question from R. Yehudah? He holds that Ein Isur Chal Al Isur, therefore there is no Chiyuv for Neveilah. If so, the Gemara asked properly! Rather, all hold that Tereifah is the beginning of Neveilah (so Ein Isur Chal Al Isur does not apply). R. Yehudah holds that even though the Tereifah gets Tum'as Neveilah, the Isur Neveilah does not take effect, just like it does not take effect on a Tamei bird.

Shulchan Aruch (YD 27:1): If the Shechitah was invalid, it is a Neveilah. If the Shechitah was proper, but something else forbids, it is a Tereifah. If the neckbone was broken and most of the flesh with it, it is a Neveilah.

Question (Beis Yosef DH u'Mah): Why did the Tur need to write what is Neveilah and what is Tereifah? Both are forbidden. The only difference is Tum'ah. The Tur does not teach laws of Tum'ah, only Isur v'Heter!

Bach (2): This is relevant for us regarding Oso v'Es Beno (the Isur to slaughter an animal and its child on the same day). If it became a Neveilah, it was not a Shechitah. If it was only a Tereifah, one may not slaughter the other on the same day. Alternatively, it affects the law of two k'Zeisim (YD 98:9. If one k'Zayis each of two different Isurim fell into 59 k'Zeisim of Heter, each k'Zayis joins with the the Heter to be Mevatel the other Isur.)

Drishah (2): Some say that it is relevant to Kisuy ha'Dam (the next Siman). If it became Neveilah, there is no Mitzvah of Kisuy. Even though one who slaughters a Tereifah is exempt, if it was Kosher and slaughtered properly and afterwards became Tereifah, he must cover the blood. This is wrong. We do not cover a Chayah's blood before checking the lungs. If it is found to be Tereifah, we do not cover the blood, even though at the time of Shechitah we had no reason to think that it is Tereifah. Some say that it is relevant to Bitul in 60. Even though the Tur discussed blood and Chelev, the same applies to two k'Zeisim of meat of different Isurim. This is wrong. He permits only when the Isurim are dissolved. When Pigul, Nosar and Tamei are mixed, each is Batel in the others regarding lashes, but one may not eat the mixture, for their taste is not Batel. Likewise, one cannot say that it is relevant to Bitul in the majority when Tereifah and Neveilah are in a dry mixture. Even though it is relevant to lashes, the Tur does not come to teach about lashes! Some say that it is relevant to Oso v'Es Beno. Also, if a chicken was slaughtered and an egg was found inside in its shell, if it is a Safek Shechutah/Safek Tereifah, the egg is forbidden. If it is a Safek Shechutah/Safek Neveilah, the egg is permitted.

Bach (Kuntres Acharon): We can say that Tereifah and Neveilah help to be Mevatel the other, e.g. they are different species, e.g. ox, ram and goat. Each helps to be Mevatel the taste of the others. The Beis Yosef (98 DH Matzasi) brings so in the name of Or Zaru'a. Also, since when they are mixed dry, Tereifah and Neveilah help to exempt for lashes for the other, even though mid'Rabanan it is still forbidden to eat the mixture, the Isur is lighter, and if there is a Safek we can be lenient about a Safek mid'Rabanan.

Avnei Nezer (YD 18): Tevu'os Shor (33) agreed with the Bach. I disagree. The Rambam says that Tereifah and Neveilah join with each other, for they are one Isur. Therefore, they are not Mevatel each other. (Magihah - i.e. all agree to this. The Rambam (Hilchos Pesulei ha'Mukdashim 18:20) holds that even Pigul, Nosar and Tamei are not Mevatel each other. The Bach holds like the first answer in Tosfos (78a), that when the Isurim are mixed, they are Mevatel each other. However, Tosfos gave two other answers, and we always hold like the last answer. A proof is from a Ben Paku'a (a fetus found inside a slaughtered animal). If the mother is Tereifah, slaughtering the calf permits it. One cannot permit it through slaughtering the mother, for then it is (considered a Tereifah) like one of the mother's limbs. If it died without Shechitah, in any case it is forbidden. We cannot permit it through the mother, for then it is a Tereifah. We cannot slaughter it itself, for then it is Neveilah. Perhaps this is the Rambam's source that Neveilah and Tereifah join. The Ritva and Ran (Sanhedrin 112a DH Behemah) say that if half an animal belongs to an Ir ha'Nidachas, it is totally forbidden to eat. The Shechitah does not pertain to one of the Simanim, so it does not permit eating it. It is an improper Shechitah. Therefore, slaughtering a Tereifah mother is an improper Shechitah and does not permit the fetus. The Isur 'Eino Zavu'ach' (it was not slaughtered) applies to every Tereifah. Therefore, it joins with the Isur Neveilah.

Avnei Milu'im (Teshuvah 4 DH uvi'Prishah): Tevu'os Shor defended the Bach. Different parts of an animal have different tastes, e.g. the liver and (Stam) meat. They should be Mevatel each other; they are not, because it is one Lav. Isur v'Heter (24) connotes unlike this, but it is possible that he agrees. In Klal 27 he says 'if Isurim have different tastes, even if they are from one Lav, or two Lavim that join for lashes, different tastes do not join.' This connotes that even if they are from one Lav, different tastes do not join. However, perhaps this is only when they are from two Lavim included in one Lav, since each by itself is Batel. The Torah included all Isurim for lashes ("Lo Sochal Kol To'evah") only when each is forbidden by itself. This Lav does not include when each is Batel by itself. When it is truly one Isur, e.g. Neveilah, even different tastes are not Mevatel each other.