Gemara

30b (Rav Yehudah): If he cut when the knife was under the skin, this is Kosher.

(Bei Rav): I do not know what the law is in this case.

Question: What would Bei Rav say if the knife was under a cloth, or covered by the animal's wool?

This question is unresolved.

Question (Rav Papa): What is the law of Chaladah (Shechitah when the knife is covered) in the minority of the Simanim?

This question is unresolved.

32a - Question (Rav Huna brei d'R. Noson): If he paused while cutting the minority of the Simanim, what is the law?

This is unresolved.

Rishonim

Rambam (Hilchos Shechitah 3:4): If one paused long enough to lift the animal and make it lie down, or to slaughter only the minority of Simanim, but not for a full Shechitah, this is Safek Neveilah.

Rebuttal (Ra'avad): The Gemara asked about a pause enough to slaughter another animal.' This implies that there is no Safek about a pause enough to slaughter the minority. Also, according to the Rambam, it should have said 'enough to slaughter the minority.' Also, we cannot explain like this regarding Chaladah in the minority of Simanim. Rather, both of these are similar. He slaughtered the majority, paused, and then finished. Since there is a tradition to disqualify Shehiyah, it is not clear. Or, perhaps we are not concerned. There is no concern for half the Kaneh of a bird, and all the more so for the majority. These questions were not resolved. It seems that we are lenient.

Lechem Mishneh and Pri Chodosh (YD 23:11): The Ra'avad means that mid'Oraisa, surely once the majority was slaughtered, it is Kosher. However, perhaps we are stringent mid'Rabanan, for it is not clear to others that he already slaughtered the majority. Or, perhaps we are not concerned. Surely we need not decree about the Kaneh of a bird. Since the question is about a decree mid'Rabanan, we are lenient about a Safek. According to Rashi, it is a Safek mid'Oraisa, so we are stringent.

Beis Yosef (YD 23 DH veha'Rambam): It seems that the Rambam's text said 'paused k'Mi'ut (like the time to slaughter) the minority of Simanim', and not 'b'Mi'ut (during the slaughter) of the minority.' The Meforshim rejected this.

Rambam (10): If one inserted the knife under the skin, or was MAchlid the knife under tangled wool, or spread a cloth on the knife and on the neck and slaughtered under the cloth, since the knife is not exposed, it is Safek Neveilah. Likewise, if he slaughtered the minority of Simanim through Chaladah, and finished the Shechitah without Chaladah, it is Safek Neveilah.

Lechem Mishneh: Rashi and the Ra'avad explained the question about Chaladah in the minority of Simanim like the question about Shehiyah in the minority of Simanim after cutting the majority. The Rambam did not want to explain like this, for this is like merely cutting meat. Rather, Chaladah was in the first minority. He did not explain the question about Shehiyah like this, for this is no question. It must be Pasul, for if not, we would never find Shehiyah in (the Kaneh of - PF) a bird! Also, a Tosefta explicitly disqualifies. Why is Shehiyah in the first minority Neveilah, but regarding Chaladah it is a Safek? Shehiyah causes that the initial cut is not considered Shechitah. It is as if it was torn on a thorn, so it is like a punctured Veshet. When the first minority was through Chaladah, the Shechitah continued, so perhaps it is Kosher.

Rosh (2:6): Rashi explains that Rav Papa asked about Chaladah in the latter minority after cutting the majority. This was not resolved, so we are stringent about Chaladah, Hagramah, and Shehiyah in the latter minority. R. Tam challenged this, for a Tosefta ia Machshir Shehiyah in the latter minority. Rather, he asked about Chaladah in the first minority.

Rosh (ibid.): R. Oshaya gave the correct explanation. After he slaughtered most of one Siman in an animal, he was Machlid the knife under the remainder of the Siman and cut the remainder of the (Ma'adanei Yom Tov - this should say 'cut the second') Siman. Even if you will say that under the skin, wool or a cloth is not Chaladah, this is because they are not considered part of the animal. Or perhaps, even if inserting the knife (underneath) is Chaladah, here is different, for it is as if the remaining minority was already cut. In Ashkenaz and France the custom is to be stringent, like Rashi. The Rif brought the question about Shehiyah, but not the question about Chaladah. This is astounding.

Ran (7a DH Hichlid): Do we say that since the minority of the Siman is not Me'akev, it is like skin, and Chaladah (in the latter minority) is Kosher? Or, is it different, for Shechitah applies to it? Therefore, it is called Chaladah. Perhaps we ask even according to Bei Rav, who were unsure about a knife under the skin. Perhaps surely Chaladah in the minority of a Siman disqualifies, since Shechitah applies to it. Or, perhaps they are unsure. This question was not resolved, we are stringent. According to this Perush, the Rif did not need to bring this. We are stringent about under the skin due to Safek, and all the more so under the minority of a Siman!

Mordechai (604): Because this was not clarified, and there are opinions about how to explain the question, we should forbid every Shehiyah and Chaladah in the first and last minority of the Kaneh and Veshet.

Poskim

Shulchan Aruch (YD 23:5): After Shechitah of most of one Siman in a bird, or two in an animal, Shehiyah does not disqualify. Therefore, Shehiyah does not apply to the Kaneh of a bird at all. Some say that as long as both Simanim were not totally slaughtered, Shehiyah disqualifies. L'Chatchilah, one should be concerned for this opinion.

Beis Yosef (DH veha'Rambam): The Rambam holds that after slaughtering the needed majority (or majorities), Shehiyah, Derasah, or any Pesul of Shechitah does not apply. It is as if he cuts the leg.

Rema: Even b'Di'eved, the custom is to consider it Tereifah.

Shulchan Aruch (YD 24:10): If after slaughtering the majority of the Simanim, one was Machlid the knife under the remaining minority of both or one of them and cut it, it is permitted. Some forbid also this. L'Chatchilah, one should be concerned for this opinion.

Rema: The custom is to consider Tereifah any Chaladah, in the first or latter minority, in the Kaneh or Veshet.

Beis Yosef (DH v'Hichlid): The Gemara did not resolve the Safek, therefore we are stringent. Rashi explains that he properly cut the majority, and did Chaladah on the remaining minority. Do we say that once he cut the majority, it is Kosher? Or, perhaps it is all one Shechitah, and there is Chaladah? R. Tam explains that the question applies to the first minority, according to Rav Yehudah, who is Machshir under the skin. Perhaps if the knife was under the minority of the Siman, and he cut the majority, this is worse. Or, perhaps even Bei Rav were unsure about under the skin, for Shechitah does not apply to skin, so (perhaps) this is Chaladah, for it is whole (not cut - PF). However, Shechitah applies to the Simanim, and even so it suffices to cut the majority, so it is as if the remaining minority was already cut. We must say that he cut the skin, and afterwards did Chaladah under the remaining minority of the Siman. If not, this is under the skin, and Rav Yehudah and Bei Rav already argued about this.

Beis Yosef (DH veha'Rav): According to R. Oshaya, the question about Chaladah in the minority of the Siman applies only to an animal. In a bird, once the majority of one Siman was slaughtered it is Kosher, and it cannot become Pasul.

Beis Yosef (DH veha'Rambam): The Rambam explains that Rav Papa asked about one who slaughtered the minority of Simanim b'Chaladah, and finished without Chaladah. Do we require (Chaladah in) the Shi'ur of Kosher Shechitah, i.e. the majority, to disqualify? Or, perhaps even a minority at the beginning disqualifies! This was not resolved, so we are stringent. The Rosh and Tur say that the Rambam is Machshir Chaladah in the latter minority. This is based on what he wrote in Halachah 10 and 13. It seems that he relied on the Tosefta regarding Shehiyah, and the same applies to other Pesulim of Shechitah.

Beis Yosef (DH u'Mah she'Chasav va'Adoni): The Tur says that the Rosh wrote like Rashi. The Rosh (2:6) taught that the Gemara did not bring the Tosefta to settle the question because it knew that one may not rely on it, for it was not taught in the academy of R. Chiya and R. Oshaya. I say that the Rosh merely explained Rashi, but other Meforshim need not reject the Tosefta, for it is not relevant to Rav Papa's question. The Rosh said that R. Oshaya's Perush is correct! He merely said that we should be stringent like Rashi and not rely on the Tosefta. The Rosh (1:24) sided with Rivam, who disqualifies Shehiyah, Derasah, Chaladah, in the latter minority, and is Machshir Hagramah and Ikur. Even so, mere reasoning is not enough to say that the Halachah does not follow a Tosefta. Even though also the Mordechai said to be stringent, letter of the law it seems that we rely on the Tosefta, since the Gemara did not explicit reject it, and all the more so since the Rambam brought it l'Halachah. However, where the custom is like Rashi, e.g. in Ashkenaz and France, one should not breach their fence.

Gra (11): Regarding the latter minority, we hold like Rashi. Regarding the first minority, we are concerned for the Veshet, for we are not skilled to check (perhaps it was nicked), like the Tosefta said about Shehiyah.