1) SLAUGHTERING WITH AN ANIMAL'S NAIL
QUESTION: The Gemara concludes that one may not perform Shechitah with a "Tziporen" (fingernail) while it is still attached.
The SHULCHAN ARUCH (YD 6:2) rules, "If one slaughters with an object that is attached to the ground or attached to a body, such as a tooth or nail that is attached to an animal, the Shechitah is invalid."
REBBI AKIVA EIGER (in Chidushim to Shulchan Aruch 6:2, and in Teshuvos #51) questions this ruling. How does the Shulchan Aruch know that a tooth or nail that is attached to an animal is invalid for Shechitah? Perhaps the Gemara here refer exclusively to a tooth or nail that is attached to a person. Perhaps only a person is considered "Mechubar," since the verse compares a person to Karka (land) -- "v'His'nachaltem Osam" (Vayikra 25:46; see Sanhedrin 16a, and SHACH end of CM 95). Consequently, only something attached to a person is considered "Mechubar l'Karka." Something attached to an animal is not considered "Mechubar," but rather "Talush." Therefore, a Shechitah performed with an animal's tooth or nail should be valid.
ANSWER: The Shulchan Aruch's ruling is based on the words of RASHI (DH Mechuberes) who states clearly that even a tooth attached to an animal cannot be used for Shechitah. Rashi understands that when the Gemara calls a tooth or nail that is attached "Mechubar," it does not refer to the general rule of "anything that is attached to land is considered like land." Rather, when the Gemara says that it is considered "Mechubar" and is thus invalid for Shechitah, it means that it is not a freely mobile implement. Accordingly, there is no logical distinction between a tooth or nail that is attached to an animal and a tooth or nail that is attached to a person.
Rashi's source may be the Gemara in Gitin (39a) that teaches that something that is about to be detached no longer has the status of "Mechubar" ("Kol ha'Omed Ligzoz k'Gazuz Dami"). Nevertheless, the Gemara here implies that Shechitah may not be performed with an attached object even if it is about to be detached. It must be that what makes "Mechubar" unfit for Shechitah is not that it is part of the ground, or that it is called "land." Rather, it is unfit for Shechitah because it is not freely mobile.
Moreover, the concept that a person is compared to Karka applies only to monetary matters. With regard to laws such as Shechitah, Tum'ah, and the writing of a Get (see Gitin 21a), there is no logical reason to compare a person to Karka. (See Hagahos of TZEMACH DAVID on TESHUVOS REBBI AKIVA EIGER #51.) (Z. Wainstein)
2) FILING DOWN THE SERRATED EDGE OF A SICKLE
QUESTION: The Mishnah teaches that if one files down the serrated blade of a sickle and makes it smooth and sharp, it is a valid knife for Shechitah.
What is the Mishnah teaching? It is obvious that a sickle may be used for Shechitah if its serrated edge was filed down and it was converted into an ordinary Shechitah knife.
ANSWER: The TIFERES YISRAEL explains that the Mishnah is teaching that such a knife is permitted even though one might have thought that the Rabanan forbid using such a knife. Perhaps such a knife should be prohibited in order to prevent people from making a mistake and thinking that a sickle may be used for Shechitah even before its jagged edge is filed down (since all of its points are bent in the same direction).
3) CUTTING AT ANY RING OTHER THAN THE TOP
OPINIONS: Rebbi Yosi b'Rebbi Yehudah maintains that if a majority of the cut of Shechitah was performed without Hagramah (slanting the cut above the point that delimits the part of the neck upon which Shechitah may be performed), the Shechitah is valid. Rav and Shmuel assert that this applies only to Shechitah performed at the top ring of cartilage surrounding the trachea (the cricoid cartilage), and not to Shechitah performed at any of the other rings.
Do Rav and Shmuel mean that one may not perform Shechitah at any other ring, or merely that the leniency of cutting a majority does not apply to Shechitah done at any other ring?
(a) RASHI explains that Rav and Shmuel mean that one may not perform Shechitah at all at the other rings, because they surround only the majority of the circumference of the trachea and not its entire circumference. Consequently, the rings are not considered part of the trachea and one must cut between them.
Rashi adds that even though the Halachah is that "Rubo k'Kulo" (the majority is like the entirety) in a case where the majority of the Shechitah was done below the top ring, the logic of "Rubo k'Chulo" does not make the lower rings -- which surround only most of the trachea -- considered part of the windpipe. (Rashi to 18b, DH Hachi, accedes that this opinion is not accepted as the Halachah.)
Rashi's reasoning may be better understood based on the teaching of RAV CHAIM SOLOVEITCHIK, who proposes that the principle of "Rubo k'Chulo" applies only to an action that is done to most of an object (such as cutting most of the trachea during Shechitah). "Rubo k'Chulo" makes the action considered as though it was done to the entire object. In contrast, "Rubo k'Chulo" cannot define an object itself and dictate that since most of the object is in a certain place, the entire object is considered to be in that place.
(b) TOSFOS and other Rishonim argue with Rashi and explain that Shechitah may be performed even at the other rings. The only difference between the other rings and the top vertebra is that when one cuts at the lower rings, one must cut through the entire thickness of the rings; it does not suffice to cut through most of their thickness. In contrast, it suffices to cut through most of the top ring, because when one cuts through most of the top ring he cuts through most of the trachea as well (which is not the case with the other rings that do not surround the entire trachea; cutting through most of their thickness would not cut most of the trachea). (See also RASHI to 18b, DH Hachi, in his second explanation of the Gemara.) (Z. Wainstein)
4) HALACHAH: FOLLOWING THE "MINHAG" OF THE PLACE
OPINIONS: The Gemara relates that when Rebbi Zeira came to Eretz Yisrael, he ate meat from an animal slaughtered in a manner which Rav and Shmuel maintain is invalid because of "Hagramah." The Gemara asks how could Rebbi Zeira eat such meat when there is a rule that one must observe the stringencies of both the place to which one comes, and the place from which one left (Mishnah, Pesachim 50a). Since, in Rebbi Zeira's hometown, the practice was to follow the stringent ruling of Rav and Shmuel, how could Rebbi Zeira act leniently when he came to Eretz Yisrael?
Abaye answers that this rule does not apply when one travels from Bavel to Eretz Yisrael. One who travels from Bavel to Eretz Yisrael is not obligated to observe the Minhagim of Bavel (because Bavel is subordinate to Eretz Yisrael).
Rav Ashi answers than Rebbi Zeira had no intention to return to Bavel. Therefore, he was no longer bound by the Minhagim of his former hometown.
Which of these answers does the Halachah follow with regard to the Minhagim that a person must observe when he travels to Eretz Yisrael?
(a) The Rishonim in Pesachim (51a) maintain that the Halachah follows the second answer. Accordingly, one who travels to a new place and does not intend to return to his former place of residence is not obligated to observe the Minhagim of his former place. If, on the other hand, one intends to return to his hometown, then he must continue to observe the Minhagim of his hometown. In public, he must observe the stringencies of the place he is visiting in order to prevent contention, but he need not observe those stringencies in private (RAN, Pesachim 50b).
(b) The ROSH adds that one is not allowed to depart, publicly, from the customs of the place he is visiting even if he wants to act more stringently than the people of that place, for doing so may cause contention. (See also Insights to Pesachim 52:1-2).