(Gemara - R. Aba): If a bird entered under the corner of one's garment [and trapped itself, on Shabbos], one may guard it until Motzei Shabbos.

Version #1 - Question (Rav Nachman bar Yitzchak - Mishnah): If Reuven sat in the doorway and filled it, and Shimon sat next to him, even if Reuven left and Shimon remained, Reuven is liable and Shimon is exempt.

Suggestion: Shimon is exempt, but it is forbidden to remain!

Answer: No, he is exempt and permitted [to do so].

Support (Seifa): [Shimon] is like one who locked his house to guard the contents, and a deer was found inside.

This shows that he is exempt and permitted.

Version #2 - Support (Rav Nachman bar Yitzchak - Mishnah): If Reuven sat in the doorway and filled it, and Shimon sat next to him, even if Reuven left and Shimon remained, Reuven is liable and Shimon is exempt.

Suggestion: Shimon is exempt, and permitted [to do so]!

Rejection: No, he is exempt and forbidden.

Rejection of rejection (Seifa): He is like one who looked his house to guard the contents, and a deer was found inside.

This shows that he is exempt and permitted.

(Shmuel): All Peturim in the Mishnayos regarding Shabbos are forbidden [mid'Rabanan], with three exceptions, which are permitted - this is one of them.

Question: What is the source that it is permitted here?

Answer (Seifa): [Shimon] is like one who looked his house to guard the contents, and a deer was found inside.

Exception #2 (Mishnah): If one pierces an abscess to make an opening, he is liable; if it is to let out the pus [now, and he does not care if it closes], he is exempt.

Question: What is the source that it is permitted?

Answer (Mishnah): A hand needle (used to sew garments) may be moved, for it is useful to remove a thorn [stuck in one's skin - even though this surely wounds, Melachah she'Einah Tzerichah l'Gufah is permitted to alleviate pain, the same applies to an abscess].

Exception #3 (Mishnah): If one traps a snake on Shabbos - if this was so it will not bite him, he is exempt; if this was to use it for a cure, he is liable.

Question: What is the source that it is permitted?

Answer (Mishnah): One may put a bowl over a Ner to prevent the ceiling beam from catching fire, and over excrement of a child, and over a scorpion so it will not bite.

If one traps or wounds any of the eight Sheratzim listed in the Torah he is liable;

Regarding other Shekatzim u'Rmashim (vermin):

If one wounds them he is exempt;

If he traps them for a need he is liable; if it was not for a need, he is exempt.

If one traps animals or birds in his domain, he is exempt; if he wounds them he is liable.

(Gemara) Inference: If one is liable for wounding [the eight Sheratzim], they must have skin (i.e. the wound will leave a scar, this is a Toladah of slaughtering; alternatively, the Chiyuv for wounding is for coloring the skin via blood).

Question: Who is the Tana of the Mishnah?

Answer #1 (Shmuel): It is R. Yochanan ben Nuri:

(Mishnah - R. Yochanan ben Nuri): The eight Sheratzim have skin [that is Halachically different than their flesh].

Answer #2 (Rabah bar Rav Huna): It is even like Chachamim:

(In Chulin 122A, Chachamim list some of the eight, for which ka'Adashah of skin [of a Nevelah] is Tamei like their flesh.) Chachamim argue with R. Yochanan ben Nuri only regarding Tum'ah, for it says "Eleh ha'Teme'im Lachem", to teach that their skin is like their flesh - but regarding Shabbos, they agree.

Question: They also argue regarding Shabbos!

(Beraisa - R. Yochanan ben Nuri): If one traps any of the eight Sheratzim or wounds it, he is liable (perhaps the Bach's Hagahah (Beis) belongs here - Oz v'Hadar);

Chachamim say, only the Sheratzim that Chachamim listed have skin.

Objection: Just the contrary - Chachamim listed the Sheratzim whose skin is the same as their flesh! (The Beraisa is errant.)

Correction #1 (Abaye): Rather, Chachamim say, only the Sheratzim that Chachamim did not list have skin different than their flesh [but one is exempt for wounding the ones listed, i.e. they argue about Shabbos]!

Objection (Rava): The text says...'only the Sheratzim that Chachamim listed have skin' (it is unreasonable to say that the text was totally reversed)!

Answer #1 (and Correction #2 - Rava): Rather, Chachamim say, skin is Metamei like the flesh only regarding the Sheratzim that Chachamim listed.

Inference: This implies that R. Yochanan ben Nuri holds that the skin of all eight is Metamei like the flesh.

Objection: But in the Mishnah he says that the eight Sheratzim have skin [that is not Metamei like the flesh]!

Answer #2 (and Correction #3 - Rav Ada bar Masnah): Rather, Chachamim say, regarding Tum'ah, only the Sheratzim that Chachamim listed have skin.

Question: We have a different source that they argue regarding Shabbos!

(Beraisa): If one traps any of the eight Sheratzim or wounds one of the Sheratzim with skin, he is liable;

If the blood gathers in one place, even if it did not leave, the wound will not recover.

R. Yochanan ben Nuri says, all eight Sheratzim have skin.

Answer (Rav Ashi): The first Tana is R. Yehudah, who says that it depends on the thickness of the skin:

(Mishnah - R. Yehudah): A lizard is like a rat (its skin is not Tamei).

Chachamim argue with R. Yochanan ben Nuri only about Tum'ah, not about Shabbos.

Question: If so, [in the Beraisa] why was R. Yochanan ben Nuri's law [regarding wounding] said only in his name - it should have been said also in the name of Chachamim that argue with him [about Tum'ah]!

Answer: Indeed, it should say 'R. Yochanan ben Nuri and the Chachamim that argue with him say...'

Question (Levi): What is the source that a wound does not recover?

Answer - Question: "Ha'Yahafoch Kushi Oro v'Namer Chavarburosav": what are these?

Suggestion: It refers to [a leopard's] spots.

Rejection: If so, it should have said 'Gavanav' (his colors)!

Answer: Rather, it [refers to a wound and] equates it to a Kushi (negro) - just like a Kushi cannot change his skin, a wound cannot revert to normal skin.

(Mishnah): Regarding other Shekatzim u'Rmashim (if one wounds them he is exempt).

Inference: If he kills them he is liable.

Question: Who is the Tana of the Mishnah?

Answer #1 (R. Yirmiyah): It is R. Eliezer:

(Beraisa - R. Eliezer): If one kills a louse on Shabbos he is [liable] like one who kills a camel.

Objection (and Answer #2 -Rav Yosef): Chachamim argue with R. Eliezer only regarding lice, for they do not reproduce [sexually], but they agree that one is liable for other Shekatzim u'Rmashim which reproduce! The footnote in Michtav me'Eliyahu (Vol 4, p.355 (4)) says in the name of the author that accepted Halachos are not changed by scientific discoveries, e.g. one may kill lice even though we find that they do reproduce sexually - Chachamim transmitted known Halachos which are not dependent on the explanations given. Menuchas Ahavah (3:18:6) suggests that since they cannot hatch without sweat, this is not considered reproduction from male and female [alone]. He cites (in the appendix) the Rambam and others who say Chazal's words on matters like this were not all based on prophecy, tradition or Ru'ach ha'Kodesh. The Yerushalmi says that one may kill lice because they have meager life (anything without a spine cannot live more than six months), but the Bavli argues with this (it obligates for killing a Pir'osh).

Both of them learn from rams (which were slaughtered for their skins for the curtains).

R. Eliezer says, just like they were killed, one is liable for killing anything;

Chachamim say, just like they reproduce, one is liable for anything that reproduces.

Objection (Abaye): Lice do reproduce,

It was taught that Hash-m feeds the entire world, from Karnei Re'emim [the biggest animals] to Beitzei Kinim (lice that just hatched).

Answer: Beitzei Kinim is the name of a species (other than lice).

Question (Beraisa): Tipuyei (a small insect) and Beitzei Kinim.

Answer: Beitzei Kinim is the name of a species.

Question: A Pir'osh reproduces, yet R. Yehoshua exempts! (Bi'ur Halachah (316:9 Lehargah) - Rambam says that Pir'osh is a flea - those that arise spontaneously from dirt (but not those that arises from mold) can reproduce. Ramban - anything that does not come from male and female cannot reproduce - Pir'osh must be some other species.)

(Beraisa - R. Eliezer): If one traps a Pir'osh on Shabbos he is liable;

R. Yehoshua exempts.

Answer (Rav Ashi): Trapping is unlike killing!

R. Eliezer obligates even if the species is not normally hunted, R. Yehoshua exempts in such a case - but R. Yehoshua agrees that he is liable for killing them!

(Mishnah): If he traps them for a need he is liable; [if it was not for a need, he is exempt].

Version #1 - Question: Who is the Tana of the Mishnah?

Answer (Rav Yehudah): It is R. Shimon, who exempts Melachah she'Einah Tzerichah l'Gufah.

Version #2 (Beraisa): If one punctures a blister [with pus inside] on Shabbos:

If it was to make a (Rashi - permanent) opening (Tosfos 3A u'Mafis - also to let in air), he is liable, if it was just to let out pus, he is exempt.

Question: Who is the Tana of the Beraisa?

Answer (Rav Yehudah): It is R. Shimon, who exempts Melachah she'Einah Tzerichah l'Gufah.

Version #3 (Mishnah): If one traps a snake on Shabbos:

If this was so it will not bite him, he is exempt;

If this was to use it for a cure, he is liable.

Question: Who is the Tana of the Beraisa?

Answer (Rav Yehudah): It is R. Shimon, who exempts Melachah she'Einah Tzerichah l'Gufah.

(Shmuel): If one removes a fish [that was already trapped before Shabbos] from the sea, once the size of a Sela (a coin) dries up, he is liable [for killing it, for it will not live].

(R. Yosi bar Avin): This is if the area that dries is between its fins.

(Rav Ashi): It need not become fully dry - it suffices even if sticky strands exude when one touches it.