Explanation: When he sees that the minority of the head is outside, he can blemish the ear, and he need not be concerned that since the ear left, perhaps the majority of the head left and returned, for since a kid's ears are big, the ears normally leave with the minority of the head.

Note: It seems to me that the coming words "Imra b'Sifvasi" begin a new Dibur ha'Maschil, but I did not find any Meforshim who say so.

Distinction: [One may blemish] a lamb in its lips, but not in its ear, for he must be concerned lest the majority of the head left and returned.

Explanation: Since now we see the minority of the head, he should not say "perhaps the majority of the head left and returned."

Assertion: This "Eimor" (say) is like Vadai (surely it left via the temples, i.e. face first), like "we are concerned lest they were outside the wall overnight", in Shabbos (151a), and "we are concerned lest they postdated it and wrote it" in Sanhedrin (32a).

Opinion #1: Rava here holds like Rabah in Chulin (69b), for according to Rav Huna, who says there that if a third left [the womb], and he sold it to a Nochri, and another third left, it is Kadosh and the sale did not take effect at all - since the majority left, it is revealed that retroactively it was Kadosh [from when it began to leave]...

If so, also here that afterwards the majority left, it is revealed that retroactively it was Kadosh from the beginning, and he is liable for making a Mum in a Bechor!

Distinction: We can establish Rav Yehudah's teaching (one may blemish a Bechor before it leaves the womb) like Rav Huna, when it did not leave at all.

Observation: Also the Sugya in Temurah (24b), which Rav Yehudah establishes to discuss nowadays that it is not proper for Hakravah, and [the Gemara] asks "if it is nowadays, what is the Chidush?", and answers that one might have thought that we decree lest the majority of the head come out and he will make a Mum. [Rav Yehudah] teaches that this is not so...

Also that is unlike Rav Huna, for according to him, also when the minority of the head came out there is an Isur. It should not have said the majority of the head!

Note: Rav Yehudah can hold like Rav Huna. Tosfos means that the Gemara there, which answered for Rav Yehudah, holds like (or wanted to give to an answer that helps even for) Rabah.

Observation: Also there, Rav Amram said to Rav Sheshes 'if one said about a Bechor when the majority was leaving "it is an Olah", is it an Olah, or a Bechor?' Also this is unlike Rav Huna, for it connotes that it was obvious [to Rav Amram] that before the majority left, he can uproot Kedushas Bechor.

Opinion #2: This is if we do not distinguish between a sale and the others. (In Temurah 24b DH Amar, Tosfos distinguished. One is more prone to err and sell after the majority left, than to make a Mum then. I.e. really, the Kedushah is not retroactive; it is a mere decree to say that it is.)

Implied question: It says above (18b) in the Chatzer of the Yisrael (the owner of the animals), and a Kohen shepherd, R. Tarfon holds that [the Yisrael] is Makneh (transfers ownership) place in his Chatzer [to the Kohen, so the Kohen will acquire Bechoros the moment they are born]!

And even R. Akiva argues only because the Yisrael has a loss (Safek Bechoros), so he is not Makneh anything!

Answer: There it discusses Makirei Kehunah, that [the Yisrael] loves him and normally gives [his Matanos Kehunah] to him.

Explanation: The first Tana holds like him. Only Kohanim shepherds, whether in a Yisrael's house or in a Kohen's house, are not believed, like he gives the reason (perhaps he will lie, for he hopes to receive some meat, or so the Ba'al ha'Bayis will do similarly for him). However, two Kohanim from the market (they do not work for the owner of the animals) are believed;

And according to R. Meir, even two Kohanim from the market are not believed, for he argues with R. Yehoshua ben Kefusai. R. Meir holds that one who is suspected about a matter may not judge it or testify about it.

Explanation (cont.): "Two from the market" that R. Yehoshua ben Kefusai said refers to Kohanim, for even one Yisrael is believed;

And according to R. Meir, whenever one is suspected, even two are not believed, like it says below "according to R. Meir, who can testify about a Safek Bechor?"

Implied Question #1: He could have said that we distinguish between a Chaver and an Am ha'Aretz, like R. Yehoshua below (36a)!

Implied Question #2: Also below, that it asks (since Kohanim are suspected about Mumim, will R. Meir say that) also they may not judge?!

Answer #1: [The Gemara] wants to resolve [R. Meir's opinion] even if he holds like R. Gamliel, who says below (36a) that we do not distinguish between a Chaver and an Am ha'Aretz.

Answer #2: R. Yehoshua himself retracted, for he said to R. Gamliel "how can a Chai (live person) contradict a Chai?" Rashi explained there that he wants to say "surely I said so, and I retract."

Rebuttal: Presumably, [he did not retract;] he said so due to the honor of R. Gamliel;

This is like regarding Tefilas Ma'ariv (Brachos 27b) that he said similarly ("how can a Chai..."), even though he did not retract from what he said initially that it is Reshus, for so Rav rules there like the one who says that it is Reshus.

Question: Above, Rav Chisda requires two from the market for a Safek Bechor in a Yisrael's house. We should challenge him "according to R. Meir, who testifies about it?", since also Yisraelim are suspected!

Answer #1: He would answer like I explained, that we distinguish between a Chaver and an Am ha'Aretz.

Answer #2: Rav Chisda would say that R. Meir would not stringent about a Safek Bechor, not to believe two from the market.

Explanation: People will suspect lest someone in the household remained inside [and made the Mum].

Explanation #1: According to Rava, who said in Sanhedrin (27a) that one who eats Neveilos to anger [Hash-m], who is evil to Shamayim, is not suspected to be evil to people, this is not difficult at all. However, according to Abaye there, it is a proper question.

Explanation #2: He asks [even] according to Rava, for it connotes to [the Makshan] that Kohanim should be Kosher for every judgment in the world, and for every ruling, for it says "[v'Al Pihem Yihyeh] Kol Riv v'Chol Naga"!

Observation: He could have asked how one may eat from what [a Kohen] slaughtered, and how all Korbanos are Kosher (even those that the Yisrael slaughters, e.g. Korban Pesach, and those that are not eaten);

And also without Bechor, he could ask according to R. Meir from the reason that Kohanim are suspected about Shevi'is, like we say in Sanhedrin (26a).