Clarification (Part 1): Not because he wants to finalize the Halachah like Beis Shamai ...

Clarification (Part 2): But it is rather because Beis Shamai gives a specific Shi'ur, (whereas Beis Hillel do not) that he refers to the Shi'ur of Beis Shamai.

Initial Explanation: Rav Yirmiyah thinks that even holes which render some of the flesh missing (as opposed to cavities) combine to make up a majority - seeing as the Gemara compares it to a sieve, implying that it is speaking about holes like a sieve, of which some of the metal is missing.

Conclusion: But the Gemara answers that it is speaking about cavities, where none of the flesh is actually missing, and the reason that it mentions 'Nafah' is because, like a sieve, it is riddled with holes.

Question: The Lashon 'Isht'mitseih however is then difficult (see Maharam).

Question: In that case, it should rather teach us 'Nikvah', and we will know Retzu'ah from a Kal-va;Chomer.

Clarification: That one places the Isar on its width to see whether it e it will enter the hole, and not the width.

Clarification: That the animal stretched out its neck excessively to take a vegetable from inside a pit.

Clarification (Part 1): Rabeinu Chananel explains that this means 'two on one side and two on the other side'.

Clarification (Part 2):And the chest mentioned here is not the same as the chest mentioned in Maseches Tamid (31.), learned in the Mishnah whish speaks where there are no ribs, as we have learned in Perek Lo Hayu Kofsin.

Clarification: Rashi explains that this probably goes according to the first Lashon, since Rebbi Yochanan concurs with that opinion above, when he says that a Kaneh which becomes holed below the chest, has the same Din as a lung with a hole.

Halachah (Part 1): And it would seem that we go Lechumra in all cases, since no ruling is issued, neither like one opinion, nor like the other. And Rebbi Yochanan too (whom we just quoted, and) who talks about the Kaneh which became holed below the chest implies that both that of the lung and that of the liver, have the Din of the lung.

Halachah (Part 2): Rabeinu Chananel too, Paskens le'Chumra, that the Shi'ur of a hole in all three is a Mashehu, both of the liver, of the heart and of the lung.

Explanation #1 (Part 1): Since it is possible that the majority of the marrow alone is T'reifah ...

Implied Question: And the reason that he mentions the majority of the skin ...

Answer: Is to teach us that even the skin requires Rov.

Explanation #2: Rabeinu Tam however, explains that the She'eilah is whether one requires the majority of the marrow as well.

Clarification (Part 1): And the reason that he mentions the skin is because the skin is the main item ...

Clarification (Part 2): Yet without the marrow too being holed, the animal will not be a T'reifah.

Question: The Rivam asks how the Gemara can bring a proof from the brain in the head, whose Shi'ur regarding a hole is a Mashehu, on to the marrow of the spinal cord, whose Shi'ur is the majority?