1)

(a)The criterion for being a B'chor ...

1. ... to receive a double portion of one's father's inheritance is - if it is sufficiently alive for his father to worry about his well-being.

2. ... regarding Pidyon ha'Ben is - if it emerges naturally from naturally out of his mother's womb.

(b)The first example quoted in the Mishnah of a B'chor for inheritance, but not for Pidyon ha'Ben is where the head of the first child (who was an eighth-month baby) came out alive from the womb,[and who is therefore considered born]), but who then withdrew it before its twin was born. The second example is - the same case, only where the first baby was a ninth-month baby whose head came out dead from the womb before he withdrew it.

(c)The Mishnah adds - the same case where a woman gives birth to a form of animal, beast or bird, according to Rebbi Meir, who considers this a birth as far as opening the womb is concerned, provided the eye-balls resemble those of a human-being.

(d)The Chachamim however maintain that - the baby must have the shape of a human-being in order to be considered a B'chor.

2)

(a)A ...

1. ... Sandal is - a baby whose limbs are not clearly defined limbs when it is born.

2. ... Shilya is - a placenta (the after-birth).

3. ... Sh'fir Merukam is - the skin of the baby when it is first formed (when it already has two eyes, but no hands and legs).

4. ... Mechutach is - a baby that is fully-formed, but which emerges from the womb in pieces.

(b)All of these are considered Petter Rechem, but do not prevent the next male son to be born from becoming the B'chor to inherit a double portion of his father's inheritance.

3)

(a)According to the Tana Kama, if a convert, or a former slave-girl, who already had children before being set free (a slave who is set free becomes a fully-fledged Jew), and then gives birth to a baby son, that son is not considered a B'chor regarding Petter Rechem, since there was a previous child. Rebbi Yossi ha'Gelili maintains that - we do not contend with births that take place before the mother became Jewish ...

(b)... based on the word "Yisrael" (in the Pasuk in Bo "Kol Petter Rechem bi'Venei Yisrael").

4)

(a)A first-born male son who is born to parents where the pregnancy began when they were still gentiles, and where the birth took place after the conversion - is considered a B'chor regarding Petter Rechem, but not regarding inheritance ...

(b)... because the Torah does not contend with the seed of a Nochri.

(c)If a woman gives birth to her first-born son together with a bas Kohen, a bas Levi or a woman who already had a first-born son, and then the babies become mixed-up, so that it is not know which is which - he is a B'chor le'Kohen but not for inheritance ...

(d)... and the father of the baby is obligated to pay the Kohen five Sela'im, even though the baby will not inherit him.

(e)A baby who is a Safek as to whether he is the ninth-month baby of his mother's first husband or the seventh-month baby of her second one - will be obligated to redeem himself when he grows up.

5)

(a)When Shmuel stated that the head of a still-born baby does not exempt, he meant that - if a twin baby boy who is an eighth-month baby, sticks out his head (alive) from the womb and then withdraws it, if his brother is subsequently born first, he is the B'chor, even as regards Petter Rechem.

(b)And he learns this from the Pasuk in No'ach (in connection with the flood) "All who had a soul of a spirit of life on his face died" - which implies that it only has the Din of a face if it is alive (to preclude the face of a still-born baby, who is not called alive - even if it is momentarily living).

(c)The Mishnah, which states that a stillborn whose head came out exempts the baby who comes after it from the Bechorah, does not pose a Kashya on Shmuel - because it really means his head and the majority of his body ...

(d)The Mishnah nevertheless specifies only the head - because of the Seifa, which talks about the head (exclusively) of a ninth-month baby, and which insinuates that, if the baby would have been alive, it would have been considered born in all respects.

6)

(a)We reject the previous answer however, and, in the process, prove Shmuel wrong, inasmuch as - when the head of the baby emerges, it is considered born, cannot be the Chidush, since we already know that from Mishnahs in Chulin both with regards to animals and with regards to human-beings.

(b)Consequently - the Chidush must lie in the Reisha, in the Din that the face of the eighth-month baby is considered born, and Shmuel is disproved.

(c)Regarding the Mishnahs in Chulin, we cannot learn ...

1. ... Adam from Beheimah - because unlike a woman, an animal does not have a P'rozdor (a passage) rendering the head born, since it is revealed.

2. ... Beheimah from Adam - since a human face, unlike that of an animal, is Chashuv, and therefore considered born.

7)

(a)Resh Lakish considers the forehead born everywhere except in the realm of inheritance (which requires the entire head to emerge) - based on the word "Yakir" (in the Pasuk in Ki Seitzei, in connection with regard to inheritance "Ki es ha'B'chor ben ha'Senu'ah Yakir"), implying that a baby must be recognizable (which, on the basis of the forehead alone, he is not).

(b)Rebbi Yochanan however - considers the forehead born everywhere, even in the realm of inheritance ...

(c)... because he maintains that - a baby is recognizable by his forehead only.

(d)When Resh Lakish says that the forehead exempts everywhere, he comes to include a case - where the baby of a pregnant gentile woman which sticks out its forehead before its mother's conversion, and which is born after she converts, in which case the baby is considered as having been born when she was not subject to the Dinim of Tum'as Leidah, so the days of Tum'ah followed by those of Taharah do not apply to her.

8)

(a)Rebbi Yochanan will explain the Beraisa which writes ...

1. ... that one can only identify a corpse (to allow a wife to remarry), by the face with the nose - by amending it to read, not 'with the nose' but 'until the nose'.

2. ... specifically that it requires the shape of the face together with the face and the nose - by pointing out that the Chachamim were more stringent, because of the ramifications of Eishes Ish.

(b)Abaye (or Rav Kahana) supports that from the Pasuk in Yeshayah - "Hakaras Panim Ansah bam".

(c)Granted, the Chachamim were more lenient by Eidus Ishah, permitting various types of testimony which are normally not accepted in Beis-Din. But that is only at the end (at the time of testimony); But at the beginning (when the witness actually gleans his testimony), they were strict, requiring that the witness gathers the facts thoroughly.

(d)Alternatively, Rebbi Yochanan only considers the forehead without the nose to be sufficient recognition in the case of inheritance, where the Torah writes "Yakir" - but with regard to the testimony of a woman, where the Torah writes "Hakaras Panim", Chazal required testimony of the face with the nose.

(e)According to the first answer (that the Chachamim were more stringent by the testimony of a woman), we will interpret the Pasuk "Hakaras Panim Ansa bam" - with reference to the faces of the children who are born from adulterous relationships, which Hash-m forms to look like the adulterer, in order that the latter should become exposed.