We learned in a Mishnah in Nidah 'Dam she'Nimtza bi'P'rozdor - S'feiko Tamei'. This ruling is based on the Reisha of the Mishnah, which compares the three sections of a woman's womb to a room (Cheder [known as the 'M'kor'] - whose blood is Tamei), an attic (Aliyah, whose blood is Tahor) and an ante-chamber (P'rozdor, whose blood we are currently discussing).

Abaye supports Rebbi Chanina's ruling ('Rov ve'Karov, Holchin Achar ha'Rov') from there - because there too, the blood from the Cheder constitutes the majority, whereas the blood from the Aliyah is closer (yet we go after the blood from the Cheder, considering the blood that one finds in the P'rozdor Vaday Tamei).

Rava initially refutes Abaye's proof. He claims that the Mishnah in Nidah is different (even though he agrees with all the facts) - inasmuch as, in addition to the blood in the Cheder being in the majority, it also flows more frequently, making it Rov u'Matzuy (common), which is why it overrides the 'Karov' of the blood in the Aliyah).

The Beraisa quoted by Rebbi Chiya states that blood found in the P'rozdor - renders the woman Tamei to the point that she will be obligated to ...

... bring a Chatas should she subsequently enter the Beis Hamikdash with regard to Bi'as Mikdash.

... burn Terumah that she subsequently touches ...

... a proof - that 'Rov ve'Karov, Holchin achar ha'Rov' is a Din Vaday, and not just a Safek.

If it was only a Safek the Din regarding Terumah would be - that one may not eat it, but neither would one burn it.

Neither would one bring a Chatas in the case of Safek Tum'ah - because it would constitute a Safek Chulin ba'Azarah.

The first of the three things that Rava extrapolates from Rebbi Chiya is Rebbi Chanina's principle 'Ruba va'Chazakah Holchin achar ha'Rov', the second - that Rov (even a 'Ruba de'Leisa Kaman' [an invisible Rov] Tosfos) is d'Oraysa.

His third inference concerns the case of 'nine shops' in Kesuvos, where, regarding a piece of meat that is found in the street, in a town where there are nine Kasher butcheries and one non-Kasher one - we go after the majority and render it Kasher.

When Rebbi Zeira comments 'Af-al-Pi she'Dalsos Medinah Ne'ulos', he means - that we do not require the doors of the town to be open, so that we have a second Rov ('Ruba de'Alma'), but that the one Rov is sufficient.

Rava applies Rebbi Zeira's ruling to our case of 'P'rozdor' - because there too, there is only one Rov.

Despite the fact that Rava initially rejected Abaye's support of Rebbi Chanina from the Mishnah in Nidah, he now extrapolates the same thing from Rebbi Chiya (who comments on the same Mishnah) - because he changed his mind

If a barrel of wine is found in the River P'ras, Rav holds that the location of where the barrel is found (i.e. in the vicinity of a town where the majority of residents are Yisre'eilim or Nochrim) determines whether the wine is Kasher or not. When Shmuel says 'Eima me'Ihi Dakra Asa'i', he means - that the barrel ought to be forbidden, because, irrespective of where it was found, it probably came from Ihi Dakra, a town from higher up the river with a majority of Nochrim.

Initially, we establish the basis of their Machlokes on Rebbi Chanina's ruling, in that Shmuel holds like Rebbi Chanina, whereas Rav holds 'Holchin achar ha'Karov'.

We conclude however, that even Rav holds like Rebbi Chanina too, only here it is different because, had the barrel come from as far upriver as Ihi Dakra, it would have been sucked under by the many whirlpools that dotted the River P'ras - or caught in the masses of un-melted snow that gathered there in the snow-melting season.

Shmuel however, maintains - that the fast-flowing waters would have carried the barrel to that point in spite of the obstacles.

Ravina permitted a barrel of wine that was found in a vineyard of Orlah fruit, even assuming that he holds 'Rov ve'Karov, Holchin achar ha'Karov' -because thieves do not tend to hide wine in the vineyard from which they originally stole the grapes.

He night have ruled differently had they found grapes there - because to hide grapes in the vineyard from which they were stolen is something that the thieves would do.

When they found flasks of wine among the vines of a Jewish-owned vineyard - Rava permitted them (despite the fact that most of the surrounding vineyards belonged to Nochrim).

We reconcile Rava's ruling with Rebbi Chanina (with whose opinion he concurs, as we learned earlier) - by establishing that the majority of those who poured the wine into flasks for selling were Jews.

This Din is confined to large flasks - because small flasks of wine might well have fallen from tourists, who tended to carry small flasks of wine with them on their travels, and who constituted a majority.

Had the finder found small flasks together with large ones, Rava would also have permitted them - because the large flasks were obviously lost by local merchants, who would use the small flasks which they obviously lost simultaneously, to balance the weights on the donkey.

The Tana Kama of our Mishnah requires someone who plants a tree to plant it at least twenty-five Amos away from the town - for reasons of aesthetics.

Carob and sycamore trees require a distance of fifty Amos - because they grow far more branches.

Aba Shaul maintains - that all non-fruit-bearing trees require fifty Amos distance from the town.

The distinction that the Tana draws between whether the town preceded the tree, or the tree, the town is - with regard to payment. Either way, the tree must be cut down, only in the event that it preceded the town, the residents are obligated to compensate the owner, which they are not, if the town was there first.

If there is a Safek which came first - then the owner of the tree must cut down the tree, and the residents of the town are exempt from paying (as we discussed in Bava Metzi'a).

In the Mishnah in Erchin, the Chachamim forbid turning 'a city into a Migrash, or a Migrash - the area within one thousand Amos of a town which the Torah requires to be left barren into a city'.

Initially, we establish our Mishnah, which finds it necessary to forbid planting trees close to the city, like Rebbi Elazar - who permits turning 'a city into a Migrash, and a Migrash into a city'.

We conclude however, that the author of our Mishnah might even be the Chachamim - who confine the prohibition to other kinds of seeds (such as vegetables), but who concede that trees are permitted.

We have a precedent for the distinction between trees and other plants with regard to Hilchos Shabbos, regarding the Din of carrying in a Karfaf - a walled area measuring two Sa'ah (fifty by a hundred Amos) or more.

The Chachamim forbade carrying there (despite the walls) - if it, or most of it, is sown with vegetables.

The Chachamim permit carrying there however - if trees ([and presumably flowers] and not vegetables) are growing there ...

... because a tree-garden is considered part of one's living conditions, whereas a vegetable-garden is an independent venture.

The Mishnah later rules that - if Reuven digs a tree too close to Shimon's pit, he must cut it down, but that Shimon is obligated to compensate him (even though his pit was there first).

Bearing that in mind, Rav Kahana initially ascribes the reasoning behind our Mishnah, which exempts the residents of the town from compensating Reuven for his tree if the town was there first, to the principle 'Kedeirah de'bei Shutfi, Lo K'rira ve'Lo Chamimah', meaning that - it is difficult to extract payment from a community, because whoever is approached tends to pass the buck on to the next man (see Tosfos DH 'Mai Sh'na').

We refute Rav Kahana's reason however, on the grounds that - the Kashya from its inception is unfounded, since presumably, the Chachamim drew an obvious distinction between damage to an individual and damage to a community.

We therefore re-apply Rav Kahana's reasoning to the Seifa of our Mishnah - 'Im ha'Ilan Kadam, ve'Nosen Damim'. In fact, Reuven should really have been able to claim compensation before cutting down his tree. The reason that Chazal ignored this right, explains Rav Kahana, is because of 'Kedeirah de'bei Shutfi, Lo K'rira ve'Lo Chamimah'.

And the reason that our Mishnah rules 'Kotzetz ve'Eino Nosen Damim', whereas that Mishnah rules 'Lo Yikotz' is because whereas in our current case, Reuven is obligated to cut down the tree irrespective of which was there first (therefore we order him to cut it down), in the later case, where cutting it down is dependent upon the pit having been there first, Reuven is not obligated to cut it down until Shimon proves that his pit was indeed there first.

Our Mishnah obligates Reuven to move his fixed granary fifty Amos away from the town or from his neighbor's fields - because, as he winnows, the wind is likely to blow the chaff into people's eyes.

This appears to clash with the Seifa, where the Tana obligates Reuven to distance his granary from Shimon's saplings and plowed furrows - implying that fifty Amos is not necessary.

To answer the Kashya, Abaye establishes the Seifa by a Goren she'Eino Kavu'a, which Rebbi Yossi b'Rebbi Chanina defines as - a pile of grain that is too small to require a shovel to be used for winnowing, and whose chaff is blown directly from the pile.

Rav Ashi Rav Ashi disagrees with Abaye. He establishes the Seifa of our Mishnah - as an extension of the Reisha (with the same Shi'ur of fifty Amos), and which the Tana inserts as the reason for the Reisha.

We are unable to reconcile Abaye with the Beraisa, which gives the distance of a granary from a neighbor's pumpkins, cucumbers, saplings and plowed furrow as fifty Amos. In fact - the Beraisa is a Kashya on Abaye.

The damage that the chaff blown away by the wind will cause ...

... pumpkins and cucumbers is that - it will blow into their blossoms, interfering with their growth and damaging them.

... the plowed furrows is - that it will over-fertilizer them (see Tosfos DH 'she'Oseh').