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1. Although the Mishnah says that a Sheretz is Tamei only while still most, there is a time when it is Tamei even when dry.
2. Dried flesh of a corpse does not cause Tum'as Mes with a k'Zayis as does normal flesh of a corpse.
3. If a Sheretz is found in an alleyway, any Taharos that are there are retroactively deemed Tamei.
4. There is a dispute about bloodstains on clothing from the people of Rekem.
5. The Mishnah discusses how to determine whether bloodstains on clothing are Tahor or Tamei.
A BIT MORE
1. Rebbi Shimon ben Yochai: The verse "from them" implies that part of a Sheretz can cause Tum'ah, while the verse "in them" implies that only all of a Sheretz causes Tum'ah. It must be that when it is moist, even part of a Sheretz causes Tum'ah, and if its entire form is still extant then it causes Tum'ah even when it is dry.
2. However, it can cause Tum'as Mes if there is a certain amount (Malei Tarvad, see Kelim 17:12) of rotted flesh.
3. This applies as long as the Taharos were processed at least a day after (or before) the last time the alleyway was swept or someone stated that he had checked the alleyway and found no Sheratzim.
4. Tana Kama: The people of Rekem are not proper converts, and therefore their bloodstains are Tahor (as such stains from Nochri women are Tahor). Rebbi Yehudah: They are Jews, and therefore their bloodstains are Tamei.
5. Bloodstains on clothing that are not clearly from the Tamei blood of a woman are presumed to be Tahor, unless they are found in private rooms or places where Nidos congregate.
Index to Revach for Maseches Kerisus