1) THE BLOOD OF A DEAD WOMAN
QUESTION: The Tana Kama of the Mishnah maintains that blood that flows from a dead woman is considered Dam Nidah (and it is Metamei even with a minimal amount) as well as Dam Mes (and it is Metamei b'Ohel). Rebbi Yehudah maintains that only blood that flows from a live woman is considered Dam Nidah. Blood that comes out when she is dead is not considered Dam Nidah but Dam Mes.
The Gemara asks how it could be, according to the Tana Kama, that blood that comes out after the woman is dead is considered Dam Nidah. The Gemara answers that the Tana Kama holds that "Makor Mekomo Tamei."
Normally, the concept of "Makor Mekomo Tamei" means that anything that passes through the womb is Tamei as an Av ha'Tum'ah. However, the Gemara here is discussing a woman who is dead. The womb (or any other part) of a dead body is Tamei as Avi Avos ha'Tum'ah. Accordingly, even the opinion (Rebbi Yehudah) that maintains that the womb does not make its contents Tamei agrees that the womb of a dead woman certainly makes its contents Tamei! How does the concept of "Makor Mekomo Tamei" explain why the blood that exits after death is considered Dam Nidah?
ANSWER: TOSFOS (DH Makor) answers that here, the phrase "Makor Mekomo Tamei" does not mean (as it usually does) that whatever comes out of the womb is an Av ha'Tum'ah. It means that blood that was ready to come out of the womb when the woman was alive is considered Dam Nidah. Rebbi Yehudah maintains that the blood must have already left the womb when the woman was alive in order to be considered Dam Nidah.
2) "DAM TEVUSAH"
OPINIONS: The Gemara records a Beraisa in which Rebbi Elazar b'Rebbi Yehudah and the Rabanan argue concerning the exact definition of Dam Tevusah. Dam Tevusah is blood that the Chachamim decreed is Metamei with Tum'as Mes mid'Rabanan. Rebbi Elazar b'Rebbi Yehudah's definition of Dam Tevusah is broader and includes much more than the Rabanan's definition of Dam Tevusah.
Rebbi Elazar b'Rebbi Yehudah's opinion is clear. He maintains that whenever there is a doubt whether the blood that came from a dying person left his body entirely after his death or entirely before his death, or part before and part after, it is Dam Tevusah and is Metamei mid'Rabanan.
The Rabanan's opinion, however, is subject to another dispute between Rebbi Yehudah and the Rabanan of Rebbi Yehudah (a different Rabanan), who argue about two points concerning the view of the Rabanan.
The Rabanan of Rebbi Yehudah maintain that every drop of blood from a dead body that falls into a puddle of blood that came from a living person becomes Batel. Therefore, the puddle of blood is not Dam Tevusah and it is not Metamei at all. The decree of Dam Tevusah applies only when blood flowed from the dead body uninterruptedly. Rebbi Yehudah, however, maintains that blood of a dead body that falls into a puddle of blood does not become Batel, and therefore the decree of Dam Tevusah applies even in such a case. In this respect, Rebbi Yehudah is more stringent.
The second point about which they argue is as follows. Rebbi Yehudah maintains that when a person dies while bound to the top of a high pole or tree, the blood that flows from him when he is dead stays on the pole or tree. The blood on the ground beneath him is assumed to be blood that flowed from him while he was still alive, and it is not Dam Tevusah and it is not Metamei. The Rabanan maintain that the blood beneath him is Dam Tevusah, since blood that came from him when he was dead flowed uninterruptedly into the puddle. In this respect, Rebbi Yehudah is more lenient.
There are two approaches to understanding the view of the Rabanan who argue with Rebbi Elazar b'Rebbi Yehudah.
(a) According to RASHI (DH Harug she'Yatza; see also DH Dam Tevusah Ika Beinaihu), blood is classified as Dam Tevusah only when we know for certain that a Revi'is of blood did not come out after death, but it is possible that less than a Revi'is came out after death. Since a Revi'is did not come out after death, its Tum'ah is only mid'Rabanan.
(b) According to TOSFOS (DH Hachi Garsinan), the Rabanan maintain that blood may be classified as Dam Tevusah when we know for certain that a Revi'is of blood came out while the person was alive, and some blood also came out after he died, but we do not know how much came out after death. In such a case, the blood is Tahor mid'Oraisa and Metamei mid'Rabanan. (The reason it is Tahor mid'Oraisa even though there is a possibility that a Revi'is came out after death is presumably because of a Sfek Sfeika: we do not know if he bled a Revi'is after he died, and even if he did, there might be more blood in the puddle that formed before death, which would be Mevatel the blood that came after death, according to Tosfos.)
3) A DEAD BODY THAT CONTINUES TO BLEED
OPINIONS: The Rabanan define Dam Tevusah as blood that flowed from a body while the person was still alive and after he died, "and he is still bleeding." What do these words mean? They cannot mean literally that he is still bleeding, because there certainly is a Revi'is of blood from after he died and the blood would be Metamei mid'Oraisa.
(a) RABEINU YEHUDAH BEN RABEINU YOM TOV (cited by TOSFOS DH Hachi Garsinan) explains that the blood was flowing forth in a steady stream from the body after death (but has since stopped flowing). If, however, the blood was merely dripping, it is Tahor. Accordingly, the words "and he is still bleeding" are another way of expressing the opinion of the Rabanan that is expressed earlier in the Gemara that every drop that drips after death becomes Batel to the Tahor blood into which it falls. (See previous Insights.)
(b) The RI (cited by Tosfos) explains that the blood was dripping steadily after the person died. Blood that merely dripped uninterruptedly is Tahor, because a Revi'is of blood from after death did not collect in the puddle of blood.
(c) RABEINU TAM (cited by Tosfos) explains that we know for sure that some blood came out after death. Even though the Beraisa expresses this clearly in the next line ("Safek Rubo b'Chayav u'Mi'uto b'Moso..."), it mentions it here to emphasize that this is the point in which the Rabanan argue with Rebbi Elazar b'Rebbi Yehudah (who maintains that even when we are unsure if blood came out at all after death, it is still Dam Tevusah).

OTHER D.A.F. RESOURCES
ON THIS DAF