Gemara

Beraisa - R. Meir and R. Shimon: Me'ilah applies to blood;

Chachamim say. Me'ilah does not apply to it.

Question: They only argue about whether or not Me'ilah applies mid'Rabanan, but all agree that mid'Oraisa Me'ilah does not apply. What is the source of this?

Answer #1 (Ula): "Va'Ani Nesativ Lachem" - blood is yours (it is not considered Hash-m's, i.e. there is no Me'ilah);

Answer #2 (Tana d'Vei R. Yishmael): "Lechaper" - it is for atonement, not for Me'ilah;

Answer #3 (R. Yochanan): "Hu" - blood has the same status before Kaparah as after;

Just like after Kaparah there is no Me'ilah, also before.

Suggestion: Perhaps just like before Kaparah there is Me'ilah, also after!

Rejection: Me'ilah never applies to something (used for a Mitzvah) after the Mitzvah was done.

60a - Question: Why do we need three exclusions to teach that Me'ilah does not apply to blood?

Answer: One teaches that Me'ilah does not apply to blood, and the others teach that Nosar and Tamei do not apply to blood.

Me'ilah 11a - Mishnah - R. Shimon: (Regarding Me'ilah,) blood is lenient at the beginning and stringent at the end. Nesachim are stringent at the beginning and lenient at the end:

At first Me'ilah does not apply to blood. After it goes to Nachal Kidron (after Zerikah), Me'ilah applies to it.

At first Me'ilah applies to Nesachim. After they descend to Shitin (at the base of the Mizbe'ach), Me'ilah does not apply.

12a - Question: Do we ever find something that never had Me'ilah mid'Oraisa and Me'ilah applies to it mid'Rabanan?!

Answer: Indeed, we find this concerning blood!

Mishnah: At first Me'ilah does not apply to blood. After it goes to Nachal Kidron, Me'ilah applies to it.

Objection: Regarding blood there is Me'ilah from the beginning!

Rav: If one let blood from a Kodshim animal, it is forbidden to benefit from the blood. Me'ilah applies to it.

Question (against Rav - Rav Hamnuna - Mishnah): It is forbidden to benefit from milk or eggs of Kodshim. Me'ilah does not apply to them. (Surely, the same applies to blood, because milk is a transformation of menstrual blood!)

Answer (Rav Huna): Blood is different, for an animal cannot live without it, but it can live without milk.

Question (Rav Mesharshiya - Beraisa): It is forbidden to benefit from dung or Peresh (excrement inside an animal) of Kodshim; Me'ilah does not apply to them.

An animal cannot live without Peresh!

Answer: Peresh comes from the food it eats, it will eat more and make more Peresh. Blood was part of its initial creation.

Rishonim

Rif (Berachos 22a): One should not pray amidst engaging in judgment or (determining) Halachah (lest it distract him during Tefilah). Rather, one prays amidst learning clear-cut Halachah, e.g. blood let from a Korban is Asur b'Hana'ah and Me'ilah applies to it.

R. Yonah (DH ha'Mekiz): Me'ilah of Dam Hakazah (from bloodletting) is mid'Oraisa. Since the animal cannot live without blood, Me'ilah applies to the blood just like it applies to the animal (Me'ilah 12b). After Kaparah there is no Me'ilah mid'Oraisa, for the Mitzvah was done. The same applies after Shechitah. Since it is fit for Kaparah, it is as if Kaparah was already done. However, there is Me'ilah mid'Rabanan after Shechitah, even after it goes to Nachal Kidron.

Rambam (Hilchos Me'ilah 2:11): Me'ilah does not apply to Dam Shechitas Kodshim before or after Kaparah, until the blood flows to Nachal Kidron. Once it reaches Nachal Kidron Me'ilah applies to it, because gardeners pay Hekdesh for it (for fertilizer). However, if one lets blood from a Kodesh animal Me'ilah applies to it, because the animal could not live without blood.

Ra'avad: The Me'ilah is only mid'Rabanan.

Ri Korkus: The verses that exclude Me'ilah from blood discuss after Shechitah, when it can bring Kaparah.

Tosfos (Me'ilah 11a DH Mai): The text should not say 'Why do Chachamim say that Me'ilah does not apply?', for this implies that R. Meir and R. Shimon hold that Me'ilah applies mid'Oraisa. (On 12a we assume that if something never had Me'ilah mid'Oraisa, there is no Me'ilah mid'Rabanan.) Yoma 59b says that all agree that mid'Oraisa Me'ilah does not apply to blood. Rather, the Gemara says that R. Shimon says that Me'ilah applies mid'Rabanan, but all agree that it is not mid'Oraisa, and asks what is the source for this.

Rebuttal (Ri Korkus ibid.): Those whose text in Me'ilah says 'Why do Chachamim say that Me'ilah does not apply?' have a similar text in Yoma, i.e. it does not say that all agree that Me'ilah is only mid'Rabanan. Alternatively, the text here says that all agree that Me'ilah is only mid'Rabanan, i.e. after Kaparah. However, after it goes to Nachal Kidron Beis Din makes it Hekdesh Bedek ha'Bayis, and Me'ilah applies mid'Oraisa.

Tosfos (Yoma 59b DH Ad): The Gemara infers that Me'ilah of blood is mid'Rabanan, for if it was mid'Oraisa (the blood still has Kedushas ha'Guf), it would be forbidden to sell it to gardeners!

Rebuttal (Ri Korkus ibid.): (The blood lost Kedushas ha'Guf. After it goes to Nachal Kidron, Beis Din gave it Kedushas Damim.) It is redeemed and sold to gardeners, like other Hekdesh Bedek ha'Bayis. Alternatively, Beis Din stipulates that after it is sold, only the money will be Kodesh.

Question (Tosfos DH Hu): R. Yochanan teaches that just like after Kaparah there is no Me'ilah, also before Kaparah. In Me'ilah (12b) we learn that Me'ilah applies to blood let from a Kodshim animal.

Suggestion: That Me'ilah is mid'Rabanan. R. Yochanan discusses mid'Oraisa.

Rejection: Me'ilah 11a says that at first Me'ilah does not apply to blood. After it goes to Nachal Kidron, Me'ilah applies to it. Since Me'ilah of Nachal Kidron is mid'Rabanan, this implies that beforehand there is no Me'ilah at all!

Answer #1 (Tosfos ibid.): 'Before Kaparah' means after Shechitah, for then blood can give Kaparah. Before Shechitah, Me'ilah applies mid'Oraisa.

Answer #2 (R. Chayim in Tosfos ibid.): Me'ilah of blood in Nachal Kidron is mid'Oraisa, for Beis Din makes the blood Hekdesh.