QUESTION: Rebbi Yehudah states that if a cow drinks Mei Chatas and is then slaughtered, the meat of the cow remains Tahor, even though Mei Chatas normally conveys Tum'ah to whatever it touches.
The Gemara explains that the Mei Chatas loses its status of an Av ha'Tum'ah because it cannot be used for sprinkling once it is in the cow's stomach. However, when the Mei Chatas is digested by the cow, it makes itself Tamei at that moment to become a Rishon l'Tum'ah like any other liquid that touches an Av ha'Tum'ah. The Gemara attempts to prove that Rebbi Yehudah maintains that liquids cannot be Metamei other items from the fact that he rules that the meat is Tahor. The Gemara rejects this proof and says that the water in the cow's stomach is a "Mashkeh Saru'ach," a putrid liquid unfit even for animal consumption, and therefore it loses its Tum'ah. RASHI (DH Rav Ashi Amar) writes that the source that liquid loses its Tum'ah when it becomes spoiled is found in the Toras Kohanim (Parshas Shemini 8:4; Tosefta, Taharos 9:7) which derives this law from a verse.
However, in the Toras Kohanim, only Rebbi Eliezer expounds the verse in this way. The Chachamim there argue and maintain that liquid that becomes spoiled does not lose its Tum'ah, because even though dogs would not drink such a liquid, birds and cows would. (The RAMBAM and RA'AVAD (Hilchos Tum'as Ochlin 2:14) rule like the Chachamim that a liquid never loses its Tum'ah.)
How can the Gemara here say that according to Rebbi Yehudah, spoiled liquids lose their Tum'ah, when the Chachamim argue and maintain that they do not lose their Tum'ah?
(a) The Gemara, at this point, assumes that Rebbi Yehudah follows the opinion of Rebbi Eliezer in the Toras Kohanim.
(b) The RA'AVAD (on the Toras Kohanim) says that everyone agrees that the spoiled liquid (Mashkeh Saru'ach) of the Gemara here loses its Tum'ah. The Chachamim maintain that a spoiled liquid remains Tamei only when it becomes spoiled by filth, or it spoils by itself. Since such a liquid remains fit for birds, it does not lose its Tum'ah. In the case of the Gemara here, however, the liquid becomes digested in the cow's stomach and is considered to be nothing more than digested waste products. Even the Chachamim agree that such a liquid is no longer considered a liquid and loses its Tum'ah. (CHAZON YECHEZKEL)