Niddah, Chapter 3, Mishnah 3. Our chapter is occupied with the woman who miscarries and with the question of what status that miscarriage leaves her in: is she temeiah as a niddah, is she temeiah as a yoledes (a woman who has given birth), or is she perhaps not temeiah at all? Each case turns on what actually emerged from her. Our mishnah takes up several such cases, beginning with matter that carries no resemblance whatsoever to a child.
Matter That Might Simply Be Blood
"Hamapeles kemin kelipah, kemin se'arah, kemin afar, kemin yavchushim adumim": a woman miscarries something resembling a membrane or husk, or something resembling a hair, or something resembling dust, or something resembling small reddish gnats. What all of these share is that they have a reddish appearance, and therefore they raise a suspicion that they are in truth congealed blood rather than solid matter.
To settle the doubt, the mishnah prescribes a simple examination with water: "tatil lemayim", the material is dropped into water and watched. "Im nimochu", should it break apart and dissolve there, that very dissolving proves that its substance was blood from the outset, and so "temeiah", the tumah of a niddah attaches to her. "Ve'im lav, tehorah": should the matter instead hold together, she remains tahor. Its refusal to dissolve establishes that blood it was not, which rules out tumas niddah, while its total lack of any human likeness rules out tumas yoledes as well. Neither form of tumah touches her.
Shapes of Creatures
"Hamapeles kemin dagim, chagavim, shekatzim, u'remasim": she miscarries something shaped like a fish, or like a grasshopper, or like one of the small creeping creatures or crawling things. "Im yesh imahem dam, temeiah": if blood emerged together with them, she is temeiah, and the reason is the blood itself, which makes her a niddah. "Ve'im lav, tehorah": if no blood came with them, she is tehorah. None of these forms counts as a vlad, a child, so there is no tumas yoledes, and without blood there is no tumas niddah.
Shapes of Animals and Birds: Rabi Meir
"Hamapeles min behemah, chayah, va'of": she miscarries something with the form of a behemah (a domesticated animal), a chayah (a wild animal), or an of (a bird). "Bein temeim bein tehorim": it makes no difference whether the species it resembles is a kosher one or a non-kosher one.
Rabi Meir maintains that a woman who expels such a form is indeed treated as a yoledes, with the full reckoning of tumah days and taharah days applied to her. "Im zachar, teishev lezachar": where the shape is that of a male, her count follows a boy, a week of tumah and then thirty-three days of taharah, forty in total. "Ve'im nekeivah, teishev lenekeivah": where the shape is that of a female, she counts as for a girl, two weeks of tumah followed by sixty-six days of taharah, eighty altogether.
"Ve'im ein yadua, teishev lezachar velanekeivah": if it cannot be determined whether the form is male or female, she must observe the stringencies of both counts together. That works out to fourteen days of tumah, taking the longer tumah period of a female, followed by twenty-six days of taharah, so that her days of taharah conclude at the end of forty days, as they would for a male. Fourteen plus twenty-six brings her to the fortieth day, and beyond that point she is no longer covered by the leniency of the days of taharah. "Divrei Rabi Meir": this is the position of Rabi Meir.
The Ruling of the Chachamim
"VaChachamim omrim: kol she'ein bo mitzuras adam, eino vlad." The Chachamim hold that anything which does not bear the form of a human being is not a vlad at all, and therefore the woman does not become temeiah as a yoledes for it. The halachah follows the Chachamim: a woman takes on tumas leidah only when what she miscarried has the form of a human child.