Literary critic Adam Kirsch is reading a page of Talmud a day, along with Jews around the world.When is a fetus not a fetus? That is the question the rabbis pursue, in graphic detail, in Chapter 3 of Tractate Nidda. As we have seen, a woman who has “an issue of her flesh in blood”—that is, a menstrual period—becomes ritually impure for seven days, during which time she can’t have sex with her husband. A woman also becomes ritually impure when she gives birth, for seven days if the child is a boy and 14 days if it’s a girl.But what happens if a woman gives birth to a tumtum, a child whose genitalia are neither clearly male nor clearly female? The tumtum problem arises at several points in the Talmud, because so much of Jewish law distinguishes between male and female. In this case, the rabbis ask, does the mother of a tumtum observe the period of impurity for a son or for a daughter? The mishna in Nidda 28a offers a typical talmudic compromise: She combines the impurity periods of both. She is impure for 14 days after the birth, like the mother of a daughter, rather than seven days, like the mother of a son. But subsequently she is considered pure up until day 40, like the mother of a son, rather than day 80, like the mother of a daughter. (Thereafter, she resumes the usual menstrual rules.)Things get more complicated when a woman miscarries, since a miscarriage is neither exactly a childbirth nor an “issue of flesh in blood.” The mishna in Nidda 21a outlines a continuum of possibilities: A woman can discharge “a piece of tissue,” “an item similar to a shell or a hair,” “an item similar to fish or to grasshoppers, repugnant creatures, or creeping animals,” or a fetus that resembles “a domesticated animal, undomesticated animal, or bird.” In such cases, is a woman considered to be tamei, impure? If so, does she have the tumah of a menstruating woman or of a new mother, or something in between?These analogies between a miscarried fetus and various kinds of inanimate objects, insects, or animals may make the reader queasy; but they apparently didn’t have that effect on the rabbis, who deal with the subject just as straightforwardly as they do any other area of Jewish law. The first thing that has to be determined is whether the miscarriage was accompanied by blood, which is the carrier of impurity. If a woman discharges a piece of tissue without any blood, the rabbis say that she is pure. But Rabbi Yehuda objects to this, on the grounds that “an opening of the womb is not impossible without blood”: Some blood must have been present, even if it wasn’t visible.The Gemara goes on to suggest that the color of the tissue should be taken into account. Some rabbis argue that if it is red or black, it resembles menstrual blood and so should be considered the equivalent of menstruation. If the tissue is green or white, however, does it have the same status? Rabbi Meir advised that the problem could be settled by a kind of autopsy: A sage should “tear” the tissue, and “if there is blood inside it, the woman is ritually impure, and if not, she is pure.” The Gemara observes that this method is more stringent than the mishna seems to require, since it holds the woman impure even if there is no freely flowing blood of her own. Rabbi Binyamin adds that if the tissue is found to contain bone, it should be considered a miscarried fetus, and so the woman contracts “the impurity of a woman who gave birth.”Rabbi Yirmeya goes on to raise a parallel question about blood. Ordinarily, a woman becomes impure when she finds blood after examining her vagina with a cloth. But what if she performs this examination by inserting a tube? If she “sees blood” in that case, does it count as “an issue of her flesh in blood,” even though the blood hasn’t come out of her body on its own? There is an analogy here with the case of the fetal tissue filled with blood: There, the rabbis said that a woman was pure even if she discharged a piece of tissue that contained blood, because “this is not menstrual blood but rather the blood of the piece of tissue.” The same logic, they decide, applies in the case of blood extracted with a tube: It does not count as menstruation because it did not emerge from the woman’s body by itself.Rabba then asks a parallel question about semen, which as we have seen imparts ritual impurity to a man in the same way that blood does to a woman. If a man extracts semen from his penis “with a sliver of wood”—why one would want to do this, I can’t imagine—does it render him impure, or does impurity only attach to semen that is ejaculated? Is it the emission of semen or bodily contact with semen that imparts impurity? Rav Huna proposes that there is a minimum measure for impurity: Only if a man emits enough semen “to cause a blockage of the tip of the penis” does he become impure.Returning to women, the Gemara goes on to ask about the discharge of “an item similar to a shell or a hair.” It becomes clear that the rabbis have in mind what we would call blood clots, and the way to test them is to immerse them in lukewarm water: If they dissolve into blood, then they count as menstrual discharge, and if they don’t dissolve, they are “a distinct entity.” The rabbis give some case histories in which women discharged unusual clots of various sizes, and offer clinical explanations. One woman, for instance, produced “items similar to red hairs,” and a rabbi deduced that they came from “a mole in her womb,” or what we might call a cyst.It is when a woman miscarries a partially developed fetus that the legal questions become particularly tricky. Does a miscarriage count as a birth? The answer has implications not just for ritual purity, but also for inheritance law. Certain rights are enjoyed by first-born sons; but can a son be considered first-born if he didn’t technically “open his mother’s womb,” since it was previously opened by a miscarriage?Today, when we discuss fetal development the key question is usually “viability”—would the fetus be able to survive outside the womb? The rabbis, however, lacked a modern understanding of fetal biology, and so they made use of analogies, in a way that can now seem bizarre. What matters, for them, is figuring out which nonhuman animal a fetus most resembles. If a woman discharges a fetus that resembles a fish or an insect, it is not considered a birth and she is not ritually impure—although she may become impure if the miscarriage was accompanied by bleeding. But if the fetus resembles a higher animal, such as a bird or a sheep, then it is a kind of birth and the woman is impure.This sounds a lot like the (now discarded) theory popularized by the 19th-century German biologist Ernst Haeckel, who said that “ontogeny recapitulates phylogeny”—in other words, that as a fetus develops, it goes through stages resembling all of the ancestral species whose evolution led to human beings. For the rabbis, however, this idea is grounded not in biology but in Scripture. In the Creation story in Genesis, the Torah uses the same word—yetzirah, “formed”—to describe God’s creation of man and of “every animal of the field and every bird of the air.” (Lower types of animals, like snakes, are not “formed” but merely “made” by God.) This verbal analogy supports the rabbis’ intuition that humans are more like mammals than they are like insects, and therefore that a stillborn fetus resembling a mammal qualifies as a real birth. As often happens in the Talmud, the rabbis’ intuitions and our own are similar; we just have different ways of justifying them.***Adam Kirsch embarked on the Daf Yomi cycle of daily Talmud study in August 2012. To catch up on the complete archive, click here.