Ohalos 2:2-3

Ohalos 2:2

More things that convey ritual impurity in a tent: a reviis (about 3 ounces) of blood or of mixed blood from a single body. (“Mixed blood” means that some came out before death and some after.) Rabbi Akiva said even a reviis of blood or mixed blood from two bodies. If all of a child’s blood flowed out, Rabbi Akiva says it conveys impurity in even the smallest measure but the Sages say it requires a reviis. Regarding an olive-sized volume of worms from a corpse – whether they’re alive or dead – Rabbi Eliezer says they convey impurity like the corpse’s flesh but the Sages declare them ritually clean. Regarding human ashes, Rabbi Eliezer says they convey impurity in a quarter-kav (about a pint) but the Sages declare them ritually clean. A fraction more than a scoop of dust from under the corpse conveys impurity but Rabbi Shimon declares it ritually clean. A scoop of rot from a corpse kneaded with water is not considered a connective in matters of ritual impurity.

Ohalos 2:3

The following convey impurity through contact and carrying but not through a tent: a barleycorn-sized bone, earth from foreign lands, a field with a grave that was plowed (called a beis p’ras), a limb from a corpse or from a living person that has insufficient flesh on it, a spine or skull that is incomplete. Beis Shammai say that two vertebrae missing renders a spine incomplete but Beis Hillel say even one vertebra. Beis Shammai say that a hole the size of one made by a drill renders a skull incomplete but Beis Hillel say as much as could be taken from a living person causing him to die. Rabbi Meir says the drill referred to is the small one used by physicians but the Sages say it refers to the large one in the Temple.