A woman was having a difficult labor, and she was moved from one house to an-other. The first [house] is tamei because of doubt, and the second [house] is certainly [tamei]. R’ Yehudah said: When [does this apply]? In a situation in which she walked with assistance; but if she was able to walk [without assistance], the first [room] is tahor, because once the womb is open, it is impossible to walk. A stillborn child does not open the womb, unless [his] head is round like [the size of] a whorl.

[If] the first [baby] was born dead and the second alive, [the living baby] is tahor. [If] the first [baby] was alive and the second dead, the [living baby] is tamei. R’ Meir says: [If they are in] one fetal sac, [the living baby] becomes tamei; however, [if they are in] two fetal sacs, the [living baby] is tahor.

[If] two sealed barrels, each containing a [piece of corpse] the size of half an olive, are located inside a house, [the barrels] remain tahor, but the house becomes tamei. [If] one of [the barrels] was opened, [that barrel] and the room are tamei, [but the other barrel] remains tahor. A similar [ruling] applies to two chambers that open into a room.

There are [items] that spread tumah and act as barriers [against tumah], [items that] spread tumah but do not act as barriers [against tumah], [items that] act as barriers [against tumah] but do not spread [tumah], and [items that] do not spread [tumah] and do not act as barriers [against tumah]. These spread [tumah] and act as barriers [against tumah]: a chest, a box, a cabinet, a large straw basket, a large reed basket, and the water tank of an Alexan-drian ship — if they have [flat] bottoms and can contain forty se’ah of liquid, which is two kors of dry measure; a curtain, a work apron, a bed cover, a sheet, matting, and a mat, if they have been made into a tent; a herd of animals, whether nonkosher or kosher; lairs of wild animals and nests of birds, a bird that is resting, and one who makes a place for her son among the stalks; the iris, the kissom, chamor greens, the Greek gourd, and food that remains tahor. R’ Yochanan ben Nuri disagrees concerning food that remains tahor, except for a pressed cake of figs.