[Furthermore,] they stated another general rule: Anything that is carried on top of a zav is tamei; [whereas] anything that the zav is carried upon is tahor, except for [something] that is suitable for [use as a] couch or seat, and [except for] a person.  How so? [In a case where] the finger of a zav is under a row of bricks, [and] the tahor [person] is on top of [the row of bricks, that person] contaminates two and invalidates one. [When] he separates, he contaminates one and invalidates one. [If] the tamei [zav] is on top of [the row of bricks] and the tahor [person] is underneath it, [that person] contaminates two and invalidates one. [When] he separates, he contaminates one and invalidates one.  [In a case where] food, bev-erages, a couch, a seat, or ordinary utensils are on top of [the row of bricks], they contaminate two and disqualify one. [When] they separate, they contaminate one and disqualify one.  But [in a case where] a couch or a seat are un-derneath [the row of bricks], they contaminate two and disqualify one. [When] they separate, they [further] contaminate two and disqualify one.  [If] food, beverages, or ordinary vessels are underneath [the row of bricks], they [remain] ta-hor.

Because they said: Anything that carries or is carried upon a [contaminated] couch is tahor, except for a person.  Anyone who carries or is carried upon an animal carcass is tahor, except for one who moves it. R’ Eliezer says: [Providing that] he carries [it].  Anything that carries or is carried upon a [human] corpse is tahor, except if it forms a roof [over the corpse], and [except for] a person who moves [the corpse].

[If] part of the tamei person was [resting] on the tahor person, [or if] part of the tahor person was [resting] on the tamei person, [or if] the connected outgrowths of the tamei person were [resting] on the tahor person, [or if] the connected out-growths of the tahor person were [resting] on the tamei person, [in all of these cases, the tahor person is rendered] tamei.  R’ Shimon says: [If] part of the tamei person was on the tahor person, [the tahor person becomes] tamei. [But, if] part of the tahor person was on the tamei person, [he remains] tahor.

[If] a tamei person was [resting] on part of a [tahor] couch, or if a tahor person was [resting] on part of a [contaminated] couch, [the tahor couch or person is rendered] tamei. [However,] if [only] part of a tamei person is [resting] on a [tahor] couch, or if [only] part of a tahor person is [resting] on a [contaminated] couch, [the tahor couch or person remains] tahor. Thus, we find that tumah enters [a couch] and exudes from it through a small part of it.  Furthermore, a loaf of te-rumah [bread] that is placed on a [contaminated] couch, with a [piece of] paper between [the loaf and the couch] —- whether it is [resting] on top [of the couch,] or [situated] underneath [the couch] —- [remains] tahor. Similarly, in a [situation involving] an afflicted stone, [the loaf would remain] tahor. [But] R’ Shimon rules [the loaf] tamei in that [case].