Separate pieces of tamei food do not combine, these are the words of R' Dosa ben Horkinas. But the Sages say: It does com-bine. One can deconsecrate maaser sheni onto an unstamped coin, [these are] the words of R' Dosa. But the Sages say: One cannot deconsecrate [maaser sheni in this manner]. One must immerse [his] hands [in a mikveh] for [the] chatas [water], these are the words of R' Dosa. But the Sages say: If one's hands had become tamei, his [entire] body is [treated as though it had become] tamei.