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摘要

A: The term "backwash," referring to the mix of beverage and saliva that sloshes back into a shared drink, has been in use only since the mid-1980s. But concerns about its disgusting nature go back centuries. Early Muslim scholars argued over whether the liquid leftover in a vessel after someone has drunk from it-called su'r in Arabic-was pure enough to be used for ritual ablutions. These days, we have hard science to settle that ancient debate.