frog
rural farmers in russia were observed purposefully placing frogs in their stored milk. the simple american perceived this as being of "rude manner"1.
but the practice is hinted in a centuries-old slavic folktale called babushka-lyagushka-skakushka. in this tale, a jug of milk was the preferred vehicle of choice for the babushka frog before hopping to i-know-not-where to find i-know-not-what2.
modern research has found that the skin of the european brown frog (Rana temporaria) produces antimicrobial peptides that prevent growth of bacteria3.
references
virtue & co. (1876) the country gentleman's magazine, january to december 1876. https://books.google.com/....↩
dixon-kennedy, m. (1997) encyclopedia of russian and slavic myth and legend, p. 28. https://archive.org/....↩
mangoni, m. l., grazia, a. d., cappiello, f., casciaro, b., & luca, v. (2016). naturally occurring peptides from Rana temporaria: antimicrobial properties and more. current topics in medicinal chemistry, 16(1), 54–64. https://doi.org/....↩