Why did people in old Russia put FROGS in milk!?

This practice ethnographers documented as late as the 19th century. In Vladimir Dal’s famous dictionary, the entry for ‘cold’ (‘kholod’), mentions the term ‘kholodena’, meaning a ‘frog’, and states that, in St. Petersburg, people “put frogs in milk intended for sale, so that it wouldn’t turn sour." It was believed that the amphibian's cold skin helped cool the liquid, thereby delaying it from souring a little longer.

However, scientists have proven that it’s not the frog’s temperature that matters, but, rather, the chemical composition of the mucus covering its skin, which is rich in peptides –  aka natural antibiotics. These substances inhibit the growth of bacteria that cause milk to sour, thus prolonging the milk’s “freshness”.

But, this method had significant drawbacks: it only delayed souring for a short time, offered no 100% guarantee and was simply unhygienic.