Myomancy was a method of divination by mice. Their behaviour was observed and taken as a omen of what was to come. If their movements were calm, aggitated or aggressive, much was read into it. Modern scientists study the movements of mice more than the ancient myomancers did, but for ends that are not dissimilar.
The FDA puts a lot of stock into studies done on mice and many a warning label has been the outcome. Seems most of the really bad side effects hit pregnant rats the hardest. So, you can feel pretty safe as long as you are not pregant or a rat.
If you look at the writings of Herodotus, mice were used to predict the outcome of Sennacherib's invation of Egypt. The night before the big seige, his army has a mice investation which gave them the willies. They fled at the bad omen and in their flight, many were slain.
Interesting how one little rodent can be so powerful.