A bat is not a noble bird. It is unlike other birds in that it gives birth to live young instead of laying eggs, and it has teeth. It feeds its young with milk, the only flying animal to do so, and carries its young with it when it flies. They are quadrupeds with wings but have no feathers; their wings are made of a stretched membrane of skin. They do not like light, preferring to fly at dusk. They are similar to mice, and like mice their voice is a squeak. Bats gather together and hang from high places like a bunch of grapes; if one falls, all the rest also fall.

The blood of a bat, when drawn with a thistle, is the chief remedy against a snake. Its blood can also be used to regrow fallen hair, but if the blood is put on the eyelids, hair will never grow there.

Hildegard von Bingen says: "If someone has jaundice, strike a bat gently, so it does not die. Tie it over his loins, with the back of the bat turned toward the person’s back. After a little while, take it off, and tie it over his stomach. Leave it there until it dies." (Throop translation)