Because ruminants cannot regurgitate (translation: cows can't vomit) and because they do groom themselves with their tongues, they are prone to getting bezoars. A bezoar is a hard, indigestible mass of anything, but most particularly hair, that forms in their digestive systems. (Actually, people get them, too. Don't ask.) Once bezoars were thought to possess magical powers, including the ability to render poisons ineffective. Yes, medicine. Yuck.