A bezoar is a compact agglomeration of hairs of a spherical shape present in the digestive system of some ruminant animals, such as cows.
Cattle have the habit of licking themselves and their peers and during these actions they swallow hairs, which cannot be digested or vomited due to the confirmation of their stomachs. The undigested hair aggregates in the rumen in a spherical mass (bezoar), where thanks to the acids present a digestion process begins. The sphere made up of hairs is digested only externally and remains inside the cow's stomach for life.
The term "bezoar" seems to derive from the Persian "pādzahr", which means "antidote against a poison": in fact, bezoars were used in oriental and medieval medicine as antidotes and as medicines against certain diseases.