In the 17th century
How was mechanical digestion discovered?Digestion was first shown as a mechanical process in the 17th century, when Borelli carried out experiments on birds. He made them swallow objects that he then found crushed, deformed and broken. He concluded that the objects had been compressed and ground in the stomach.
So, in the 17th century, two types of mechanical transformation were recognised: the action of teeth and the stomach on food. Borelli compared jaws to pincers and the stomach to a vice.