Cows don't have any incisors on their upper jaws. That's why they hold grass firmly between the teeth on their lower jaw and the dental pad on their upper jaw. Then they pinch it off with a powerful tug of their tongue. The coarsely shredded grass is swallowed, regurgitated as cud and then chewed a second time. This process is called rumination. It is often said that cows have four stomachs, but in fact they only have one, with three small compartments that food passes through first: the rumen, the reticulum, the omasum and, finally, the actual stomach: the abomasum.