Paul Junghans, age 8, of Burlington, Illinois, for his question:

What exactly is a cow's cud?

The cow eats her meal in two stages. First she moistens each bite in her mouth and swallows it down without chewing. Later she gives a hiccup to cough up each ball of moist food into her mouth again. This time she takes plenty of time to chew it properly. Then she swallows it a second time. The food that comes back to be chewed is called the cud  and after a good meal the cow takes a long lazy time to chew her cud.

A cow needs a fancy stomach because she eats every meal twice. Actually her stomach has four compartments, somewhat like four bags that empty into each other. The bites are moistened in her mouth and swallowed down into the first compartment and sent on to the second compartment. There the food is partly digested and stored until the cow is ready for stage two. Then the balls of cud come back up into her mouth and she chews them. When she .swallows her food the second time, it goes on down to be digested thoroughly in the third and fourth compartments of her stomach.