Carlos Martinet, age 10, of San Antonio, Tex., for his question:

WHAT IS A GIZZARD?

A gizzard is a special organ of the digestive system of birds and a few other animals. It breaks up and grinds hard, solid foods.

The gizzard in birds is a muscular part of the stomach and is lined with a thick, tough membrane. It contains stones and gravel that the birds has swallowed.

Food enters a pouch of the gullet called the crop and it is moistened there. It passes from the crop to the glandular part of the stomach where it is mixed with gastric juices.

The food next passses into the gizzard where it is crushed by the movements of the muscular walls and the gravel.

Gizzards of grain eating birds are better developed than those of insect eating birds.