Paul Shields, age 11, of Jackson, Miss., for his question:

WHAT DOES THE THYMUS GLAND DO?

Up until 1961, medical authorities didn't know exactly what function the thymus gland had in the human body. Then that year a London physician named Jacques Miller in a medical research center discovered that the thymus helps protect young children from disease.

The thymus gland aids in the development of lymphocytes, a type of white blood cell. Lymphocytes play a role in the production of substances called antibodies, which destroy disease bearing bacteria and viruses.

The thymus is a flat, pinkish gray organ located high in the chest behind the breastbone. It is large in relation to the rest of the body in an unborn child and during early childhood. The gland then grows slowly until the child reaches the age of 12, when it begins to shrink.

By about the age of 12, the lymph nodes and the spleen have taken over the task of producing lymphocytes. By adulthood, the gland has shrunk so much that it may be hard to distinguish from the fatty tissue that surrounds it.