Danny Caldwell, age 13, of Portland, Ore., for his question:

WHAT IS A SOLAR PLEXUS PUNCH?

The solar plexus is a large network of nerves back of the stomach. It is part of the autonomic nervous system. This system controls all the abdominal viscera, or internal organs. The nerve threads of the autonomic nervous system connect by branches with the organs of the abdominal cavity.

A blow on a spot between the navel and breastbone, a little to the right, is called the solar plexus punch. A fighter can be knocked out by this punch if it is hard enough. The exact manner in which this occurs has not been determined.

The solar plexus first became well known in 1897 as a result of the championship boxing match between James Corbett and Robert Fitzimmons. Fitzimmons knocked out Corbett with a blow to the solar plexus.

The autonomic nervous system regulates the internal organs and also the blood vessels. This control is largely automatic and is strongly affected by an individual's emotional state. Some degree of voluntary control can be developed by a conditioning method called biofeedback.