John Belcher, age 11, of San Diego, Calif., for his question:

What causes hiccups?

Hiccups are caused by spasms of the diaphragm. Spasms are jerky, involuntary muscular motions over which you have no control. In the case of hiccups, the trouble originates in the diaphragm, a large flat muscle that lies at the base of the chest. Normally the diaphragm contracts and relaxes in a regular, peaceful rhythm. Its motions help to pull air into the lungs and expel it, breath by breath.

Sometimes the diaphragm is startled by a sudden irritation. Then it forgets its regular rhythm and performs a series of jerky spasms. When air is drawn into the lungs, it passes the voice box. During a diaphragm spasm, the air snaps the voice box shut    with a "hic" sound. Sometimes a few deep breaths help the diaphragm to calm down. And some people say that hiccups may go away if you blow up a big paper bag  ¬which is another form of deep breathing.