Sonia Eraser, age 9, of Great Falls, Mont., for her question:

WHAT CAUSES HICCUPS?

A hiccup is an irregular, jerky in breathing that makes a sound similar to the word "hiccup." In both animals and man, the hiccup is caused by a sudden strong contraction or tightening of the diaphragm and closing of the glottis.

The glottis is part of the upper breathing system just above the larynx. The diaphragm is the curved wall between the chest and abdominal cavities. When its strong muscle contracts, the chest cavity gets larger and a breath is drawn in.

In a hiccup the air starts to rush in but the opening to the larynx closes just as sharply. These sharp, jerky movements are felt deep in the chest.

Babies and children hiccup more often than adults.

Laughing very long and hard or swallowing gulps of air with hot liquids seems to start hiccups at times. Holding the breath or drinking a glass of cold water often stops them.

Hiccups that last a short time cause no harm. If the hiccups continue, they may be more serious. Continuing hiccups may be caused by a disease near the diaphragm. Or the problem may be in the stomach, which is close to the diaphragm.

Breathing in and out of a paper bag will give a person less oxygen and more carbon dioxide, which sometimes helps to get rid of hiccups.