BOB DOUGHTY: In the past, people were advised to stop severe bleeding with a tourniquet. This device is made with a stick and a piece of cloth or a belt. But experts now say tourniquets are dangerous because they can crush blood passages and nerves.

If a wound seems infected, let the victim rest. Physical activity can spread the infection. Treat the wound with a mixture of salt and water until medical help arrives. Add nine and one-half milliliters of salt to each liter of boiled water. Place a clean cloth in the mixture and then put the cloth on the wound. But be sure not to burn the skin.

PAT BODNAR: To learn more about first aid, ask a hospital or organization like a Red Cross or Red Crescent Society for information. Training may be offered in your area.

If you know first aid methods, you can be calmer and more helpful in case of emergency.

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BOB DOUGHTY: This SCIENCE IN THE NEWS was written by Jerilyn Watson. Our producer was Mario Ritter. I'm Bob Doughty.

PAT BODNAR: And I'm Pat Bodnar. Listen again next week for more news about science in Special English on the Voice of America.