A chicken egg in order to hatch must be kept warm. A mother hen sits on her eggs to hatch them. Her body keeps them just warm enough. But many little chickens are hatched from eggs that were kept warm in a different way. The eggs were kept warm in an incubator. Ducks and turkeys and even game birds are sometimes hatched in incubators, too.
An incubator is a kind of oven. The first incubators were heated with oil lamps and had to be watched carefully. There was danger that they would get too warm or too cool. Most incubators today are heated with electricity. It is easy to keep them at an even temperature. For chickens, the temperature should be kept at about 102 °F. The eggs are turned from time to time so that they are heated evenly all over. The air inside the incubator must be kept fresh and moist as well as warm.
Incubators of another kind are found in hospitals. They are for babies that are especially tiny and weak when they are born. These babies need to be kept as warm as they were when they were still in their mothers' bodies. As a rule they are soon big and strong enough to leave the incubators. Incubators, now that they are in common use in hospitals, are saving the lives of a great many babies.
