Scientists use white mice in great numbers. Biologists use them to study principles of heredity and the nature of certain diseases such as cancer; psychologists use them in studies of learning; and physiologists use them in determining the properties of medicines. Mice are often chosen for experiments in preference to other animals for several reasons. They are small, and thus require little living space and food. Because they are mammals, their bodies are similar to other domestic mammals and man. Because from five to eight baby mice are born at a time, in only three weeks after the parents mate, they make inexpensive laboratory animals. One disadvantage is that they are short-lived, becoming old near their third year.
