In order to more completely understand biology, researchers sometimes conduct experiments on animals. Animal experimentation has a lengthy and productive history in biological research, especially in biomedicine. For example, the organ transplant pioneer Thomas E. Starzl conducted his early surgical transplantation experiments on dogs in the 1960s before successfully attempting them on humans. Psychiatrist John Cade made the discovery that lithium aids manic-depressive patients by experimenting with guinea pigs in the 1940s. Today, many animals are used for a variety of purposes in experimental science. While some studies use primates or other animals, over 90 percent of studies involve mice and rats, for experiments from immunological projects to cancer research. While animal research is enormously important to the advancement of biomedical science, some activists feel that animals should not be used as experimental subjects.

The Animal Welfare Act (1966)

To ease undue suffering inflicted on these experimental subjects...