More than 25 million animals are used for research, testing and educational purposes in the U.S. each year. But the use of animals in many of these experiments is often gratuitous or just plain ineffective -92 percent of drugs that succeed in animal tests, for example, never receive approval for human use.
In honor of World Day for Laboratory Animals on Friday, here are four rare happy endings where animals were finally freed after lifetimes of lab research.
1. These nine beagles who were freed from a laboratory in Nevada.
Here they are seeing grass and sunshine - and meeting their fellow captives - for the first time.