Abstract
In laboratory work which involves the large-scale routine assay of biologically-active substances the sponsors of "alternative" (in vitro) methods and the scientists have a common aim: a reduction in the use of living animals. In vitro methods are usually more accurate, easier to perform, and cheaper. Animals are no longer required for the production of certain antiviral vaccines.Those engaged in medical research where new knowledge is being sought also need no incentive to develop in vitro methods because they make refined analysis possible. Nevertheless, such in vitro methods are usually not alternatives in the sense that they substitute for animals; they complement experiments on animals. A legal requirement "that no experiment on a living animal may be performed if the purpose of the experiment can be achieved by alternative means not involving an experiment on a living animal" would be unenforceable.