Animal experiments only became a virtually indispensable tool of medical research in the modern era, although back in Antiquity anatomical and indeed physiological investigations had been carried out on animals. The French physiologist Claude Bernard (1813-1878) played a driving role in establishing animal experiments as a research tool.

In a sense Bernard laid the theoretical scientific foundations for experimental medical research. It had long been assumed that medicine - unlike chemistry and physics - could not be a science. Vitalism, a view that was widely shared at that time, held that all living things were permeated by a life force; organic processes were not subject to laws, had no causal factors and consequently could not be predicted. Hence they were not accessible to scientific investigation. Bernard, on the other hand, established the understanding that life phenomena too - in common with physiological processes or diseases - could be scientifically explored since all bodily processes were also subject to immutable natural laws (determinism).

Bernard rejected "passive hospital medicine", i.e. the observation of patients and analysis of tissue samples etc. Instead, he called upon scientists to use laboratory experiments to exert a targeted influence on specific physiological factors and study the consequences. He believed that the knowledge gained from such laboratory experiments - and especially animal experiments - could then help scientists understand the causes of diseases and assist with the development of new therapeutic procedures. Bernard set out his concept for medical research in the book "An Introduction to the Study of Experimental Medicine", which can probably still be attributed a major influence on current scientific understanding.