Animals have been used repeatedly throughout the history of biomedical research. Early Greek physician-scientists, such as Aristotle, (384 – 322 BC) and Erasistratus, (304 – 258 BC), performed experiments on living animals. Likewise, Galen (129 – 199 / 217 AD), a Greek physician who practiced in Rome and was a giant in the history of medicine, conducted animal experiments to advance the understanding of anatomy, physiology, pathology, and pharmacology. Ibn Zuhr (Avenzoar), an Arab physician in twelfth century Moorish Spain, introduced animal testing as an experimental method for testing surgical procedures before applying them to human patients.