Animal testing is defined as the use of non-human animals in tests and experiments (Wikipedia, 2014). Whether the experiment encompasses actual testing affecting some aspect of animals or simply encompasses the observation of an animal's behavior, it is classified as animal experimentation. Animal testing can often be done in many locations, such as a university, medical schools, pharmaceutical companies, farms, defense installations, and commercial establishments that use animal testing for commercial purposes. commercial, such as a cosmetics company (Wikipedia, 2014). Tests that animals have been involved in include toxicology tests, cosmetic tests, behavioral studies and developmental biology tests. In total, it is estimated that approximately 100 million animals are used each year for animal treatment and that approximately 80 million animals were used in the United States alone in 2001 (Wikipedia, 2014). After being used in various experiments, the animals are euthanized (Wikipedia, 2014). Humans have used animals as models of anatomy and physiology since the beginnings of medicine. It has been reported that the ancient Greeks dissected animals for certain anatomical studies (Franco, 2013). The dissection of animals was and still is called vivisection. The term vivisection can be considered the definition of animal experimentation for medical research since it is the practice of performing operations on living animals for the purposes of experimentation and research (Franco, 2013) . Some of the first doctors to perform vivisections include Alcmaeon in the 6th and 5th centuries BCE, Aristotle, Diocles and Praxagoras in the 4th century BCE, Erasistratus and Herophilus in the 3rd century BCE (Franco, 2013). Initially, the Greeks did not believe that we... middle of article ...... practiced clinical trials of drugs before their marketing rather than using an animal as such (Kehinde, 2013). The counter-argument put forward was that the difficulties encountered with this method mainly came from the wide and varied side effects that could appear after the product was put on the market (Kehinde, 2013). Indeed, most initial clinical trials of a new drug in humans would typically require testing the new drug in approximately 3,000 human volunteers and patients. Therefore, if a side effect occurs in 1 in 10,000 patients, it may not become apparent until after the product is marketed. Additionally, human clinical trials often involve a relatively homogeneous sample of patients in order to clearly distinguish the effects of therapy against the backdrop of variation between different patient responses..