From ancient times, humans have relied on animals for their survival either as food (sheep, cow) or for competition (horses) and companionship (dogs). As humans became more familiar to their environment, they then also started utilizing animals for attainment of knowledge dating back to the days of the great physician Galen (129-200 AD), who used animals to exhibit that arteries contain blood and not the air (qtd. in Giridharan). This observation of humans about biological similarity and capability of animals to suffer same health problems as that of humans marked the beginning of usage of animals for research and experimentation. Although vivisection (animal testing) is regarded as an act of cruelty by many people on ethical and moral grounds and is not considered efficient however, animals should be used for scientific research and experimentation because this methodology of research has provided cure for many diseases, has improved our living standards and has proved beneficial for environment.
Since most of the organs in animal body (heart, liver, lungs) resemble human organs and work in somewhat similar manner to that of organs in human body, testing and experimentation on animals for scientific research have played a vital role in providing cure for many diseases. There are many diseases and health problems that involve processes which can only be studied in living organisms, for which animals according to medical experts are the most suitable models as opposed to using humans which is very complex and impractical. It is because of animal usage in research that medical experts had been able to discover and provide cure for many fatal and incurable health problems such as heart diseases, HIV/AIDS, bacterial infection, cancer and so on. According to American Physiological Society (APS), research on dogs contributed the most in studying and understanding of the ways of managing heart diseases