Pro & Con Arguments: "Should Animals Be Used for Scientific or Commercial Testing?"
PRO Animal Testing : Animal testing has contributed to many life-saving cures and treatments. The California Biomedical Research Association states that nearly every medical breakthrough in the last 100 years has resulted directly from research using animals.  Experiments in which dogs had their pancreases removed led directly to the discovery of insulin, critical to saving the lives of diabetics.  The polio vaccine, tested on animals, reduced the global occurrence of the disease from 350,000 cases in 1988 to 223 cases in 2012. [112, 113] Animal research has also contributed to major advances in understanding and treating conditions such as breast cancer, brain injury, childhood leukemia, cystic fibrosis, malaria, multiple sclerosis, tuberculosis, and many others, and was instrumental in the development of pacemakers, cardiac valve substitutes, and anesthetics. [10, 11, 12, 13] Chris Abee, Director of the University of Texas M.D. Anderson Cancer Center's animal research facility, states that "we wouldn't have a vaccine for hepatitis B without chimpanzees," and says that the use of chimps is "our best hope" for finding a vaccine for Hepatitis C, a disease that kills 15,000 people every year in the United States. 
There is no adequate alternative to testing on a living, whole-body system. Living systems like human beings and animals are extremely complex. Studying cell cultures in a petri dish, while sometimes useful, does not provide the opportunity to study interrelated processes occurring in the central nervous system, endocrine system, and immune system.  Evaluating a drug for side effects requires a circulatory system to carry the medicine to different organs.  Also, conditions such as blindness and high blood pressure cannot be studied in tissue cultures.  Computer models can only be reliable if accurate information gleaned from animal research is used to build the models in the first place.  Furthermore, even the most powerful supercomputers are unable to accurately simulate the workings of complex organs such as the brain. 
Animals are appropriate research subjects because they are similar to human beings in many ways. Chimpanzees share 99% of their DNA with humans, and mice are 98% genetically similar to humans.  All mammals, including humans, are descended from common ancestors, and all have the same set of organs (heart, kidneys, lungs, etc.) that function in essentially the same way with the help of a bloodstream and central nervous system.  Because animals and humans are so biologically similar, they are susceptible to many of the same conditions and illnesses, including heart disease, cancer, and diabetes. 
Animals must be used in cases when ethical considerations prevent the use of human subjects. When testing medicines for potential toxicity, the lives of human volunteers should...