Guinea pigs are used in medical research. They have many biological similarities to humans, beyond the simple fact that they are mammals, which make them useful in many fields of research. Guinea pigs have been used as experimental animals for centuries; hence 'guinea pig' for a human experimental subject. Guinea pigs led to the discovery of: Vitamin C, tuberculosis bacterium, adrenaline. And were used in development of vaccines for diphtheria and TB, replacement heart valves, blood transfusion, kidney dialysis, antibiotics, anticoagulants, asthma medicines. Vitamin C was discovered using guinea pigs. Also used in research for allergies and respiratory diseases, nutritional research, Hearing, Safety testing.