Have you ever gotten in trouble for asking questions? Or felt stupid for challenging a certain theory because you didn’t think it was right? If you have you should know that it is actually in our human nature to question what we are taught. If we didn’t, we would never discover anything new. In fact, it is this innate desire to challenge certain theories and hypotheses that has driven the evolution of science and technology to what it is today.
This is especially true for the evolution of medicine. Claudius Galen (129 AD) was a prominent Roman physician, surgeon and philosopher. Galen contributed greatly to the understanding of numerous scientific and medical theories in his time. One theory involved the function of the heart and blood, which he based on the dissection of animals (rather than humans as this was prohibited by Roman law), remained uncontested for almost 2000 years because no one could prove him wrong. Galen believed that the circulatory system consisted of two separate one-way systems of blood flow, rather than a single unified system of veins and arteries. His understanding was that venous blood was generated in the liver, and flowed to all organs of the body known as the natural system. He also claimed that arterial blood originated in the heart, and flowed to all the organs of the body. The blood was then destroyed, and then regenerated in either the liver or the heart, completing the cycle. This is was known as the vital system.
This theory of the circulatory system endured for almost two millennia until 1628 when William Harvey questioned its accuracy, and set out to challenge Galen’s belief.William Harvey believed that blood flowed through one circulation, not two, and was propelled only by the heart, not the liver. In order to prove his theory, Harvey carried out dissections on the bodies of executed criminals. Through this careful and detailed research, Harvey was able to disprove Galen's theory. He proved that the heart was a pump which forced the blood around the body through arteries and that the blood was returned to the heart through the veins. This was an outstanding discovering in the history of medicine, simply by questioning what was taught. However, the dominance of Galen widely taught theory remained accepted in western and eastern medical encyclopedic references. Harvey’s publication of the circulation of the blood came into conflict with Galen theory, it incited considerable controversy. Some doctors maintained that they would "rather err with Galen than proclaim the truth with Harvey.” Therefore, this goes to show that it does pay to question what we learn; especially if we think it is wrong. Adapted from Wikipedia entry re: William Harvey