William Harvey's On The Motion On The Heart And Blood In Animals

Harvey William Harvey’s seminal work “On the Motion on the Heart and Blood in Animals” initiated modern medicine. Harvey’s arguments were detailed readily verifiable and though they did endure a fair bit of criticism when released, in most areas, they were accepted within his lifetime. Once his simple notion of the circulation of blood was carefully described others were able to see and understand its validity themselves. I will argue that William Harvey’s theory which used inductive reasoning to show, with experiments, how blood flowed from veins to arteries through the heart and deduced the existence of capillaries to return blood from arteries to veins.

One of the main understandings of the day, proposed by Galen of Pergamon nearly 1500 years earlier, was that blood was a resource that was produced in the liver and consumed in the tissues and the brain. Harvey took immediate quarrel with this theory and set out to disprove it. He did this convincingly with what may be called a “Mass-Balance” calculation or quantitative argument. He determined that the left ventricle could hold approximately two ounces of blood through his study of cadavers. This information was essential because he could use this to approximate how much blood passes through the heart every half hour. It was readily verifiable that the

Vesalius had observed, by dissection, that there were no pores in the septum of the heart. This meant that direct transfer of blood was not possible. Harvey’s explanation for how blood was transferred from the right ventricle to the left ventricle was that it went through the lungs via the pulmonary arteries and returned through veins to the left auricle, and subsequently to the left ventricle. Once again this description was a simplified explanation of flow in line with his observations and those of Vesalius and