Vesalius (Chapter 4) and William Harvey brought light into the study of human anatomy and physiology, medicine, neurology, and stroke during the sixteenth century. Before their contributions, Galenic writings, teachings, and proclamations had dominated medical practice for almost 1500 years. Galen was born in the Greek city of Pergamon in 130 CE. Galen introduced the principle that the sick could be properly treated only if physicians understood how the body works and how disease disturbs function [1]. To know the normal workings of the body, physician healers required a detailed knowledge of structure (human anatomy) and function (human physiology). Galen dissected mostly animals. His own proclamations and writings were not based on any scientific research. He was the major advocate of the humoral theory of disease. Illness was attributable to an imbalance of the four humors in the body: blood, phlegm, yellow bile, and black bile. Galen taught that blood was the dominant humor and he promoted the practice of bloodletting that held sway for centuries. The liver was the source of the blood. Blood was thought to be constantly manufactured in the liver’s ample spongy depths made from the digested food brought there from the intestines. Treatments for most ailments were therefore designed to restore the balance of these humors and were comprised of enemas, emetics, and bloodletting [2].