9.4: Medicine

While astronomy and physics advanced by leaps and bounds, medical science and biology advanced much more slowly. At the time, there were a host of preconceived notions and prejudices, especially against work on human cadavers, that prevented large-scale experimentation. Most doctors continued to rely on the work of the Greek physician Galen (129-216 CE), who supported the Aristotelian idea of the four “humors” that supposedly governed health: blood, phlegm, yellow bile, and black bile. According to this theory, illness was the result of an overabundance of one humor and a lack of another. Hence, the centuries-old practice of bleeding someone who was ill in hope of reducing the "excess" blood.

While the belief in humors continued to hold sway, important advances did occur in anatomy. The Italian doctor Andreas Vesalius (1514 – 1564) published a work on anatomy based on cadavers. Another doctor, William Harvey (1578 – 1657), conclusively demonstrated that blood flows through the body by being pumped by the heart, not emanating out of the liver as had been previously believed. Other doctors used a new invention, the microscope, to detect the capillaries that connect arteries to other tissues.

Figure 9.4.1: One of Vesalius’s illustrations, in this case of human musculature.

Many medical advances would not have been possible without the Renaissance. Renaissance artistic techniques made precise, accurate anatomical drawings possible, and print ensured that works on medicine could be distributed across Europe rapidly. Thus, scientists and doctors were adding their discoveries to a more widespread understanding of how the body worked. Even though the concept of the humors (as well as other ideas like miasmas causing disease) remained prevalent, doctors now had a better idea of how the body was designed and what its constituent parts actually did.

The new understanding of anatomy did not lead to an understanding of contagion. The Dutch scientist Antonie Van Leeuwenhoek (1632-1723) invented the microscope. In the 1670s, he was able to identify what was later referred to as bacteria. Unfortunately, he did not deduce that bacteria were responsible for illness. Indeed, it would take until the 1860s with the French doctor and scientist Louis Pasteur for definitive proof of the relationship between germs and sickness to be established.