Centuries of medical practice centered on honoring the beliefs of ancient philosophers and tradition. Interestingly enough, ancient cultures from around the world, despite their differing justifications, seemed to agree on the merits of bloodletting, the practice of bleeding out your patients for even the mildest of ailments. Even though intellectuals of the Renaissance began to question the wisdom of their ancestors, it wouldn’t be until the death of George Washington after several rounds of bloodletting for a case of epiglottitis that people would begin to question the practice itself (leading to the Edinburgh conference on bloodletting). Even then, the medical community was slow to break from tradition.

Ancient Chinese texts from 350 BC argue in favor of the practice, claiming that puncturing the affected area would allow negative energy to escape, taking the maladies with it. This philosophy ultimately led to the development of acupuncture, a milder treatment still in use today. Greek philosophers of the same era, led by Hippocrates, argued that disease was a consequence of imbalance of the four elements (earth, water, fire, and air) in the body itself and bloodletting could be used to remove the excess element(s) and restore balance.

Around 160 AD, a Greek philosopher, and Hippocrates’s biggest fan, named Claudius Galen, published over 2 million words about his perspective on medicine. Galen was fascinated by the human body, and he wished to study it, but since dissections of cadavers were banned in his time, everything he wrote, he surmised from his observations with animals and the gladiators he would tend to after matches. Brilliant as he was, he lacked the humility to qualify his statements, and his readers wouldn’t think to question his teachings on the anatomy of the human body and the merits of bloodletting for centuries to come.

Around 700 AD, the Abbassad empire, led by Caliph Harun Al-Rashid and eventually his son, Caliph Al-Ma’mun, became the dominant leaders of trade and innovation. Its geographical location as the center of European and Asian trade routes provided it with optimal exposure to many different cultures. Al-Rashid’s vizier, Jafar Al-Balmiki, taught him about paper, a new Chinese invention making its way down the silk road, and convinced him to make their own paper making factories in Baghdad. Impressed by the versatility and cost of production when compared to other forms of parchment and animal skin, Al-Rashid began opening schools and libraries filled with paper all over the capital city of Baghdad, charging its scholars with collecting, transcribing, translating, and analyzing ancient texts from around the world. This movement gained significant expansion under his son, Al-Ma’mun, and continued under their successors until the end of the Abassad empire. This period, known as the translation movement, is when many of the texts from the original Greek philosophers, including Galen, were immortalized and distributed all over the world, including Europe.

The primary method by which intellectuals learned up until this point was by trusting the wisdom of ancient philosophers. In many respects, the intellectuals of Baghdad were the epitome of this thinking, by translating, debating, and ultimately, honoring their works. Perhaps the most influential intellectual of the Abassad Caliphate, however, was someone who was forced to think on his own. Around 1000 AD, trapped in a small room while on house arrest, Hasan Ibn al-Haytham was shocked to see the image projected on the wall of his cell. The tiny hole on the opposite wall let a projection of the outside world in for him to see, but to his surprise, the image of the world appeared upside down. Fascinated by this, he decided to conduct a set of experiments using lanterns to test whether or not his instinct that light travels in a straight line was correct. Within a couple centuries, his book on the nature of optics had captured the world's attention, influencing physicists for centuries to come.

But the impact of this book was much deeper than optics. What people realized after reading his book was that a truly valid theory should be testable. This idea, which many argue as the idea at the center of the Renaissance and the enlightenment periods, would eventually lead to Galen's abdication as the supreme authority on medicine. In 1534, after a lifetime of stealing bodies and performing dissections, an Italian physician by the name of Vesalius published De Humani Corporis Fabrica, the first anatomically accurate human anatomy book with diagrams, challenging many of the ideas proposed by Galen.

He was met with hesitation, but the evidence spoke for itself, and eventually, Vesalius’s ideas about anatomy prevailed. It would take much longer, however, for people to begin questioning bloodletting as a valid practice. Nonetheless, humans had begun their journey to discover evidence based medicine. Our next big stride came when we took a closer look to answer the question, what is blood actually made of?

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