Inner Explorers: 3 of History’s Indispensable Anatomists

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There is no doubt that the sheer volume of information that anatomy students are required to digest, dissect, commit to memory, and then reconquer in live, clinical settings is daunting. However, it might be helpful to recognize that this knowledge is the golden insight that mysterized countless scholars for centuries, many of whom spent their lives contemplating their physicality in a metaphysical crisis.

Human Anatomy, the branch of biology dedicated to understanding the structural makeup of the body, is the basis of medicine. The collective understanding in this field surged in the last three centuries when Renaissance artists and anatomists came together, fueling an interdisciplinary interaction that bred a revolution in science and medical education. This collaboration led to the development of highly detailed, three-dimensional wax anatomical models that could be studied well beyond the onset of decay during cadaver dissections. Ultimately, this learning tool empowered scientists with the necessary knowledge to design the landmark interventions and treatments that now routinely stave off death and disease by decades.

However, for most of human history, scientists were not allowed to study the inside of the human body. Since human dissections were strictly forbidden, early anatomists would spend their days peering into wounds, thinking deeply about the structures that lie far underneath, and making inferences, many of which were massive misinterpretations that went unchallenged for centuries. When human dissections were permitted during  early modern times, the entire field was flipped on its head and reborn, as anatomists could finally look at the body on a surface level and do away with the older misconceptions. 

The history of anatomy is rich with interesting people and intriguing stories. Below are three individuals who are arguably, among a few others, the most influential anatomists in human history. Sharing a keen eye and tremendous dedication, each of them revolutionized what man knew about his composition for centuries on end. 

 

Herophilus [335-280 BC] The Father of Anatomy

Herophilus, born in 335 B.C., is an Ancient Greek Physician with a controversial reputation in history for having dissected at least 600 live prisoners. His home – Alexandria, Egypt – was one of the few places that allowed dissections for a 40-year duration, during which Herophilus made a series of groundbreaking discoveries, was the first person to perform systematic dissection of the human body, and established himself as the Father of Anatomy.

During his time, conventional medicine propagated Hippocrates’ Theory of the Four Humors, which says that the body is made up of four substances (black bile, yellow bile, blood, and phlegm), each of which must coexist in a perfect balance for good health. Without dissections to prove otherwise, many individuals supported Hippocrates’ Theory, and even came to believe that veins carried air, water, and blood. While Herophilus shared similar medical beliefs, arguing that pneuma – a medium for neural transmission – flowed through arteries alongside blood, he found through his dissections that veins only contained blood, serving as one of the first in history to challenge this concept. Still, he built on Hippocrates’ theory by adding that diseases were products of the four humors impeding the pneuma from reaching the brain.

Herophilus also battled the Aristotelian concept that the brain was a “cooling agent” for the heart, suggesting instead that the brain was the “seat of the intellect” and the human soul. Even though he lived well before the common era, Herophilus insightfully recognized that damage to the motor nerves could induce paralysis, was the first person to distinguish the cerebrum and cerebellum, described the optic and oculomotor nerve for vision, and differentiated between nerves, arteries, and veins, being the first to point out that arteries had thicker walls than veins. In addition to discovering the different sections and layers of the eye, Herophilus is credited with helping midwives and other doctors more fully understand pregnancy as a result of his contributions to the understanding of the female reproductive system. 

An advocate for exercise and a healthy diet, he said that “when health is absent, wisdom cannot reveal itself, art cannot become manifest, strength cannot be exerted, wealth is useless, and reason is powerless.” [1]

After Herophilus’ time, human dissections were banned for an 1800-year hiatus, setting the stage for flawed ideas to be nurtured for generations on end. 

 

Galen [129 AD – 210 AD] An Unchallenged Authority

Galen, a surgeon and philosopher of the Roman Empire, was a pioneering anatomist influenced deeply by Plato, Aristotle, and Hippocrates. He revered medical knowledge and devoted his life to treating patients and deciphering the architecture of the human body. Unfortunately, Roman law prohibited human dissections since 150 BC, and Galen was forced to resort to other means to make sense of the human body – this predicament cost the scientific community for 1400 years. 

Galen led his early life studying at Pergamon, Smyrna and eventually Alexandria, the grandest medical center of the ancient world. At 28, he returned to Pergamon – his hometown and a major center for intellectuals and artists of the time. There, after eviscerating an ape and challenging multiple physicians to repair the damage, each of whom couldn’t, Galen performed an impressive surgery and won himself the opportunity to serve as the chief physician to the troop of Gladiators maintained by the High Priest of Asia. After moving to Rome in 162 AD, Galen treated multiple affluent patients that had been proclaimed as incurable by other physicians. With wealth, great rhetorical skills, and a relationship with Eudemus, an old philosophy teacher, his reputation as a philosopher and physician advanced. However, his impatience with others brought him into conflict with many Roman medical practitioners, and he feared that he’d be exiled or poisoned, eventually leaving the city.

Since human dissections were not allowed, Galen resorted to performing experiments and dissections on living and dead African monkeys, pigs, sheep, goats, and other animals. He felt that the anatomical structures of these animals mirrored those of humans, and would gather insight then make inferences about the human body. Even though Galen’s research was centered on animal physiology, this fact got lost in translation over time and it took centuries until the academic world realized that his work was a body of inferences and speculations about the human body that needed to be corroborated. 

Galen viewed the body as three connected systems: the brain and nerves, responsible for sensation and thought; the heart and arteries, responsible for life-giving energy; and the liver and veins, responsible for nutrition and growth. From studying animals, Galen built on Herophilus’ work and illustrated that the arteries also carry blood and not air. He distinguished seven pairs of cranial nerves, described the valves of the heart, established the functions of the spinal nerves, and demonstrated that the brain controls the voice by tying off the recurrent laryngeal nerve. He also depicted the kidney and bladder functions by tying off the ureters. Another follower of Hippocrates’ Theory of the Four Bodily Humors, he believed that vital health required blood, black bile, yellow bile, and phlegm to be in a state of equilibrium. However, he added that humoral imbalances could be localized to specific organs to improve diagnostic processes. Specifically, Galen felt that blood originates from the liver and is carried by the veins throughout the body, where it is transformed into flesh and other substances. Alongside his landmark findings, the errors of Galenic physiology were difficult to challenge by the prevailing disinterest in human dissections, and his work influenced the medical landscape for 1400 years.

Ironically, one of Galen’s greatest virtues – his emphasis on observing for oneself rather than relying on authority – was lost over time. Professors would read Galen’s work to their students, instilling many of the unfounded ideas into medical curricula for generations. Eventually, Andreas Vesalius illustrated in 1543 that Galen’s version of human anatomy was more animal than human. [2]

 

Andreas Vesalius [1514-1564] – The Founder of Modern Human Anatomy

After a 1400-year duration that cemented Galenic concepts in the academic world, Andreas Vesalius, the Founder of Modern Human Anatomy and a pioneer who paved the road to modern medicine, reformed the discipline. His contributions were so profound that it has been suggested that “few disciplines are more surely based on the work of one man than is Anatomy on Vesalius.” [3]

As referenced, the medical establishment taught students in a two step process: first, professors would read anatomical text (mostly Galenic physiology) to students following which a surgeon would perform an animal dissection for students to observe. Having acquired his medical foundation under this practice, Vesalius had no reason to question Galen’s theories. 

In 1541, however, Vesalius broke with the tradition of relying on Galen and openly began doing dissections himself, relearning anatomy from cadavers, and scrutinizing ancient texts, a practice that he also encouraged his students to do to gain a deep understanding of the human body. In doing so, he came to recognize that most of Galen’s research had been restricted to animals. 

Conducting human dissections for the first time in centuries, he began to rewrite anatomical text based on his own research. He called attention to Galen’s errors and even faced resentment by many scholars and physicians of the time who continued to hold Galen as a medical authority.

In 1543, Vesalius published the seven-volume De Humani Corporis Fabrica (On the Fabric of the Human Body), a landmark textbook of Human anatomy which was based on live dissections and filled with highly detailed 2-D illustrations. With the extensive and elegant nature of the 2D illustrations, the work provided contemporary students and scholars with an immediate learning opportunity: the academic world could sit with highly detailed information for extended periods of time, ultimately resulting in a reorganization of the discipline. This set of books contained Vesalius’ strongest claims against Galenic theories, bringing anatomists to rethink the skeletal, muscular, circulatory, and nervous systems. Supporting parallel dissections, Vesalius would encourage his students to dissect an animal and human cadaver simultaneously, as a means of illustrating the differences between human and animal anatomy, disproving Galen’s assertions. 

Among countless other errors, Vesalius disproved the common belief that men had one fewer rib than women as well as the Aristotelian concept that men had more teeth than women (Aristotle and 1800 years of successors never bothered to check their wives’ teeth). Introducing human dissections into medical curricular, Vesalius led his work with a fierce attention to detail and reorganized man’s understanding with far-reaching implications for both physiology and biology. [4]

 

In addition to these three anatomists are a line of pioneers that contributed to the field of anatomy tremendously. Less theoretical scientific disciplines – like Anatomy – have potential to be reorganized again in the coming years (or centuries). For the most part, our understanding of the human body is constrained to what we see at a surface level. However, imaging modalities (utilizing infrared radiation and other forms of Electromagnetic Radiation) allow insight to be gathered at a much deeper level. Perhaps future scholars will come to recognize details that we lack visual access to, turning the field on its head one more time. 

It has been said that sickness and disease are a language through which deviations from physical normalcy are expressed. The syntax of this language is rooted in anatomy class, and it is a historical feat that high schoolers can now delve deep into this material. For the three anatomists above and the countless others who devoted their lives to understanding human physiology, this is an excellent time to be alive.

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