Galen - Contributions To Medicine

Contributions To Medicine

Galen contributed a substantial amount to the Hippocratic understanding of pathology. Under Hippocrates’ bodily humors theory, differences in human moods come as a consequence of imbalances in one of the four bodily fluids: blood, yellow bile, black bile, and phlegm. Galen promoted this theory and the typology of human temperaments. An imbalance of each humor corresponded with a particular human temperament (blood-sanguine, black bile-melancholic, yellow bile-choleric, and phlegm-phlegmatic). Individuals with sanguine temperaments are extroverted and social. Choleric people have energy, passion and charisma. Melancholics are creative, kind and considerate. Phlegmatic temperaments are characterized by dependability, kindness, and affection.

Galen’s principal interest was in human anatomy, but Roman law had prohibited the dissection of human cadavers since about 150 BC. Because of this restriction, Galen performed anatomical dissections on living (vivisection) and dead animals, mostly focusing on pigs and primates. This work turned out to be particularly useful because in most cases, the anatomical structures of these animals closely mirror those of humans. Galen clarified the anatomy of the trachea and was the first to demonstrate that the larynx generates the voice. Galen may have understood the importance of artificial ventilation, because in one of his experiments he used bellows to inflate the lungs of a dead animal.

Among Galen’s major contributions to medicine was his work on the circulatory system. He was the first to recognize that there were distinct differences between venous (dark) and arterial (bright) blood. Although his many anatomical experiments on animal models led him to a more complete understanding of the circulatory system, nervous system, respiratory system and other structures, his work was not without scientific inaccuracies. Galen believed that the circulatory system consisted of two separate one-way systems of distribution, rather than a single unified system of circulation. His understanding was that venous blood was generated in the liver, from where it was distributed and consumed by all organs of the body. He posited that arterial blood originated in the heart, from where it was distributed and consumed by all organs of the body. The blood was then regenerated in either the liver or the heart, completing the cycle. Galen also believed in the existence of a group of blood vessels he called the rete mirabile, near the back of the human brain. Both of these theories of the circulation of blood were later shown to be incorrect.

In his work De motu musculorum, Galen explained the difference between motor and sensory nerves, discussed the concept of muscle tone and explained the difference between agonists and antagonists.

Galen was also a highly skilled surgeon, and he performed surgical operations on human patients. Many of the procedures and techniques that he utilized would not be used again for centuries. Of particular note are procedures that Galen performed on patients’ brains and eyes. In order to correct cataracts in patients, Galen performed an operation that was similar to what is performed by contemporary ophthalmologists. Using a needle-shaped instrument, Galen attempted to remove the cataract from behind the lens of the eye. His surgical experiments included using ligatures on the arteries of living animals.

At first reluctantly, but then with increasing vigour, Galen promoted Hippocratic teaching, including venesection and bloodletting, then unknown in Rome. This was sharply criticised by the Erasistrateans, who predicted dire outcomes, believing that it was not blood but pneuma that flowed in the veins. Galen, however, staunchly defended venesection in his three books on the subject, and in his demonstrations and public disputations.