Galenic Physiology

As with astronomy, ideas about how the human body works were governed by assumptions handed down from the ancient world—especially the Greek physician Galen (129-210 CE). For Galen, health and disease were functions of harmony and disharmony between four bodily fluids or “humors”—blood, phlegm, yellow bile, and black bile. These four humors corresponded, in turn, to the four elements of the natural world: Earth, Air, Fire, and Water. As with the Anthropocentric universe, these elements were associated with physical properties and human termperaments:
Bodily Humor: Temperament: Natural Element:
Yellow Bile Choleric, Bilious Fire
Black Bile Melancholy Earth
Phlegm Phlegmatic Water
Blood Sanguine Air

Zodiac Man

The assumption underlying Galenic medicine, like the Aristotelian/Ptolemaic universe, was anthropocentric: according to this system of human physiology, the “microcosm” of the human body corresponded with the “macrocosm” of the universe, the planets and stars and their motions. For this reason, astrology could assist in the diagnosis and remedy of disease. The woodcut at the left shows which constellation, symbolized by a sign of the zodiac, governed which region of the body. Aries governs the head as well as the month of March, and so on. The table advises that a region of the body should not receive medication when the corresponding sign is dominant. So, it is ill-advised to treat the head in March, and “anyone who does so will cause a concussion or die.”  Similarly the legend for Cancer says: “The Crab is the sign of June: avoid treating the stomach, the spleen, the lungs or the eyes.”

 
A Diagnostic Uroscopy Chart

Just as the physical world was governed by the “natural” and “violent” motions of the elements, so health was determined by the relationship between the four humors and their motions within the body. An excess of any one humor resulted in dyscrasia, an abnormal mixture. Thus an excess of black bile produced melancholia, and so on. Medical diagnosis aimed, therefore, to discover the nature of that imbalance and what had caused it; medical cures were meant to restore equilibrium between the four humors.

Galen also believed that a disease-causing imbalance could be located within an organ or region within the human body, which enabled him to device cures that targeted particular organs. Because health and disease were thought of in terms of equilibrium and disequilibrium, Galen's cures treated disease with contraries, that is, they aimed to correct imablance by adding to or removing humors. The use of opposites to treat diseases was accomplished though the use of pharmacological agents or other “balancing” procedures, such as bloodletting or purging.

The diagram at the right illustrates how fifteenth- and sixteenth-century Galenic physicians used this understanding of health and disease to diagnose bodily ailments. It is a uroscopy chart and is intended to help physicians determine the balance of humors by measuring the color, contents, and consistency of urine. In this chart, the focus is on the color of urine. The wheel shows twenty-one flasks, each containing urine of a particular color, each of which corresponds to a specific relationship among the four humors. Equipped with a color wheel such as this, a physician could quickly determine whether the patient was suffering from an excess of choler (yellow bile), blood, phlegm, etc., and then take the appropriate corrective measure. The image comes from Johannes de Ketham, Fasiculo de medicina (Venice: Zuane & Gregorio di Gregorii, 1494), one of the earliest published Galenic handbooks of diagnostic medicine and the first to include anatomical illustrations.

Image source: National Institutes of Health.