Old Democritus under a tree,
Sits on a stone with book on knee;
About him hang there many features,
Of Cats, Dogs and such like creatures,
Of which he makes anatomy,
The seat of black choler to see.
—Robert Burton, The Anatomy of Melancholy

The spleen could be described as occupying a special place between medicine and science versus art and literature. The modern physician thinks of the spleen as a dark purple organ situated under the left rib cage and engaged in filtering out aged red blood cells, storing platelets, and housing lymphocytes essential to immune defense. It can become greatly enlarged in patients suffering from liver cirrhosis or from a variety of cancers or myeloproliferative diseases for which new therapies are being devised. The spleen can be injured and ruptured, presenting as a surgical emergency. It was used in the old days to trap medical students taking their board exams to erroneously diagnose enlargement of the liver and spleen instead of polycystic kidney disease, to the displeasure of severe examiners who felt they should have been able to tell the difference when palpating the abdomen.

In an even more distant past, graduating medical students would have been expected to be familiar with the classical doctrine of the four humors, as articulated by Hippocrates and elaborated by Galen. It postulated that the spleen was the source of an excess of black bile (melaina chole) responsible for “melancholy,” an inherited or acquired state of sadness, gloom, brooding, and depression. Not much could be done for the unfortunate sufferer of melancholy, although some skilled Middle Ages and Renaissance physicians would have successfully rebalanced their patients’ humors with purges, bloodletting, or diets. Melancholic individuals might also have been advised to avoid cold, dry foods and to seek warmth, music, companionship, and moderate exercise.

In the seventeenth century, Robert Burton published The Anatomy of Melancholy, a medical encyclopedia of its causes. His concept of melancholy was more extensive than mere sadness. It included features that today would be thought of not only as depression but also as anxiety disorders, obsessive compulsive disorder, psychosomatic illness, and even certain psychotic states. The book is huge and does not make for easy reading, being, as Samuel Johnson once put it, “a valuable work, perhaps overloaded with quotation.” It catalogued all supposed causes of melancholy—astrological influences, diet, solitude, disappointed love, and many others—as well as its proposed remedies—ranging from herbs to more aggressive approaches. Although Burton’s scholarship extended far beyond strict humoral doctrine, the spleen remained perceived mainly as a source of depression and black thoughts.

By the eighteenth century, however, as anatomy advanced and dissection revealed that the spleen had no duct for black bile, the spleen’s true functions were gradually reevaluated. Language rarely changes completely, and the expression “to vent one’s spleen” is a survivor of the old belief that certain emotions are physically located within the body itself and therefore are treatable as an organic disease. The concept was erroneous but at least acknowledged that depression and other mental diseases were real illnesses that deserved medical attention.