HIPPOCRATES & THE HUMORS

Greek Medicine before Galen


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Part of an illuminated manuscript with lines of black and red text. In the square illumination, two figures in blue robes attend to a sickly man draped in red.

Hippocrates shown as a medieval university physician administering medication from a sponge or dish to a bedridden patient, attended by a student or an assistant. From De regimine acutorum in the medical text known as the Articella. (Paris, 1st quarter of 14th century), folio 39r. British Library: MS Harley 3140. Photo: British Library.

Galen revered the Greek physician Hippocrates (ca. 460–ca. 370 BCE), the so-called Father of Medicine. Hippocrates’s legacy cannot be underestimated: the Hippocratic writings collectively established the discipline as a science, distinguished it from other fields, and argued that disease had natural causes rather than mystical or divine origins. The continued importance of these foundational texts shaped Roman medicine as a whole and Galen’s approaches specifically. Not only did he build upon the work of his respected predecessor, but his assessments also guided later generations in their choice to recopy delicate handwritten Hippocratic documents, thus ensuring their transmission. Galen is a significant reason why we know as much as we do about Hippocrates today. 

The Hippocratic Corpus is a collection of about sixty medical texts attributed to Hippocrates or associated with his teachings. Ancient and modern scholars alike recognize that these were the work of multiple authors, despite their traditional attribution to Hippocrates; however, where modern scholars are content to think of them as a variously and anonymously penned collection, ancient readers were intent on identifying the “genuine” texts that they could attribute to Hippocrates himself.

A profile view of a stone bust depicting a bearded, balding man.

Bust of Hippocrates. Roman copy from the 1st century CE after a Greek original from the mid-2nd century BCE. Marble. Museo Archeologico Nazionale di Napoli: 6131. Photo: Azoor Photo / Alamy Stock Photo.

Galen, like many of his peers, studied the corpus closely, and commentaries on Hippocrates constitute a large fraction of his voluminous extant output. One of the Hippocratic texts Galen believed to be most important and to contain genuine Hippocratic doctrine was On the Nature of Man, which articulates the famous humoral theory of the body. It offers a coherent presentation of the four humors: blood, phlegm, yellow bile, and black bile. The number of humors is not always consistent within the Hippocratic Corpus (some texts include only two or three, black bile being the latecomer). Nevertheless, the idea that humors were fundamental elements of the body and that health required their proper balance was pervasive. 

Humoralism was already an established cornerstone of medicine in Galen’s day, and he took the notion as a given:

“It seems that health is characterized by the equality and symmetry of these humors. Diseases occur when the humors decrease or increase contrary to what is usual.” 

Different medical sects also claimed Hippocrates as their own authority, though never the Methodists so detested by Galen. By the Roman period, the four humors and their associated elemental qualities (hot, cold, wet, and dry) were largely codified. Galen’s development and codification of these ideas led to their widespread dispersal in the late antique and medieval world, where they were further elaborated and became entrenched. Even today, the humoralist language of melancholic, bilious, choleric, and phlegmatic dispositions remains embedded in our vocabulary.

Diagram with a young man standing inside a vertical rectangle divided into four equal parts. Each quadrant features text, symbols, and illustrations coded by a unique color: brown, red, yellow, and gray.

The four humors. From Leonhardt Thurneysser zun Thurn, Quinta Essentia (Leipzig, 1574), clxii. Photo: Chronicle / Alamy Stock Photo.

The humoral theory in On the Nature of Man provided Galen with an explanation for the causes of illnesses, but to support his understanding of diseases’ progress, he turned to another important work from Hippocrates: Epidemics. Fever—often presented as a disease in itself rather than a symptom—is frequently described in these case histories. Diagnosing a fever (by elevated pulse rate and other clinical features, since there were no thermometers) was one part of evaluating short-term and long-term cases, but identifying “critical days,” a crisis point in a disease’s progress, was a central feature of Hippocratic medicine to which Galen subscribed. By observing the patterns of an illness, the physician was able to predict which days were the most dangerous. Following Hippocrates, Galen believed that intervening in the right way at the right time during these critical days could bring about a favorable outcome. 

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