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Cholera Epidemics in the 19th Century

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“Pestilence” and the Printed Books of the Late 15th Century

Spanish Influenza in North America, 1918–1919

Syphilis, 1494–1923

Tropical Diseases and the Construction of the Panama Canal, 1904–1914

Tuberculosis in Europe and North America, 1800–1922

The Yellow Fever Epidemic in Philadelphia, 1793

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Humoral Theory

>Galen, in Pathfinders in Medcine, New York: 1912. From the holdings of Francis A. Countway Library of Medicine, Harvard Medical School.
Galen, in Pathfinders in Medcine. From the holdings of Francis A. Countway Library of Medicine—Harvard Medical School.

Humoral theory was one of the central principles in Western medicine from antiquity through the 19th century. “Humoral” derives from the word “humor,” which, in this context, means “fluid.” The human body was thought to contain a mix of the four humors: black bile (also known as melancholy), yellow or red bile, blood, and phlegm. Each individual had a particular humoral makeup, or “constitution,” and health was defined as the proper humoral balance for that individual. An imbalance of the humors resulted in disease.

The humors were also used to refer to four individual psychological temperaments: melancholic, sanguine, choleric, and phlegmatic. This reflects the humoral concept that physical health and individual personality were part of the same whole.

The development of humoral theory is associated originally with Hippocrates (ca. 460–370 BCE). In the second century CE, Galen elaborated on this theory, which was further developed by Arabic writers beginning in the 9th century and by European writers beginning in the 11th. Though several important publications—Andreas Vesalius’s De Humani Corporis Fabrica in 1543 and William Harvey’s De Motu Cordis in 1628—challenged aspects of humoral theory, it remained dominant among both physicians and the public through the 19th century.

Equilibrium and the Environment

Each humor was associated with one of the four seasons, and each was considered to have characteristic qualities of hotness, coldness, dryness, and wetness. Because each individual’s humoral balance was holistically connected with other phenomena—such as climate, diet, occupation, geographic location, planetary alignment, sex, age, and social class—what was healthy for one person might not be so for another. Humoral treatments, or “regimens,” were designed to restore the proper humoral balance by bloodletting, vomits, enemas, and other purges, and they were accompanied by diet and lifestyle changes and by medications that were based on a person’s humoral disposition and its relationship to the rest of the environment. Anything that upset this equilibrium—such as a change in season or climate, a sudden shift in the weather, or the onset of puberty—was a possible health crisis.

Disease and Humoral Theory

In humoral theory, individual diseases did not exist in the way that we understand them today. Diseases were not seen as forces or entities separate from the body, but instead were understood as states of bodily imbalance. Physicians trained in humoral theory relied not only on a knowledge of medical texts, but also on personal understanding of the patient; on the inspection of blood, urine, and other fluids produced by the body; and on the patient’s description of his or her symptoms.

Extensive physical examinations were rare. Prognosis was a finely honed skill, and works published by physicians before the 20th century often contain detailed observations of the stages and crisis periods in illness. Authors typically refer to the eruption of lesions on the skin, the movement of fluids through the body, and the problems caused by any blockages. Preventative treatment was also of central importance, and public health practices developed in the early 19th century were based in part on basic humoral presuppositions—especially on the relationship between environment, individual lifestyle, and health. These ideas were often criticized, however, especially after mid–century.


Bloodletting as a treatment was closely associated with humoral theory. In cases of an overabundance of one or another humor (called “plethora,” “congestion,” “inflammation,” and a variety of other terms), letting blood was believed to allow the body to reach a healthier balance. How much bleeding was done and where in the body the blood came from could change depending on individual conditions and on the training and beliefs of individual doctors—some of whom took a dangerously extreme approach. Bloodletting was also done seasonally as a tonic.

After the first decades of the 19th century, bloodletting was discredited in many parts of Europe and the United States, though the practice continued well past mid–century.

Other Traditions

Medical traditions in other cultures, such as Ayurvedic medicine in India, traditional Chinese medicine, and Native American medicine, are also based in versions of humoral theory. Even today, our health is still often evaluated in terms of the analysis of fluids like urine and blood.


Selected Contagion Resources

This is a partial list of digitized materials available in Contagion: Historical Views of Diseases and Epidemics. For additional materials on the topic “Humoral Theory,” click here or search the collection’s Catalog and Full Text databases.

Web Pages

Concepts of Contagion and Epidemics
Medical Geography
“Pestilence” and the Printed Books of the Late 15th Century
Public Health
The Yellow Fever Epidemic in Philadelphia, 1793


William Norton Bullard Collection
Solomon M. Hyams Collection
   [Miscellanea medica], [ca. 1450]
Papers of Benjamin Waterhouse, 1786–1836 (inclusive)
   “The Effects of Cold and of Catarrh,” [Lecture], 1806
   “A Dissertation Upon the Effects of Blood–letting,” by John Fothergill Waterhouse, 1814


Clark, John. Observations on the Diseases in Long Voyages to Hot Countries: and Particularly on Those Which Prevail in the East Indies. London: Printed for D. Wilson and G. Nicol, MDCCLXXIII [1773].
Drake, Daniel. A Systematic Treatise, Historical, Etiological, and Practical, on the Principal Diseases of the Interior Valley of North America, as They Appear in the Caucasian, African, Indian, and Esquimaux Varieties of its Population. Philadelphia: Lippincott, Grambo & Co., 1854.
Gilles, de Corbeil. Carmina de Urina[rum] Iudiciis. [Padua: I[m]pressus [per] m[a]g[ist]r[u]m Matheu[m] Cerdonis [de] Uuindischgrecz, die 12 Iulli, anno 1483].
Hippocrates. The Genuine Works of Hippocrates: Translated from the Greek with a Preliminary Discourse and Annotations. New York: William Wood & Co., [189-?].
Ketham, Joannes de. Fasciculus medicine. Impressum Venetijs: per Johanne[m] & Gregoriu[m] Fratres de Forliuio, Anno D[omi]ni Millesimo Quadringe[n]tesimo Nonagesimo Primo Mensis Iulij die XXVI [1491 July 26].
Sibley, Ebenezer. A Key to Physic, and the Occult Sciences. Opening to Mental View, the System and Order of the Interior and Exterior Heavens; the Analogy Betwixt Angels, and Spirits of Men; and the Sympathy Between Celestial and Terrestrial Bodies … London: Printed for the Author, and Sold by Champante and Whitrow, Jewry-Street, Aldgate; and at the British Directory-Office, Ave-Maria Lane. [1800?] .

Publications Related to Bloodletting

Almanach für Österreich auf das Jahr 1491 Nuremberg: Kaspar Hochfeder, 1495?.
Johnson, James Rawlins. A Treatise on the Medicinal Leech: Including its Medical and Natural History, with a Description of its Anatomical Structure: Also, Remarks Upon the Diseases, Preservation and Management of Leeches. London: Longman, Hurst, Rees, Orme, and Brown, 1816.
Louis, P. C. A. Recherches Sur les Effets de la Saignée dans Quelques Maladies Inflammatoires, et Sur l’Action de l’Émétique et des Vésicatoires dans la Pneumonie. Paris: J.B. Baillière, Libraire de l’Académie Royale de Médecine, 1835.
Magni, Pietro Paolo. Discorsi di Pietro Paolo Magni Piacentino Intorno al Sanguinar i Corpi Humani, il Modo di Ataccare le Sanguisuche e Ventose è far Frittioni è Vesicatorii: Con Buoni et Utili Avertimenti. Roma: Appresso Bartolomeo Bonfadino, & Tito Diani, MDLXXXIIII [1583].
Mills, Thomas. An Essay on the Utility of Blood-letting in Fever: Illustrated by Numerous Cases: With Some Inquiry into the Seat and Nature of this Disorder. Dublin: Printed by J. Barlow …: sold by Gilbert and Hodges … ; [London]: and Longman, Hurst, Rees, Orme, and Brown, London, 1813.

Other Traditions

Royle, J. Forbes. An Essay on the Antiquity of Hindoo Medicine: Including an Introductory Lecture to the Course of Materia Medica and Therapeutics Delivered at King’s College. London: W.H. Allen: J. Churchill, 1837.
Wang Bing zhu. Chong Guang bu Zhu Huangdi Nei Jing su Wen ;er shi si Uuan. China: Gu Cong De, Ming Jiajing Geng xu i.e. 29 Nian, 1550.


The following sources were used in writing this page.

Arikha, Noga. Passions and Tempers: A History of the Humours. New York: Ecco, 2007.
Kupperman, Karen Ordahl. “Fear of Hot Climates in the Anglo-American Colonial Experience.” The William and Mary Quarterly, Vol. 41, No. 2 (Apr., 1984), pp. 213-240.
Lindemann, Mary. Medicine and Society in Early Modern Europe. Cambridge: Cambridge University Press, 1999.
Rosenberg, Charles. “The Therapeutic Revolution.” In Explaining Epidemics and Other Studies in the History of Medicine. Cambridge: Cambridge University Press, 1992.
Siraisi, Nancy G. Medieval and Early Renaissance Medicine: An Introduction to Knowledge and Practice. Chicago: University of Chicago Press, 1990.


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