Sydenham Advocates Clinical Observation

Thomas Sydenham’s publication in 1676 of his major work, Observationes Medicae, was a milestone in the progress of modern clinical medicine. Both in this book and by personal example, he encouraged physicians to build their practice on direct evidence and experiment rather than on following the authority of the ancients.

Summary of Event

Until the time of Thomas Sydenham, the practice of clinical medicine in Europe was chiefly determined by physicians following the authority of ancient authors, primarily Hippocrates and Galen. These physicians were not blind followers, but they were led more by the content of standard texts than by the actual details of each patient’s disease or injury. They learned more about medicine by reading and by being taught than by observing, experimenting, or doing. Sydenham was always distrustful of material gleaned from textbooks, believing instead that medicine could be learned only at the bedside of the patient. His mind was open to whatever he could learn directly from his patients but often closed to even the most promising clinical advances from the purely scientific approach. Biology;clinical medicine and
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Sydenham, Thomas

Sydenham was not impressed by William Harvey’s Harvey, William discovery of the circulation of the blood in 1628 or by any other recent advances in physiology, anatomy, or academic medicine. Despite his physiological studies with Christopher Wren Wren, Sir Christopher at Oxford, Sydenham was not persuaded that Wren’s laboratory experiments with injection would have any clinical importance. He was a supremely practical man, not given to theorizing or abstraction, and was more interested in curing diseases than in speculating about their causes. Despite this rigorous empiricism, his observations led him to develop several theories of the origins and transmissions of certain diseases. He accepted the humoral theory of Hippocrates that the healthy body is in balance with nature but realized that the authority of Hippocrates, Galen, and other ancient authors derived from their own original use of empirical methods in medicine and concluded that subsequent physicians would honor these founders of medicine more by emulating their methods than by following their words.

In 1655, Sydenham left his fellowship at All Souls College, Oxford University, moved to London, and established the medical practice in Westminster that he kept until his death. He resolved to bring to patient care the strictly empirical methods that Francis Bacon Bacon, Francis had recently brought to general scientific inquiry. Encouraged by Robert Boyle, Boyle, Robert Sydenham observed his patients very closely, taking special note of environments, atmospheric conditions, and any other factors that might influence their fevers, epidemics, or acute distress, even such apparently disjoint factors as the presence of fleas near typhus cases.

Sydenham, Boyle, and John Locke Locke, John shared similar social, political, and scientific goals that enhanced their solid friendship. Locke and Sydenham collaborated on several philosophical and medical projects, and certainly the way that Sydenham conducted his medical practice was influenced by Locke’s liberalism. The three friends enjoyed such a close and creative intellectual symbiosis that their biographers sometimes have difficulty sorting out who contributed what to their collaborative results. They shared the belief that medicine must constantly experiment in order to serve its primary function, to cure disease.

Thomas Sydenham.

(Library of Congress)

Sydenham’s influence during his lifetime was stronger on the Continent than in Britain. Locke’s Huguenot friend, Charles de Barbeyrac, Barbeyrac, Charles de shared Sydenham’s commitment to Hippocratic empiricism over non-experimental methods of practicing medicine. Sydenham may have visited Montpellier around 1659 to study under Barbeyrac, but more likely, Sydenham never left England and Barbeyrac learned from Sydenham through Locke. Barbeyrac is generally thought to be the author of the controversial Traités nouveaux de medecine
Traités nouveaux de medecine (Barbeyrac) (1684; new essays in medicine), published anonymously in Lyons.

In 1676, Sydenham published Observationes Medicae
Observationes Medicae (Sydenham) (medical observations), a monumental revision and expansion of his Methodus curandi febres
Methodus curandi febres (Sydenham) (1666; method of curing fevers), which had been dedicated to Boyle. Sydenham wrote the first edition while in the country to escape the London plague of 1665. A revised edition of 1668 bore the fruits of two decades of precise and detailed observations of patients. It offered the first useful distinction between measles and scarlet fever. In subsequent editions of Observationes Medicae and in other books, he presented clear and patient-oriented descriptions of rheumatism, smallpox, dysentery, pneumonia, malaria, edema, tuberculosis, rheumatic chorea, anemia, nervous disorders, and various fevers, as well as gout, from which he himself suffered. His investigations into the causes of diseases were aimed at learning how to treat symptoms and prevent outbreaks, rather than at just increasing the store of medical knowledge.

Sydenham’s trial-and-error experiments with diverse therapies led to several significant advances, such as prescribing cinchona bark (“Peruvian bark”) for malaria, opiates to ease suffering, fresh air and exercise for tuberculosis and other chronic debilitating conditions, and iron tonic for anemia. Like most physicians of his time, he used bloodletting but did not take great quantities of blood, and he relied chiefly upon vegetable materia medica and noninvasive methods. He invented laudanum, the solution of opium in alcohol that was the standard remedy for many ailments until the end of the nineteenth century. He claimed that opium was the most widely applicable and most effective of all remedies.

Sydenham’s respect for nature augmented his flexible approach to diagnosis and therapy. His clinical reputation rests largely on the fact that his patients felt better after he visited them. Even if he could not cure them, they appreciated his fatherly concern and gentle therapeutics. He believed that even though each disease must run its natural course, the physician, by enlisting nature, could reduce the patient’s suffering along this course.


Modern empirical methods in clinical medicine began with Sydenham. His many followers, especially the posthumous ones, extended his positive influence on the everyday practice of medicine for at least two centuries. Several professional medical organizations in Great Britain have been named for him, most notably the Sydenham Society, which existed from 1843 to 1857, and the New Sydenham Society, which existed from 1859 to 1907. Both published important series of medical classics.

Since Sydenham’s observations and case reports often later proved to be the basis of new scientific knowledge, the science of medical statistics can be said to have begun with these investigations. His statistical methods and data, and especially his tendency to differentiate sharply and subtly between diseases, contributed to the development of epidemiology. His belief that each disease was a specific product of nature made him a precursor of nosology, the eighteenth century medical philosophy that sought to classify all diseases as if they were entities. His use of cinchona was probably his most influential therapeutic innovation. By the time Pierre Joseph Pelletier and Joseph Beinaimé isolated quinine from it in 1820 and François Magendie publicized its chemical preparation in 1822, cinchona was already one of the most successful and frequently used drugs in European and American medicine.

Sydenham might even be considered the ultimate source of the “evidence-based medicine” (EBM) movement, which has been steadily gaining favor among physicians ever since it was founded by David Sackett, Gordon Guyatt, and Archibald Cochrane at McMaster University in the early 1990’. EBM is the systematic process of using the best evidence from current medical literature to treat each particular case.

Further Reading

  • Bates, Donald George. Thomas Sydenham: The Development of His Thought, 1666-1676. Unpublished doctoral dissertation, Johns Hopkins University, Department of the History of Medicine, 1975. Frequently cited study of the most significant decade in Sydenham’s life.
  • Dewhurst, Kenneth, ed. Dr. Thomas Sydenham, 1624-1689: His Life and Original Writings. London: Wellcome Historical Medical Library, 1966. Selected texts with biographical analysis.
  • French, Roger Kenneth, and Andrew Wear, eds. The Medical Revolution of the Seventeenth Century. New York: Cambridge University Press, 1989. Includes Andrew Cunningham’s “Thomas Sydenham: Epidemics, Experiment, and the ’Good Old Cause,’” an account of how medical innovation confronts medical tradition.
  • Meynell, Geoffrey Guy. Authorship and Vocabulary in Thomas Sydenham’s “Methodus” and “Observationes,” with an Appendix on Isolating Key Words and Phrases. Dover, England: Winterdown Books, 1995. Brief key to Sydenham’s masterpiece.
  • Milton, J. R. “Locke, Medicine, and the Mechanical Philosophy.” British Journal for the History of Philosophy 9, no. 2 (June, 2001): 221-243. Examines Locke’s relationship with Sydenham, Barbeyrac, and other physicians.
  • Newman, George. Thomas Sydenham: Reformer of English Medicine. London: British Periodicals, 1924. Commendatory pamphlet in honor of the three-hundredth anniversary of Sydenham’s birth.
  • Rather, Lelland J. “Pathology at Mid-Century: A Reassessment of Thomas Willis and Thomas Sydenham.” In Medicine in Seventeenth-Century England: A Symposium Held at UCLA in Honor of C. D. O’Malley, edited by Allen G. Debus. Berkeley: University of California Press, 1974. Argues that Sydenham was the better doctor, but Willis was the better scientist.
  • Walmsley, Jonathan Craig. John Locke’s Natural Philosophy (1632-1671). Unpublished doctoral dissertation, King’s College, University of London, 1998. Concentrates on the mutual influence of Boyle, Locke, and Sydenham in the philosophy of medicine.
  • Walmsley, Peter. Locke’s Essay and the Rhetoric of Science. Lewisburg, Pa.: Bucknell University Press, 2003. Shows how Boyle’s and Sydenham’s ideas on science and medicine influenced Locke’s later work.

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Sydenham, Thomas