From Hippocrates to the four humors, from the germ theory to the mRNA vaccine — a chronological tour of how humans came to understand and treat disease.
"It is more important to know what sort of person has a disease than to know what sort of disease a person has." — attributed to Hippocrates of Kos (c. 460 — c. 370 BCE).
Greek medicine before Hippocrates was largely supernatural — diseases were sent by gods. The Hippocratic Corpus shifted the frame: disease arises from natural causes (imbalances of the four humors — blood, phlegm, black bile, yellow bile) and is studied by careful observation. The Hippocratic Oath, in modernized forms, still anchors medical ethics.
In Rome, Galen of Pergamon (129 — c. 216 CE) systematized anatomy and physiology through dissections of Barbary apes and pigs. His authority dominated Western medicine for fourteen centuries — including many errors that direct human dissection would have corrected.
Between the 8th and 14th centuries, scholars in Baghdad, Cairo, Córdoba, and Damascus translated Greek medical works into Arabic, expanded them, and created some of the world's first hospitals (bimaristans). Major figures:
Distinguished smallpox from measles; wrote the encyclopedic Kitab al-Hawi.
The Canon of Medicine (1025) — a Latin-translated standard text in European universities into the 17th century.
Father of modern surgery; described 200+ instruments still recognizable today.
For more than a millennium, European medical students learned anatomy from Galen — and, when discrepancies appeared in cadavers, blamed the cadaver. Andreas Vesalius (1514–1564), a Flemish anatomist at Padua, did the dissecting himself and corrected hundreds of Galen's errors.
His De humani corporis fabrica (1543), illustrated with woodcuts of unprecedented accuracy, was published the same year as Copernicus's De revolutionibus. Two revolutions — the heavens and the human — began together.
Fig. 3.1 · After Vesalius, 1543.
William Harvey (1578–1657), an English physician trained in Padua, demonstrated in De Motu Cordis (1628) that blood circulates in a closed loop driven by the heart — overturning Galen's theory that blood was continuously produced by the liver and consumed in the tissues. Harvey reasoned by quantification: the volume the heart pumps per hour vastly exceeds what could be produced; therefore it must return.
The capillaries closing the loop awaited Marcello Malpighi (1661), with the new microscope.
In 1796, Edward Jenner observed that milkmaids who had contracted cowpox (a mild disease) seemed protected from smallpox (a devastating one). He inoculated 8-year-old James Phipps with material from a cowpox lesion, then with smallpox; Phipps did not develop smallpox. The Latin vacca (cow) gave us "vaccination."
Smallpox killed an estimated 300 million people in the 20th century alone. The WHO declared it eradicated in 1980 — the only human disease ever eliminated.
"The annihilation of the smallpox, the most dreadful scourge of the human species, must be the final result of this practice." — Edward Jenner, 1801.
Before October 16, 1846, surgery was performed on conscious patients restrained by force or alcohol. Speed mattered more than precision. On that day, dentist William T. G. Morton publicly demonstrated diethyl ether anesthesia at Massachusetts General Hospital — surgeon John Collins Warren removed a tumor from a patient's neck without pain. "Gentlemen, this is no humbug," Warren reportedly said.
Chloroform soon followed (James Young Simpson, 1847), then cocaine for local anesthesia (Carl Koller, 1884), and the modern menagerie of inhaled and intravenous agents.
| Year | Event |
|---|---|
| 1847 | Ignaz Semmelweis cuts puerperal-fever death rates by hand-washing in Vienna; ridiculed by colleagues. |
| 1854 | John Snow traces London cholera outbreak to Broad Street pump. |
| 1861 | Louis Pasteur disproves spontaneous generation; proposes germ theory. |
| 1865 | Joseph Lister introduces carbolic acid surgical antisepsis at Glasgow Royal Infirmary. |
| 1876 | Robert Koch isolates Bacillus anthracis, founds modern bacteriology. |
| 1882 | Koch identifies Mycobacterium tuberculosis. |
| 1885 | Pasteur saves Joseph Meister with rabies vaccine. |
| 1890 | Koch's postulates for establishing causation. |
In 1928, Alexander Fleming returned from a holiday to find a Staphylococcus culture contaminated by a mold (Penicillium notatum) that was clearing the bacteria around it. He named the antibacterial substance penicillin and published. He could not produce it in quantity.
It took Howard Florey, Ernst Chain, and Norman Heatley at Oxford a decade later to purify and produce penicillin in clinical doses. By D-Day (1944), Allied forces had supplies; by 1945, the Nobel committee honored all three. Penicillin began the antibiotic era — and the resistance era it created.
Refused to patent the vaccine. "Could you patent the sun?" Polio cases dropped 90% in five years.
Live attenuated; cheaper, easier to deliver. Backbone of global polio eradication.
The most prolific vaccinologist in history; estimated to save ~8 million lives a year.
In 1953, James Watson and Francis Crick — using X-ray diffraction images obtained by Rosalind Franklin and Maurice Wilkins — proposed the double-helix structure of DNA. The molecular era of medicine had begun.
Sequencing of the first human genome (Human Genome Project, completed 2003, $2.7 billion) took 13 years. By 2024, a clinical-grade human genome cost under $200 and could be done in a day. This compression underwrites pharmacogenomics, precision oncology, and gene therapies.
Wilhelm Röntgen's X-rays (1895), Godfrey Hounsfield's CT (1971), Paul Lauterbur and Peter Mansfield's MRI (1973), and PET in the 1970s gave medicine the ability to see inside without cutting. Heart-lung bypass (Gibbon, 1953) made open-heart surgery possible. Christiaan Barnard's first heart transplant (Cape Town, 1967), kidney transplants from Joseph Murray (1954), and bone-marrow transplant from E. Donnall Thomas (1957) extended the boundary of what could be replaced.
A modern operating theatre. The descendants of Lister's carbolic spray are now sterile fields, laminar airflow, and electronic monitoring.
Hungarian biochemist Katalin Karikó spent decades pursuing messenger RNA as a therapeutic platform — through tenure denials, demotions, and a cancer diagnosis. With Drew Weissman at Penn (2005), she discovered that pseudouridine modification could prevent mRNA from triggering destructive immune responses. The breakthrough enabled the BioNTech and Moderna COVID-19 vaccines, deployed at unprecedented speed in 2020. Karikó and Weissman won the Nobel Prize in Physiology or Medicine in 2023.
The platform now extends to influenza, RSV, and personalized cancer vaccines in trial.
Hank Green's accessible series traces the history of science, with several episodes dedicated to the development of medicine.
Books: Roy Porter, The Greatest Benefit to Mankind (1997); Sherwin Nuland, Doctors: The Biography of Medicine (1988); Siddhartha Mukherjee, The Emperor of All Maladies (2010); Atul Gawande, Better (2007).
Educational content. Historical figures and dates are widely documented; details vary by source. Not medical advice.