Advances in medical knowledge
From Ancient Authority to Scientific Method
Medical knowledge in Britain between c.500 and the present day has been transformed by a succession of intellectual revolutions. For over a thousand years, the dominant framework was ancient Greek theory — particularly the works of Galen and the theory of the four humours. This began to be challenged in the sixteenth century, overthrown by germ theory in the nineteenth, and transformed again by molecular biology in the twentieth.
Galen and the Medieval Framework
Galen was a Greek physician who lived in the Roman Empire (c.129–c.216 AD). His prolific writings on anatomy, physiology and disease became the standard medical texts of medieval Europe, preserved and transmitted through the Islamic world to European universities. Galen taught that the body’s four humours governed health, that the liver produced blood, and that the heart attracted air through the lungs. Much of this was wrong — he worked largely from animal dissections rather than human ones — but the Church’s support for ancient authority meant his ideas went unchallenged for centuries. Medieval physicians were trained to reconcile patients’ symptoms with Galenic theory rather than to observe and question.
Galen’s works dominated European medicine from the medieval period until the sixteenth century. The Church’s backing of ancient authorities, combined with the rarity of books before printing, made it dangerous and difficult to challenge his theories.
Vesalius, Paré and Harvey: A New Anatomy
The sixteenth and seventeenth centuries saw the beginning of a systematic challenge to Galenic medicine, enabled by the Renaissance emphasis on observation and the printing press, which spread new ideas rapidly. Andreas Vesalius published his landmark work De Humani Corporis Fabrica in 1543. Based on his own careful dissections of human cadavers at the University of Padua, it corrected over 200 errors in Galen’s anatomy — demonstrating, for example, that the human jaw is a single bone (Galen had claimed it was two). Vesalius showed that medical knowledge must be grounded in direct observation.
Ambroise Paré (c.1510–1590), a French surgeon, developed new practical techniques for treating wounds. Rather than cauterising gunshot wounds with boiling oil (the standard treatment), he accidentally discovered that a simple salve was less harmful and led to better recovery. Paré also designed artificial limbs and improved ligation — tying blood vessels rather than burning them to stop bleeding after amputation. His work applied an empirical approach to surgical treatment.
The most significant advance of this period was William Harvey’s demonstration of the circulation of blood. Harvey, an English physician, published De Motu Cordis in 1628. Through systematic experiments — tying off veins and arteries and measuring the volume of blood pumped by the heart — he proved that blood circulates continuously around the body, pumped by the heart. This directly contradicted Galen, who believed blood was produced in the liver and consumed by the organs. Harvey’s work established experiment as the method of medical advance.
The transformation of medicine in the nineteenth century centred on germ theory. Louis Pasteur, a French chemist, published his germ theory in 1861, demonstrating that fermentation was caused by microorganisms and that spontaneous generation of life did not occur. German physician Robert Koch built on this in the 1870s and 1880s, developing techniques to isolate and culture specific bacteria and proving that particular bacteria caused particular diseases. Koch identified the bacterium causing anthrax (1876), tuberculosis (1882) and cholera (1883). Koch formulated a set of criteria — now known as Koch’s postulates — for establishing that a specific bacterium causes a specific disease. Germ theory provided the scientific basis for vaccines, antiseptics, antibiotics and the modern understanding of infection.
Scanning Technology: X-Rays, Ultrasound, MRI
The ability to see inside the living body without surgery transformed diagnosis in the twentieth century. Wilhelm Röntgen discovered X-rays in 1895; within months they were being used medically to reveal broken bones and foreign objects inside patients. Ultrasound imaging, developed from the 1950s and 1960s, used sound waves to create images of soft tissue — particularly valuable in obstetrics for monitoring foetal development. Magnetic Resonance Imaging (MRI), developed in the 1970s and 1980s, uses magnetic fields and radio waves to create detailed images of organs and tissue without radiation. Together, these technologies enabled diagnosis of conditions that would previously have required exploratory surgery or been entirely invisible.
X-rays were discovered by Wilhelm Röntgen in 1895. Ultrasound developed from the 1950s–1960s (especially valuable in monitoring pregnancy). MRI developed in the 1970s–1980s, providing detailed soft-tissue images without radiation. All three transformed the ability to diagnose disease without invasive surgery.
The most profound advance in medical knowledge in the twentieth century was the discovery of the structure of DNA. In 1953, James Watson and Francis Crick, working at Cambridge and drawing on X-ray crystallography data produced by Rosalind Franklin and Maurice Wilkins, published their model of the double helix structure of deoxyribonucleic acid (DNA). Understanding that DNA is the molecule of heredity opened the entire field of molecular biology and genetics. Scientists could now begin to understand why some diseases are inherited, how viruses replicate, and which genes are associated with cancer. The Human Genome Project, completed in 2003, mapped the full sequence of human DNA. This knowledge is enabling the development of targeted drug therapies and, in the future, possibly gene-editing treatments for inherited conditions.