I. Origins: Hexham to Hunter’s London

William Hewson was born on 14 November 1739 in Hexham, Northumberland — a market town perched above the River Tyne near Hadrian’s Wall. He was one of eleven children, though, as was common in 18th-century England, very few of his siblings would survive to adulthood. The precariousness of life that surrounded his childhood may have sharpened his curiosity about the body and its fragility.

At fourteen, he began his formal medical training at the Newcastle Infirmary — the institution that would later become the Royal Victoria Infirmary — under its founder, Richard Lambert. This apprenticeship gave Hewson his first systematic exposure to anatomy and clinical care, embedding in him the empiricist’s instinct: observe first, theorise second.

In 1759, drawn by London’s reputation as the world’s foremost centre of anatomical instruction, Hewson enrolled at William Hunter’s Great Windmill Street anatomy school — one of the most celebrated private teaching establishments in Europe. Hunter was a Scottish obstetrician and anatomist of towering intellect, and his younger brother John was already emerging as one of the most formidable experimental surgeons of the century. Hewson flourished in this environment. His intellect and manual dexterity so impressed the Hunter brothers that within a few years, he was permitted to teach the school’s junior students — an extraordinary mark of trust.

From 1761 to 1762, Hewson supplemented his London training with time in Edinburgh, then the world capital of medical education, before returning to London as Hunter’s formal partner. The stage was set for a career of exceptional scientific productivity — if tragically brief duration.

II. The Copley Medal: Illuminating the Lymphatic System

Hewson’s first major scientific contribution — and the work that earned him the Copley Medal in 1769, the Royal Society’s highest honour — was his systematic investigation of the lymphatic system. This network of thin-walled vessels, nodes, and organs had been partially described in earlier decades, but its precise anatomy, extent, and function across species remained poorly understood.

Working with extraordinary methodological ingenuity, Hewson demonstrated the existence of lymphatic vessels across not only humans but also birds, fish, and amphibians — establishing, in a single body of work, that the lymphatic system was a fundamental feature of vertebrate biology rather than a peculiarity of mammalian anatomy. His technique of injecting mercury and coloured dyes into the vessels allowed anatomical artists to render the system in unprecedented detail.

III. The Blood’s Secret Glue: Isolating Fibrinogen

Hewson’s most consequential contribution to what we now call haematology was his isolation and characterisation of the substance he termed “coagulable lymph” — the protein we know today as fibrinogen. Before Hewson, it was widely assumed that blood clotted because of the aggregation of blood cells — particularly the red cells, or erythrocytes. The mechanism of coagulation was, in the language of the day, deeply mysterious.

Through careful experimental manipulation — cooling blood, diluting it, observing its behaviour under different conditions — Hewson demonstrated that the crucial agent in coagulation was a soluble plasma protein, not the formed cellular elements. When blood was allowed to stand or was cooled, this protein precipitated as fibrin, forming the scaffold of the clot. Remove it, and the blood would not coagulate normally. The insight was transformative.

What Hewson got right

In separating the plasma fraction from the cellular fraction, and in demonstrating that clotting resided in the plasma, Hewson established the foundational distinction in haematology between the formed elements (cells) and the fluid matrix (plasma) — a conceptual division that remains the organising architecture of clinical haematology today. Every coagulation screen, every fibrinogen assay, every D-dimer test ordered in a modern hospital laboratory traces its intellectual lineage to Hewson’s workbench.

What Hewson got wrong

In fairness, Hewson was not infallible. He erroneously believed that some red cells originated from white cells — an understandable mistake given the primitive microscopy of his era. He also could not distinguish between the different varieties of white blood cells; the differential white cell count would have to wait for Paul Ehrlich’s aniline dyes more than a century later. But even his errors illuminate the boundaries of 18th-century knowledge, and his correct observations far outweighed his mistakes.

IV. The Shape of Blood: Correcting van Leeuwenhoek

A century before Hewson’s work, the Dutch microscopist Antonie van Leeuwenhoek had observed red blood cells through his remarkable single-lens microscopes — the first human to see them — and concluded they were spherical. The error was understandable: primitive magnification, no staining techniques, and the inherent challenge of interpreting three-dimensional objects through an early optical instrument.

Hewson, working with improved microscopy and rigorous comparative observations, demonstrated that erythrocytes were in fact flattened discs — biconcave in shape. This was not merely a geometric correction. The discoid morphology of the red cell has profound physiological implications: it maximises the surface-area-to-volume ratio for gas exchange, allows deformation through the narrowest capillaries, and produces the characteristic pattern of rouleaux formation on a peripheral blood film. Every time a clinical scientist evaluates red cell morphology under a light microscope — looking for target cells, spherocytes, sickle cells, or elliptocytes — they are working within the conceptual framework Hewson established.

V. The Craven Street Circle: Franklin, Hunter, and a Basement Full of Bones

No biography of William Hewson would be complete without an account of the remarkable social and intellectual network in which he operated — and the extraordinary archaeological discovery that, more than two centuries after his death, brought his work back to public attention.

In 1770, Hewson married Mary (“Polly”) Stevenson — the daughter of his landlady, Margaret Stevenson, at 36 Craven Street, near what is now Trafalgar Square in central London. The house’s other long-term boarder was Benjamin Franklin, at that point the colonial agent for Pennsylvania and one of the most celebrated intellects in the Atlantic world. Franklin became something of a surrogate father figure to both Polly and Hewson, attending Hewson’s lectures, mediating his disputes with William Hunter, and helping to engineer his election to the Royal Society.

By 1772, after a bruising professional rupture with Hunter over credit for joint discoveries, Hewson had left the Great Windmill Street school and established his own anatomy theatre — in the garden behind 36 Craven Street, with Franklin’s encouragement and tacit approval. Anatomy schools in Georgian London operated in a legal grey zone: demand for cadavers for teaching far exceeded the legal supply, and the trade in bodies was closely entangled with London’s criminal underworld.

In 1998, during restoration works at what is now the Benjamin Franklin House museum, workers discovered a pit approximately one metre wide and one metre deep in the basement. It contained over 1,200 bone fragments belonging to at least 15 individuals, alongside animal remains and artefacts including glass microscope slides and metal surgical instruments. Mercury was found alongside turtle bones — precisely matching Hewson’s documented 1770 Royal Society experiment in which he traced the lymphatic system through turtle anatomy using mercury injection.

The discovery illuminated the clandestine infrastructure of 18th-century anatomical science. Subsequent analysis confirmed the presence of at least 28 human individuals (over half of whom were children, likely supplied by resurrectionists who targeted smaller bodies as easier to conceal) and 43 animal species — from domestic cats and dogs to green turtles and mallards. Cut marks on the bones attested to both surgical training and Hewson’s own experimental comparative anatomy.

VI. A Life in Chronology

VII. Legacy: Why Hewson Still Matters

William Dameshek’s 1963 essay in Blood was not simply a historical tribute. It was a correction — a recognition that haematology had for too long undervalued the man who first saw its essential architecture. By the time Dameshek wrote, Ehrlich’s staining techniques, Landsteiner’s blood groups, and the discovery of coagulation factors I through XIII had transformed the discipline. Yet the bedrock concept — that blood’s cellular and fluid compartments play distinct roles in haemostasis — was Hewson’s.

Hewson was, in the truest sense, a systems biologist before systems biology existed. He did not merely catalogue isolated findings; he linked the lymphatic system to immune function, the thymus to lymphoid biology, and the plasma to coagulation — seeing the blood and its allied tissues as an integrated physiological system. This holistic vision anticipated the integrative approaches that now define computational haematology.

The international claim

Dameshek’s praise of Hewson provoked spirited French counter-proposals. Gabriel Andral (1797–1876) and Alfred François Donné (1801–1878) described blood cell changes in systemic disease; Georges Hayem (1841–1933) is credited as the first to count platelets. Each contributed enormously to the discipline. But the claim that Hewson’s trio of discoveries — fibrinogen isolation, erythrocyte morphology, lymphatic mapping — represents a foundational moment of original synthesis is difficult to contest.

The septicaemia irony

There is a particular irony in the cause of Hewson’s death. He died of septicaemia contracted during cadaveric dissection — the same microbial invasion of the bloodstream that his fibrinogen research was, unknowingly, laying the groundwork to understand. The coagulation cascade he described is central to the body’s innate immune response to infection. He died from the process he had begun to map.

Lister’s antiseptic techniques would not arrive until 1867. Pasteur’s germ theory not until the 1860s. Hewson was operating nearly a century before either. His death was not a failure of courage or intellect — it was a tragic consequence of the knowledge horizon of his time.

VIII. Conclusion: The Short Life That Built a Science

William Hewson lived for thirty-four years and eight months. In that time, he earned the Copley Medal, was elected to two of the most prestigious scientific societies in the Atlantic world, ran his own anatomy school, raised a young family, and produced the body of work that William Dameshek would, two centuries later, characterise as the founding contribution of a discipline.

He did not work in a vacuum. His science was shaped by the Hunt brothers’ surgical tradition, by Edinburgh’s rigorous empiricism, by Franklin’s philosophical curiosity, and by the clandestine networks that supplied the corpses without which 18th-century anatomy could not exist. The Craven Street bones are not a scandal — they are evidence of a man who sacrificed social comfort and legal safety for the advancement of knowledge, in the way that every transformative scientist of every era has had to.

Modern haematology operates at a scale and precision Hewson could not have imagined: single-cell RNA sequencing, mass cytometry, next-generation sequencing of clonal haematopoiesis, AI-powered morphology classification. Yet the conceptual pillars of the field — that blood has cellular and plasma compartments with distinct functions, that red cell shape encodes physiological information, that the lymphoid system is an integrated biological architecture — were laid by a young man from Northumberland, in a basement on Craven Street, with mercury and candlelight.

He deserves his title. And his story deserves to be told.

The EEHLSS Computational Haematology Team produces educational content spanning the history, science, and technology of blood medicine. Our 72-week curriculum integrates foundational haematological science with modern AI-driven laboratory informatics. Visit eehlss.io to learn more.