November 14, 1739 (Hexham, Northumberland, England)
May 1, 1774 (London, England)
anatomist, medical researcher
Hewson, son of a country surgeon, was trained in medicine at Newcastle-on-Tyne and went in 1759 to William Hunter's anatomy school in London, where he also attended St. Thomas's and Guy's hospitals. After a winter's course at Edinburgh in 1761-1762, he became assistant and partner in Hunter's school. In 1767 he published the first practical account of paracentesis of the thorax in cases of emphysema, later admitting that this operation had been proposed by others.
During 1768-1769 Hewson read three papers to the Royal Society on his exploration of the lymphatic system in the lower vertebrates, which led to a priority dispute with Alexander Monro II; John Hunter also claimed to have preceded him. Hewson had in fact made a more complete demonstration of his subject than any of his predecessors through the previous century. He was elected a fellow of the Royal Society on 8 March 1770 and was awarded the Copley Medal in November. He continued as Hunter's resident assistant until his marriage to Mary Stevenson on 10 July 1770. Hunter proposed in 1771 to dissolve the partnership because Hewson no longer lived in the school, while Hewson claimed personal ownership of preparations that he had made while teaching there. Benjamin Franklin effected their reconciliation, but Hewson set up his own school in Craven Street in September 1772.
Hewson had reported his microscopical research on blood to the Royal Society during 1770. By well-planned experiments and precise thermometry he ascertained the role of fibrinogen and gave the first valid account of coagulation. Microscopy was little practiced because the compound microscopes of the time produced distortions and current methods of preparing tissue for examination were inadequate. Hewson relied on a single lens and devised a satisfactory means of mounting "wet" specimens. He was the first to observe the lymphocytes in the thymus and spleen and concluded that their production was the function of these glands. He republished his papers on the blood in 1771, adding a long appendix on his dispute with Monro about the lymphatics. He reported his observations on the red corpuscles in 1773, showing that they were discoid -- not spherical, as was believed -- but mistaking the dark center of the disk for a nucleus. He was also the first to describe clearly the three parts of the blood, components already known to contemporary anatomists.
Early in 1774 Hewson republished his papers on the lymphatics. After his death, from the effects of a dissection wound, his school and researches were continued by Magnus Falconar, who married Hewson's sister Dorothy on 7 September 1774. Falconar repeated Hewson's experiments on the spleen and thymus and in 1777 published his corroboration with a reprint of Hewson's paper on the red corpuscles. He died of phthisis on 24 March 1778, aged twenty-three; his and Hewson's joint museum was sold that October.
-- William LeFanu
Photo: Courtesy of the National Library of Medicine.