Niall Ó Glacáin

Nial O'Glacan (; 1563 – 1653) was an Irish physician and plague doctor who worked to treat victims of bubonic plague outbreaks throughout continental Europe. He was a physician to Hugh Roe O'Donnell and King Louis XIII.

Working as a physician to the prominent O'Donnell clan during the Nine Years' War, he may have followed their chief to Spain after the Siege of Kinsale, where he spent two decades practicing medicine. He moved to France in the 1620s, settling in Toulouse to publish his work , a treatise on plague treatment. Later in life he took up a post at the University of Bologna as Professor of Medicine.

O'Glacan was a pioneer in pathological anatomy, with his work predating that of anatomist Giovanni Battista Morgagni by several decades.

Early life and education Nial O'Glacan and other historians estimate it as 1600, though Conall MacCuinneagáin has pointed out that as O'Glacan treated Hugh Roe O'Donnell in 1602, these birthdates are unlikely.

O'Glacan's medical education was founded on the works of Greek physicians Galen and Hippocrates, whom he refers to in his later works. He probably received his early education from the local Donlevy family, a family of physicians. At the time, most medical families were attached to a powerful clan—the Donlevys were the personal physicians of Tyrconnell's ruling O'Donnell clan. Conversely, Charles Cameron suggests O'Glacan received his medical education abroad.

Owen Ultach MacDonlevy—the last-recorded ollam leighis (official physician) of the O'Donnells—died in 1586. By the early 1600s, it is clear O'Glacan was working as the O'Donnells' physician.

Spain and France After the Irish confederacy's defeat at the Battle of Kinsale, clan chief Hugh Roe O'Donnell travelled to Spain to secure reinforcements. Historians Kate Newmann and David Murphy have suggested that O'Glacan left Ireland after the defeat at Kinsale, due to his support for O'Donnell. In July 1625, he graduated from the (later part of the University of Toulouse) with a bachelor's degree of medicine.

Around 1628, he worked as a travelling plague doctor, treating victims at local hospitals in towns such as Fons, Figeac, Capdenac, Cajarc, Rouergue and Floyeac. around 1630.

By now a respected authority on plague treatment, O'Glacan published his most famous work, ('A Treatise on Plague, or A Short, Easy, and Expert Method for the Curing of Plague'), at Toulouse in May 1629.

O'Glacan eventually moved to Italy. He was "head-hunted" by the Faculty of Medicine at the University of Bologna, which had a tradition of employing very eminent foreign doctors as their (Professor of Medicine). To this end, the university's senate asked Giorgio Scharpes (Professor of Medicine, 1634–1637) to write a report on O'Glacan, whose fame by then spanned all of Europe. Scharpes's reply was as follows:

In 1646, O'Glacan became Professor of Medicine at the University of Bologna. He held this office until his death.

During his years in Bologna, O'Glacan wrote his final work, ('A Physician's Course'), which was published in three volumes in 1655. The first volume dealt with physiology, the second pathology, and the third—published after his death—on the theory of signs. This final volume dealt with the different diagnosis by doctors, descriptions of diseases, and was overall an introduction to the modern concept of differential diagnosis. Two Irish residents of Bologna, Gregory Fallon and Jesuit Phillip Roche, wrote commendatory verses prefixing the second volume. O'Glacan was also an associate of Irish bishop Peter Talbot and Portuguese physician Gabriel da Fonseca, personal physician to Innocent X. Other friends in Italy include Gerard O'Fearail and John O'Fahy.

Death and legacy O'Glacan died in Bologna in 1653, The final volume of begins with his eulogy, as written by Peter von Adrian Brocke, Professor of Eloquence at Lucca: