THOMAS**, Baron, an English physician, greatly distinguished by his practice of inoculation for the smallpox, was the son of a surgeon and apothecary at Theydon-Gernon, in Essex, and was born in 1712. His family belonged to the society of Quakers; and his grandfather, after having accompanied William Penn to America, had returned and settled in his native village. Thomas was educated for the medical profession, and commenced his practice at Hertford about 1734. Here he married the only daughter of Nathaniel Brassey, an eminent London banker; and at her death in 1744 he became assistant physician to the forces under the Duke of Cumberland, and continued with the army till the surrender of Carlisle. Having returned to Hertford, he married, in 1746, Anne Iles, and by her fortune he was enabled to retire from practice. He afterwards resumed it, and took the degree of doctor of medicine in 1761. His reputation procured him an invitation to inoculate the Empress Catherine of Russia and her son in 1768; and for his services he was rewarded with the appointments of counsellor of state and physician to her Majesty, with an annuity of £500. He was also raised to the rank of a Russian baron, and received a present of £10,000, besides miniature pictures of the empress and her son. After having inoculated great numbers of the inhabitants of Moscow, he went to the court of Frederick II, king of Prussia, at Sans Souci, and thence returned to England. In 1776 he published his treatise on inoculation, a work which was translated into all the modern languages, not excepting the Russian, and widely circulated over the Continent. In 1779 he lost his second wife; but afterwards married Elizabeth, daughter of William Dimsdale of Bishops-Stortford, who survived him. He was elected representative of the borough of Hertford in 1780, and went again to Russia in 1781, to inoculate some of the imperial family. On returning to England, he again fixed his residence at Hertford, where he died, Dec. 30, 1800, after an illness of about three weeks.