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Dimsdale, Thomaslocked

  • T. E. Kebbel
  • , revised by Andrea Rusnock

Thomas Dimsdale (1712–1800)

attrib. Nathaniel Plimer, 1780s

Dimsdale, Thomas (1712–1800), physician, was born on 29 May 1712 in Theydon Garnon, Essex, the fourth son and one of the eight children of John Dimsdale, of Theydon Garnon, a surgeon and a member of the Religious Society of Friends. The family held property in Essex for many years. Dimsdale's mother was Susan, daughter of Thomas Bowyer, of Albury Hall, near Hertford. His grandfather, Robert Dimsdale, accompanied William Penn to America in 1684. Dimsdale was trained first by his father, and later at St Thomas's Hospital, London, under Joshua Symons and John Girle; he began to practise medicine at Hertford in 1734. He married in 1739 Mary (d. 1744), only daughter of Nathaniel Brassey MP. There were no children. In 1745 Dimsdale offered his services to the duke of Cumberland, and accompanied the English army as far north as Carlisle, on the surrender of which he returned home. In 1746 he married Anne Iles (d. 1779), daughter of John Iles, and a relative of his first wife; they had seven sons and two daughters.

Dimsdale retired from practice on inheriting a fortune, but having a large family, he resumed practice and took the MD degree from King's College, Aberdeen, in 1761. In 1767 he published, The Present Method of Inoculating for the Small-Pox, which enjoyed great popularity, going through six large editions in five years. It was also translated into several foreign languages. In this work, Dimsdale described a safer, less invasive inoculation procedure, which had first been pioneered by Daniel Sutton. In 1768 he was invited to St Petersburg by the Empress Catherine the Great to inoculate herself and her son, the Grand Duke Paul. The empress seems to have been confident of Dimsdale's good faith, but she could not answer for her subjects, and therefore had relays of post-horses prepared for him so that his escape might be instant and rapid in case of disaster. Fortunately both patients did well, and Dimsdale was created a councillor of state, with the hereditary title of baron. He received a sum of £10,000, with an annuity of £500, and £2000 for his expenses. The empress presented him with miniatures set in diamonds of herself and her son, and granted him an addition to his family arms in the shape of a wing of the black eagle of Russia. The patent, embellished with the imperial portrait and other ornaments, was preserved at Essendon, the family seat in Hertfordshire. Dimsdale was admitted a fellow of the Royal Society in 1769. In 1779 he married Elizabeth, daughter of Joseph Dimsdale, of Bishop's Stortford.

In 1784 Dimsdale returned to Russia to inoculate the Grand Duke Alexander and his brother Constantine, and the empress presented him with her own muff, made of the fur of the black fox, which only the royal family were allowed to wear. On his first return journey he paid a visit to Frederick the Great at Sans Souci, and on his second, to the emperor Joseph at Vienna. When Prince Omai came to England with Captain Cook in 1775, he was inoculated by Dimsdale.

Dimsdale wrote several additional works on inoculation, including: Thoughts on General and Partial Inoculation (1776); Observations on the Plan of a Dispensary and General Inoculation (1780); and Tracts on Inoculation, written and published at St Petersburg in 1768 and 1781. At Hertford he opened an inoculating house, and, about the same time, entered banking, eventually retiring from the business in 1776. Dimsdale was an independent whig and served as MP for Hertford between 1780 and 1790. Of his one speech to parliament it was said that he 'spoke for some time, but in so low a tone, that we could not distinctly hear him' (HoP, Commons). He died at Hertford on 30 December 1800 and was buried in the Quakers' burial-ground at Bishop's Stortford, Hertfordshire. He was survived by his wife.


  • P. H. Clendenning, ‘Dr Thomas Dimsdale and smallpox inoculation in Russia’, Journal of the History of Medicine and Allied Sciences, 28 (1973), 109–25
  • P. Razzell, The conquest of smallpox: the impact of inoculation on smallpox mortality in eighteenth century Britain (1977)
  • private information (1888)
  • GM, 1st ser., 71 (1801), 88, 209, 669
  • ‘Memoirs of the Hon. Baron Dimsdale’, European Magazine and London Review, 42 (1802), 83–7


  • Herts. ALS, papers
  • priv. coll.


  • attrib. N. Plimer, watercolour, 1780–89, NPG [see illus.]
  • H. Bone, pencil, 1800, NPG
  • W. Ridley, stipple, 1802, BM, NPG; repro. in European Magazine (1802)
  • H. R. Cook, stipple, 1820, Wellcome L.
  • T. Burke, mezzotint (after T. Burke), Wellcome L.
  • Ridley, portrait, repro. in Munk, Roll
  • Tulley, engraving
  • line engraving (after C. L. Christeneke), Russian Museum, Leningrad
  • oils, Hertford county hall
W. Munk, , 2 vols. (1861) 2nd edn, 3 vols. (1878)
Gentleman's Magazine