His father died in Thomson's infancy, and his mother married Mr. McDougal, proprietor of the 'Galway Express' newspaper.

Having obtained a post on the Dublin 'Daily Express,' Thomson began to attend lectures at the Carmichael School of Medicine, and in 1872 he graduated M.D.

On obtaining his medical degrees he became house surgeon to the Richmond Hospital, Dublin, and demonstrator of anatomy in the Carmichael School.

In 1882 he became the first general secretary of the newly formed Royal Academy of Medicine in Ireland, his principal duty being to edit its 'Transactions.'

In December 1899 he was invited by Lord Iveagh to organise a field hospital for service in South Africa.

He proved his powers of rapid organisation by establishing, immediately on entering that capital, a hospital of 600 beds in the Palace of Justice, and it was in great part due to him and his colleagues that Pretoria escaped the outbreak of enteric fever which proved disastrous elsewhere.

He returned home in November 1900, and he and his colleagues were entertained at a public banquet at the Royal College of Surgeons, Dublin (24 Nov.).

For his services in the South African war he was mentioned in despatches and received the Queen's medal with three clasps.

In later years he devoted attention to the surgery of the geni to -urinary organs, and was the first among Dublin surgeons to remove an enlarged prostate.

Thomson, who was a polished speaker and ready debater, died at his residence, 54 St. Stephen's Green, Dublin, on 13 November 1909.