Henry Tonks (1862-1937) studied medicine and became a doctor at the Royal Free Hospital in London. Tonks also attended drawing lessons at the London Technical Institute where he met the artist Frederick Brown. When Brown became principal of Slade Art School, he convinced Tonks to give up medicine and become one of its teachers. He joined the New English Art Club and would be a big supporter of it his whole life. At the outbreak of WWI Tonks returned to medicine and was stationed in France. In 1918 Tonks was invited to be an official war atist along with Sargent.
From the war Tonks produced "An Advanced Dressing Station in France" (thumbnail left). Tonks also completed another painting with a medical theme "An Underground Casualty Clearing Station" (1918)
After the war Tonks returned to the Slade Art School. He continued to paint and his most well-known work, Saturday Night in the Vale, was completed just before his retirement in 1930.
(in large part from Spartacus.schoolnet)
John Singer Sargent, An Exhibition -- Whitney Museum, NY & The Art Institute of Chicago 1986-1987