Gilbert Girdwood, physician and chemist, was born in London and educated at University College and St. George's School of Medicine. He came to Canada in 1862 as assistant surgeon of the Grenadier Guards. In 1864 he retired from the army, and began to practise in Montréal as a surgeon to local regiments and staff member of the Montreal Dispensary, the Montreal General Hospital, and the Children's Hospital. Girdwood's scientific interests were catholic, but he was fundamentally a chemist. As lecturer, and later Professor of chemistry in McGill's Medical Faculty (1870-1903), he introduced practical chemistry into the programme of medical training. His major research interest was toxicology. While still in London, he worked with a chemist to produce the Rogers and Girdwood test for detecting strychnine and in Canada he frequently testified as medical-legal witness in poisoning cases. He was also consulted in forgery trials, and he was the first to use enlarged photographs and reagents to reveal counterfeits. He published a number of studies on stereoscopic photography. A pioneer in the medical use of X-rays, Girdwood consulted in this field for Royal Victoria Hospital, and was president of the Roentgen Society of America.