he received in 1906 the research degree of BSc for work done at Oxford's physiology laboratory under the supervision of John Scott Haldane.
In 1910 Nathan Zuntz organised a high-altitude expedition to Tenerife in the Canary Islands; the participants included Douglas from Oxford, Joseph Barcroft from Cambridge, and Arnold Durig from Berlin.
In 1911 J. S. Haldane, Douglas, Yandell Henderson, and Edward C. Schneider were the four principal members of an Anglo-American expedition to Pikes Peak in Colorado to do research on high-altitude breathing.
Mabel Purefoy FitzGerald joined the expedition to conduct research of mining town residents at lower altitudes.
[7] During World War I, Joseph Barcroft, John Scott Haldane, and Douglas were among the leading technical experts on gas warfare.
[1] His older brother James Sholto Cameron Douglas was appointed to the Joseph Hunter chair of pathology at the University of Sheffield.