He was graduated at Williams in 1843, and in the medical department of the University of Pennsylvania in 1847. 

He sailed for Europe in 1849, and, after spending the intervening period in study and travel, returned in 1851, but again visited Europe in 1854 and in 1868. 

He had in the meantime begun to practice in New York City, where from 1856 till 1862 he edited twelve volumes of the "American Medical Monthly," and front 1865 till 1866 three volumes of the "' New York Medical Journal," then a monthly, but now a weekly publication. He has also contributed to the columns of the" New Orleans Medical and Surgical Journal," the " New Orleans Hospital Gazette," the " Boston Medical and Surgical Journal," and other periodicals. 

Dr. Douglas was the attending physician of General U. S. Grant from 22 October 1884, till the death of the latter, 23 July 1885.