Civil War Union Brigadier General. He was resident physician at Blockley Hospital in Philadelphia, Pennsylvania when he was commissioned an assistant surgeon at the United States Military Academy at West Point, New York in June 1840. After a few months, he served at various duty stations in Florida, before joining the 2nd United States Dragoons in actions during the Mexican American War. At the start of the Civil War, he was assigned to duty as a attending surgeon at Washington D.C. and was later advanced to the position of Colonel Medical Inspector General in August 1863. On August 22, 1864, he was promoted to the position of Surgeon General, with the grade Brigadier General and was brevetted Major General on March 13, 1865, for faithful and meritorious service during the war. The morning after the assassination of President Abraham Lincoln's death, Dr. Barnes attended the death bed of Lincoln and oversaw his autopsy. Remaining in the Army, he also was one of the surgeons who for weeks served in the chamber of the dying President James A. Garfield, after he was mortally wounded by an assassin in July 1881. He retired on June 30, 1882 and died at his home from a chronic problem at age 65 (findagrave.com)