United States. Army. Medical Corps

Greenleaf was born in Pennsylvania and educated at the Medical College of Ohio, graduating in 1860. During the Civil War, he oversaw construction of Philadelphia's Mower Hospital on Chestnut Hill, which was at the time the largest military hospital in the world. He introduced a system of personal identification used by the army and organized the army's Hospital Corps.

Russell as an early researcher into the inoculation of typhoid. He was assigned the duty of implementing an immunization program within the U.S. Army from 1910-1911. Following his military career he served as the director of the International Health Board of the Rockefeller Foundation, continuing his public health research and focusing on yellow fever.