After serving in the war between the United States and Mexico in 184648, Bell went to work for his brother-in-law, Philadelphia daguerreotypist John A. Keenan, and opened his own studio there in 1860. During the Civil War, Bell served with the First Regiment of Pennsylvania Volunteers; after the war, he became head of the photographic department at the newly created Army Medical Museum in Washington, D.C.
The museum collected and commissioned photographs to study "all specimens of morbid anatomy, surgical or medical, which may be regarded as valuable... to the study of military medicine or surgery." According to a report written by the editor of the Philadelphia Photographer, "The principal work of the photographer is to photograph shattered bones, broken skulls, and living subjects, before and after surgical operations. Of course, all these subjects were created by the war." Besides forming an in-house archive his photographs were used to aid the engraver in making woodcuts to illustrate medical books.
Merry A. Foresta American Photographs: The First Century (Washington, D.C.: National Museum of American Art with the Smithsonian Institution Press, 1996)