The Photographic History of The Civil War: in ten volumes, Thousands of Scenes Photographed 1861-65, with Text by many Special Authorities, Volume 7: Prisons and Hospitals.
Francis Trevelyan Miller, Ed.

Inside a Federal General hospital

In the first part of the war, whenever the capacity of the regimental hospital canvas was exceeded, some neighboring dwelling-house would be taken over as a hospital annex. When it was fully recognized that the chief duty of the medical department at the front was the getting rid of the sick and wounded, after such preliminary assistance as put them in suitable condition to withstand the journey to the rear, the importance of the function which the general hospitals performed was better appreciated. At once the establishment of general hospitals, of suitable size and at convenient points, was pushed with great vigor. Shortly many such hospitals were in operation which, though perhaps in buildings of only temporary character, rivaled the best civil hospitals in completeness of equipment and professional service, and far surpassed the very largest of them in accommodations for patients. The best type of army hospital was constructed on the unit and pavilion system, which permitted prompt and almost indefinite enlargement at need.

Inside a Federal General hospital—the armory square, Washington

Another view of ward K at the armory square