Calorimetry and metabolism research, 1899. Front view of respiration calorimeters that are used to measure the energy expended in human metabolism. The equipment includes an air pump, a water meter, an observer's table and an entrance to the respiration chamber. The large balance at left is used for weighing the carbon dioxide and water absorbers and the oxygen cylinder. Photographed in Judd Hall, Wesleyan University, Middletown, Connecticut, USA. This image is from the US Department of Agriculture collections relating to the research by Wilbur Olin Atwater (1844-1907), a US chemist who studied human nutrition and metabolism.