Abstract
A description is given of a closed space respiration apparatus which can be used to determine the amount of gas used or liberated by living blood or tissue cells, or chemical substances. Continuous observations can be made and repeated measurements recorded without interrupting the vital processes or destroying the cells. Studies of the oxygen consumption by whole blood in normal individuals and in patients with leucocytosis and myelogenous leucemia, as well as by white cells suspended in plasma, will be reported in subsequent papers.