An automatic manometric apparatus for the continuous determination of oxygen consumption in animals is described. A fixed manometric aliquot of oxygen ranging from 1 cc to 300 cc or larger is admitted through a solenoid valve controlled from an attached mercury manometer, and the time required to consume this aliquot is recorded on a continuous record. The apparatus is simple, compact, convenient, and very flexible, being adaptable for use with many animals under a variety of conditions.