A new type of respirometer is described. The method involves a ``diver'' which is composed of a rigid respiratory chamber containing a CO2 absorbent and an O2‐containing collapsible sack feeding O2 into the chamber by way of a capillary tube. As O2 is used by the organism in the respiratory chamber, replacement O2 arrives from the collapsible sack thereby decreasing the buoyancy of the system. The change in buoyancy is recorded on a kymograph drum by an ink‐recording spring scale. The method has been put in practice using 50 ml Soxhlet distilling flasks with rubber stoppers penetrated by 27‐gauge hypodermic needles as the respiratory chamber and sections of Saran tubing (Visking Corporation of Chicago) with an O2 capacity of 40–50 ml attached to the stopper as the collapsible sacks. Recording spring scales with variable ranges from 2 to 20 g which have served satisfactorily for measuring natural variations in rates of O2 consumption for certain small animals are described.
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