A NEW FORM OF DIFFERENTIAL MICRORESPIROMETER.

1. A microrespirometer suitable for measuring oxygen uptakes from 0.1 to 10lambda per hour is described. 2. The sensitivity of the instrument may be readily altered by substituting different sizes of capillary tubing. 3. By means of replaceable brass plugs the chamber volume of this instrument may be varied from 700 to less than 40lambda. 4. No thermostat is required for the operation of the instrument at room temperature. 5. It may be charged at one temperature and used at a widely different one. 6. The chambers may be filled with any desired gas mixture. 7. Two solutions may be mixed during the course of an experiment. 8. The entire apparatus may be sterilized.