Microvolumetric Respirometry

When the Arctic Research Laboratory at Point Barrow, Alaska, was ready for use in 1947, it was late autumn. Frost could set in at any time and render unavailable precious material for our projected respiratory studies. This situation brought about an acute need for many more micro respirometers than the dozen we had, and prompted the construction of simple, plastic respirometers drilled in blocks of lucite. Standard specimen vials attached by rubber stoppers were used as respiration and compensating vessels and tuberculin syringes for the measurements of the oxygen consumption (Scholander, 1950). In a few days our Eskimo friends made enough new respirometers to fill our needs. A micro model was similarly constructed and both sizes proved eminently useful on a wide variety of animal and plant material. A model for tissue respiration was designed using standard Warburg vessels. Wennesland (1949) at the same laboratory modified this design to contain an internal rod chamber. The present respirometers are a further development of the "Barrow respirometers" which are all based on the volumetric principle introduced by Winterstein (1912, 1913). In the volumetric system, the pressure is maintained constant, and the volume changes are*read directly. The principle involved can be stated as follows: The pressure of the respiration chamber is balanced against a compensating chamber through a manometer. As gas is absorbed or evolved, it is exactly compensated for by a volumetric device so as to maintain pressure balance with the compensating chamber. The change in gas volume is measured directly on the volumetric device. The volumetric system offers some conspicuous advantages. The volume changes are read directly as such, and are independent of the gas volume of the apparatus. The only calibrated part is the compensating device (piston 375