MANOMETRIC TECHNIQUE 81 



and Warburg give a basis for further study. Two monographs on the subject are by 

 Dixon and Umbreit, Burris and Stauffer. In the constant volume apparatus of the 

 Warburg type a flask containing the cell and substrate is attached to a manometer, 

 one end of which is open to the air, whereas in the Barcroft differential manometer each 

 limb of the U-tube manometer is attached to a flask and the difference in pressure 

 developed in the two flasks is measured. Inthelatter case differences in temperature 

 and atmospheric pressure are automatically compensated, but since there are variations 

 in both the pressure and volume of the flasks the theoretical treatment of the signifi- 

 cance of the manometer readings is more complicated. In either case the apparatus 

 is cahbrated before the experiment begins. 



The amount of oxygen absorbed by the respiring system may be determined 

 directly by absorbing the carbon dioxide produced in alkali so that the pressure 

 changes are due entirely to the oxygen absorption. By carrying out the same 

 experiment in another flask without absorbing the CO 2 some measure may be obtained 

 of the CO 2 output since the difference between the two flasks should give the volume 

 of CO 2 liberated. In order to avoid complications due to CO 2 absorption by the 

 contents of the flask, acid may be added from a side tube at the end of the experiment 

 and all the CO 2 liberated. 



The production of lactic acid by glycolysis may be measured manometrically by 

 carrying out the experiment in a bicarbonate medium when any lactic acid produced 

 will liberate an equivalent amount of carbon dioxide. By using an atmosphere of 

 either oxygen or nitrogen the aerobic and anaerobic glycolysis can be determined. 



A micro-manometric method based on the Cartesian diver has been worked out 

 by Linderstr5m-Lang, Boell and Needham. In this method a small bulb is used to 

 contain the respiratory system and the capillary tube leading from the bulb is sealed 

 with a drop of oil. The bulb is loaded so that it just floats in a suitable solution. Gas 

 absorption in the bulb will cause the diver to sink whilst gas evolution will lower the 

 density and cause flotation. The whole apparatus is enclosed in a larger vessel fitted 

 with a manometer and the pressure is adjusted throughout to maintain the diver 

 floating at the same level. The readings on the external manometer reflect changes of 

 pressure in the diver and the respiration of minute amounts of tissue can be followed. 



In consideration of respiratory changes the symbol Qo 2 represents the volume of 

 oxygen (in cubic millimetres at 0°C and 760 mm. pressure) absorbed in an hour by one 

 milligram of tissue or cells. QCO2 represents the volume of carbon dioxide evolved in 

 the same units. The respiratory quotient is the ratio of carbon dioxide evolved to 

 oxvgen absorbed : — 



KQ = ^' 



Q02 

 When carbohydrates are oxidised completely : — 



CeHi206 + 6O2 -> 6C62 + 6H2O 

 the RQ is 1. In the case of fat oxidation the RQ is 0-7 and it is 0-8 when proteins are 

 oxidised. 



The symbols Q^ ^^ and Q^ ^2 represent aerobic and anaerobic glycolysis respectively, 

 being the amounts of CO 2 liberated from bicarbonate by the lactic acid produced 

 during glycolysis in atmospheres of oxygen and of nitrogen, (Volumes are in cmm. 

 per 1 mg. of cells per 1 hr.) 



