382 



THE RESPIRATION 



bottles and the manometer serves to permit communication of the 

 manometer with the outside air. 



An equal quantity of hemoglobin solution that has been saturated 

 with oxygen i. e., oxyhemoglobin is plac'ed in the bottle on the other 

 end of the manometer tube from that containing the bottle with the un- 

 saturated hemoglobin solution. The bottles having been attached to 

 the manometer with the stopcocks open to the outside, the apparatus 

 is placed in a water-bath until the temperature conditions are constant. 

 The manometers are then closed to the outside air and the bottles are 

 shaken in order that the hemoglobin solution that is unsaturated with 

 0, may take up 2 from the atmosphere in the bottle until it becomes 



Fig. 136. Barcroft blood gas manometer. This form can be used either as a differential 

 manometer (page 390) or for direct measurement of pressure. For the latter purpose one bottle 

 is removed and the pressure of gas generated in the other bottle is measured by the height to 

 which it raises the clove oil in the distal tube of the manometer, the meniscus in the proximal 

 limb being readjusted to its original level by compression with the brass screw of the rubber tube 

 shown in the center. 



saturated. The resulting shrinkage in the volume of the atmosphere 

 on the side of the unknown hemoglobin solution causes the clove oil 

 meniscus to move towards that side, the degree of movement being pro- 

 portional to the initial unsaturation of the hemoglobin. The manometer 

 tubes are then again brought into communication with the atmosphere 

 so that the meniscus of clove oil may move back to its old level, and the 

 bottle with saturated hemoglobin is removed from the manometer and a 

 drop or two of a saturated solution of potassium ferricyanide placed 

 in the separate compartment of the bottle without allowing it to mix 

 with the hemoglobin. The bottle is then reattached, the temperature 



