408 PEACTICAL PHYSIOLOGY 



For example, suppose the blood was found to be 46% saturated 

 (corresponding to '06% CO in air), and the actual percentage of CO 

 breathed was '08, then the oxygen tension of the blood would be 



.0 



20-9 x 7^ = 27-9. As the alveolar air contains about 6% of aqueous 



vapour this result has to be reduced to 2 6 -2. 



In rnan the determination can be made by substituting a mouthpiece 

 and inspiratory and expiratory valves (Fig. 264) in place of the bottle B. 



The finger is pricked and a sample of blood obtained, from which the 

 CO determination is made. Haldane finds the oxygen tension in 

 human blood to be higher than in the atmosphere. Lowering the 

 body temperature or pneumonia abolishes the 2 absorptive power of the 

 lungs, while diminishing the amount of 2 in the air breathed excites it. 



CHAPTER XLVII. 

 OXYGEN CAPACITY AND MASS OF THE BLOOD. 



Total Oxygen Capacity and Mass of the Blood in Man (Haldane's 

 Method). A known volume of CO* is administered until completely 

 absorbed. Then, by the carmine method, the percentage to which the 

 Hb has become saturated with CO is determined. We thus estimate 

 the volume of CO (or O 2 ) capable of being taken up by the whole of 

 the blood. Also, we determine at the same time the volume of CO 

 (or 2 ) capable of being taken up by 100 grms. of blood. We can 

 then, knowing the total volume taken up, calculate the total mass of 

 blood in the body. 



The subject breathes through a mouthpiece into a rubber bag 

 1-2 litres in capacity. Between the bag and mouthpiece there is 

 interposed a cylinder made of tinned iron, and filled with soda lime to 

 absorb the expired C0 2 . The cylinder is made of two tins which 

 slide over one another, the junction being made air-tight with wax. 

 The soda lime is kept in position by a piece of wire gauze at either 

 end of the cylinder. Oxygen is supplied to the bag from an oxygei 

 bottle. The gas is bubbled through a test tube containing a little 

 water to roughly gauge the rate of supply. 



A measure bottle filled with CO is arranged as in Fig. 264 and 

 connected with the bag. The temperature and barometer are noted. 



*To ensure correctness the CO in the cylinder should be analysed, for it 

 always contains a trace of air. 



