424 



RESPIRATION 



It will be seen that the maximum error was 2.0 per cent, this including 

 any error in making the blood mixtures and standardizing the carmine 

 solutions. With double determinations the error was considerably less. 



E. Determination of Blood Volume in Man during Life by CO 



Since CO is not oxidized or otherwise destroyed in the living body, 

 and since it forms a relatively very stable molecular compound with 

 haemoglobin, but with no other substance in the body, it is evident that 

 if we administer to an animal a known amount of CO, and then de- 

 termine the percentage saturation of the haemoglobin with CO and the 

 total CO capacity of a given volume of blood, we can determine the CO 

 capacity of the total blood in the body, and hence deduce also the blood 

 volume. The blood volume during life was first determined in this way 

 by Grehant and Quinquaud, 18 who used dogs for the purpose and em- 

 ployed the blood pump for the blood-gas analyses. In 1900 Lorrain 

 Smith and I introduced a much simpler method, easily applicable to 

 man; 19 and this method has been extensively used for physiological, 

 clinical, and pathological work, as mentioned in Chapter X. 



The apparatus required for administering the CO to a man is shown 

 diagramatically in Figure 104. The subject breathes through a glass 

 mouthpiece A, the nose being clipped or held. The mouthpiece communi- 

 cates by ^-inch rubber tubing with a bladder or india-rubber bag B of 



18 Grehant and Quinquaud, Journ. de I'anat. et de la -physwl., p. 564, 1882. 

 M Haldane and Lorrain Smith, Journ. of Physwl., XXV, p. 331, 1900. 



