CARBON MONOXIDE— REDUCED HEMOGLOBIN 153 



oxyhsemoglobin (in the trough) and an unknown quantity of CO- 

 hsemoglobin (in the tube). The position of the bands will tell him 

 the ratio of the one to the other, from which the quantity of CO- 

 hsemoglobin may be deduced. This method of observation, ingenious 

 enough, has the disadvantage of being much less accurate at the ends 

 of the scale than in the middle, i.e. it is unreliable when there is less 

 than 30 per cent, saturation of COHb in the tube and also when 

 there is more than 70 per cent, of CO-haemoglobin. 



To overcome this difficulty the authors adopted a method so bold as 

 to be the admiration of anyone familiar with their type of technique. 

 It was one of those experimental salUes which could only be 

 contemplated by a worker with a complete knowledge of the factors 

 at stake. Instead of putting a layer of oxyhaemoglobin behind the 



CO Water 



Mlninff 

 Chamber 



YSpecbroscope 



Hemoglobin Oxj^^Water 



Fig. 48. 



observation tube they actually ran oxygen into the tube. Supposing 

 at a certain point A in the tube the reduced haemoglobin and the 

 CO -haemoglobin were in the ratio of 30 to 60 per cent., and at that 

 point oxygen water was introducgd through a mixing chamber, the 

 oxygen would at once unite with the reduced haemoglobin, having 

 tenfold the reaction velocity of the carbon monoxide, so that the 

 quantity of carboxyhaemoglobin would be for an instant fixed. In 

 time of course the oxygen would tend to break down the COHb, 

 but for that time would be required, and in the interval the spectro- 

 scopic observation can be made. The technical difficulties presented 

 by the measurement of the dissociation phase 



HbCO -* Hb + CO 



are more difficult to overcome, and further work is still to be desired. 

 For instance, the dissociation can only be measured in solutions so 

 dilute that the fluid appears colourless in an ordinary test-tube. 

 The strongest concentration suitable corresponds to about I part 



