168 



HAEMOGLOBIN 



of carboxyhsemoglobin. The possibility of using spectrophotographic 

 methods was discussed, but finally Hecht decided to make use of a 

 photographic method which had been worked out by Hartridge and 

 Roughton(8) for another purpose. For this purpose the mixture of 

 CO and reduced haemoglobin is taken into a trough, protected from 

 air and a measured quantity of aerated water added to convert the 

 100 



50 100 150 200 



Pressure of CO in thousandths of a millimetre 



Fig. 50. 



250 



reduced haemoglobin into oxyhsemoglobin. The spectrum is then 

 photographed imder standard conditions and the proportion of CO 

 estimated from the photographic plate by analysis with the densi- 

 tometer. 



This technique, so far as the making of all the estimations is con- 

 cerned, is in many ways a decided advance on any of its predecessors. 

 The improvement was aptly expressed by someone who, looking at 

 one of Hecht and Morgan's cm^es, said, "This is the first dissociation 

 curve I have seen where the points really lie on the curve." 



