CARBON MONOXIDE— REDUCED HEMOGLOBIN 



157 



will give both the percentage saturation and the CO-pressure. The 

 use of 5 tonometers will give five points on a curve, and other points 

 may be obtained by varying the amount of haemoglobin solution 

 which is used. In our experiments the tonometers are made so that 

 5, 10 or 15 c.c. of fluid can easily be measured into them. 



Even this simple technique bristles with difficulties — chiefly those 

 which only appear when an effort is made to obtain real accuracy. This 

 was found to be so by Hecht, and confirmed by Forbes and Morgan (7), 

 who for a year devoted the most untiring energy (to use a rhetorical 

 phrase, for by the time the vacation came they each required a rest- 



FiG. 49. 



cure) to the method. The difficulty of being certain of an equilibrium 

 could be overcome with ease, for it was possible either to strike it 

 from above simply by shaking out the CO, or to strike it from below 

 by driving out all the CO and allowing the haemoglobin to unite 

 again with the gas. The expulsion of the CO from the haemoglobin 

 is effected by a strong Hght. 



It soon appeared that the reversion spectroscope as ordinarily used 

 was not sufficiently accurate for the purpose, though more accurate 

 in most peoples' hands than any previous method for the estimation 



