Ferrihaemoglobin in Normal Blood 



of the quantity of gas, the technique used for the saturation of the 

 pigment solution with the gas, and the fact that the system under 

 investigation must be presumed to be stable during the time normally 

 allowed for the experiment. The precision of the actual Van Slyke 

 analysis is beyond question, but the mere fact that both oxygen and 

 carbon monoxide capacity tend to increase in drawn blood exposed 

 to the atmosphere throws doubt on the validity of the earlier stages 

 of gasometric determinations of ferrihaemoglobin. The complexity of 

 the matter is indicated by some experiments carried out by the author 14 , 

 which show that although fresh blood may, under certain experimental 

 conditions, take up to an hour to attain an apparently maximal oxygen 

 capacity, the same blood, if deoxygenated in vacuo immediately after 

 oxygenation, may be reoxygenated in a few minutes. This effect 

 cannot be due to the presence of carbon dioxide, since evacuation of 

 fresh, unoxygenated blood does not result in an increased rate of 

 oxygen uptake. Treatment of the fresh blood with a reducing agent 

 does, however, change the system in such a way that the pigment 

 takes up its maximum quota of oxygen from air in a few minutes. 

 These experiments were done with horse blood, which has such a high 

 sedimentation rate that the technique of the rotating tonometer cannot 

 be used for saturating it with oxygen. The apparatus which was 

 used is probably less efficient than the usual one, and it seems possible 

 that most of these effects might be masked by the use of a more 

 efficient oxygenator. Conant, Scott and Douglass 12 , however, found 

 it necessary to aerate blood in a tonometer for only five minutes after 

 reduction with titanous tartrate. Other interesting observations have 

 been made on the carbon monoxide technique by S. Kallner 15 , who 

 repeated successfully the experiments of Ammundsen, using as she 

 did a CO pressure equivalent to about 25 mm Hg, in accordance with 

 the recommendation of Van Slyke and Hiller 9 . He noted also the 

 disappearance of the difference between the CO capacities before and 

 after reduction as the blood stood in air, and then repeated the whole 

 series of experiments, using 150 mm CO for the saturation instead of 

 25 mm. This time the initial CO capacity was equal to the value 

 formerly obtained only after reduction, and neither reduction nor 

 exposure to the atmosphere caused any further increase. Kallner 

 himself, without further evidence, attributed the results to the fact 

 that fresh blood contained C0 2 , which in some way inhibited the 

 uptake of CO, whereas the blood which was allowed to stand had lost 

 its C0 2 . Although the verification of this theory, or its replacement, 

 if necessary, by some alternative must await the results of further 

 investigation, it does seem that we do not yet know sufficient about 

 the uppermost regions of the equilibria between ferrohaemoglobin 



235 



