The acquisition of oxygen by the blood in the lung 203 



6. That all the haemoglobin is either oxyhaemoglobin or CO 

 haemoglobin. They really measured the ratio of CO haemoglobin to 

 total haemoglobin. In so far as there was reduced haemoglobin in 

 the blood on which they worked, this would vitiate their result. 



We must add one consideration, which, though dealt with by 

 Haldane in another way, was not investigated quantitatively by him 

 the influence of light. 



These points had either been assumed or had been incompletely 

 investigated in the research of Haldane and Lorrain Smith to which 

 I have alluded. Such assumptions if not warranted were at least not 

 in serious conflict with the scientific knowledge of the time (1895). 

 But in the light of the additions to knowledge recounted in the first 

 five chapters of the present volume it will be seen that each of the 

 six propositions was eminently likely to be erroneous. 



Probably the fourth and fifth are approximately correct. The 

 rest are certainly wrong in a greater or less degree. In the light of 

 these facts the work of Haldane and Lorrain Smith was done over 

 again by Haldane and Douglas (5) for the purpose of ascertaining 

 whether these errors were serious or negligible. 



The Oxford observers concluded that carbonic and non-volatile 

 organic acids did not affect the partition of the haemoglobin between 

 the oxygen and the carbon monoxide, but that the balance was 

 affected to some extent by temperature and that there were individual 

 differences between different persons and different species which 

 could not be overlooked. But although these complications had 

 arisen Haldane and Douglas were able to balance their errors in 

 a way which had not been open to Haldane and Lorrain Smith, for 

 actual samples of alveolar air had become available by the discovery 

 of Haldane and Priestley. Therefore the blood of a person was 

 exposed outside his body to his alveolar air at 37 C., and within 

 it to alveolar air, modified by the pulmonary epithelium, each con- 

 taining the same concentration of carbon monoxide, and the partition 

 of the haemoglobin between the oxygen and the CO was compared 

 in the two cases. The titrations were both carried out in the same 

 light. If the proportion of CO haemoglobin in the blood from the 

 body exceeded that in the blood exposed to the alveolar air, the 

 pressure of CO being the same in each case, then it would follow that 

 the blood was exposed to a less pressure of oxygen in the lung than 

 in the alveolar air : and if the proportion of CO haemoglobin in the 

 blood from the body was less than in the blood exposed extra vitam 



