254 RESPIRATION 



of the arterial blood were made, both by the ferricyanide method 

 and with the pump, and agreed closely. Samples of alveolar air 

 were also taken, and part of the arterial blood saturated with air 

 of about the same composition. The saturation of the haemoglobin 

 of this blood, when corrected for the slight difference in oxygen 

 pressure between the air in the saturator and the sample of 

 alveolar air, was found to be 91 to 92 per cent, which is distinctly 

 higher than the saturation of the arterial blood. The oxygen pres- 

 sure of the sample of alveolar air was, however, quite unac- 

 countably high. It was 6S mm., instead of about 45 mm. which was 

 the value actually found in a determination made a few hours 

 previously, and was also the value to be expected from the curve 

 shown in Figure 98 of this book. Had the actual alveolar gas pres- 

 sures corresponded with those of the sample, the respiratory quo- 

 tient would have been about 2 ; and such a quotient occurs only 

 during forced breathing, which could not have occurred. It seems, 

 therefore, that there must have been some mistake about the al- 

 veolar sample; but what this was is far from clear. If the actual 

 alveolar oxygen pressure had been about 45 mm., as would cor- 

 respond to the alveolar CO2 pressure, the oxygen saturation of 

 the blood from the saturator would have been considerably lower 

 than that of the arterial blood. The experiment is thus inconclusive, 

 apart altogether from the question as to whether the subject was 

 acclimatized at all, or to what extent. 



The experiment during work is much more consistent. The 

 arterial haemoglobin was found to be only 83.5 per cent saturated 

 with oxygen. A lower saturation during work of the character 

 chosen corresponds well with all our observations on Pike's Peak 

 and at Oxford. Unacclimatized persons became very blue in the 

 face on Pike's Peak with comparable work ; and even after acclima- 

 tization there were clear indications of some anoxaemia. In me, for 

 instance, the alveolar oxygen pressure rose about 8 mm., and the 

 alveolar CO2 pressure fell, on walking at 4 miles an hour; and 

 this, as we pointed out, indicated arterial anoxaemia. The haemo- 

 globin of the blood exposed to the alveolar air in the saturator 

 gave a saturation of 89.2 per cent, which is 5.7 per cent higher 

 than the saturation of the arterial blood. This result furnishes no 

 evidence of secretion, but to show that there was actually no secre- 

 tion it would, I think, be necessary to make a control experiment 

 on a person who had spent only a short period in the chamber, and 

 was undoubtedly unacclimatized. 



Barcroft and his associates consider that the results of the 



