RESPIRATION 255 



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 

 experiments were against the secretion theory. In this I cannot 

 agree with them. It seems to me evident that if there was any 

 acclimatization in these experiments it was very imperfect, and 

 not comparable to the acclimatization commonly observed at high 

 altitudes, and closely studied by us on Pike's Peak. Acclimatization 

 occurs much more readily in certain persons than in others, and 

 seems also to be greatly affected by accompanying conditions. An 

 experiment in which marked acclimatization occurred in myself 

 in a respiration chamber was referred to above. On endeavoring 

 to repeat this experiment in the summer of 1920 there was no 

 effective acclimatization, and on account of severe symptoms of 

 anoxaemia, accompanied by blueness of the lips, etc., I had to 

 stop before the oxygen pressure had fallen to quite as low a point 

 as on Pike's Peak, or to nearly as low a point as in the previous 

 experiment where no pathological signs of anoxaemia were pro- 

 duced. It was about a week before I recovered from the effects of 

 this unsuccessful experiment. The weather was hot, and the 

 chamber correspondingly uncomfortable. I was also several years 

 older. In this experiment my arterial blood was analysed by Pro- 

 fessor Meakins, who found the haemoglobin to be considerably 

 below its normal saturation with oxygen. There was evidently 

 little or no acclimatization. 



I should like to correct here one or two misunderstandings which 

 occur in the paper of Barcroft and his associates. Through a mis- 

 reading of the paper by Douglas and myself he concluded that 

 on lowering the oxygen pressure of the inspired air to what cor- 

 responded to about the oxygen pressure on Pike's Peak we found 

 in a short experiment at Oxford that by the carbon monoxide 

 method the arterial oxygen pressure was 70 mm. above the al- 

 veolar oxygen pressure. The actual difference was only trifling 

 (about 8 mm.), as shown in the table reproduced above. It re- 

 quired prolonged acclimatization to produce as great a difference 

 as even 35 mm. There is also a misunderstanding as to our experi- 

 ments on the effects of work. Though we made no observations by 

 the carbon monoxide method on the effects of work such as was 



