READJUSTMENTS OF REGULATION 55 



improved the method further, and found that both 

 in animals and in ourselves we got results wholly con- 

 sistent with the diffusion theory, provided that the 

 percentage of CO was kept very low. If sufficient 

 CO was given to produce symptoms of oxygen want 

 we got active secretion. We also got active secretion 

 if oxygen want was produced in a group of muscles 

 by fatiguing work. Nevertheless the human experi- 

 ments gave on the whole a much less striking result 

 than the former ones, and we could not at the time 

 see any reason for this. 



The apparent acclimatisation to oxygen want in 

 mountaineers or persons living at high altitudes then 

 attracted our attention, and in conjunction with Yan- 

 dell Henderson the Pike's Peak Expedition (in which 

 he, Douglas, Schneider and I participated, while Miss 

 Fitz Gerald made observations at neighboring mining 

 camps and towns) was planned. When we reached 

 the summit of Pike's Peak (14,100 feet) we were all 

 more or less blue in the lips, as were other newcomers. 

 We then suffered in various degrees for two or three 

 days from mountain sickness, after which the blueness 

 entirely disappeared, although our alveolar oxygen 

 pressures remained nearly the same as while the blue- 

 ness was present, and our haemoglobin percentages 

 had not as yet risen appreciably. After this we made a 

 number of determinations of the arterial oxygen pres- 

 sure, and each one without exception showed a consid- 

 erably higher pressure of oxygen in the arterial blood 

 than in the alveolar air. On the other hand, when we 

 breathed during the experiment air rich in oxygen, so 



