READJUSTMENTS OF REGULATION 59 



tion, just as I was in the case of CO poisoning. On 

 rereading Glaisher's account of his balloon expe- 

 riences I was much interested to see that though he did 

 not clearly understand the cause of mountain sickness 

 he was quite convinced that repeated ascents produced 

 acclimatisation. I have recently found that the effects 

 of acclimatisation can easily be observed at ordinary 

 atmospheric pressure in a closed chamber in which the 

 oxygen percentage has been greatly reduced. An 

 acclimatised person remains of a normal colour, and 

 has no unpleasant symptoms, while an unacclimatised 

 person soon becomes blue in the face, and may faint. 



In acclimatisation to high altitudes there are evi- 

 dently three factors the increased activity of the 

 lung epithelium in absorbing oxygen, the increased 

 breathing, and the increased percentage of haemo- 

 globin. Of these the last raises the oxygen pressure 

 in the capillaries of the body, the second diminishes 

 the fall in alveolar oxygen pressure, and the first 

 raises the arterial oxygen pressure much above the 

 alveolar oxygen pressure, whereas at sea level the 

 arterial oxygen pressure is no higher, as a rule, than 

 the alveolar oxygen pressure. The teleological sig- 

 nificance of these changes seems clear, and a vitalist 

 would naturally point to this as evidence of the inter- 

 ference of the vital principle. But we must analyse 

 the facts further. 





