24 THE NEW PHYSIOLOGY. 



living cells lining its walls, and cannot be explained 

 mechanically. 



The case of the swim-bladder threw grave doubt on 

 the current mechanical explanation of the absorption 

 of oxygen into the blood through the epithelial cells 

 lining the alveoli of the lungs ; for this might also be 

 partly or wholly a case of active absorption and not 

 of mere diffusion. The question was taken up by 

 Bohr and others, but the evidence was not conclusive. 

 Experiments with improved methods by Krogh l of 

 Copenhagen, and by Douglas and myself 2 at Oxford, 

 then showed that under normal resting conditions the 

 phenomena are consistent with the diffusion theory. 

 Our own experiments gave, however, the clear result 

 that under conditions where oxygen-want is produced 

 in the tissues, active absorption occurs. Perhaps the 

 most striking results were obtained as the outcome 

 of an expedition to the summit of Pike's Peak, Colorado, 

 in order to observe to what extent, and by what means, 

 acclimatisation to diminished atmospheric pressure 

 occurs. 3 It was experimentally shown many years ago 

 by Paul Bert in his book La pression barometrique, Paris, 

 1878, that the various physiological disturbances, such 

 as mountain sickness, associated with exposure to 

 diminished atmospheric pressure, are due to want of 

 oxygen, depending on the fact that although the oxygen 

 percentage in air at high altitudes is precisely the same 

 as elsewhere, the partial pressure of the oxygen in the 



1 Skand. Archiv fur Physiologic, xxiii. p. 179, 1910. 



2 Journal of Physiology, xliv. p. 305, 1912. 



3 Douglas, Haldane, Henderson and Schneider, Philosophical 

 Transactions, B, vol. 203, p. 185, 1913. 



