RESPIRATION 367 



correspond with those accompanying excess of lactic acid in the 

 blood, and Ryffel was unable to find any such excess in the blood 

 or urine. Accordingly the conclusion was drawn by my colleagues 

 and myself after careful observations during the Pike's Peak 

 Expedition, that the diminution in available alkali in the blood 

 must be due to a lowering in the level of concentration to which 

 the kidneys regulate the fixed alkali in the blood. We thought 

 that the anoxaemia must influence the kidneys specifically in this 

 direction. 



The Anglo-American Pike's Peak Expedition 6 was planned 

 with the special object of studying acclimatization to the oxygen 

 deficiency of the air at high altitudes. We selected Pike's Peak 

 (14,100 feet) because it was possible, not only to get apparatus 

 and supplies to the summit easily by the cogwheel railway, but also 

 to live there without the disturbing effects of cold and hardship. 

 We were thus enabled to watch in ourselves the progress, which 

 was very striking, of acclimatization, and to observe the effects of 

 the rarefied air on the numerous unacclimatized persons who came 

 up. 



It is evident that a simple increase in the breathing must 

 greatly diminish the arterial anoxaemia at high altitudes : for not 

 only will the alveolar oxygen pressure be increased, but in conse- 

 quence of excessive removal of CO 2 , the haemoglobin passing 

 through the lungs will combine more readily with oxygen, in 

 accordance with the discovery, already often alluded to, of Bohr 

 and his pupils. It might thus appear as if a simple increase in 

 breathing were the natural adaptive response to the anoxaemia 

 of high altitudes and other conditions. But, as already pointed 

 out, such a response is, except for a very short period, or to a very 

 limited extent, prevented, owing to the effect of the lowered CO 2 

 pressure in diminishing the breathing; and an increased circula- 

 tion rate (which would also tend to diminish the fall of oxygen 

 pressure in the tissues) is also prevented in the same way. More- 

 over the increase in percentage saturation of the haemoglobin in 

 the tissues is in any case of only limited advantage, since, owing 

 to the lowered CO 2 pressure, the haemoglobin holds on more 

 tightly to the oxygen. Nevertheless there will be some increase in 

 breathing and circulation rate; and this will represent a com- 

 promise between the effects of want of oxygen and of deficiency 



8 Douglas, Haldane, Henderson, and Schneider, Phil. Trans. Roy. Soc., B, 

 203, 1913- 



