50 ORGANISM AND ENVIRONMENT 



thought that the teleological significance at any rate is 

 clear enough, since lowering of alveolar CO2 pres- 

 sure means raising of the oxygen pressure, thus com- 

 pensating to some extent for any want of oxygen 

 caused by the lowered oxygen pressure. But there 

 may be no evident signs of want of oxygen, and lower- 

 ing of alveolar CO2 pressure is in itself a very dis- 

 turbing influence, as has already been shown. When 

 we first observed the persistent lowering of alveolar 

 CO2 pressure in connection with shorter experiments 

 in a steel chamber we thought that lactic acid must 

 have been formed in consequence of oxygen want, and 

 that the persistence of the lowered alveolar CO2 

 pressure after the experiment was due to lactic acid 

 remaining in the body. But further observations by 

 Boycott and Ryffel failed to confirm this theory ; and 

 the persistence observed after longer observations in 

 the chamber, and stays in the Alps, was far too great 

 to justify the lactic acid theory. As already men- 

 tioned the excess of lactic acid produced by muscular 

 work disappears from the blood within about an hour. 

 Barcroft meanwhile found on the Peak of Teneriffe 

 that the dissociation curve of the oxyhaemoglobin in 

 human blood was displaced to the right if the deter- 

 mination is made in presence of 40 mm. pressure of 

 CO2 (that of the alveolar air at sea level), but was 

 normal if made in presence of the existing lowered 

 alveolar CO2 pressure. From this it could be con- 

 cluded that there is no appreciable change in the 

 reaction of the arterial blood within the body at the 

 higher altitude. The lowered alveolar CO2 pressure 



