io8 CONTEMPORARY SCIENCE 



alkali passes out of the blood to compensate what would 

 otherwise be a condition of alkalosis. 



We regard the current explanation, based on the pro- 

 duction of lactic acid, as needing- reversal. 



The application of this idea to the changes of breath- 

 ing and of the blood alkali in acclimatization clears up 

 some of the points which heretofore have been obscure. 

 Thus on Pike's Peak we saw that persons whose breathing 

 under the stimulant of oxygen deficiency increased quickly 

 to the amount normal for the altitude suffered correspond- 

 ingly little, while those whose respiratory center was rela- 

 tively insensitive to this influence suffered severely. The 

 one type readily developed the acapnia and in consequence 

 the pseudo-acidosis which the altitude requires. The 

 other did not. 



Here let me pause a moment to bring these conceptions 

 into some degree of harmony with fundamental doctrines 

 regarding respiration. For more than a century, in fact 

 ever since the days of Lavoisier, the argument has been 

 active whether our breathing is controlled by oxygen need 

 or by the output of CO 2 . For the past thirty years, and 

 especially during the last ten or twelve, the theory of regu- 

 lation by CO 2 , or in its later form by C, has held the 

 field. Indeed it is established now almost beyond the 

 possibility of contradiction, it would seem that during 

 any brief period of time, and under conditions to which 

 the individual is accustomed, the amount of CO 2 produced 

 in the tissues of the body, through its influence on the CH 

 of the blood, is the factor controlling the volume of air 

 breathed. Its effects are immediate. 



But when we view the matter more broadly it is clear 

 that this is by no means the whole story. The oxygen 

 tension of the air is the influence which determines just 

 how sensitive the respiratory center is to excitement by 

 CO 2 . But the effects of any change of oxygen tension 

 are slow in developing, requiring in some persons, as we 

 .saw on Pike's Peak, hours to begin and several days to 



