THE PHYSIOLOGY OF THE AVIATOR 105 



the oxygen is progressively decreased by the breathing of 

 the man himself. Dr. Haldane found that after a day 

 or two in this chamber he had reduced the oxygen to an 

 extent comparable to Pike's Peak. At the same time there 

 had evidently occurred in himself a gradual process of 

 adjustment, for he felt quite well. At this stage he in- 

 vited another person to come into the chamber with him, 

 and he had the satisfaction of observing the immediate 

 development of blueness and the other symptoms of 

 oxygen collapse in his companion. 



Evidently acclimatization is a very real phenomenon 

 and of the utmost importance to any one exposed to a 

 lowered tension of oxygen. 



As we observed it in ourselves during our stay on 

 Pike's Peak acclimatization consists in three chief alter- 

 ations: (i) increased number of red corpuscles in the 

 blood; (2) some change in the lungs or blood (Haldane 

 considers it the secretion of oxygen inward by the pul- 

 monary tissue) which aids the absorption of oxygen, and 

 (3) a lowering of the CO 2 in the alveolar air of the 

 lungs. This lowering of the CO 2 in the lungs is bound up 

 with increased volume of breathing. It is the concomitant 

 of a decreased alkaline reserve in the blood just as in 

 nephritis and diabetes. Acclimatization in this respect 

 consists therefore in the development of a condition which 

 would nowadays be called acidosis. 



All of these changes are of a quantitative character. 

 Miss FitzGerald 5 has supplemented the results obtained 

 on Pike's Peak by an extensive series of careful observa- 

 tions on the inhabitants of towns of closely graded alti- 

 tude from sea level up to that of the highest inhabited 

 place in our western country. She has thus shown that 

 the mean hemoglobin and the mean alveolar CO 2 of the 

 inhabitants of any town are functions of the mean baro- 

 metric pressure of the place. 



5 FitzGerald, M. P., Phil. Trans., 1913, B. 203, p. 351, and Proc. 

 Royal Soc., 1914, B. 88, 248. 



