THE ACTIVE FORCES OF LIVING ORGANISMS 57 



to lower levels when transported suddenly to heights 



above 8,000 to 9,000 feet. Mosso mentions, on the 



authority of Hiifner, that hemoglobin artificially 



prepared would absorb a normal amount of oxygen 



even on the top of the Himalayas.* Analyses of 



dogs' blood by Geppert and Fraenkel showed that 



the amount of oxygen in it was not diminished until 



the atmospheric pressure had fallen to 410 mm.,t 



although mountain sickness is often observed in a 



violent form at a pressure of 500 mm., the equivalent 



of a height of 3,300 metres. Hiifner even goes so 



far as to say that mountain sickness cannot be 



attributed to a chemical or physical change in the 



blood until you reach a height of 9,000 feet. 



The analyses just referred to demonstrated another The rela- 

 tive 

 important fact, to which Paul Bert had also drawn diminution 



attention, viz., that as the air becomes more and acid and 

 more rarefied, the carbonic acid in the blood S the" 

 diminishes more rapidly than the oxygen, the pro- 

 portion being 1'63 of the former to I'O of the latter. 

 Mosso, who has performed many experiments and 

 collected a good deal of evidence all tending to 

 support this statement, is inclined to regard the 

 diminution of carbonic acid in the blood as the main 

 or most direct cause of mountain sickness.! Doubt- 

 less the amount of carbonic acid in the blood 

 exercises a considerable influence on the respira- 

 tory centre, and it may be on the nervous system 



* Mosso, he. cit., p. 400. 



t Ihid., p. 401. I Ibid. 



