THE ACTIVE FORCES OF LIVING ORGANISMS 6i 



the greater ease with which the air enters the lungs, 

 necessitating less respiratory effort, and also to the 

 diminution in the amount of carbonic acid in the 

 blood, whereby the natural stimulus to the respiratory 

 centre is lessened. 



There is a certain amount of evidence which tends pi™'"ii- 



tion of 



to show that this intensity of chemical action is chemical 



intensity 



diminished as the atmospheric pressure falls. Ac- in high 



n ■ !• -I 11 altitudes. 



cordmg to Dr. Saussure fire does not burn well on 

 Mont Blanc,* and it is necessary to blow it continually 

 in order to prevent it from going out. Although 

 water boils at 84'03° it requires more time, and an 

 amount which takes half an hour before reaching the 

 boiling point upon the mountain would, with the 

 same apparatus and the same amount of alcohol, 

 attain that degree in twelve minutes at sea-level, f 

 Tyndall found that stearin candles lasted longer on 

 Mont Blanc than in the valleys below, and attributed 

 this fact to the cold. But this conclusion was 

 disproved by Benedicenti, who raised the temperature 

 of the air surrounding the candles and oil-lamp which 

 he used, and still noticed a marked decrease in the 

 rate of consumption.} These examples tend to show 

 that as you rise in height oxidation becomes less 

 rapid. Curiously enough, however, an increase of 

 the pressure of oxygen when carried beyond certain 

 limits produces the same results. When the pressure 

 of oxygen is very high, even phosphorus will not 



* Mosso, loc. cit., p. 267. 



+ Ihid. I Ibid., p. 268. 



