EFFECT OF PULMONARY VENTILATION 227 



in place of 7*9, and the oxygen tension 14*0 per cent, in place 

 of 9-6. 



Loewy found on lowering the 2 tension in the respired air 

 from 12-1 per cent, to 7' 81 per cent, the alveolar 2 tension 

 remained the same, as the breathing volume per min. increased 

 from 5-51. to 11 '4 1. These considerations show how a man by 



> 



FIG. 10. Haldane's method of estimating- the Alveolar Tension of 2 and COa. 

 The subject breathes into the spirometer, and at the end of expiration closes the 

 mouthpiece with his tongue. A sample of the air in the tube is drawn into A, 

 the measuring tube of Haldane's air analysis apparatus. This sample is alveolar 

 air, and its analysis yields the tension of O 2 and 



deep breathing can maintain his alveolar oxygen tension in high 

 altitudes. 



Loewy notes that a superficial breather normally breathing 

 270 c.c. twenty times a minute became affected at 500 mm. Hg 

 = 3300 m. Loewy himself breathing 440 c.c. fourteen times a 

 minute became affected at 360 mm. = 6000 m., while Zuntz, 

 breathing 700 c.c. eight times a minute, was not affected at 

 330 mm. = 6500 m. 



