BREATHING IN RAREFIED AND COMPRESSED AIR 



417 



The anoxemia acts on the various nerve centers, producing symptoms 

 which vary in different individuals according to their relative susceptibili- 

 ties. In some, the digestive centers are affected and nausea and vomiting oc- 

 cur; in others, the higher cerebral centers are affected, causing depression 



Fig. 142-A. CO 2 -tension at various altitudes. The horizontal interrupted lines represent the 

 mean normal alveolar CO 2 and O 2 pressures at sea level (i.e., Oxford and New Haven); the thick 

 line, alveolar CO 2 pressure; and the thin line, alveolar O 2 pressure. (From Douglas, Haldane, 

 Henderson, and Schneider.) 



and general mental apathy, great drowsiness, muscular weakness, or it may 

 be mental excitement and loss of self-control. As to whether it is the anoxe- 



