794 



CHANGE OF COMPOSITION OF ALVEOLAR AIR, 



of the breath is continued. These movements, as will be shown 

 later, markedly hasten the passage of carbon dioxide into the 

 alveolar air. The total rise of the tension of carbon dioxide, on 

 holding the breath for 35 seconds, is ll-5inm.Hg. 



//o 



/GO 



90 



so 



70 



Tfiye 



10 



20 



30 



^o 



Text-fig. 1. — Variation of alveolar tensions of carbon dioxide and of oxygen 

 with period of holding the breath (A, B), and with period of re- 

 breathing expired air (C, D). Times (abscissie) in seconds, tensions 

 (ordinates) in mm.Hg. 

 Curve B, in the above diagram, shows how the alveolar tension 



of oxygen changes as the breath is held. It will be seen that 



