THE CONTROL OF THE RESPIRATION 



383 



Fig. 131. Curves showing variations in alveolar gas tensions after forced breathing for two 

 minutes. Thin line = O 2 tension; thick line = CO 2 tension. Double line = normal alveolar 

 CO2 tension. Dotted line shows the alveolar CO2 tension at which breathing would recommence 

 at the end of apnea with the alveolar O 2 pressures shown by the thin line. The actual breathing 

 is indicated at the lower part of the figure. It is periodic to start with. (From Douglas, and 

 Haldane.) 



