368 



THE RESPIRATION 



ventilation as to demonstrate the changes produced in the sensitivity of 

 the respiratory center in pneumonia. 



Possibility that C0 2 Specifically Stimulates Center. After showing 

 that C0 2 acts as an excitant of the respiratory center, the question arises 

 as to whether the action depends on the raising of the C H of the blood, or 

 whether it may be a specific action of the C0 2 . Many attempts have 



SOQ 



400 



300 



ZOO 



/OO 



L 



Fig. 129. Composite curve obtained from the data on sixteen experiments, showing the re- 

 spiratory response to CO 2 in the decerebrate cat. Abscissae = percentage of CO 2 in the inspired 

 air. Ordinates = the percentile increase the tidal air per minute. (From R. W. Scott.) 



been made to decide this question experimentally, the general principle 

 of the experiments being to determine whether C H of the blood runs 

 parallel with the C0 2 content of the respired air and with the hyperpnea. 

 Using the gas-chain method (page 31), Hasselbalch and Lundsgaard 22 

 found that the hyperpnea produced in rabbits by breathing in C0 2 -rich 



