806 



CHANGK OF COMPOSITION OF ALVEOLAR AIR, 



percentages when one and three respirations, respectively, are 

 made in this period. 



Table iv. 

 Efftd of frequency of reitpiratory mocemeufs on gaseou-s exchamje. 



The above experimental results show that the alveolar tension 

 of carbon dioxide is not raised any higher, above that found 

 after holding the breath for 20 seconds, by making three respi- 

 rations than by making one respiration in the same period. In 

 creasing the rate of the respiratory movements three times, 

 therefore, causes no parallel increase in the alveolar percentage 

 (and tension) uf carbon dioxide, within these limits. 



The following experiments show that not only is the increase 

 in the respiratory exchange in a given time independent, within 

 the limits of the work, of the number of respiratory movements 

 in a "-iven time, but also of the extent of these movements. In 

 these experiments, the alveolar tensions of carbon dioxide, after 

 holding the breath quietly for L'O seconds, are compared with 

 those reached when the four respiratory eftbrts are made in the 

 same time with the pharynx closed, "d". 



Table v. 

 Effect of rti^piratory ejj'urts irith closed chest on yaseous exclianije. 



Expt. 



9 



10 



Mean 



6 36 

 6-26 

 631 



Increase 



676 

 6-71 

 674 



0-43 



The increase in the respiratory exchange in this case is as 



