810 



CHANGE OF COMPOSITION OF ALVEOLAR AIR, 



reduced to a common period of holding tlie breath of 20 seconds, 

 in the manner explained above. 



Tablk vii. 



Effect of decreu.sed pres.wre on afreofar perreiifayef of carlton dioxide 

 after holding (he breath for JU »tcond». 



These figures show at once that holding the breath under 

 pressures less than that of the atmospliere increases the gaseous 

 exchange in the lungs. As the percentage of carbon dioxide is 

 rising, in this case at, a rate about equal to that at which it rises 

 when the contents of the lungs are breathed to and from a bag, 

 the data given in Table ii. have been used for the calculation of 

 the percentages of carbon dioxide after holding the breath for 20 



