BY H. S. HALCEO WARDLAW. 549 



negative pressure or when the same air was rebreathed, in the previous experi- 

 ments. It is still lower than the final values which the tig-ures seemed to be ap- 

 proaching. The highest values reached in those experiments were 7.45 % or 

 53.9 mm. Hg, and the final value approached was 8.35 % or 60.5 mm. Hg. 

 as already stated. 



In the following Table are shown the figures for the alveolar carbon dioxide 

 content when a series of inspirations is held under negative pressure as before, 

 but in this case the initial inspiration was made from a bag containing a mixture 

 of air with a percentage of carbon dioxide higher than that expected in the 

 alveolar air, so that the values rose during the first part of each experiment. 



Table 4. 

 Alveolar carbon dioxide content after holding expired air in lungs under 

 negative pressure. Initial inspiration from mixture of air with carbon dioxide. 



Number of 



I 



Alveolar 



carbon 



dioxide 



content 





Expt. 



9 



1 





Expt. 



10 





Percent. 



Tension 



I 



Percent. 



Tension 



1 



10.25 



73.9 





10.73 





77.2 



2 



7.42 



53.5 





7.49 





5i.O 



3 



7.03 



50.5 





7.17 





51.6 



4 



7. 01 



50.5 





6-77 





48.8 





6.99 



50.4 





7.11 





51.2 



6 



7.11 



51.2 





7.00 





.50.4 



7 



7.03 



50.5 





7.03 





50.6 



8 



7.08 



51.0 





6.89 





49.6 



The above figures show that during the last six inspirations of these experi- 

 ments approximate constancy had been reached. The mean value of the alveolar 

 carbon dioxide content for this portion of the experiments is 7.02 % or 50.3 

 mm. Hg. This value is nearly the same as that obtained in the previous ex- 

 periments. 



These results show that when the breath is held under negative pressure as 

 described, final constant values are reached for the alveolar carbon dioxide con- 

 tent, and these values are but slightly higher than those reached when the breath 

 is held under normal pressure in a similar manner. 



Oxi/geu. 



In the following Table are shown the values for the alveolar oxygen content 

 when the breath is held in the manner described under noi-mal and under negative 

 pressure respectively; the initial inspirations were made from the atmosphere in 

 each ease. 



Table 5. 



Alveolar oxygen content after holding expired air in lungs under normal 

 pressure {Expt. 3) and under negative pressure [Expt. II). 





Alveolar 



oxygen 



content 



inspiration 



Expt. 3 



Normal press. 



Percent. Tension 



Expt. 11 



Negative press. 



Percent. Tension 



2 

 3 

 4 

 5 

 6 



16.2 115.3 

 13.9 99.4 

 11.97 S6.1 

 10.37 74.7 

 10.15 73.1 

 10.40 74.9 





17.0 121.7 

 14.04 100.2 

 11.35 SI. 3 

 10.81 77.4 

 10.20 73.0 

 10.61 76.0 



