BY H. S. HALCRO WARDLAW. 



797 



Table ii. — rontiiintil. 



1 lie intei'vals of time between the taking of each sample of 

 alveolar air and that of the next in the above series of experi- 

 ments, are not considered to be uniform enough to allow average 

 values to be calculated from them arithmetically. The average 

 figures given in the last portion of the Table, therefore, have been 

 determined graphically by plotting the individual experiments 

 on squared paper, drawing a curve through the points represent- 

 ing each series of results, and, from the curves, detei'mining the 

 tensions of carbon dioxide and of oxygen for corresponding times. 

 From the figures got thus, the average values have been calcu- 

 lated in the ordinar}^ way. These values are represented in the 

 diagram by the points on the curves C and D. 



The curve C represents the manner in which the alveolar 

 tension of carbon dioxide rises when the contents of the lungs 

 are breathed into and out of a closed, empty bag. It will be seen 

 that the alveolar tension of carbon dioxide rises at a continually 

 decreasing rate. During the first 5 seconds of the experiment, 

 the tension of carbon dioxide rises 3"5 mm.Hg, or by practically 

 the same amount as when the breath is held in the lungs. 

 Between the 2oth and 30th seconds, however, the rise is 1-4 mm. 

 Hg, or about thrice as great as when the breath is held. The total 

 rise in the alveolar tension of carbon dioxide in 35 seconds is 

 from 380 to 53*0, 15"0 mm.Hg, or nearly 40% greater than the 

 rise occurring in the same period when the breath is simply held. 



Curve D shows the rate at which the alveolar tension of 

 oxygen falls when the contents of the lungs are breathed into 



