RESPIRATION 



33 



The investigations of Priestley and myself brought out the 

 remarkable fact that the composition of the alveolar air is the 

 same no matter how deep the breath may be from the last portion 

 of which the sample is taken. According to descriptions commonly 



3000 2600 



200 



2200 1800 1400 1000 

 air pressure mm Hg 



Figure 7. 



Effects of variation in barometric pressure on alveolar gas pres- 

 sures and percentage of CO 2 in A. E. B. The dotted lines show results 

 when oxygen was added to the air. 



current of the anatomical relations of bronchioles to alveoli one 

 would have expected that the deeper parts of a breath, coming 

 from alveoli far from the bronchioles, would contain more CO 2 , 

 since these alveoli must get less fresh air than the alveoli near a 

 bronchiole. It was somewhat of a puzzle that this was not the case. 

 I was unaware of the anatomical investigations which had been 

 carried out ten years earlier by a distinguished American investi- 

 gator, W. S. Miller, who by using the laborious "reconstruction" 

 method had discovered the true anatomical arrangement. 18 Figure 

 8, modified from a colored plate in Miller's latest paper, shows 



18 Miller, Journ. of Morphol., VIII, p. 165, 1893, and XXIV, p. 459, 1913. 



