246 THE RESPIRATORY APPARATUS 



inspiration and expiration varies from 20 to 30 cubic 

 inches. (2) The complemental volume or the amount 

 of air taken into the lungs, in addition to the tidal 

 volume, resulting from a forcible inspiration, which 

 amounts to 110 cubic inches. (3) The reserve volume 

 or the amount of air which flows out of the lungs, in 

 addition to the tidal volume resulting from a forcible 

 expiration, which amounts to 100 cubic inches. (4) 

 The residual volume or amount of air remaining in the 

 lungs, as a permanent volume, after the most forcible 

 expiration. 



The vital capacity is the amount of air which can 

 be expelled from the lungs after they are filled by the 

 most forcible inspiration. This amounts to 230 cubic 

 inches (3593 c.c.). * 



Changes in the Composition of Inspired and Expired 

 Air as a Result of Respiration. 



INSPIRED AIR, 100 VOLUMES 



Oxygen 20.80 



Carbon dioxide traces 



Nitrogen 79.20 



Watery vapor variable 



EXPIRED AIR, 100 VOLUMES 



Oxygen 16.02 



Carbon dioxide 4.38 



Nitrogen 79.60 



Water vapor saturated 



Organic matter (Brubaker) 



The above analyses show that the air under ordinary 

 conditions loses oxygen to the extent of 4.37 per cent., 

 and gains in carbon dioxide to the extent of 4.38 per 

 cent.; it gains in nitrogen to the extent of 0.4 per cent., 

 and watery vapor to the point of saturation, also 

 organic matter. 



From experiments with the spirometric apparatus, 

 and the taking of the percentage loss of oxygen and 

 gain in carbon dioxide shown by the analysis of the 



