i6o 



BIOLOGICAL CHEMISTRY 



is a mixture of air from the dead space and alveolar air. If 

 we wish to obtain a sample of the alveolar air we must take 

 a sample of the expired air at the end of expiration after the 

 dead space has been flushed out with the air from the alveoli. 



Maximum inspiration ~7~~ 



Complemental air- 



?uiet inspiration 

 ic" 



Tidal air 

 Quiet expiration - 



Supplemental air 



Maximum expiration _ 



Residual air 



V Vital capacity 



Capacity of equilibrium 



FIG. 36. Amounts of air contained by the lungs in various phases of 

 quiet and of forced respiration. 

 From " Unman Physiology." A.D. Waller (Longmans). 



TABLE XXXII 

 Volume of Air Spaces in Man. 



c.c. 



Dead space 170 



Quiet respiration (tidal air) 500 



Amount that can be inspired at^ the end of a 



quiet inspiration . . 2000 



Amount that can be expired at the end of a 



quiet expiration 15 



Total possible respiratory volume (vital capacity) 4000 

 Amount left after greatest possible expiration 



(Residual air) 1500 



From these figures we see that a quiet respiration 

 is the mixing of about 330 c.c. (500 170) fresh air, with- 

 about 3500 c.c. of air and the removal of 330 c.c. of the 

 mixture after exchange has taken place between it and the 

 blood. Deeper respirations such as occur during performance 

 of work increase the amount of exchange. 



