380 PHYSIOLOGY. 



must be ineffective except in 

 so far as there may be a 

 limited gaseous exchange be- 

 tween the air of the air-pas- 

 sages and the blood-supply 

 to the mucous membrane of 

 the air-passages. Thus, if 

 the alveolar air contains 6 

 per cent, of C0 2 , and the 

 expired air 4 per cent., with 

 a total volume of GOO cubic 

 centimeters, the expired air 



may be regarded as made up 

 4 



of 600 X = 400 cubic 

 6 



centimeters alveolar air and 

 200 cubic centimeters pure 

 air. The effective dead 

 space will be 200 cubic centi- 

 meters. 



The capacity of the 

 bronchi and upper air-pas- 

 sages will then be, according 

 to Haldane, 200 cubic centi- 

 meters. Haldane believes 

 that the air in the alveoli 

 does not get there by the 

 process of diffusion, but that 

 the inspired air is drawn 

 into the alveoli, which is a 

 mixture of the air of the 

 bronchi and which is derived 

 from the upper air-passages, 

 having, in proportion to the 

 other parts of the air-pas- 

 sages, more atmospheric air. 



In expiration, the alveolar 

 Fig ISS.-Ludwig's Mercurial Air Pump to air % j h j 



Extract Blood Gases. (LAHOUSSE.) ., /. _ ' . . * 



considerable CO.,, which air 



O, Receptacle for the blood. . ,., . ., . 



is diluted by the air in the 



bronchi containing more oxygen and with the atmospheric air holding 

 still more oxygen. 



