20 RESPIRATORY MECHANISMS 



On the basis of these few experimental results we make ten- 

 tatively the sweeping generalization that diffusion and con- 

 vection are the only processes responsible for the oxygen 

 transport into respiratory organs and within organisms. 



The diffusion rate for G0 2 in water and tissues is about 

 25 times higher than for O2, and it should be safe therefore 

 to assume that diffusion is also responsible for the transport 

 of this gas in solution. This assumption is strongly supported 

 by the facts that CO2 moves regularly in the direction of the 

 tension gradient and that the tension in the arterial blood is 

 always practically identical with that of the alveolar air. 



