Mingling of Molecules 



273 



FIG. 151. Pouring the syrup into the "osmosis tube." 



It is by this sort of diffusion that chicks which are being 

 incubated get air, and that growing plants get food. 

 It is in this way that the cells of our body secure food 

 and oxygen and get rid of their wastes. There are no 

 little holes in our blood vessels to let the air get into them 

 from our lungs. The air simply diffuses through the 

 thin walls of the blood vessels. There are no holes from 

 the intestinal tract into the blood vessels. Yet the 

 dissolved food diffuses right through the intestinal wall 

 and through the walls of the blood vessels. And later 

 on, when it reaches the body cells that need nourish- 

 ment, the dissolved food diffuses out through the walls 



