OXIDATIOIN OF FOOD 



57 



is placed in the firebox and lighted, and the lower door of the 

 furnace is opened so as to make a draft of air which will reach 

 the coal. You know the result. The coal burns, heat is re- 

 leased, causing the water in the boiler to make steam, the engine 

 wheels to turn, and work to be done. Let us see what happens 

 from the chemical standpoint. 



Coal, Organic Matter. — Coal is formed largely from dead 

 plants, long ago pressed into its present hard form. It contains 

 a large amount of the chemical element carbon. We have al- 

 ready observed (page 11) one of the effects of the oxidation of 

 carbon as proved by the limewater test. Let us now apply this 

 test to the oxidation of food substances in our own bodies. 



Oxidation in our Bodies. — If we expel the air from our lungs 

 through a tube into a bottle of limewater, we notice that the lime- 

 water becomes milky. Evidently carbon dioxide is formed in our 

 own bodies. In fact, the heat of the body (98.6° Fahrenheit) is due 

 to oxidation within the body. Food is also oxidized within the 

 human body to release energy for our daily work. In fact, all 

 living things, both plant and animal, release energy as the result of 

 oxidation of food within 

 their cells. Let us prove 

 this by an experiment 

 with some peas. 



Food oxidized in Ger- 

 minating Seeds. — If we 

 take equal numbers of 

 soaked peas, placed in 

 two bottles, one tightly 

 stoppered, the other hav- 

 ing no stopper, both 

 bottles being exposed to 

 identical conditions of 

 light, temperature, and 

 moisture, we find that 

 the seeds in both bottles 

 start to germinate, but 

 that those in the closed 

 bottle soon stop, while those in the open jar continue to grow. 



Experiment that shows the necessity for air 

 in germination. 



