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THE FOODS WE EAT 



Moisten a slice of bread and expose it to the air of the kitchen 

 for a half hour and then place it in a jar and cover lightly. Keep 

 the bread moist and in a warm place. Place a slice of dry bread 

 in another jar and screw the cover on tightly so that no dust or air 

 may enter. Note the appearance of the bread in the two jars from 

 day to day. What is happening to the moist bread ? Leave it for 

 several days. What happens to the color of the fuzzy growth on 

 the bread? 



When examined with the lens, the dark objects will be seen to 

 be filled with tiny bodies called spores. These spores get into the 

 air, settle on food, and develop into mold. 



Expose to the air in a moderately warm location a few moist 

 beans in a cup. Place an equal number of dry beans in another 

 cup. Examine after a day or two. What has happened to the 

 moist beans? Do they look different from the dry beans? Is 

 there any odor present? What causes it? 



The changes that we have just observed are caused by 

 tiny organisms, most of which are far too small to be seen 

 without the aid of a compound microscope. Hence they 



Wright Pierce 



This picture shows at the left two tubes of sterilized beef broth, a good substance 

 for the growth of bacteria. One tube was plugged with absorbent cotton, the 

 other left open. Both tubes were left in a warm place for a week. At the end 

 of this time the contents of tube A was unchanged while that in tube B smelt 

 and tasted of decay. How do you account for this ? 



