8i 



EXPERIMENT 79. THE EFFECT OF HEAT ON BACTERIA 



(a) Put some bits of raw meat in a test tube of water, 

 plug with raw cotton, and set aside in a warm place. 



(b) Put an equal amount of raw meat in a test tube of 

 water, but boil the contents for half an hour before plug- 

 ging and setting aside in a warm place. 



At the end of a day are the contents of the two vessels 

 in equally good condition ? At the end of two days ? 



(c) Put a small quantity of milk in a test tube, and im- 

 merse the vessel in a water bath. When the water is at 

 or near the boiling point, remove the test tube of milk, 

 plug it with cotton, and set it aside in a warm place. Is 

 the milk sour at the end of a day ? Try the experiment 

 with unheated milk and compare results. 



Explain how cooking assists the preservation of food. 



CL. LAB. 6 



