THE BACTERIA. 139 



C. Putrefaction. 

 THE CAUSE OF PUTREFACTION. 



Materials. 300 c.c. of hay infusion. To make hay infusion, 

 pour hot water on hay, allow it to stand a few hours and then filter 

 through paper. 



Apparatus. 3 glass flasks. Cotton-batting. Cork to fit one 

 flask. 



Pour 100 c.c. of hay infusion into each flask and boil 

 for an hour. Allow the first flask to stand uncorked. 

 Cork the second air-tight while boiling. Plug the third 

 with cotton-batting while boiling. Allow the three to 

 stand side by side on the table and watch from day to 

 day. Explain the results. 



a. Why will preserves keep in a thick syrup? 



6. Why are pickles preserved in vinegar ? 



c. Why does tripe keep in brine ? 



d. Explain the conditions in canned beef. 



D. Conditions Necessary for the Growth of Bacteria. 

 I. HEAT. 



Materials. 300 c.c. of fresh milk. Ice. 



Apparatus. 3 bottles. Hot water-bath. Bunsen burner. 



a. Pour 100 c.c. of fresh milk in one bottle. Cork it 

 and place it on ice. 



b. Pour 100 c.c. of the milk in another bottle. Cork it 

 and allow it to stand on the table. 



c. Boil for an hour the other 100 c.c. of milk in the 

 third bottle, plug the bottle with cotton-batting and allow 

 it to stand on the table. 



