DISTRIBUTION OF DISEASE GERMS 101 



it is distributed to patrons who unsuspectingly purchase the 

 material which may give them the disease. 



If the water and milk are not polluted with typhoid bac- 

 teria, or if, when polluted, they are sterilized, they do not 



FIG. 60. Bacteria in milk 



Each colony was produced by a single bacterium. The upper plate was inocu- 

 lated with sterilized milk, the left-hand plate with certified milk, and the right- 

 hand plate with ordinary milk. After J. C. Olsen, " Pure Foods " 



carry the disease. Milk may be pasteurized (that is, heated 

 for twenty minutes to between 140 and 150 F.), and this 

 kills the typhoid germs. The number of bacteria in a cubic 

 centimeter of milk or water may be very large. There may 

 also be wide variations in the number of these bacteria, due 

 to the different ways in which milk and water are handled 



