40 FUNGI 



Simple Fission. The usual method of reproduction is by 

 simple fission. This is so rapid under favorable conditions 

 that the bacteria often form groups or chains. One bac- 

 terium can produce eighteen million bacteria in twelve hours 

 by this method. 



Spore Formation. Under favorable conditions the proto- 

 plasm draws away from the cell wall and rounds off, develop- 

 ing a spore with a thick wall inside the wall of the mother 

 cell. In this state spores can be dried out, blown about, 

 heated to a high temperature, or subjected to the action of 

 chemicals, and still, when placed under favorable conditions, 

 they will develop into bacteria. 



Object of Cooking Food. Food is cooked in order to break 

 the cell walls and to free the cell contents so that they can be 

 acted upon by the digestive ferments. Another reason for 

 cooking food is to destroy the bacteria found in it. No 

 uncooked food should ever be eaten in countries like China 

 and India where the plague is common; in fact, it is always 

 safer to eat cooked food. 



Pasteurization of Milk. Milk contains all the food neces- 

 sary for the growth of bacteria and it is used as a culture 

 medium for growing bacteria artificially. Milk is contami- 

 nated by bacteria from the body of the cow, from the hands 

 and clothing of the milker and from the air. Frequently 

 tubercle bacilli occur in the milk of tubercular cows. 



Bacilli of typhoid fever frequently occur in milk because 

 pails and cans have been washed in polluted water. That 

 milk is also a carrier of diphtheria has been proven by the 

 fact that milk bottles returned unsterilized to the milkman 

 have been the cause of spreading this disease. 



If milk is boiled for a few minutes all the bacteria are 

 killed; the public, however, will not use boiled milk; therefore, 

 milk is pasteurized by heating at a temperature of 86 to 



