Bacteriology of the Household. 723 



pre&ent. We bake bread for a full hour, or longer if the loaf is very- 

 large, in order to kill bacteria, yeast and molds, as all three may be 

 present in a poorly baked loaf of bread and interfere not only with the 

 keeping quality of the bread, but with the health of the consumer. The 

 careful housekeeper will have clean dishes in which to measure her 

 ingredients and to mix her bread and will not sweep nor cause a dust to 

 rise in the room, because the bacteria are in this way raised into the 

 air and may settle on the dough. She will cover the dough to keep out 

 the dust. With all her care there will always be some bacteria present 

 but these do not thrive in the sugar solution as well as healthy yeast 

 plants do and they want a higher heat than the yeast plants. However, 

 they do like the alcohol which the yeast makes from the sugar and so 

 dough is kept at summer heat only long enough for the yeast to pro- 

 duce sufficient gas to raise the bread but not long enough for the bacteria 

 to get a start. It is better not to wrap cloth around hot bread just taken 

 from the oven because moisture and warmth favor the growth of bac- 

 teria, and bread that is cooled slowly may not keep sO' well. 



Germs are not all bad. — Some bacteria are of great value in nature's 

 economy. They tear down organic matter and pass it back to its simpler 

 elements through the process of decay and thus rid the earth of many 

 harmful substances. There is advantage in which is called incipient 

 decay. When bacteria grow in food the products of decomposition are 

 different from the original nature of the food, giving new odors and 

 tastes. We often need these flavors to stimulate the flow of the diges- 

 tive juices. The gamey taste of meat is the beginning of decomposition 

 of some of its constitutents and the strong flavor of limburger cheese is 

 due to the same cause. Gamey food, however, soon becomes objection- 

 able; and cheese is ruined by the development of a too strong flavor of 

 putrefaction. 



The action of bacteria is very useful in the production of linen, of jute 

 and hemp, the tanning of leather, the maceration of skeletons, in butter 

 and cheese making. To a certain class of bacteria is due the destruction 

 of garbage by means of the septic tank. 



The Battle with Bacteria 

 Bacteria are carried on particles of dust, in liquids, on the surface of 

 fruits and vegetables and on other articles of food exposed in the market. 

 They may find their way into the house by means of drains and they 

 are carried by insects. Normally, they are found in the air, in the soil, 

 in water, in food, in the mouth and digestive tract, on the skin, under 

 the nails, in the hair, in the clothing. 



