22 BACTERIA, YEASTS, AND MOLDS 



I. Microorganisms and the Preservation of Food 



Although household duties are varied in character, the 

 larger part of them concern the preparation and the pres- 

 ervation of foods. The preparation of food belongs pri- 

 marily to the department of cooking, although certain 

 other factors are concerned. But the science of cooking 

 has little to do with the preservation of food. This latter 

 problem is intimately related to modern bacteriology. It 

 is largely for this reason that the study of bacteriology 

 and kindred subjects has in recent years come to be 

 looked upon as a part of the necessary training of the 

 housewife. 



At the outset we may properly ask, Why is it that food 

 spoils? Why will not food keep indefinitely without the 

 many contrivances designed to prevent its spoiling .' The 

 answer to this question is, briefly, that other living things 

 besides ourselves are fond of the same foods of which we 

 are fond, and that these other living beings take every 

 occasion to consume the material which we design for our 

 own food. Preserving the food in our pantries, cellars, 

 and refrigerators, therefore, simply means protecting it 

 from consumption by other living organisms ; and if we 

 can keep these organisms away, food may be indefinitely 

 preserved. On the other hand, if we cannot protect our 

 food from the attack of these organisms, it spoils ; for the 

 spoiling of food is simply the result of its consumption by 

 living beings for whom we have not designed it. 



The living beings that endeavor to consume our food 

 comprise, in the first place, some of the larger animals 

 with which every one is familiar, Every one knows about 



