ELEVENTH ANNUAL YEAR BOOK— PART XI 649 



Countless numbers of tiny living things called micro-organisms, a 

 word meaning simply "small living things," are everywhere found, which 

 will grow in the food man has prepared for his own use and cause it to 

 spoil. Indeed, the kind of food required by man and animal seems to 

 be that which is also best suited to these microscopic plants. 



These microscopic plants flourish in the kitchen, storeroom, ice-box, 

 milk room and cellar. 



If the conditions are favorable they reproduce themselves with incredi- 

 ble rapidity, one bacterium in the course of a day producing a million 

 more minute plants like itself. The bulk of these minute forms of life 

 are harmless, at least under usual conditions some are useful, like those 

 which ripen milk and; many are harmful, since they cause waste or 

 maybe, what is much more serious, a direct cause of disease. 



Molds, yeasts, and bacteria may be found in the cleanest room, but 

 they exist in far greater numbers in dirty quarters, where, for instance, 

 crumbs of food have been allowed to decay and dust to accumulate. 



Not only do the micro-organisms appropriate our food, with the result 

 that the food sours, rots, or putrefies, but they sometimes, in addition, 

 leave behind disagreeable consequences, like the musty and moldy odor 

 and flavor of some spoiled foods, or the substances called ptomaines, 

 which are poisonous. 



The housekeeper's success in preserving food from becoming impaired 

 depends very largely on her ability to reduce the number of these un- 

 bidden guests to the lowest possible limit. 



The science of bacteriology has given us a new meaning for the scrub- 

 bing, airing, and sunning that for many generations good housekeepers 

 have successfully practiced; it shows us that the storing and handling of 

 foods are bacteriological questions, and on that account some knowledge 

 of the nature of these microscopic plants is essential. 



It is said that the numbers of bacteria are in direct relation to the 

 density of population. 



"We cannot get away from them without going into the highest mountain 

 or to the polar regions; but we can protect our food supply from their 

 undue growth by reversing all the conditions that they require for their 

 development. It is of primary importance that bacteria be prevented 

 from getting their start. 



The flesh of healthy living animals is free from them, but when 

 slaughtered and marketed the surface is almost certain to acquire bacteria, 

 like all things which are exposed to the air and dust. 



They are inside the human body, often performing important uses, as in 

 intestinal digestion. 



Bacteria require at least 25 per cent of moisture in which to live 

 and multiply, and they prefer darkness to light, and while as a class 

 they grow best at a comparatively high temperature, 80 deg. to 95 deg. F., 

 most of them are killed by an exposure to 150-160 deg. F. of moist heat. 



A repeated application of boiling temperature is necessary, however, 

 to kill the spores which certain kinds produce. 



