Bacteriology of the Household. 



719 



In about twenty-four hours little specks appeared, which rapidly or 

 slowly grew larger and developed different colors. Unfortunately, 

 the photograph does not give the delicate greens, yellows and blues 

 which the different spots showed. As they grew larger, some spots 

 showed a feathery or velvety surface, and, like the one at the left side, 

 a dark center with dust flying from it. 



The other spots were shiny, wet or waxy in appearance, and never 

 showed any increase in height, or any dark, dusty color. 



Every housewife who 

 has seen mold on her 

 bread, her jelly, in her 

 pickle jar, or possibly 

 on shoes and books, 

 will mistrust that the 

 velvety, dark-centered 

 spots are of similar 

 nature. Molds spread 

 their cells over the food 

 supply, sending some 

 cells down into the sub- 

 stance, and others up- 

 ward. From the tops 

 of the upright cells 

 grov\r others, and in or 

 on them are formed the 

 thousands of dust-like 

 specks called spores. 

 Each of these may start 



a new bed of mold. The infinitely tiny spores falling upon some soft 

 substances as cheese or bread will send their invisible lacy threads 

 dow:n into the substance, while on books, leather, wood, cloth, they 

 may grow only over the surface and may remain invisible. 



The other spots in the dust-garden are colonies of bacteria. Each 

 spot shows where one plant or cell touched the jelly. This fed, and 

 divided itself in the middle. These two repeated the process, until 

 perhaps there were a hundred or more. Then a tiny pin-point speck 

 became visible. No one ever saw, with the naked eye, a bacterium or 

 a miold spore. 



A dust-garden is shown in Fig, 43 with soil exactly like that in Fig. 42, 

 but the dust which planted it was thrown into the air by using a feather 

 duster. 



Fig. 43, — Another dust-garden 



