40 THE STORY OF GERM LIFE. 



In short, wherever on the face of Nature there 

 is a lodging place for dust there will be found 

 bacteria. In most of these localities they are 

 dormant, or at least growing only a little. The 

 bacteria clinging to the dry hair can grow but lit- 

 tle, if at all, and those in pure water multiply very 

 little. When dried as dust they are entirely dor- 

 mant. But each individual bacterium or spore 

 has the potential power of multiplication already 

 noticed, and as soon as it by accident falls upon 

 a place where there is food and moisture it will 

 begin to multiply. Everywhere in Nature, then, 

 exists this group of organisms with its almost in- 

 conceivable power of multiplication, but a power 

 held in check by lack of food. Furnish them 

 with food and their potential powers become 

 actual. Such food is provided by the dead bod- 

 ies of animals or plants, or by animal secretions, 

 or from various other sources. The bacteria which 

 are fortunate enough to get furnished with such 

 food material continue to feed upon it until the 

 food supply is exhausted or their growth is 

 checked in some other way. They may be re- 

 garded, therefore, as a constant and universal 

 power usually held in check. With their uni- 

 versal presence and their powers of producing 

 chemical changes in food material, they are ever 

 ready to produce changes in the face of Nature 5 

 and to these changes we will now turn. 



