10 THE STORY OF GERM LIFE. 



producing profound changes in Nature. There is 

 no one family of plants that begins to compare 

 with them in importance. It is the object of this 

 work to point out briefly how much both of good 

 and ill we owe to the life and growth of these 

 microscopic organisms. As we have learned 

 more and more of them during the last fifty years, 

 it has become more and more evident that this 

 one little class of microscopic plants fills a place 

 in Nature's processes which in some respects bal- 

 ances that filled by the whole of the green plants. 

 Minute as they are, their importance can hardly 

 be overrated, for upon their activities is founded 

 the continued life of the animal and vegetable 

 kingdom. For good and for ill they are agents 

 of neverceasing and almost unlimited powers. 



HISTORICAL. 



The study of bacteria practically began with 

 the use of the microscope. It was toward the 

 close of the seventeenth century that the Dutch 

 microscopist, Leeuwenhoek, working with his sim- 

 ple lenses, first saw the organisms which we now 

 know under this name, w T ith sufficient clearness 

 to describe them. Beyond mentioning their ex- 

 istence, however, his observations told little or 

 nothing. Nor can much more be said of the stud- 

 ies which followed during the next one hundred 

 and fifty years. During this long period many a 

 microscope was turned to the observation of these 

 minute organisms, but the majority of observers 

 were contented with simply seeing them, marvel- 

 ling at their minuteness, and uttering many excla- 

 mations of astonishment at f he wonders of Nature. 

 A few men of more strictly scientific natures paid 



