94 THE STORY OF GERM LIFE. 



maker will be able to produce at will any particu- 

 larly desired flavour in his cheese by the addition 

 to it of particular species of bacteria, or particular 

 mixtures of species of bacteria which have been 

 discovered to produce the desired effects. 



CHAPTER IV. 



BACTERIA IN NATURAL PROCESSES. 



AGRICULTURE. 



THUS far, in considering the relations of bac- 

 teria to mankind, we have taken into account only 

 the arts and manufactures, and have found bac- 

 teria playing no unimportant part in many of the 

 industries of our modern civilized life. So im- 

 portant are they that there is no one who is not 

 directly affected by them. There is hardly a mo- 

 ment in our life when we are not using some of 

 the direct or indirect products of bacterial action. 

 We turn now, however, to the consideration of a 

 matter of even more fundamental importance ; 

 for when we come to study bacteria in Nature, 

 we find that there are certain natural processes 

 connected with the life of animals and plants that 

 are fundamentally based upon their powers. Liv- 

 ing Nature appears limitless, for life processes 

 have been going on in the world through count- 

 less centuries with seemingly unimpaired vigour. 

 At the very bottom we find this never-ending ex- 

 hibition of vital power dependent upon certain 

 activities of micro-organisms. So thoroughly is 

 this true that, as we shall find after a short con- 

 sideration, the continuance of life upon the surface 



