CHAPTER III 



THE WORLD OF MICROSCOPIC LIFE 



At this stage of our history it may be advantageous 

 to consider briefly some of the peculiarities of the 

 minute organisms to whose study Pasteur was des- 

 tined to devote the remainder of his life. Readers 

 who are familiar with microscopic organisms and 

 their ways will probably prefer to omit the perusal 

 of this chapter. In fact, they are advised to do 

 so. I am throwing this chapter in for the benefit 

 of those, — and my experience as a teacher of 

 biology has shown them to be very numerous, — 

 who have never been introduced to this vast and 

 important assemblage of living beings which have 

 remained so long unknown because they happen to 

 be so very small in size. But they make up for 

 their smallness by their prodigious numbers, their 

 variety, their rapidity of multiplication and the 

 magnitude of their mass effects. 



Science has proven that microscopic organisms 

 play a very important role in nature which was 



entirely unsuspected a century ago. We may 



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