MICROBES, OR BACTERIA. 87 



of fine dust ; this dust consists of myriads of bacteria. 

 If we take a drop of this water and place it under 

 a cover-glass, in order to examine it under a micro- 

 scope with a magnifying power of about 500 dia- 

 meters, we shall, as soon as the instrument is properly 

 focussed, see a really surprising spectacle. 



The whole field of the microscope is in motion ; 

 hundreds of bacteria, resembling minute transparent 

 worms, are swimming in every direction with an un- 



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Fig. 49. Bact. termo in different stages of development, a-h (much ma 



dulatory motion like that of an eel or snake. Some 

 are detached, others united in pairs, others in chains 

 or chaplets or cylindrical rods which are partitioned 

 or articulated (Fig. 49) ; these are only less mature or 

 younger than the first. Finally, we see a multitude of 

 small globules which result from the rupture of the 

 chaplets. All these forms represent the different 

 transformations of Bacterium termo, or the microbe of 



