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 magnified }. 
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 Bacteriwm termo, or the microbe of 
