86 MICEOBES, FEEMENTS, AND MOULDS. 



lower forms, which have been by some united in the 

 kingdom Protista. 



Microbes, or bacteria (Schizophyta or Sddzomycetes) , 

 appear, in liquids examined under the microscope, as 

 small cells of a spherical, oval, or cjdindrical shape, 

 sometimes detached, sometimes united in pairs, or 

 in articulated chains and chaplets (Fig. 

 48). The diameter of the largest of these 

 cells is two micro-millimetres, and that 

 of the smallest is a fourth of that size, 

 . so that at least 500 of the former and 



Fig. 48. Ferment 



cLlrmf aceti\ 2000 of tne latter must be placed end 

 fereni n form e s di o f f to end in order to attain the length of 

 edor [n a 'charTets a millimetre. It is therefore plain that a 

 fled). magnifying power of 500 to 1000 dia- 



meters, or even still higher, is required to make these 

 beings clearly visible under the microscope. 



One very common bacterium may be found every- 

 where, and can be easily procured for microscopic 

 observation : Bacterium termo, or the microbe of im- 

 pure water. This bacterium is not injurious to health, 

 since there is no potable water in which it is not 

 found in greater or less quantity. In order to obtain 

 numerous specimens, it is enough to take half a glass 

 of ordinary water from a spring or river, and to leave 

 it for some days on a table or chimney-piece, the 

 vessel being uncovered to allow the access of air. We 

 may soon observe that a thin coating is formed on 

 the surface of the water, which looks like a deposit 



