CHAPTER II 



STRUCTURE, MODE OF DEVELOPMENT, AND COMPO- 

 SITION OF BACTERIA 



Morphology is the science which deals with 

 the form and structure of organisms. 



Bacteria are the smallest and simplest known 

 form of vegetable organisms. They are jinicellur. 

 lar (having but one cell) and multiply, by fisgi^Ji 

 (splitting into equal parts). 



The individual cells differ in size, shape, and 

 structure, which can be determined only by the 

 use of the microscope; but in masses of cells or 

 " colonies," as they are called, which develop 

 in suitable substances, they often present differ- 

 ences in form, color, and consistency which may 

 be detected with the naked eye. 



Size. — Different bacteria vary greatly in size, 

 the average of the rod-shaped bacterium being 

 about O j/x, in diam eter-^ 1 /a = 1 micron or micro- 

 miUimeter = x^Vo '^™- = about 25000 inch). The 

 bacillus of typhoid fever ranges from 1/u, to 3/x ( 25000 



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