CHAPTER II. 

 BACTERIA : THEIR FORMS AND REPRODUCTION. 



I. The Forms of Bacteria. The body of a bacterium 

 consists of a single cell, into the minute structure of 



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FIG. 5. Forms of bacteria, i, Coccus ; 2, bacillus ; 3, vibrio ; 4, spirillum. 



which it is not necessary to enter here. It is sufficient 

 to note that there is a central body of protoplasm which 

 stains readily with aniline dyes of various kinds, and 

 a skin or capsule, usually so thin as to be practically 

 invisible except by the aid of the highest powers of the 

 microscope. The capsule, or cell-wall, is not composed 

 of cellulose as in the higher plants, but of a material 

 apparently allied to the protein substances. The whole 

 body or cell is met with in many forms, as indicated in 

 Fig. 5. Some kinds of bacteria are spherical, each 

 individual being then termed a coccus. When much 

 longer than broad, the bacterium is known as a bacillus ; 

 a comma-shaped form is spoken of sometimes as a 



