CHAPTER II. 



Morphology i of bacteria Chemical composition of bacteria Mode 

 of multiplication Spore-formation Motility. 



IN structure the bacteria are unicellular, always de- 

 veloping from pre-existing cells of the same character 

 and never appearing spontaneously. They are seen to 

 occur as spherical, rod- and spiral-shaped bodies that 

 multiply by the simple process of transverse division, 

 belonging, therefore, to the schizomyeetes or fission 

 fungi. 



In size the bacteria are among the smallest living 

 creatures with which we are acquainted, being visible 

 only when very highly magnified. In order that 

 some conception of their microscopic dimensions may be 

 formed, it has been computed that of the average size 

 bacteria about thirty billion would be required to weigh 

 a gramme, and that about one billion seven hundred 

 million of the small spherical forms might readily be 

 suspended in a drop of water. 



Under what we are accustomed to regard as normal 

 conditions of development, and by the ordinary methods 

 of examination, bacteria appear very simple in form and 

 structure. They are cells consisting of a protoplasmic 

 mass within a membranous hull that is discernible with 

 more or less difficulty. The protoplasmic body is of 

 material closely allied, chemically speaking, to ordinary 

 vegetable proteid. It is often homogeneous, but in par- 



i Morphology : pertaining to shape, outline, structure. 

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