CHAPTER I 



DEFINITION, MORPHOLOGY, AND PHYSIOLOGY 



Bacteriology is the study of micro-organisms, especi- 

 ally in their relation to health and disease. 



Bacteria, microbes, micro-organisms, or germs are 

 practically synonymous terms, designating the lowest 

 form of plant life of the class fungi. They are minute 

 single-celled organisms composed of protoplasm, nuclear 

 chromatin, and surrounded by a cell wall containing 

 cellulose or an albuminous membrane. In size they 

 average i mmm. in diameter and may, therefore, only 

 be seen by means of the high-power microscope. 



Form. Bacteria are classified according to their 

 shape as follows: 



Bacilli, cylindric or rod-shaped organisms. 



Spirilla, curved or spiral rods. 



Cocci, spheric or globular organisms.' 



Flagella. Attached to many bacteria are found fine 

 thread- or hair-like projections, teimed flagella, which 

 keep up a constant movement. They are doubtless 

 organs of locomotion, as they are found most frequently 

 in motile bacteria. 



Motile bacteria are those forms which possess the 

 power of moving themselves from place to place. 



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