CHARACTER OF BACTERIA 



17 



only a single spore. Spore formation is limited to the 

 bacilli. The fact that spores are so resistant is practi- 

 cally important, and necessitates a careful study of the 

 principles underlying sterilization. Among the spore- 

 forming bacilli encountered in medicine may be men- 

 tioned the bacillus of tetanus (lockjaw), the bacillus of 

 anthrax, and the bacillus of malignant edema. 



Some bacteria possess the power to move about. 

 They are, therefore, spoken of as being motile. By em- 



Fig. 4. Flagella: Proteus vulgaris and large spirillum belonging to 

 the group of sulphur bacteria (Zettnow). 



ploying suitable methods the motile bacteria are seen 

 to have little hair-like appendages, called flagella 

 (singular flagettum), which act as swimming arms. 

 Some bacteria have but a single flagellum, others have 

 a little tuft at one or both ends, while still others have 

 flagella on all sides. The typhoid bacillus is a good ex- 

 ample of a motile bacterium; it has flagella on all sides. 

 It is well to remember, that not all bacteria produce 

 disease. In fact, those that do (the so-called patho- 

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