MOTILITY. 



45 



loses its regular rod shape and becomes that of a club, 

 a drum-stick, or a lozenge, depending upon whether 

 the location of the spore is to be at the pole or in the 

 centre of the cell. (See Fig. 4, e and d.) 



In addition to the property of spore-formation there 

 is another striking difference between the rod-shaped 

 organisms, namely, the property of motility which 

 many of them are seen to possess. This power of mo- 

 tion is due to the possession by the motile bacilli of very 



FIG. 7. 



a. Spiral forms with a flagellum at only one end. b. Bacillus of typhoid 

 fever with flagella given off from ail sides, c. Large spirals from stagnant 

 water with wisps of flagella at their ends (spirillum undula). 



delicate, hair-like appendages or flagella, by the lashing 

 motions of which the rods possessing them are propelled 

 through the fluid. In some cases the flagella are located 

 at but one end of a bacillus, either singly or in a bunch ; 

 again, they may be seen at both poles, and in some 

 cases, especially with the bacillus of typhoid fever, they 

 are given off from the whole surface of the rod. (See 

 Fig. 7.) In a few instances similar locomotive organs 

 have been detected on spherical bacteria i. e., motile 

 micrococci have been observed. 



For a long time this property of independent motion 

 that is peculiar to certain species of bacteria was sup- 



