MOTILITY. 45 



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 motion is 

 due to the possession by the motile bacilli of very deli- 

 cate, 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 



FIG. 7. 



a 6 c 



a, spiral forms with a flagellum at only one end ; 6, bacillus of typhoid 

 fever with flagella given off from all sides ; c, large spirals from stagnant 

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



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 the motility of bacteria was only 

 supposed to be due to the possession of some such form 

 of locomotive apparatus because similar appendages had 

 been seen in certain of the large, motile spirilla found in 



