MOTILITY. 45 



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 members of 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 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 





Fig. 



I* he 



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

 fever with flag^ella given off from all sides ; c, large spirals from stagnant 

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



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.) 



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 stagnant water, and it was not until very 

 recently that the accuracy of this suspicion was actually 



3* 



