66 BACTERIOLOGY. 



hering to a spore which has not yet become com- 

 pletely free. 



By the ordinary methods of staining, spores do not 

 become colored, so that they appear in the stained 

 cells as pale, transparent, oval bodies, surrounded by 

 the remainder of the cell, which has taken up the dye. 



A single cell produces but one spore. This may be 

 located either at an extremity or in the centre of the 

 cell. (Fig. 6.) 



Occasionally spore-formation is accompanied by an 

 enlargement of the cell at the point at which the proc- 

 ess is in progress. As a result, the outline of the cell 

 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. 6, e and d.) 



MOTILITY. In addition to the property of spore-for- 

 mation there is another striking difference between vari- 

 ous species of the rod-shaped organisms, namely, the prop- 

 erty of motility, by which some of them are distinguished. 

 This power of motion is due to 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 are located at 

 but one end of a bacillus, either singly (monotrichic) or 

 in a tuft (lophotrichic) ; and in some cases, especially 

 with the bacillus of typhoid fever, they are given off 

 from the whole surface of the rod (peritrichic). (See Fig. 

 7.) In a few instances similar locomotive organs have 

 been detected on spherical bacteria i. e., motile micro- 

 cocci have been observed. 



For a long time this property of independent motion 

 could only be assumed to be due to the possession of 



