36 



BACTERIOLOGY. 



delicacy they can only very rarely be seen in the living' 

 condition. Moreover, they do not color with anilin dyes in 

 the same way as the mass of the bacterial cell, and for that 

 reason they are not visible in the ordinary stained prepara- 

 tion. In order to demonstrate the presence of flagella or 

 whips it is necessary to resort to a very special method of 

 staining. They then appear as slender, wavy filaments. 

 It is the lashing of theSe whips that propels the organism 

 through the liquid. 



Fig. -6. Motile organs or whips on bacteria. «— Micrococcus; b — Bacillus witli term- 

 inal whips; c — Bacillus with diffuse whips; d — Vibrio; e — Single spirillum with bunch of 

 whips; /^Spirillum after division with whips at each end. 



The fiagella will vary considerably in size in different 

 species, and even at times in individuals of the same spe- 

 cies. Their width is usually less than sV of the width of 

 of the cell. Their length will usually be two or three times 

 the length of the cell, but it is not uncommon to find some 

 bacteria with whips that are ten or twenty times as long as 

 the cell. 



The flagella project from the outer border of the organ-, 

 ism. They are supposed by some to be directly continuous 

 with the protoplasm within, the cell. In that case the 

 protoplasmic threads are supposed to pass through minute 

 openings in the cell-wall. Plasmolytic experiments, how- 

 ever, do not indicate a protoplasmic continuity. On 

 treatment with saline solutions, as indicated above, the 

 protoplasm of the living cell withdraws completely from 

 the cell- wall and gathers in one or two round masses. If 



