CHAPTER XI. 



STAINING OF FLAGELLA. 



It has already been mentioned that some bacteria 

 manifest lively movements : it is only, however, in a 

 few rare instances that we are able to see the organs 

 of movement without further treatment of the pre- 

 paration. Occasionally, though not frequently, they 

 may be seen in the Spirillum undula, for example, 

 which is, so to speak, a giant amongst bacteria ; but 

 even here nothing can be made out very clearly ; even 

 in the most favourable cases, we can only just see 

 some moving points and lines at the poles of the 

 curved cell, which indicate to us that we are dealing 

 with the organs in question. In order to demonstrate 

 them clearly it is necessary to have recourse to a com- 

 plicated and ingenious system of staining, for they 

 cannot be stained by any of the methods already 

 described, as they are unaffected by aniline dyes, un- 

 less prepared beforehand in a special manner with a. 

 mordant. 



We will again make use of the hay bacillus, in order 

 to obtain material for our experiments, not because it 



