PATHOGENIC SPIRILLA. 



curve is about one-third of a single turn of a spiral. 

 In other cases, especially in rather old bouillon cul- 

 tures, long screw-like threads, having three, five, ten, 

 or even more turns, develop. These constitute the 

 spirillum form of the comma bacillus. The rodlets are 

 more or less curved, with rounded off ends. It is true 

 that they often, when examined with the microscope, 

 appear to be straight, but this is when they are lying, 

 as it were, on their dorsal or ventral surfaces. They 

 are often very actively motile, especially in recent 

 cultivations ; aud by Loffler's method of staining 

 .flagella, their motile organs have been successfully 

 demonstrated. These are placed either singly or in 

 pairs (very rarely in threes) at one or both poles of 

 the cells. The statement that each cell possesses only 

 one polar flagelluoi is not quite correct ; even those 

 authors which make this statement show in the photo- 

 graphs accompanying their writings that the cholera 

 bacillus occasionally possesses two polar flagella. 



These bacilli, as a rule, are easily stained, but they 

 do not generally become intensely coloured; the bac- 

 teria seem sometimes, without any apparent reason, to 

 have more aflBnity for the staining reagents than at 

 others. If strongly coloured preparations are desired 

 it is best to leave the fixed cover-glasses for at least 

 twelve hours in a cold solution of carbolic fuchsine (1 

 of carbolic fuchsine to 3 of water). Such preparations 

 on account of their' intense coloration, are especiall}'' 



