150 



In January 1920 about 50 strains were inoculated on haemo- 

 globin broth. There was a good growth in all the tubes in about 

 21 hours, and each culture was then examined microscopically in 

 a hanging drop preparation at 37°. The microscopic morphology 

 in broth corresponded in all its essentials to that found in stained 

 smears. Similar differences between the individual cultures were 

 observed especially as regards the length of the elements. In most 

 of the cultures the majority of the bacilli were situated more or 

 less in masses. In some cases they were all collected in masses 

 while in others a large number were lying free. 



Undoubted motility was observed in no case, but it was very 

 difficult to determine as Brownian movement, on account of the 

 lightness of the bacilli, was often exceedingly lively. In one of the 

 cultures (I 71) a single element was observed which seemed to be 

 distinctly motile. 



In order to investigate this matter further, staining of the same 

 strains by Zettnow's (1 5 2) method was carried out. The tech- 

 nique was first practised and tested on a number of different motile 

 species of bacteria, and constantly gave satisfactory staining of the 

 flagella, which was also the case with preparations of typhoid, 

 cholera, and proleus \vhich were stained at the same time as 

 Pfeiffer's bacillus. 



In several of the preparations bacilli were found with long, 

 only slightly curved threads of similar appearance to those depicted 

 by Ellis (1,2). In a few preparations some bacilli were also seen with 

 curved threads which more resembled flagella. There were 1, 2, 

 or a whole tuft. Unfortunately I was unable to continue these 

 investigations, as apparently several months' work would be required 

 to clear up the question of the motility of Pfeiffer's bacillus. 



Pfeiffer's bacillus is regarded by all the authors who have 

 expressed an opinion on the subject, as non-motile and from 

 my own investigations as well as those of others, there is no 

 doubt that it does not generally possess any marked motility. 

 But there is nothing at present to exclude the possibility that 

 by a thorough investigation of the question it might be discove- 

 red that Pfeiffer's bacillus as a rule could, under suitable 

 conditions, form flagella. The question is however scarcely 

 of great importance from the point of view of classification. 

 Even if only a minority of bacteriologists will be able to 

 entirely agree w r ith Orla-Jensen (1, 2) that the presence or 

 absence of flagella is of no importance in the classification 

 of bacteria, the general view is that it cannot be reckoned 

 among the best marks of distinction. 



On the whole there was correspondence between the ma- 



