TYPHOID 165 



other organisms ; in fact, it is not uncommon to find some 

 stained specimens which have a curved appearance exactly 

 like Koch's * comma ' or the Finkler-Prior bacillus. 



If a fragment of a recent culture of the typhoid bacillus 

 is rubbed up with a drop of water (or, better, a twenty- 

 four-hour broth culture), and examined with a xV i'^^'h 

 objective, the bacilli will be seen in active movement, this 

 motility being due to the great number of hair-like flagella 

 by which the organism is covered. The best methods of 

 demonstrating these flagella by staining are given on p. 89^ 

 et seq. 



Methods of Staining. — The typhoid baciUus stains well 

 with all the ordinary aniline dyes, although somewhat 

 more slowly than usual. It is decolourised by Gram's 

 method of staining. 



Growth on Media. — The true Eberth-Gaffky bacillus is 

 readily distinguished from all others by its characteristic 

 growth on the various culture media. Repeated subculture, 

 as in the case of many other organisms, produces longer 

 and abnormal forms. Yery lengthened forms of the bacillus, 

 which are somewhat characteristic, are sometimes seen in 

 cover-glass preparations; these long bacilli are known as 

 ' leptothrix ' forms. 



The Bacillus coli communis, which is always present in 

 the intestines of both man and animals, closely resembles the 

 typhoid bacillus. It is slightly shorter than the typhoid 

 bacillus, and, like it, owes its power of motion to flagella, 

 but it never possesses the profusion usually seen in the 

 case of the Eberth-Gaffky bacillus. 



The following table shows the main points of difference 

 between the typhoid bacillus and the Bacillus coU com- 

 munis, for which it might be mistaken : 



