424 



DIPHTHERIA 



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The organism is a shorter bacillus than the diphtheria bacillus, 

 with usually a single unstained septum running across it, though 

 sometimes there may be more than one (Fig. 122). The typical 

 beaded appearance is rarely seen, and the characteristic reaction 

 with Neisser's stain is not given, though in old cultures a few 

 granules which stain deeply may sometimes be found. It grows 

 readily on the same media as the diphtheria bacillus, but the 

 colonies are whiter and more opaque. It does not form acid 

 from glucose or other sugars, and is non-pathogenic to the 

 guinea-pig. Involution forms may sometimes be produced 



by it. It is usually a 

 relatively easy matter to 

 distinguish this organ- 

 ism from the diphtheria 

 bacillus. 



Hofmann's bacillus is 

 of comparatively common 

 occurrence in the throat 

 in normal as well as 

 diseased conditions, in- 

 cluding diphtheria ; it 

 seems to be specially fre- 

 quent in poorly nourished 

 children of the lower 

 classes. Cobbet found 

 it 157 times in an ex- 

 amination of 692 persons 

 examined, of whom 650 

 were not suffering from 

 diphtheria. Boycott's 

 statistics show that the 



time of its maximum seasonal prevalence precedes that of the 

 diphtheria bacillus. To what extent, if any, it is responsible 

 for pathological changes in the throat, must be considered a 

 question which is not yet settled. Hewlett and Knight have 

 found evidence that a true diphtheria bacillus may assume the 

 characters of Hofmann's bacillus, but attempts to effect the 

 transformation have met with negative results in the hands of 

 other observers. The general opinion is that the two organisms 

 are distinct species with comparatively easily distinguished 

 characters. 



Xerosis Bacillus. This term has been given to an organism first 

 observed by Kuschbert and Neisser in xerosis of the conjunctiva, and 

 which has been since found in many other affections of the conjunctiva 



FIG. 122. Pseudo -diphtheria bacillus (Hof- 

 mann's). Young agar culture. See also 

 Plate HI., Fig. 14. 



Stained with thiouin-blue. x 1000. 



