PSEUDO-DIPHTHERIA BACILLUS 411 



it. It is usually a relatively easy matter to distinguish this 

 organism from the diphtheria bacillus. 



Hofmann's bacillus is of comparatively common occurrence in 

 the throat in normal as well as diseased conditions, including 

 diphtheria ; it seems to be specially frequent in poorly nourished 

 children of the lower classes. Cobbett found it 157 times in an 

 examination 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 compara- 

 tively easily distinguished 



characters. Flf; ns.Pseudo-diphtheria bacillus (Hof- 



mann's). Young agar culture. See also 

 Xerosis Bacillus. This pi a te III., Fig. 14. 



term has been given to an Stained with thionin-blue. x 1000. 



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 and also in normal conditions. Morpho- 

 logically it is practically similar to the diphtheria bacillus, and even in 

 cultures presents very minor differences ; it, however, grows more slowly 

 on serum, and its colonies have a tougher consistence and a more irregular 

 margin. It is non-virulent to animals, and does not produce an acid 

 reaction in glucose bouillon, or does so to only a slight extent ; in this 

 way it can be distinguished from the diphtheria bacillus. It is still 

 doubtful whether it is pathogenic to the human subject. Its morpho- 

 logical characters are shown in Fig. 119. 



Action of the Diphtheria Bacillus Summary. From a 

 study of the morbid changes in diphtheria and of the results 

 produced experimentally by the bacillus and its toxins, the 



