274 HOFMANN'S BACILLUS 



the whole organism decolourizes. (Occasionally a minute granule may be seen 

 at the poles of some of the bacilli, but these minute specks present a very 

 different appearance to the granules seen in the diphtheria bacillus, and are 

 relatively few in number.) If stained with Neisser's blue, washed in water 

 and counterstained with Bismarck brown (1 minute in each stain) the bacilli 

 will be stained uniformly brown ; blue granules will be absent or very 

 indistinct. 



[The organism like the diphtheria bacillus retains the violet by Gram's 

 method. 



[Cultural characteristics. On serum or alkalized glucose serum the growth 

 is more rapid than that of the diphtheria bacillus, and the colonies are larger 

 and whiter and do not take up the pigment in the serum. 



[Bio-chemical reactions. When grown for 48 hours in a nutrient broth 

 neutral to litmus and containing 1 per cent, glucose no acid is formed ; on 

 the contrary a slight increase in alkalinity takes place.] 



Rothe recommends the following medium. 



Neutral broth,. 1 part. 



Ox serum, - 4 parts. 



10 per cent, glucose litmus solution, - part. 



Solidify. 



The diphtheria bacillus on the other hand turns this medium red. 



[Virulence. A guinea-pig inoculated with 2 c.c. or more of a 48-hour 

 culture in broth remains perfectly well, not even a local oedema resulting. 



[Immunity. Hofmann's bacillus produces no substances toxic to laboratory 

 animals. Petrie experimenting with Hofmann's bacillus finds that " no 

 substances capable of neutralizing diphtheria antitoxin are present in the 

 nitrates of the pseudo-diphtheria bacillus"; and his attempts to immunize 

 horses with this bacillus against diphtheria toxin were negative.] 



The relation of Hofmann's bacillus to the diphtheria bacillus. [Petrie's 

 experiments on immunity accentuate- the differences between the two 

 organisms which have been detailed above and diminish the probability 

 that they stand in close relation to each other. 



[Further support of the latter view is afforded by the fact that no satis- 

 factory evidence of the conversion of the one organism into the other has yet 

 been brought forward, though numerous experiments have been conducted 

 for that purpose. 



[The non-identity of the diphtheria bacillus with Hofmann's bacillus 

 receives further confirmation from certain practical observations. In the 

 first place, as has already been shown, the distribution of the diphtheria 

 bacillus is limited to the throats of those who have been in contact with cases 

 of diphtheria or with diphtheria-infected contacts, while Hofmann's bacillus 

 is a widely distributed organism present in the throats of a considerable pro- 

 portion of the ordinary healthy population. Secondly, Cobbett successfully 

 stamped out two epidemics of diphtheria, one at Colchester and one at 

 Cambridge, by isolating only those in whose throats diphtheria bacilli were 

 found, those who harboured the bacillus of Hofmann and no diphtheria 

 bacilli being treated as non-infected individuals. Other observers have had 

 similar experiences. 



[The above then is the case of those who regard the Klebs-Lceffler and 

 Hofmann's bacillus as distinct species. 



[The following arguments, which are advanced in favour of the identity of the 

 two organisms, may be prefaced by a quotation from Graham-Smith supporting 

 an earlier statement to the same effect by Cobbett. " The authority of Roux (1890) 

 whose opinion justly carries great weight has often been quoted in support of the 



