DIPHTHERIA BACILLUS. 351 



Pseudodiphtheria Bacilli. Beside the typical baciili 

 which produce diphtheria toxin and those which do not, 

 but which, so far as we can determine, are otherwise iden- 

 tical with the Loffler bacillus, there are other bacilli 

 found in positions similar to those in which diphtheria 

 bacilli abound, which, though resembling these organ- 

 isms in many particulars, yet differ from them as a class 

 in others equally important. The variety most preva- 

 lent is rather short, plump, and more uniform in size 

 and shape than the true Loffler bacillus (Fig. 45). On 

 blood-serum their colony growth is very similar to that 

 of the diphtheria bacilli. The great majority of them 

 in any culture show no polar granules when stained 

 by the Neisser method, and stain evenly throughout 

 with the alkaline rnethylene-blue solution. They do 

 not produce acid by the fermentation of glucose, as 

 do all known virulent and many non-virulent diph- 

 theria bacilli; therefore, there is no increase in acidity 

 in the bouillon in which they are grown during the 

 first twenty-four hours from the fermentation of the 

 meat sugar regularly present. They are found in vary- 

 ing abundance in different localities in about 1 per 

 cent, of the normal throat and nasal secretions, in New 

 York City, and seem to have now at least no con- 

 nection with diphtheria; whether they were originally 

 derived from diphtheria bacillus is doubtful; they cer- 

 tainly seem to have no connection with it now. They 

 never produce diphtheria toxin, and to them properly 

 has been applied the name pseudodiphtheria bacilli. In 

 bouillon they grow, as a rule, less luxuriantly than the 

 diphtheria bacilli. Some of the varieties of the psewdo- 

 diphtheria bacilli are as long as the shorter forms of 

 the virulent bacilli. When these are found in cultures 



