PSEUDODIPHTHERIA . 141 



cultures, and which greatly resemble the virulent Bacillus 

 diphtherice, but have no pathogenic power. 

 These pseudobacilli are of two kinds: 



I. It is not possible to separate the first kind from the 

 true diphtheria bacilli either by morphology or cultural 

 properties. When injected into the lower animals they are 

 non-virulent, because they secrete no toxin. 



II. The second kind, in the opinion of the author, are 

 very improperly so-called, for they are not diphtheria bacilli, 

 and can with little difficulty be differentiated from true diph- 

 theria bacilli by their appearance, mode of staining, and their 

 cultural properties. 



Differential Diagnosis. The method of staining suggested by 

 Neisser, as mentioned in the beginning of the chapter, is 

 applicable especially to the recognition of the second form of 

 pseudobacilli. 



For the recognition of the non-toxin-producing form, ex- 

 periment on animals is the only means of differentiating. 



What appear to be true diphtheria bacilli have been found 

 in the throat and mouth in about 1 per cent, of a number 

 of healthy persons examined, but generally in individuals 

 who have come into contact with diphtheria patients, or when 

 diphtheria was prevalent in the community at the time of 

 the examination. Those persons are always a source of 

 danger to others, and they no doubt are in a great measure 

 responsible for the spread of the disease. 



The experiments of Roux and Yersin have shown that the 

 various cultures of diphtheria bacilli have different potency 

 in the production of toxins, and that occasionally bacilli 

 grown under conditions, the same as much as possible, may at 

 different times produce more or less toxins, and of a greater 

 or lesser virulence. These facts bacteriologists are in no 

 position to explain, and the toxicity of a diphtheria culture 

 may only be determined by experimentation on animals. 



The Antitoxin Treatment of Diphtheria. 



The discovery made by Roux, that the diphtheria bacilli 

 secrete a toxin which, when injected into susceptible ani- 



