Upon the Pseudo- Diphtheria, etc. 27 



absence of acid and of toxic production it is not a simple 

 matter to recognize them as such promptly under the 

 microscope when taken from throat cultures, unless the 

 observer has had considerable training. It is highly prob- 

 able, therefore, that Roux and Yersin in their earlier work 

 may have mistaken pseudo-diphtheria for true diphtheria 

 bacilli, when they found virulent and non-virulent forms 

 together in the throats of convalescents. 7 ' 



E. A. Peters (27) states that the relation of the Hofmann 

 bacillus to the true diphtheria bacillus is clear on certain 

 points : 



(a) "The Hoffmann bacilli resemble the diphtheria 

 bacilli in mode of growth, and slightly in microscopical 

 character. 



(b) "The cases in which they are found are liable to be 

 mistaken for mild diphtheria. The prognosis in such 

 cases is good. 



(c) " There is no proof forthcoming that this bacillus is 

 an attenuated form of the diphtheria bacillus ; though the 

 short diphtheria bacillus, when it becomes non-pathogenic, 

 tends to resemble the Hofmann bacillus." 



Schanz (28) employed as a differential diagnostic method 

 tests of the acidity of the bouillon cultures. Earlier in- 

 vestigators have shown that the pseudo-diphtheria bacilli 

 are also able, like the diphtheria bacilli, to produce acid. 

 Neisser was able to substantiate this, yet the amount of 

 acid with the pseudo-diphtheria bacilli after growing for 

 forty-eight hours was from four to five times smaller than 

 with the diphtheria bacilli. Schanz found only one excep- 

 tion, with a xerosis culture, which showed an equal acidity 

 with that found in the diphtheria culture. The amount 

 of acid formed, he says, is dependent to some extent upon 

 the amount of the culture inoculated into a tube. 



Trumpp (29) differentiated between the diphtheria and 

 pseudo-diphtheria bacilli by means of simultaneous inocu- 

 lations of diphtheria toxin. The amount of toxin inocu- 



