420 PATHOGENIC BACTERIA. 



with Loffler's alkaline methylene blue solution, can be, 

 with reasonable safety, regarded as pseudodiphtheria 

 bacilli, especially if it be found that they produce an 

 alkaline rather than an acid reaction by their growth in 

 bouillon. The pseudodiphtheria bacilli were found in 

 about i per cent, of throats examined in New York; they 

 seem to have no relationship to diphtheria. They are 

 never virulent. 



The observation of Martini, 1 that the diphtheria ba- 

 cillus will not grow in fluid antitoxic serum in which 

 the pseudodiphtheria bacillus thrives I have not been 

 able to confirm. Both the real and the pseudobacilli 

 flourish upon coagulated antitoxic serum. 



Having practically the same cultural and staining re- 

 actions as the diphtheria bacillus, the question presents 

 itself, Is the pseudodiphtheria bacillus the diphtheria ba- 

 cillus in an attenuated condition ? This question we are, 

 as yet, unable to answer. Every attempt to bring back 

 virulence to the pseudobacilli has failed, and we know it 

 only as a saprophyte, except upon the conjunctivae, when, 

 if it is identical with the Bacillus xerosis conjunctivae, it 

 seems able to take up parasitic existence very successfully 

 and lead to recognized lesions. It seems to me that inas- 

 much as it is, as a rule, almost impossible to increase the 

 virulence of any diphtheria bacillus, its persistent attenu- 

 ation should not stand in the way of regarding it as the 

 extreme decree of attenuation to which a bacterium can 

 descend, and accepting it as a non-virulent and non- 

 infectious form of diphtheria bacillus. 



1 Centralbl.f. Bakt. u. Parasitenk., Jan. 30, 1897, Bd. xxi., No. 3. 



