DIPHTHERIA. 295 



bacillus seems to be shorter than the diphtheria bacillus 

 when grown upon blood-serum; that the cultures in 

 bouillon seem to progress much more rapidly at a tem- 

 perature of from 2o-22 C. than those of the true bacillus; 

 and that the pseudobacillus is not pathogenic for ani- 

 mals. These slight distinctions are all exactly what 

 should be expected of an organism whose virulence had 

 been lost, and whose vegetative powers had been altered, 

 by persistent manipulation or by unfavorable surround- 

 ings. 



Park l carefully studied this subject, and found that 

 all bacilli with the exact morphology of the diphtheria 

 bacillus, found in the human throat, are virulent Klebs- 

 LofHer bacilli, while forms found in the throat closely 

 resembling them, but more uniform in size and shape, 

 shorter in length, and of more equal staining properties 

 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. 



A difference of possibly much greater importance is that 

 observed by Martini, 2 that the diphtheria bacillus will not 

 grow in fluid antitoxic serum in which the pseudodiph- 

 theria bacillus thrives. Both the real and the pseudoba- 

 cilli flourish upon coagulated antitoxic serum. If this dif- 

 ference in the behavior of the bacilli bears any relation 

 to the so-called "specific immunity-reaction" of cholera 

 and typhoid fever, it may be of great future importance. 



The diphtheria bacilli are always present in the throats 

 of patients suffering from diphtheria, and constitute the 

 element of contagion by being accidentally discharged 

 by the nose or mouth by coughing, sneezing, vomiting, 



1 Scientific Bulletin No. i, Health Department, City of New York, 1895. 

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



